Patent Publication Number: US-2023143332-A1

Title: Leaflet attachment configurations to the frames of prosthetic valves

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of a PCT Application No. PCT/US2021/041002, filed Jul. 9, 2021, which claims the benefit of U.S. Provisional Pat. Application No. 63/211,417, filed Jun. 16, 2021 and U.S. Provisional Pat. Application No. 63/050,657 filed Jul. 10, 2020, where each of above-referenced applications is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to implantable prosthetic devices, such as prosthetic heart valves, and to attachment configurations and methods of attaching soft components, such as leaflets or skirts, to frames of such prosthetic valves. 
     BACKGROUND OF THE INVENTION 
     Native heart valves, such as the aortic, pulmonary and mitral valves, function to assure adequate directional flow from, and to, the heart, and between the heart’s chambers, to supply blood to the whole cardiovascular system. Various valvular diseases can render the valves ineffective and require replacement with artificial valves. Surgical procedures can be performed to repair or replace a heart valve. Since surgeries are prone to an abundance of clinical complications, alternative less invasive techniques of delivering a prosthetic heart valve over a catheter and implanting it over the native malfunctioning valve have been developed over the years. 
     Different types of prosthetic heart valves are known to date, including balloon expandable valve, self-expandable valves and mechanically-expandable valves. Different methods of delivery and implantation are also known, and may vary according to the site of implantation and the type of prosthetic valve. One exemplary technique includes utilization of a delivery assembly for delivering a prosthetic valve in a crimped configuration, from an incision which can be located at the patient’s femoral or iliac artery, toward the native malfunctioning valve. Once the prosthetic valve is properly positioned at the desired site of implantation, it can be expanded against the surrounding anatomy, such as an annulus of a native valve, and the delivery assembly can be retrieved thereafter. 
     One of the complications that may be associated with implanted prosthetic heart valves is thrombus formation on the prosthetic structures, which can result in reduced leaflet motility or impaired coaptation, reduced effective valve orifice area, increased transvalvular pressure gradient, or transvalvular regurgitation. Thrombus may be formed by tissue ingrowth in fabric components of the prosthetic valves, such as fabrics utilized as intermediaries for coupling leaflets of a prosthetic valve to its frame. Thus, a need exists for leaflet-to-frame coupling methods and configurations, that will minimize or eliminate the need for incorporation of fabric components, thereby reducing the risk of tissue ingrowth and thrombus formation. 
     SUMMARY OF THE INVENTION 
     The present disclosure is directed toward prosthetic heart valves that include an expandable frame and a leaflet assembly, wherein the leaflets are coupled to struts of the frame via a primary suture threaded in an in-and-out pattern along the cusp end portions of the leaflets, and a secondary suture is threaded through the primary suture and around the struts, having a plurality of self-tightening constructs configured to constrict under tension over the struts. 
     According to one aspect of the invention, there is provided a prosthetic valve comprising a frame movable between a radially compressed configuration and a radially expanded configuration, and a leaflet assembly mounted within the frame and comprising a plurality of leaflets configured to regulate flow through the prosthetic valve. The frame comprises a plurality of intersecting struts. Each leaflet comprises a rounded cusp end portion defining a cusp edge, a free edge opposite to the cusp edge, and a pair of oppositely-directed tabs separating the cusp edge and the free edge. 
     Each cusp end portion is coupled to at least one strut via at least one primary suture threaded at penetration points therethrough in an in-and-out pattern, and a secondary suture threaded through the primary suture and around at least one section of at least one strut, wherein the secondary suture comprises a plurality of self-tightening constructs, and wherein each self-tightening construct comprises at least one loop configured to constrict under tension around the strut. 
     According to some embodiments, the leaflet comprises a leaflet inner surface and a leaflet outer surface, and the primary suture comprises a plurality of inner stitch portions disposed along the leaflet inner surface, and plurality of outer stitch portions disposed along the leaflet outer surface, each inner stitch portion and each outer stitch portion defined between respective penetration points. 
     According to some embodiments, the self-tightening construct is defined between two penetrations points that define at least one outer stitch portion there-between. 
     According to some embodiments, the at least one loop of each self-tightening construct comprises two loops. 
     According to some embodiments, each self-tightening construct further comprises a u-shaped section partially extending between the at least one loop and the strut. 
     According to some embodiments, the secondary suture further comprises a plurality of suture pull portions extending over the leaflet inner surface. 
     According to some embodiments, at least one of the suture pull portions spans over more than one inner or outer stitch portions. 
     According to some embodiments, the suture pull portions are pressed against portions of the at least one primary suture. 
     According to some embodiments, the diameter of the secondary suture is smaller than the diameter of the primary suture. 
     According to some embodiments, a secondary to primary sutures diameter ratio is equal to or smaller than 0.8. 
     According to some embodiments, a secondary to primary sutures diameter ratio is equal to or smaller than 0.5. 
     According to some embodiments, a secondary to primary sutures diameter ratio is equal to or smaller than 0.3. 
     According to some embodiments, the cusp end portion of each leaflet comprises a series of pre-formed apertures. 
     According to some embodiments, the apertures are dimensioned to accept the at least one primary suture, thereby serving as the penetration points. 
     According to some embodiments, the apertures are equally spaced from each other. 
     According to some embodiments, the diameter of the apertures is equal to or smaller than the diameter of the primary suture. 
     According to some embodiments, the diameter of the apertures is equal to or smaller than the combined diameters of the primary suture and the secondary suture. 
     According to some embodiments, the secondary suture is threaded through all successive penetration points. 
     According to some embodiments, the at least one primary suture comprises two primary sutures, which are inversely threaded in an in-and-out pattern, through the same penetration points. 
     According to some embodiments, the diameter of the apertures is equal to or smaller than the diameter of the two primary sutures. 
     According to some embodiments, the diameter of the apertures is equal to or smaller than the combined diameters of the two primary sutures and the secondary suture. 
     According to some embodiments, the at least one primary suture tracks the curvature of the at least one cusp edge. 
     According to some embodiments, the primary suture comprises a multi-filament suture. 
     According to some embodiments, the secondary suture comprises an ultra-high-molecular-weight polyethylene. 
     According to some embodiments, the prosthetic valve is devoid of fabric strips and/or cloth between the cusp end portions of the leaflets and the struts they are attached to. 
     According to another aspect of the inventions, there is provided a method of assembling a prosthetic valve, the method comprises threading a primary suture in an in-and-out pattern through a cusp end portion of a leaflet. The method further comprises approximating the cusp end portion with the primary suture threaded there-through to at least one strut of a frame of the prosthetic valve. The method further comprises stitching a secondary suture through the primary suture and around the at least one strut, in a manner that forms a plurality of self-tightening constructs, wherein each self-tightening construct is formed to comprise at least one loop configured to constrict under tension around the strut. 
     According to some embodiments, the stitching a secondary suture includes threading the secondary suture radially outward through the primary suture at a penetration point, thereby forming the at least one loop around the at least one strut. 
     According to some embodiments, the stitching a secondary suture comprises looping the secondary suture again around the at least one strut after forming a first loop, thereby forming two loops for each self-tightening construct. 
     According to some embodiments, the stitching a secondary suture comprises passing the secondary suture under the at least one loop, between the at least one loop and the at least one strut, to form a u-shaped section. 
     According to some embodiments, the method comprises a further step of extending the secondary suture over a leaflet inner surface, and then threading the secondary suture once again through the primary suture in a radially-outward direction, thereby forming at least one suture pull portion extending over the leaflet inner surface. 
     According to some embodiments, the cusp end portion of each leaflet comprises a series of pre-formed apertures, and wherein the step of threading a primary suture comprises threading the primary suture in an in-and-out pattern through the series of pre-formed apertures. 
     According to another aspect of the invention, there is provided a prosthetic valve comprising a frame movable between a radially compressed configuration and a radially expanded configuration, and a leaflet assembly mounted within the frame and comprising a plurality of leaflets configured to regulate flow through the prosthetic valve. The frame comprises a plurality of strut sections intersecting at junctions. Each junction is defined between: two opposite axial sides comprising a junction proximal side and a junction distal side; two opposite radial sides comprising a junction inner side and a junction outer side; and two opposite lateral sides comprising a junction first lateral side and a junction second lateral side. 
     Each leaflet comprises a rounded cusp end portion defining a cusp edge, a free edge opposite to the cusp edge, and a pair of oppositely-directed tabs separating the cusp edge and the free edge. Each cusp end portion is coupled to at least one strut section via at least one primary suture threaded at penetration points therethrough in an in-and-out pattern, and a secondary suture threaded through the primary suture and wrapped around the strut section in a series of whip stitches spaced from each other along the length of the strut section 
     The cusp end portion is further coupled to at least one junction at an end of the strut section via a junction lock-knot formed by the second suture, wherein the junction lock-knot is configured to maintain tension on the plurality of the whip stitches wrapped around the corresponding strut section leading to the junction first lateral section. 
     According to some embodiments, each junction lock-knot comprises: (1) a transition section extending over one axial side of the junction, in a direction from the junction first lateral side to the junction second lateral side, (2) a first loop extending from the transition section and around a strut section extending from the junction second lateral side, and (3) a second loop extending from the first loop, between the transition section and the junction, and folded over itself to extend through the first loop. 
     According to some embodiments, the transition section extends in a diagonal direction from one radial side of the junction toward the opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     According to some embodiments, both the first loop and the second loop are tightly tensioned around the junction. 
     According to some embodiments, each plurality of whip stitches wrapped around a single strut section are angled whip stitches, oriented in the same direction along the length of the corresponding strut section. 
     According to some embodiments, the cusp end portion is sutured to at least two strut sections extending from both lateral sides of a selected junction, via a plurality of whip stitches wrapped around each of the respective strut sections and a junction lock-knot around the junction positioned there-between, wherein the plurality of whip stitches around one of the strut sections are angled in a direction opposite to that of the plurality of the whip stitches wrapped around the other strut section. 
     According to some embodiments, the diameter of the secondary suture is smaller than the diameter of the primary suture. 
     According to some embodiments, a secondary to primary sutures diameter ratio is equal to or smaller than 0.8. 
     According to some embodiments, a secondary to primary sutures diameter ratio is equal to or smaller than 0.5. 
     According to some embodiments, a secondary to primary sutures diameter ratio is equal to or smaller than 0.3. 
     According to some embodiments, the cusp end portion of each leaflet comprises a series of pre-formed apertures. 
     According to some embodiments, the apertures are dimensioned to accept the at least one primary suture, thereby serving as the penetration points. 
     According to some embodiments, the apertures are equally spaced from each other. 
     According to some embodiments, the diameter of the apertures is equal to or smaller than the diameter of the primary suture. 
     According to some embodiments, the diameter of the apertures is equal to or smaller than the combined diameters of the primary suture and the secondary suture. 
     According to some embodiments, the at least one primary suture comprises two primary sutures, which are inversely threaded in an in-and-out pattern, through the same penetration points. 
     According to some embodiments, the diameter of the apertures is equal to or smaller than the diameter of the two primary sutures. 
     According to some embodiments, the diameter of the apertures is equal to or smaller than the combined diameters of the two primary sutures and the secondary suture. 
     According to some embodiments, the at least one primary suture tracks the curvature of the at least one cusp edge. 
     According to some embodiments, the primary suture comprises a multi-filament suture. 
     According to some embodiments, the secondary suture comprises an ultra-high-molecular-weight polyethylene. 
     According to some embodiments, the prosthetic valve is devoid of fabric strips and/or cloth between the cusp end portions of the leaflets and the strut sections and junctions they are attached to 
     According to another aspect of the inventions, there is provided a method of assembling a prosthetic valve, the method comprises threading a primary suture in an in-and-out pattern through a cusp end portion of a leaflet. The method further comprises approximating the cusp end portion with the primary suture threaded there-through to at least one strut section of a frame of the prosthetic valve. The method further comprises stitching a secondary suture through the primary suture and around the at least one strut section, in a manner that forms a plurality of whip stitches wrapped around the strut section up to a final whip stitch. 
     The method further comprises forming a junction lock-knot extending from the final whip stitch around a junction at a respective end of the corresponding strut section, wherein the junction lock is configured to maintain tension on the plurality of whip stitches wrapped around the strut section leading to the junction first lateral section. 
     According to some embodiments, the step of forming a junction lock-knot comprises extending the secondary suture from the final whip stitch disposed at a first lateral side of the junction, over one axial side of the junction, in a direction toward a second lateral side of the junction, thereby forming a transition section of the junction lock-knot. 
     According to some embodiments, the step of forming a junction lock-knot further comprises extending the secondary suture from the transition section around a strut section extending from the second lateral side of the junction, thereby forming a first loop of the junction lock-knot. 
     According to some embodiments, the step of forming a junction lock-knot further comprises extending the secondary suture from the first loop, between the transition section and the junction, folding the secondary suture back over itself and passing it through the first loop, thereby forming a second loop of the junction lock-knot. 
     According to some embodiments, the step of forming a junction lock-knot further comprises forcibly pulling the tail of the second loop to tighten both the first loop and the second loop around the junction. 
     According to some embodiments, forming the transition section comprises extending the secondary suture in a diagonal direction from one radial side of the junction toward an opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     According to some embodiments, forming the plurality of whip stitches around any single strut section comprises forming a plurality of angled whip stitches oriented in the same direction around the length of the corresponding strut section. 
     According to some embodiments, stitching the secondary suture around the at least one strut section comprises stitching around at least two strut sections separated from each other by a mutual junction, such that all whip stitches around one of the strut sections are formed as angled whip stitches oriented in one direction, while all whip stitches around the other strut section are formed as angled whip stitched oriented in a second direction, opposite to the first direction. 
     According to some embodiments, the cusp end portion of each leaflet comprises a series of pre-formed apertures, and wherein the step of threading a primary suture comprises threading the primary suture in an in-and-out pattern through the series of pre-formed apertures. 
     According to another aspect of the invention, there is provided a prosthetic valve comprising a frame movable between a radially compressed configuration and a radially expanded configuration, and a leaflet assembly mounted within the frame and comprising a plurality of leaflets configured to regulate flow through the prosthetic valve. The frame comprises a plurality of strut sections intersecting at junctions. Each leaflet comprises a rounded cusp end portion defining a cusp edge, a free edge opposite to the cusp edge, and a pair of oppositely-directed tabs separating the cusp edge and the free edge. 
     Each cusp end portion is coupled to at least one strut section via at least one primary suture threaded therethrough in an in-and-out pattern, and a secondary suture forming a series of non-penetrating whip stitches spaced from each other along the length of the strut section. Each non-penetrating whip stitch comprises a strut-wrapping section looped around the strut section, and a primary-suture-wrapping section extending therefrom, looped around the primary suture and passing between the primary suture and the leaflet. 
     According to some embodiments, the primary suture defines a series of running stitch portions, wherein each primary-suture-wrapping section is looped around a corresponding running stitch portion and extends between the running stitch portion and the rounded cusp end portion. 
     According to some embodiments, the secondary suture does not penetrate through the leaflet. 
     According to some embodiments, the secondary suture does not penetrate through the primary suture. 
     According to some embodiments, the cusp end portion is further coupled to at least one junction at an end of the strut section via a junction lock-knot formed by the second suture. Each junction is defined between: two opposite axial sides comprising a junction proximal side and a junction distal side; two opposite radial sides comprising a junction inner side and a junction outer side; and two opposite lateral sides comprising a junction first lateral side and a junction second lateral side. Each junction lock-knot is configured to maintain tension on the plurality of the non-penetrating whip stitches wrapped around the corresponding strut section leading to the junction first lateral section. 
     According to some embodiments, each junction lock-knot comprises: (1) a transition section extending over one axial side of the junction, in a direction from the junction first lateral side to the junction second lateral side, (2) a first loop extending from the transition section and around a strut section extending from the junction second lateral side, and (3) a second loop extending from the first loop, between the transition section and the junction, and folded over itself to extend through the first loop. 
     According to some embodiments, the transition section extends in a diagonal direction from one radial side of the junction toward the opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     According to some embodiments, the transition section extends in a diagonal direction from one radial side of the junction toward the opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     According to some embodiments, both the first loop and the second loop are tightly tensioned around the junction. 
     According to some embodiments, each plurality of non-penetrating whip stitches wrapped around a single strut section are angled non-penetrating whip stitches, oriented in the same direction along the length of the corresponding strut section. 
     According to some embodiments, the cusp end portion is sutured to at least two strut sections extending from both lateral sides of a selected junction, via a plurality of non-penetrating whip stitches wrapped around each of the respective strut sections and a junction lock-knot around the junction positioned there-between, wherein the plurality of non-penetrating whip stitches around one of the strut sections are angled in a direction opposite to that of the plurality of the non-penetrating whip stitches wrapped around the other strut section. 
     According to some embodiments, the at least one primary suture comprises two primary sutures, which are inversely threaded in an in-and-out pattern. 
     According to some embodiments, the at least one primary suture tracks the curvature of the at least one cusp edge. 
     According to some embodiments, the primary suture comprises a multi-filament suture. 
     According to some embodiments, the secondary suture comprises an ultra-high-molecular-weight polyethylene. 
     According to some embodiments, the prosthetic valve is devoid of fabric strips and/or cloth between the cusp end portions of the leaflets and the strut sections they are attached to. 
     According to another aspect of the inventions, there is provided a method of assembling a prosthetic valve, the method comprises threading a primary suture in an in-and-out pattern through a cusp end portion of a leaflet. The method further comprises approximating the cusp end portion with the primary suture threaded there-through to at least one strut section of a frame of the prosthetic valve. The method further comprises looping a secondary suture around the at least one strut section and around the primary suture, in a manner that forms a plurality of non-penetrating whip stitches wrapped around the strut section up to a final non-penetrating whip stitch. Each non-penetrating whip stitch comprises a strut-wrapping section looped around the strut section and a primary-suture-wrapping section extending therefrom, passing between the primary suture and the leaflet and looped around the primary suture. 
     According to some embodiments, forming each non-penetration whip stitch comprises forming the strut-wrapping section by: extending the secondary suture across one radial side of the strut section, folding it over an axial side of the strut, and extending it backward across the opposite radial side of the strut. 
     According to some embodiments, forming each non-penetration whip stitch further comprises forming the primary-suture-wrapping section by: passing the secondary suture between a running stitch portion of the primary suture and the cusp end portion of the leaflet, and folding it over the running stitch portion. 
     According to some embodiments, forming each non-penetration whip stitch further comprises forming the primary-suture-wrapping section by: passing the secondary suture over a running stitch portion of the primary suture, and looping it back over the running stitch portion and between the running stitch portion and the cusp end portion of the leaflet. 
     According to some embodiments, the running stitch portion is an outer stitch portion of the primary suture. 
     According to some embodiments, the method further comprises a step of forming a junction lock-knot extending from the final non-penetrating whip stitch around a junction at a respective end of the corresponding strut section, wherein the junction lock is configured to maintain tension on the plurality of non-penetrating whip stitches wrapped around the strut section leading to the junction first lateral section. 
     According to some embodiments, the step of forming a junction lock-knot comprises extending the secondary suture from the final non-penetrating whip stitch disposed at a first lateral side of the junction, over one axial side of the junction, in a direction toward a second lateral side of the junction, thereby forming a transition section of the junction lock-knot. 
     According to some embodiments, the step of forming a junction lock-knot further comprises extending the secondary suture from the transition section around a strut section extending from the second lateral side of the junction, thereby forming a first loop of the junction lock-knot. 
     According to some embodiments, the step of forming a junction lock-knot further comprises extending the secondary suture from the first loop, between the transition section and the junction, folding the secondary suture back over itself and passing it through the first loop, thereby forming a second loop of the junction lock-knot. 
     According to some embodiments, the step of forming a junction lock-knot further comprises forcibly pulling the tail of the second loop to tighten both the first loop and the second loop around the junction. 
     According to some embodiments, forming the transition section comprises extending the secondary suture in a diagonal direction from one radial side of the junction toward an opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     According to some embodiments, forming the plurality of whip stitches around any single strut section comprises forming a plurality of angled whip stitches oriented in the same direction around the length of the corresponding strut section. 
     According to some embodiments, forming the plurality of whip stitches around the at least one strut section comprises forming a plurality of whip stitches around at least two strut sections separated from each other by a mutual junction, such that all whip stitches around one of the strut sections are formed as angled whip stitches oriented in one direction, while all whip stitches around the other strut section are formed as angled whip stitched oriented in a second direction, opposite to the first direction. 
     According to another aspect of the invention, there is provided a prosthetic valve comprising a frame, a leaflet assembly mounted within the frame, and a skirt disposed around the frame. The frame is movable between a radially compressed configuration and a radially expanded configuration, and comprises a plurality of strut sections intersecting at junctions. The leaflet assembly comprises a plurality of leaflets configured to regulate flow through the prosthetic valve. The skirt comprises a skirt proximal end and a skirt distal end. 
     Each junction is defined between: two opposite axial sides comprising a junction proximal side and a junction distal side; two opposite radial sides comprising a junction inner side and a junction outer side; and two opposite lateral sides comprising a junction first lateral side and a junction second lateral side. 
     The skirt proximal end is coupled to at least one strut section via at least one primary suture threaded at penetration points therethrough in an in-and-out pattern, and a secondary suture threaded through the primary suture and wrapped around the strut section in a series of whip stitches spaced from each other along the length of the strut section. 
     The skirt proximal end is further coupled to at least one junction at an end of the strut section via a junction lock-knot formed by the second suture, wherein the junction lock-knot is configured to maintain tension on the plurality of the whip stitches wrapped around the corresponding strut section leading to the junction first lateral section. 
     According to some embodiments, the skirt proximal end follows a zig-zag pattern. 
     According to some embodiments, the at least one primary suture tracks the zig-zag pattern of the skirt proximal end. 
     According to some embodiments, each junction lock-knot comprises: (1) a transition section extending over one axial side of the junction, in a direction from the junction first lateral side to the junction second lateral side, (2) a first loop extending from the transition section and around a strut section extending from the junction second lateral side, and (3) a second loop extending from the first loop, between the transition section and the junction, and folded over itself to extend through the first loop. 
     According to some embodiments, the transition section extends in a diagonal direction from one radial side of the junction toward the opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     According to some embodiments, both the first loop and the second loop are tightly tensioned around the junction. 
     According to some embodiments, each plurality of whip stitches wrapped around a single strut section are angled whip stitches, oriented in the same direction along the length of the corresponding strut section. 
     According to some embodiments, the skirt proximal end is sutured to at least two strut sections extending from both lateral sides of a selected junction, via a plurality of whip stitches wrapped around each of the respective strut sections and a junction lock-knot around the junction positioned there-between, wherein the plurality of whip stitches around one of the strut sections are angled in a direction opposite to that of the plurality of the whip stitches wrapped around the other strut section. 
     According to some embodiments, the skirt distal end is coupled to at least one strut section at an inflow end portion of the valve via at least one additional primary suture threaded at penetration points therethrough in an in-and-out pattern, and an additional secondary suture threaded through the primary suture and wrapped around the strut section at the inflow end portion in a series of whip stitches spaced from each other along the length of the strut section, wherein the skirt distal end is further coupled to at least one junction at an end of the strut section at the inflow end portion via an additional junction lock-knot. 
     According to some embodiments, the additional primary suture tracks the shape of the strut sections disposed around the inflow end portion. 
     According to some embodiments, the diameter of the secondary suture is smaller than the diameter of the primary suture. 
     According to some embodiments, a secondary to primary sutures diameter ratio is equal to or smaller than 0.8. 
     According to some embodiments, a secondary to primary sutures diameter ratio is equal to or smaller than 0.5. 
     According to some embodiments, a secondary to primary sutures diameter ratio is equal to or smaller than 0.3. 
     According to some embodiments, the skirt proximal end comprises a series of pre-formed apertures. 
     According to some embodiments, the apertures are dimensioned to accept the at least one primary suture, thereby serving as the penetration points. 
     According to some embodiments, the apertures are equally spaced from each other. 
     According to some embodiments, the diameter of the apertures is equal to or smaller than the diameter of the primary suture. 
     According to some embodiments, the diameter of the apertures is equal to or smaller than the combined diameters of the primary suture and the secondary suture. 
     According to some embodiments, the at least one primary suture comprises two primary sutures, which are inversely threaded in an in-and-out pattern, through the same penetration points. 
     According to some embodiments, the diameter of the apertures is equal to or smaller than the diameter of the two primary sutures. 
     According to some embodiments, the diameter of the apertures is equal to or smaller than the combined diameters of the two primary sutures and the secondary suture. 
     According to some embodiments, the primary suture comprises a multi-filament suture. 
     According to some embodiments, the secondary suture comprises an ultra-high-molecular-weight polyethylene. 
     According to some embodiments, the skirt is an outer skirt, disposed around an outer surface of the frame. 
     According to another aspect of the inventions, there is provided a method of assembling a prosthetic valve, the method comprises threading a primary suture in an in-and-out pattern through a skirt proximal end of a skirt. The method further comprises approximating the skirt proximal end with the primary suture threaded there-through to at least one strut section of a frame of the prosthetic valve. The method further comprises stitching a secondary suture through the primary suture and around the at least one strut section, in a manner that forms a plurality of whip stitches wrapped around the strut section up to a final whip stitch. The method further comprises forming a junction lock-knot extending from the final whip stitch around a junction at a respective end of the corresponding strut section, wherein the junction lock-knot is configured to maintain tension on the plurality of whip stitches wrapped around the strut section leading to the junction first lateral section. 
     According to some embodiments, the step of forming a junction lock-knot comprises extending the secondary suture from the final whip stitch disposed at a first lateral side of the junction, over one axial side of the junction, in a direction toward a second lateral side of the junction, thereby forming a transition section of the junction lock-knot. 
     According to some embodiments, the step of forming a junction lock-knot further comprises extending the secondary suture from the transition section around a strut section extending from the second lateral side of the junction, thereby forming a first loop of the junction lock-knot. 
     According to some embodiments, the step of forming a junction lock-knot further comprises extending the secondary suture from the first loop, between the transition section and the junction, folding the secondary suture back over itself and passing it through the first loop, thereby forming a second loop of the junction lock-knot. 
     According to some embodiments, the step of forming a junction lock-knot further comprises forcibly pulling the tail of the second loop to tighten both the first loop and the second loop around the junction. 
     According to some embodiments, forming the transition section comprises extending the secondary suture in a diagonal direction from one radial side of the junction toward an opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     According to some embodiments, forming the plurality of whip stitches around any single strut section comprises forming a plurality of angled whip stitches oriented in the same direction around the length of the corresponding strut section. 
     According to some embodiments, stitching the secondary suture around the at least one strut section comprises stitching around at least two strut sections separated from each other by a mutual junction, such that all whip stitches around one of the strut sections are formed as angled whip stitches oriented in one direction, while all whip stitches around the other strut section are formed as angled whip stitched oriented in a second direction, opposite to the first direction. 
     According to some embodiments, the skirt proximal end comprises a series of pre-formed apertures, and wherein the step of threading a primary suture comprises threading the primary suture in an in-and-out pattern through the series of pre-formed apertures. 
     According to some embodiments, the skirt is an outer skirt, disposed around an outer surface of the frame. 
     According to another aspect of the invention, there is provided a prosthetic valve comprising a frame, a leaflet assembly mounted within the frame, and a skirt disposed around the frame. The frame is movable between a radially compressed configuration and a radially expanded configuration, and comprises a plurality of strut sections intersecting at junctions. The leaflet assembly comprises a plurality of leaflets configured to regulate flow through the prosthetic valve. The skirt comprises a skirt proximal end and a skirt distal end. 
     The skirt proximal end is coupled to at least one strut section via at least one primary suture threaded therethrough in an in-and-out pattern, and a secondary suture forming a series of non-penetrating whip stitches spaced from each other along the length of the strut section, each non-penetrating whip stitch comprising a strut-wrapping section looped around the strut section and a primary-suture-wrapping section extending therefrom, looped around the primary suture and passing between the primary suture and the leaflet. 
     According to some embodiments, the skirt proximal end follows a zig-zag pattern. 
     According to some embodiments, the at least one primary suture tracks the zig-zag pattern of the skirt proximal end. 
     According to some embodiments, the primary suture defines a series of running stitch portions, wherein each primary-suture-wrapping section is looped around a corresponding running stitch portion and extends between the running stitch portion and the skirt proximal end. 
     According to some embodiments, the secondary suture does not penetrate through the skirt. 
     According to some embodiments, the secondary suture does not penetrate through the primary suture. 
     According to some embodiments, each junction is defined between: two opposite axial sides comprising a junction proximal side and a junction distal side; two opposite radial sides comprising a junction inner side and a junction outer side; and two opposite lateral sides comprising a junction first lateral side and a junction second lateral side. The skirt proximal end is further coupled to at least one junction at an end of the strut section via a junction lock-knot formed by the second suture, and wherein the junction lock-knot is configured to maintain tension on the plurality of the non-penetrating whip stitches wrapped around the corresponding strut section leading to the junction first lateral section. 
     According to some embodiments, each junction lock-knot comprises: (1) a transition section extending over one axial side of the junction, in a direction from the junction first lateral side to the junction second lateral side, (2) a first loop extending from the transition section and around a strut section extending from the junction second lateral side, and (3) a second loop extending from the first loop, between the transition section and the junction, and folded over itself to extend through the first loop. 
     According to some embodiments, the transition section extends in a diagonal direction from one radial side of the junction toward the opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     According to some embodiments, both the first loop and the second loop are tightly tensioned around the junction. 
     According to some embodiments, each plurality of whip stitches wrapped around a single strut section are angled whip stitches, oriented in the same direction along the length of the corresponding strut section. 
     According to some embodiments, the skirt proximal end is sutured to at least two strut sections extending from both lateral sides of a selected junction, via a plurality of non-penetrating whip stitches wrapped around each of the respective strut sections and a junction lock-knot around the junction positioned there-between, wherein the plurality of non-penetrating whip stitches around one of the strut sections are angled in a direction opposite to that of the plurality of the non-penetrating whip stitches wrapped around the other strut section. 
     According to some embodiments, the skirt distal end is coupled to at least one strut section at an inflow end portion of the valve via at least one additional primary suture threaded at penetration points therethrough in an in-and-out pattern, and an additional secondary suture threaded through the primary suture and wrapped around the strut section at the inflow end portion in a series of whip stitches spaced from each other along the length of the strut section, wherein the skirt distal end is further coupled to at least one junction at an end of the strut section at the inflow end portion via an additional junction lock-knot 
     According to some embodiments, the additional primary suture tracks the shape of the strut sections disposed around the inflow end portion. 
     According to some embodiments, the primary suture comprises a multi-filament suture. 
     According to some embodiments, the secondary suture comprises an ultra-high-molecular-weight polyethylene. 
     According to some embodiments, the skirt is an outer skirt, disposed around an outer surface of the frame. 
     According to another aspect of the inventions, there is provided a method of assembling a prosthetic valve, the method comprises threading a primary suture in an in-and-out pattern through a skirt proximal end of a skirt. The method further comprises approximating the skirt proximal end with the primary suture threaded there-through to at least one strut section of a frame of the prosthetic valve. The method further comprises looping a secondary suture around the at least one strut section and around the primary suture, in a manner that forms a plurality of non-penetrating whip stitches wrapped around the strut section up to a final non-penetrating whip stitch, each non-penetrating whip stitch comprising a strut-wrapping section looped around the strut section and a primary-suture-wrapping section extending therefrom, passing between the primary suture and the skirt proximal end around the primary suture. 
     According to some embodiments, forming each non-penetration whip stitch comprises forming the strut-wrapping section by: extending the secondary suture across one radial side of the strut section, folding it over an axial side of the strut section, and extending it backward across the opposite radial side of the strut section. 
     According to some embodiments, forming each non-penetration whip stitch further comprises forming the primary-suture-wrapping section by: passing the secondary suture between a running stitch portion of the primary suture and the skirt proximal end, and folding it over the running stitch portion. 
     According to some embodiments, forming each non-penetration whip stitch further comprises forming the primary-suture-wrapping section by: passing the secondary suture over a running stitch portion of the primary suture, and looping it back over the running stitch portion and between the running stitch portion and the skirt proximal end. 
     According to some embodiments, the skirt is an outer skirt and the running stitch portion is an inner stitch portion of the primary suture. 
     According to some embodiments, the method further comprises a step of forming a junction lock-knot extending from the final non-penetrating whip stitch around a junction at a respective end of the corresponding strut section, wherein the junction lock-knot is configured to maintain tension on the plurality of non-penetrating whip stitches wrapped around the strut section leading to the junction first lateral section. 
     According to some embodiments, the step of forming a junction lock-knot comprises extending the secondary suture from the final non-penetrating whip stitch disposed at a first lateral side of the junction, over one axial side of the junction, in a direction toward a second lateral side of the junction, thereby forming a transition section of the junction lock-knot. 
     According to some embodiments, the step of forming a junction lock-knot further comprises extending the secondary suture from the transition section around a strut section extending from the second lateral side of the junction, thereby forming a first loop of the junction lock-knot. 
     According to some embodiments, the step of forming a junction lock-knot further comprises extending the secondary suture from the first loop, between the transition section and the junction, folding the secondary suture back over itself and passing it through the first loop, thereby forming a second loop of the junction lock-knot. 
     According to some embodiments, the step of forming a junction lock-knot further comprises forcibly pulling the tail of the second loop to tighten both the first loop and the second loop around the junction. 
     According to some embodiments, forming the transition section comprises extending the secondary suture in a diagonal direction from one radial side of the junction toward an opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     According to some embodiments, forming the plurality of whip stitches around any single strut section comprises forming a plurality of angled whip stitches oriented in the same direction around the length of the corresponding strut section. 
     According to some embodiments, forming the plurality of whip stitches around the at least one strut section comprises forming a plurality of whip stitches around at least two strut sections separated from each other by a mutual junction, such that all whip stitches around one of the strut sections are formed as angled whip stitches oriented in one direction, while all whip stitches around the other strut section are formed as angled whip stitched oriented in a second direction, opposite to the first direction. 
     Certain embodiments of the present invention may include some, all, or none of the above advantages. Further advantages may be readily apparent to those skilled in the art from the figures, descriptions, and claims included herein. Aspects and embodiments of the invention are further described in the specification herein below and in the appended claims. 
     Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the patent specification, including definitions, governs. As used herein, the indefinite articles “a” and “an” mean “at least one” or “one or more” unless the context clearly dictates otherwise. 
     The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, but not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other advantages or improvements. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Some embodiments of the invention are described herein with reference to the accompanying figures. The description, together with the figures, makes apparent to a person having ordinary skill in the art how some embodiments may be practiced. The figures are for the purpose of illustrative description and no attempt is made to show structural details of an embodiment in more detail than is necessary for a fundamental understanding of the invention. For the sake of clarity, some objects depicted in the figures are not to scale. 
       In the Figures: 
         FIG.  1 A . shows a view in perspective of a mechanically expandable prosthetic valve, according to some embodiments. 
         FIG.  1 B . shows a view in perspective of a balloon expandable prosthetic valve, according to some embodiments. 
         FIG.  2    shows a single leaflet, according to some embodiments. 
         FIG.  3    shows a leaflet assembly defined by three leaflets, prior to assembly, according to some embodiments. 
         FIG.  4    shows an enlarged sectional view through a cusp end portion of a leaflet, with a primary suture threaded there-through in an in-and-out pattern, according to some embodiments. 
         FIGS.  5 A- 5 E  shows various stages of an exemplary technique for coupling a leaflet along its cusp end portion to struts of a frame, according to some embodiments. 
         FIG.  6    shows an exemplary configuration of a leaflet coupled to a strut via a first and a secondary suture, according to some embodiments. 
         FIG.  7    shows an enlarged sectional view through a cusp end portion of a leaflet, with two primary sutures threaded there-through in an in-and-out pattern, according to some embodiments. 
         FIG.  8    shows another exemplary configuration of a leaflet coupled to a strut via a first and a secondary suture, according to some embodiments. 
         FIGS.  9 A- 9 D  shows various stages of an exemplary technique for coupling a leaflet along its cusp end portion to strut sections and junctions of a frame, according to some embodiments. 
         FIG.  10    shows a partial view of a prosthetic valve with leaflets coupled to a plurality of strut sections and junctions, according to some embodiments. 
         FIGS.  11 A- 11 D  shows various stages of another exemplary technique for coupling a leaflet along its cusp end portion to strut sections and junctions of a frame, according to some embodiments. 
         FIGS.  12 A- 12 D  shows various stages of another exemplary technique for coupling a leaflet along its cusp end portion to strut sections and junctions of a frame, according to some embodiments. 
         FIG.  13    shows another exemplary stitching configuration. 
         FIG.  14    shows yet another exemplary stitching configuration. 
         FIG.  15    shows a view in perspective of a prosthetic valve with an outer skirt, according to some embodiments. 
         FIG.  16    shows a partial view of the prosthetic valve of  FIG.  15    with the skirt coupled to a plurality of strut sections and junctions, according to some embodiments. 
         FIG.  17    shows a view in perspective of another exemplary prosthetic valve with an outer skirt, according to some embodiments. 
         FIG.  18    shows a partial view of the prosthetic valve of  FIG.  17    with the skirt coupled to a plurality of strut sections and junctions, according to some embodiments. 
     
    
    
     DETAILED DESCRIPTION OF SOME EMBODIMENTS 
     In the following description, various aspects of the disclosure will be described. For the purpose of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the different aspects of the disclosure. However, it will also be apparent to one skilled in the art that the disclosure may be practiced without specific details being presented herein. Furthermore, well-known features may be omitted or simplified in order not to obscure the disclosure. In order to avoid undue clutter from having too many reference numbers and lead lines on a particular drawing, some components will be introduced via one or more drawings and not explicitly identified in every subsequent drawing that contains that component. 
       FIGS.  1 A and  1 B  show perspective views of two exemplary types of a prosthetic valve  100 , according to some embodiments. It will be appreciated that reference numerals with prime marks (′) or double prime marks (″) are used throughout  FIGS.  1 A- 1 B  to denote different embodiments of the same elements. Embodiments of the disclosed devices and systems may include any combination of different embodiments of the same elements. Specifically, any reference to an element without single or double prime marks may refer to any alternative embodiment of the same element denoted with a single prime mark or double prime marks. 
     The prosthetic valve  100  is deliverable to a patient’s target site over a catheter (not shown), and is radially expandable and compressible between a radially compressed, or crimped, configuration, and a radially expanded configuration- shown in  FIGS.  1 A- 1 B . The expanded configuration may include a range of diameters to which the valve  100  may expand, between the compressed configuration and a maximal diameter reached at a fully expanded configuration. Thus, a plurality of partially expanded configurations may relate to any expansion diameter between radially compressed or crimped configuration, and maximally expanded configuration. A prosthetic valve  100  of the current disclosure may include any prosthetic valve configured to be mounted within the native aortic valve, the native mitral valve, the native pulmonary valve, and the native tricuspid valve. 
     The term “plurality”, as used herein, means more than one. 
     As stated above, a prosthetic valve  100  can be delivered to the site of implantation via a delivery assembly carrying the valve  100  in a radially compressed or crimped configuration, toward the target site, to be mounted against the native anatomy, by expanding the valve  100  via various expansion mechanisms.  FIG.  1 A  shows an exemplary mechanically expandable valve  100 ′, wherein all reference numerals with prime marks (&#39;) shown in  FIG.  1 A  refer to like elements comprised within a mechanically expandable valve. Mechanically expandable valves are a category of prosthetic valves that rely on a mechanical actuation mechanism for expansion. The mechanical actuation mechanism usually includes a plurality of actuator assemblies, releasably coupled to respective actuation arm assemblies of the delivery apparatus, controlled via a handle of the delivery apparatus for actuating the actuator assemblies to expand the prosthetic valve to a desired diameter. 
       FIG.  1 B  shows an exemplary balloon expandable valve  100 ″, wherein all reference numerals with double prime marks (′’) shown in  FIG.  1 B  refer to like elements comprised within a balloon expandable valve. Balloon expandable valves generally involve a procedure of inflating a balloon within a prosthetic valve, thereby expanding the prosthetic valve  100  within the desired implantation site. Once the valve is sufficiently expanded, the balloon is deflated and retrieved along with the delivery apparatus. While mechanically expandable valves  100 ′ and balloon expandable valves  100 ″ are described and illustrated in conjunction with  FIGS.  1 A- 1 B , it will be clear that a prosthetic valve  100  may include other expansion mechanisms, such as self-expandable valves. Self-expandable valves include a frame that is shape-set to automatically expand as soon as an outer retaining structure, such as a capsule or a portion of a shaft (not shown), is withdrawn proximally relative to the prosthetic valve. 
     A prosthetic valve  100  can comprise an inflow end portion  104  defining an inflow end  105 , and an outflow end portion  102  defining an outflow end  103 . The prosthetic valve  100  can define a valve longitudinal axis  10  extending through the inflow end portion  104  and the outflow end portion  102 . In some instances, the outflow end  103  is the proximal end of the prosthetic valve  100 , and the inflow end  105  is the distal end of the prosthetic valve  100 . Alternatively, depending for example on the delivery approach of the valve, the outflow end can be the proximal end of the prosthetic valve, and the inflow end can be the distal end of the prosthetic valve. 
     The term “proximal”, as used herein, generally refers to a position, direction, or portion of any device or a component of a device, which is closer to the user and further away from the implantation site. 
     The term “distal”, as used herein, generally refers to a position, direction, or portion of any device or a component of a device, which is further away from the user and closer to the implantation site. 
     The term “outflow”, as used herein, refers to a region of the prosthetic valve through which the blood flows through and out of the valve  100 , for example between the valve longitudinal axis  10  and the outflow end  103 . 
     The term “inflow”, as used herein, refers to a region of the prosthetic valve through which the blood flows into the valve  100 , for example between inflow end  105  and the valve longitudinal axis  10 . 
     The valve  100  comprises an annular frame  106  movable between a radially compressed configuration and a radially expanded configuration, and a leaflet assembly  130  mounted within the frame  106 . The frame  106  can be made of various suitable materials, including plastically-deformable materials such as, but not limited to, stainless steel, a nickel based alloy (e.g., a cobalt-chromium or a nickel-cobalt-chromium alloy such as MP35N alloy), polymers, or combinations thereof. When constructed of a plastically-deformable materials, the frame  106 , such as frame  106 ″ (and thus the balloon expandable valve  100 ″) can be crimped to a radially compressed configuration on a delivery shaft (not shown), and then expanded inside a patient by an inflatable balloon or equivalent expansion mechanism. Alternatively or additionally, the frame  106 ″ can be made of shape-memory materials such as, but not limited to, nickel titanium alloy (e.g., Nitinol). When constructed of a shape-memory material, the frame  106 , such as frame  106 ′ (and thus the mechanically expandable valve  100 ′) can be crimped to a radially compressed configuration and restrained in the compressed configuration by insertion into a shaft or equivalent mechanism of a delivery apparatus (not shown). 
     In the examples illustrated in  FIGS.  1 A- 1 B , the frame  106  is an annular, stent-like structure comprising a plurality of intersecting struts  110 . In this application, the term “strut” encompasses vertical struts, angled struts, attachment posts, commissure windows, and any similar structures described by U.S. Pat. Nos. 7,993,394 and 9,393,110, which are incorporated herein by reference. A strut  110  may be any elongated member or portion of the frame  106 . The frame  106  can have one or more multiple rows of cells  108  defined by intersecting struts  110 . The frame  106  can have a cylindrical or substantially cylindrical shape having a constant diameter from an inflow end  105  to an outflow end  103  of the frame as shown, or the frame can vary in diameter along the height of the frame, as disclosed in U.S. Pat. No. 9,155,619, which is incorporated herein by reference. 
     The end portions of the struts  110  are forming apices  120  at the outflow end  103  and apices  118  at the inflow end  105 . The struts  110  can intersect at additional non-apical junctions  116  formed between the outflow apices  120  and the inflow apices  118 . The non-apical junctions  116  can be equally or unequally spaced apart from each other, and/or from the apices  120 ,  118 , between the outflow end  103  and the inflow end  105 . 
     According to some embodiments, the struts  110  are arranged in a lattice-type pattern. In the exemplary embodiments illustrated in  FIG.  1 A , the struts  110 ′ are positioned diagonally, or offset at an angle relative to, and radially offset from, the valve longitudinal axis  10 , when the valve  100 ′ is in an expanded position. It will be clear that the struts  110 ′ can be offset by other angles than those shown in  FIG.  1 B , such as being oriented substantially parallel to the valve longitudinal axis  10 . 
     According to some embodiments, the struts  110 ′ are pivotably coupled to each other. Frame  106 ′ may comprise openings or apertures at the regions of inflow apices  118 ′, outflow apices  120 ′ and non-apical junctions  116 ′ of the struts  110 ′. Respective hinges can be included at locations where the apertures of struts  110 ′ overlap each other, via fasteners, such as rivets or pins, which extend through the apertures. The hinges can allow the struts  110 ′ to pivot relative to one another as the frame  106 ′ is radially expanded or compressed. 
     According to some embodiments, the struts  110  include a plurality of angled struts and vertical struts. In the exemplary embodiments illustrated in  FIG.  1 B , the frame  106 ″ comprises a plurality of angled struts  110 ″, and axially extending struts  114 . In such embodiments, the struts are not necessarily coupled to each other via respective hinges, but are otherwise pivotable or bendable relative to each other, so as to permit frame expansion or compression. For example, the frame  106 ″ can be formed from a single piece of material, such as a metal tube, via various processes such as, but not limited to, laser cutting, electroforming, and/or physical vapor deposition, while retaining the ability to collapse/expand radially in the absence of hinges and like. 
     The leaflet assembly  130  comprises a plurality of leaflets  132  (e.g., three leaflets), positioned at least partially within the frame  106 , and configured to regulate flow of blood through the prosthetic valve  100  from the inflow end  105  to the outflow end  103 . While three leaflets  132  arranged to collapse in a tricuspid arrangement, are shown in the exemplary embodiment illustrated in  FIGS.  1 A- 1 B , it will be clear that a prosthetic valve  100  can include any other number of leaflets  132 . The leaflets  132  are made of a flexible material, derived from biological materials (e.g., bovine pericardium or pericardium from other sources), biocompatible synthetic materials, or other suitable materials as known in the art and described, for example, in U.S. Pat. Nos. 6,730,118, 6,767,362 and 6,908,481, which are incorporated by reference herein. 
       FIG.  2    shows a single representative leaflet  132 , and  FIG.  3    shows three separated leaflets prior to attachment to the frame  106  and to each other, collectively defining the leaflet assembly  130 , according to some embodiments. Each leaflet  132  has a rounded cusp end portion  134  defining a cusp edge  135  opposite a free edge  136 , and a pair of generally oppositely-directed tabs  138  separating the cusp edge  135  and the free edge  136 . The cusp edge  135  forms a single scallop. The leaflet  132  further comprises an inner surface  152 , defined as the surface facing the valve longitudinal axis  10 , and an outer surface  154 , opposite thereto so as to face the frame  106 . 
     When the leaflets  132  are coupled to the frame and to each other, the lower edge of the resulting leaflet assembly  130  desirably has an undulating, curved scalloped shape. By forming the leaflets with this scalloped geometry, stresses on the leaflets  132  are reduced which, in turn, improves durability of the valve. Moreover, by virtue of the scalloped shape, folds and ripples at the belly of each leaflet, which can cause early calcification in those areas, can be eliminated or at least minimized. The scalloped geometry also reduces the amount of tissue material used to form the leaflet structure, thereby allowing a smaller, more even crimped profile at the inflow end of the valve. 
     The leaflets  132  define a non-planar coaptation plane (not annotated) when their free edges  136  co-apt with each other to seal blood flow through the prosthetic valve  100 . Leaflets  132  can be secured to one another at their tabs  138  to form commissures  140  of the leaflet assembly  130 , which can be secured, directly or indirectly, to structural elements connected to the frame  106  or embedded therein, such as commissure posts. When secured to two other leaflets  132  to form leaflet assembly  130 , the cusp edges  135  of the leaflets  132  collectively form the scalloped shaped lower edge portion of the leaflet structure  130 . 
     According to some embodiments, a mechanically expandable valve  100 ′ comprises a plurality of actuator assemblies  122 , configured to facilitate expansion of the valve  100 ′, and in some instances, to lock the valve at an expanded configuration, preventing unintentional recompression thereof. Although  FIG.  1 A  illustrates three actuator assemblies  122 , mounted to, and equally spaced, around an inner surface of the frame  106 ′, it should be clear that a different number of actuator assemblies  122  may be utilized, that the actuator assemblies  122  can be mounted to the frame  106 ′ around its outer surface, and that the circumferential spacing between actuator assemblies  122  can be unequal. In some cases, as further illustrated in  FIG.  1 B , the actuator assemblies  122  can further serve as commissure posts, to which commissures  140  of the leaflet assembly  130  can be coupled. Details regarding the structure and operation of mechanically expandable valves and delivery system thereof are described in U.S. Pat. No. 9,827,093, U.S. Pat. Application Publication Nos. 2019/0060057, 2018/0153689 and 2018/0344456, and U.S. Pat. Application Nos. 62/870,372 and 62/776,348, all of which are incorporated herein by reference. 
     According to some embodiments, such as the exemplary embodiment illustrated in  FIG.  1 B , the upper row of cells comprises a plurality of axially extending window frame portions  112  (which define commissure windows) and a plurality of axially extending struts  114 . Each axial strut  114  and each window frame portion  112  extends from a junction  116 ″ defined by the convergence of the lower ends of two angled struts  110 ″ to another junction  116 ″ defined by the convergence of the upper ends of two angled struts  110 ″. Each commissure window frame portion  112  mounts a respective commissure  140  of the leaflet structure  130 . 
     Additional frame configurations may include commissure posts attached to the frame, configured to accept commissures  140  extending either through window portions defined therein, or supporting commissure attachment thereto in various other manners. Alternatively, some of the cells  108  may be configured to receive commissures  140  attached thereto. For example, the uppermost row of cells  108  can be configured to receive tabs  138  of the leaflets  132 . Further details regarding prosthetic valves, including the manner in which commissures may be mounted to their frames, are described in U.S. Pat. Nos. 6,730,118, 7,393,360, 7,510,575, 7,993,394, 8,252,202, and 9,393,110; U.S. Publication Nos. 2018/0325665, 2019/0105153, U.S. Application Nos. 62/869,948 and 62/813,643; and PCT Application No. PCT/US2019/61392, all of which documents are incorporated herein by reference. Any of the techniques and mechanisms disclosed in the prior documents can be used to connect the commissures  140 , directly or indirectly, to the frame  106 . 
     According to some embodiments, the prosthetic valve  100  can further comprise a skirt  123 , such as an outer skirt  124  (shown for example in  FIGS.  15  and  17   ) mounted on the outer surface of the frame  106 , configure to function, for example, as a sealing member retained between the frame  106  and the surrounding tissue of the native annulus against which the prosthetic valve  100  is mounted, thereby reducing risk of paravalvular leakage past the prosthetic valve  100 . Such an outer skirt can be made of various suitable biocompatible materials, such as, but not limited to, various synthetic materials (e.g., PET) or natural tissue (e.g. pericardial tissue). 
     According to some embodiments, a primary suture  144  is threaded through the cusp end portion  134  in an in-and-out pattern, also known in the art as a running stitch pattern.  FIG.  3    shows primary sutures  144  stitched along the cusp end portions  134  of the leaflets  132 .  FIG.  4    shows an enlarged sectional view through a cusp end portion  134  and the primary suture  144  threaded there-through. As shown, the running stitch extends through penetration points  150  in an in-and-out pattern along the cusp end portion  134 , thereby defining a plurality of running stitch portions that include a plurality of inner stitch portions  146  disposed along the leaflet inner surface  152 , and a plurality of outer stitch portions  148  disposed along the leaflet outer surface  154 , wherein each inner stitch portion  146  and each outer stitch portion  148  is defined between a couple of consecutive penetration points  150 . Optionally, but in some embodiments preferably, the primary suture  144  tracks the curvature of the cusp edge  135 , meaning that the primary suture  144  runs along or is generally parallel, with the cusp edge  135 . 
     With particular reference to  FIGS.  5 A- 5 E , an exemplary technique for coupling a leaflet  132  along its cusp end portion  134  to at least one section of at least one strut  110  of a frame  106  will now be discussed in accordance with the present teachings. As shown in  FIG.  5 A , the cusp end portion  134 , with the primary suture threaded there-through in an in-and-out pattern, is approximated to a strut  110 , such that the cusp end portion  134  is preferably positioned radially inward (and optionally in contact with) the inner side of the strut  110 . According to some embodiments, a secondary suture  156  is stitched through the primary suture  144  and around at least one section of at least one strut  110 , wherein the secondary suture  156  comprises a plurality of self-tightening constructs  158 . Each self-tightening construct  158  includes at least one loop configured to constrict under tension around the strut  110 . 
     While the strut  110  is shown to have a rectangular cross-section in  FIGS.  5 A- 5 E , it will be clear that this is merely for illustrative purpose, and that the cross-section of a strut  110  can have a rounded, circular, having a polygonal shape, have an irregular shape, or have a shape that changes along the length of the strut. The cross-sections of the struts can also remain the same shape, but change size along the length of the strut. 
     A self-tightening construct  158  is formed by threading the secondary suture  156  radially outward through the primary suture  144  at penetration point  150   a , and forming at least one loop  160  around the strut, such as loop  160   a  shown in  FIG.  5 B . According to some embodiments, the self-tightening construct  158  includes more than one loop  160  around the strut  110 . For example, the secondary suture may be looped again to form a second loop  160   b   around the strut  110  as shown in  FIG.  5 C . It will be clear that while two loops  160   a  and  160   b  are described and illustrated in conjunction with  FIGS.  5 A- 5 E , the self-tightening construct  158  can include, in alternative variations, any other number of loops. 
     As shown in  FIG.  5 D , the secondary suture  156  is then passed under the at least one loop  160 , such as between both loops  160   a ,  160   b  and the strut  110 , to form a generally horseshoe-shaped, or u-shaped section  162 , which is threaded thereafter through the primary suture  144  in a radially inward direction at penetration point  150   b . Thus, the resulting self-tightening construct  158  is defined between two penetrations points  150  that define at least one outer stitch portion  148  there-between. 
     A “radially inward” direction is a direction toward the valve longitudinal axis  10 , while a “radially outward” direction is oppositely oriented away from the valve longitudinal axis  10 . 
     The secondary suture  156  further comprises a plurality of suture pull portions  164  extending over the leaflet inner surface  152 , and may be defined between consecutive self-tightening constructs  158 . As shown in  FIG.  5 E , a suture pull portion  164  of the secondary suture  156  is defined by extending the secondary suture  156  over the leaflet inner surface  152 , for example - in parallel to at least one inner stitch portion  146 , and then threading the secondary suture  156  once again through the primary suture  144  in a radially-outward direction, at a consecutive penetration point  150   c , at which point another self-tightening construct  158  can be formed in a similar manner.  FIG.  5 E  shows a section of a stitch pattern that includes three exemplary self-tightening constructs  158 . 
     The self-tightening constructs  158  are configured to tighten their grip on the leaflets  132  the more their cusp end portions  134  are pulled radially inward. During diastole, the leaflets  132  collapse radially inward to effectively close the prosthetic valve. This collapse exerts pull forces oriented radially inward in the cusp end portions  134 , which tend to pull the suture pull portions  164  radially inward therewith. The suture pull portions  164 , disposed over the leaflet inner surfaces  152 , pull the tails on both sides of each self-tightening construct  158  there-along, which causes the at least one loop  160  to constrict about the strut  110 . This constriction reduces the diameter of the at least one loop  160 , thus forming a mechanical interface between the exterior surfaces of the strut  110  and the interior surfaces of the at least one loop  160 . This constriction results in static friction between the interior and exterior surfaces at the mechanical interface, causing the at least one loop  160  of each self-tightening construct  158  to tighten in a reduced size or diameter configuration in which tension may be maintained. In other words, the loops  160  are configured to reduce in diameter when tension is applied to both end portions of the self-tightening construct  158 , which increase the grip of the secondary suture  156  around the struts  110 , thereby preventing the leaflets  132  from sliding over the struts  110  along the resulting scallop line. 
     Advantageously, the primary suture  144 , which is threaded in an in-and-out pattern through the cusp end portion  134 , may serve as a pledget or cushion between the secondary suture  156  and the leaflet  132 . For example, the suture pull portion  164 , disposed over the leaflet inner surface  152 , may be pressed during the repetitive systolic and diastolic cycles against the inner stitch portions  146  of the primary suture  144 , which serves as a pledget or cushion so as to prevent direct abrasion that may be otherwise applied to the leaflet  132 . 
     The term “suture”, as used herein for either the primary suture  144  or the secondary suture  156  (as well as secondary suture  170  described further down below), includes, but is not limited to, polymer materials, thread, strand, fiber, wire, other windable materials, organic and inorganic materials, or any other material that is acceptable for medical applications for threading and/or joining together components used in the various embodiments of the valve  100 . The primary suture  144  can be a multi-filament suture, such as Ethibond Excel® PET thread (Johnson &amp; Johnson, New Brunswick, N.J.) among other types of suture. The secondary suture  156  (as well as secondary suture  170  that will be described further down below) can include ultra-high-molecular-weight polyethylene (UHMwPE), such as a FORCE FIBER® suture (Teleflex, Wayne, Pa) or DYNEEMA® fiber (Koninklijke DSM, the Netherlands), among other types of sutures. 
     Preferably, the diameter of the secondary suture  156  is sufficiently smaller than that of the primary suture  144 , so that threading the secondary suture  156  through the primary suture  144  does not tear or disrupt the primary suture  144 . A ratio of the diameter of the secondary suture  156  to the diameter of the primary suture  144  is defined as the secondary to primary sutures diameter ratio. According to some embodiments, the secondary to primary sutures diameter ratio is less than 0.8. According to some embodiments, the secondary to primary sutures diameter ratio is less than 0.5. According to some embodiments, the secondary to primary sutures diameter ratio is less than 0.3. 
     In prior art prosthetic valve devices, an inner skirt is attached to an inner surface of the frame, so as to form a more suitable attachment surface for the leaflets. In contrast, the currently disclosed attachment configuration does not require utilization of intermediate fabric strips, since the primary suture  144  serves as a support structure through which the leaflet  132  may be attached to the frame  106 , via a secondary suture  156  threaded through the primary suture  144 . Fabric strips along the inner surface of the frame  106  pose a risk of promoting tissue ingrowth and proliferation after implantation. Thus, the absence of such fabric or cloth components along the inner side of the frame may significantly reduce such risks, thereby improving the valve’s long-term durability and functionality. 
     According to preferred embodiments of the present invention, leaflet attachment to the frame of a prosthetic valve along the scalloped edge of the leaflets, is devoid of intermediate fabric strips and/or cloth there-between. While tissue ingrowth may still occur along suture materials, such as the primary suture  144 , the overall surface area of a suture is significantly smaller than that of traditionally used fabric strips that serve, for example, as inner skirt components. 
     As shown, the attachment of the leaflets  132  to the struts  110  of the frame  106  is achieved via the secondary suture  156 , which is threaded through the primary suture  144  instead of being threaded directly through the leaflet material. Thus, the primary suture  144  serves as a reinforcement member that resists suture tear-through along the cusp end portions  134 , thereby reducing stress concentrations on the leaflets  132  in the vicinity of the scallop line. Advantageously, the forces applied to the leaflets  132  during transitioning between the open and closed or coapting states, at the regions of leaflets attachment to the frame, are distributed along the length of the primary sutures  144 . In such manner, the primary suture  144  serves as a force-distributing element which enhances the durability of the leaflets  132  over time, because the forces are distributed over the primary suture  144  in a substantially equal manner along its length. 
     With further reference back to  FIG.  2   , the leaflet  132  can be provided, in some embodiments, with a series of apertures  142  pre-formed along its cusp end portion  134 , configured to accept the primary suture  144  and define penetration points  150  through which it may extend in an in-and-out pattern. In such embodiments, the apertures  142  may serve as the penetration points  150 . The apertures  142  can be equally spaced from each other in some embodiments. 
     The secondary suture  156  is threaded through the primary suture  144  at the penetration points  150 , potentially within the apertures  142 . According to some embodiments, the secondary suture  156  extends through the primary suture  144  at each penetration point  150 . Alternatively, the secondary suture  156  may extend through only some of the penetration points  150 , as will be further disclosed herein below. 
     Since in such embodiments the primary suture  144  is threaded through pre-formed apertures  142  along the cusp end portion  134 , accuracy of the penetration points  150  for the primary and/or secondary suture  144  and/or  156 , respectively, can be pre-set, leading to more accurate placement of the sutures and less errors. 
     The apertures  142  are dimensioned to accept the primary suture  144 . According to some embodiments, the diameter of the apertures  142  is equal to or smaller than the diameter of the primary suture  144 , such that when the primary suture  144  is pass there-through, each aperture  142  tightly retains the primary suture  144  extending there-through. Since the secondary suture  156  extends the boundaries the primary suture  144  at the penetration zones outward, alternative embodiments may include apertures  142  having a diameter that is equal to or smaller than the combined diameters of the primary suture  144  and the secondary suture  156 , such that when the secondary suture  156  extends through the primary suture  144  within the aperture  142 , the aperture  142  tightly retains them both therein. 
     According to some embodiments, the cusp end portions  134  include markings that may follow the undulating scallop line, such as by tracking the curvature of the cusp edges  135 . Such markings, which may be utilized either alternatively to, or in addition to, apertures  142 , can further assist the assembler in stitching of the primary suture  144  there-along. 
     According to some embodiments, as shown in  FIG.  5 E , the secondary suture  156  is threaded through all successive penetration points  150 , such that each self-tightening construct  158  is positioned over a single outer stitch portion  148 , and each suture pull portion  164  spans over a length of a single inner stitch portion  146 . 
     According to alternative embodiments, the secondary suture  156  is not necessarily threaded through all successive penetration points  150 , and may actually skip over one or more penetration point  150 , such that a single suture pull portion  164  may span over more than one inner  146  or outer  148  stitch portions.  FIG.  6    shows an exemplary configuration in which each self-tightening construct  158  is positioned over a single outer stitch portion  148 , while the suture pull portion  164  spans over two inner stitch portions  146  and a single outer stitch portion  148  positioned there-between. It will be understood that other configurations are contemplated, wherein either the self-tightening construct  158  and/or the suture pull portion  164  is threaded through non-successive penetration points  150 . 
     The term “non-successive penetration points” refers to any couple of penetration points that include at least one additional penetration point  150  there-between. Advantageously, the self-tightening configuration of the secondary suture  156  enables it to be threaded through non-successive penetrations points  150 , while retaining a sufficient grip to prevent or at least significantly reduce lateral movement of the cusp end portions  134  over the struts  110 . Thus, the number and position of the self-tightening constructs  158  can be designed and modified in various different manners, based on the desired attachment points, and to facilitate easier attachment by an assembler of the valve  100 . 
     According to some embodiments, two primary sutures  144  are inversely threaded in an in-and-out pattern, through the same penetration points  150 .  FIG.  7    shows a sectional view of a cusp end portion  134  which is similar to the view shown in  FIG.  4   , except that two primary sutures  144   a  and  144   b  are threaded in opposite directions, through the same penetration points  150 , such that each couple of successive penetration points  150  define both an inner stitch portion  146  of one of the primary sutures, and an outer stitch portion  148  of the other primary suture.  FIG.  8    shows a secondary suture  156  threaded through a cusp end portion  134  that includes two primary sutures  144  as shown in  FIG.  7   . Advantageously, this configuration results in a pattern in which an outer stitch portion  148  and an inner stitch portion  146  extend between each couple of successive penetration points  150 , thereby simplifying the assembly procedure by allowing the assembler to thread the secondary suture  156  through any penetration points  150  conveniently available during such a procedure. 
     According to some embodiments, the diameter of the apertures  142  is equal to or smaller than the diameter of two primary sutures  144 , such that when both primary sutures  144  extend there-through, each aperture  142  tightly retains them both. Since the secondary suture  156  extends the boundaries of at least one of the primary sutures  144  at the penetration zones outward, alternative embodiments may include apertures  142  having a diameter that is equal to or smaller than the combined diameters of two primary suture  144  and the secondary suture  156 . 
     Generally, threading sutures through a leaflet  132  involves using a needle or other sharp tool that can pierce through leaflet  132 . However, use of a needle or other sharp tools might lead to unintended cuts, punctures, or other damage to the leaflets  132 . Such damage is also difficult to foresee or predict by the manufacturer, and can also be difficult to detect by the end user even when it occurs. The primary suture  144  is threaded in an in-and-out manner through penetration points  150 , that also serve as the penetration sites through which the secondary suture  156  is threaded. Thus, as the secondary suture  156  is threaded through the primary suture  144  and not directly into the leaflet, additional penetrations or cuts to the leaflets may be avoided. Advantageously, the proposed arrangement enables utilization of a secondary suture  156  to attach the leaflet  132  to the struts of the frame, without further puncturing the tissue of the leaflet, thereby improving the leaflets’ long-term durability. 
     A stitching pattern that includes self-tightening constructs  158  for directly attaching leaflets  132  to the struts  110  of the frame  106 , according to any of the embodiments described above, can be implemented for any type of prosthetic valves  100 , such as either mechanically expandable valves  100 ′ or balloon expandable valves  100 ″. However, the advantage of self-tightening constructs  158  is more prominent for mechanically expandable valve  100 ′ of the type illustrated in  FIG.  1 A , shown to include two layers of intersecting struts  110 ′, namely inner struts and outer struts, that intersect (for example, via pins or other hinges) at the junctions  116 ′. A unique challenge with such double-layered frames  106 ′ is the difficulty to form knots of the sutures at the pivot junctions  116 ′, as relative movement between the intersecting struts  110 ′ can exert scissor-like shearing forces that may compromise the integrity of the sutures in such regions. 
     Unlike the double-layered frames  106 ′ of mechanically expandable valves, such as valve  100 ′ shown in  FIG.  1 A , frames of prosthetic valve formed with a unitary frame, such as the frame  106 ″ of balloon expandable valves  100 ″ shown, for example, in  FIG.  1 B , do not suffer from the this problem to the same effect, and stitching pattern utilized to directly couple leaflets  132  to such frames  106 ″ can include knot formed around non-apical junctions  116 ″ in a manner that will preserve tight attachment there-between, without necessarily utilizing self-tightening constructs. 
     With particular reference to  FIGS.  9 A- 9 D , an exemplary technique for coupling leaflets  132  along their cusp end portions  134  to strut sections  111  interconnected at non-apical junctions  116  will now be discussed in accordance with the present teachings. The views illustrated in  FIGS.  9 A- 9 D  are taken from a bottom view point of a section of a prosthetic valve, such as a section of prosthetic valve  100 ″. A strut section  111 , as used herein, refers to any section of a strut defined between two non-apical junctions  116  of a frame  106 . 
     The frame  106 ″ of the exemplary balloon expandable valve  100 ″ illustrated in  FIG.  1 B , is shown to include flat inflow apices  118 ″ (as well as flat outflow apices  120 ″). In some embodiments, a strut section can be either a relatively linear strut section, such as strut section  111 ″ b  shown in  FIG.  1 B , extending between two non-apical junctions that are axially spaced from each other, such as non-apical junctions  116 ″ b  and  116 ″ c , and/or a curved strut section, such as strut section  111 ″ a , extending between two non-apical junctions that are laterally spaced from each other, but may be aligned with each other at the same level of height between the inflow end  105 ″ and the outflow end  103 ″, such as non-apical junctions  116 ″ a  and  116 ″ b . In such embodiments, the peak of the curvature of a curved strut section can define an apex, such as inflow apex  118 ″ a  defined by curved strut section  111 ″ a . 
     As shown in  FIGS.  9 A-B , Each strut section  111  and each non-apical junction  116  is defined between opposite axial sides and opposite radial sides. For example, each strut section  111  is defined between a strut proximal side  190  facing the outflow end  103 , and a strut distal side  191  facing the inflow end  105  (sides  190  and  191  being the opposite axial sides of the strut section). Each strut section  111  is also defined between a strut inner side  192  facing the valve longitudinal axis  10 , and a strut outer side  193  facing away from the axis  10  (sides  192  and  193  being the opposite radial sides of the strut section). If the strut has a rectangular cross-sectional profile, as illustrated in the example of  FIG.  5 A- 6   , then each of the sides  190 ,  191 ,  192 ,  193  can be defined by a corresponding planar face of the strut. Nevertheless, as mentioned above, other cross-sectional shapes for the struts are contemplated, such that a side may not necessarily include a planar face. 
     Each non-apical junction  116  is defined between a junction proximal side  194  facing the outflow end  103 , and a junction distal side  195  facing the inflow end  105  (sides  194  and  195  being the opposite axial sides of the junction). Each non-apical junction  116  is similarly defined between a junction inner side  196  facing the valve longitudinal axis  10 , and a junction outer side  197  facing away from the axis  10  (sides  196  and  197  being the opposite radial sides of the junction). Each junction is also defined between two opposite lateral sides, namely a junction first lateral side  198  and a junction second lateral side  199 . In the illustrated example, two strut sections  111  converge on each lateral side of a non-apical junction  116 . 
     A primary suture  144  can be threaded through the cusp end portions  134  in an in-and-out pattern, in the same manner described above in conjunction with  FIG.  4   . In some embodiments, two primary sutures  144   a  and  144   b  are threaded in opposite direction through penetration point  150 , in a similar manner to that described above in conjunction with  FIG.  8   . Thus, any reference to a primary suture described below in conjunction with  FIG.  9 A- 10    can refer either to a configuration of a single primary suture or to two oppositely threaded sutures, with equal force. 
     As shown in  FIGS.  9 A-B , the cusp end portion  134 , with the primary suture  144  threaded there-through in an in-and-out pattern, is approximated to a strut section  111 , such that the cusp end portion  134  is preferably positioned radially inward (and optionally in contact with) the strut inner side  192 . A secondary suture  170  is stitched through the primary suture  144  and around the strut section  111  in a manner that forms a series of loops or whip stitches  172  spaced from each other along the length of the strut section  111 . The secondary suture  170  can be similar to any embodiment of the secondary suture  156 , except that the secondary suture  170  does not form self-tightening constructs  158 , but rather wraps around at least one strut section  111  by a series of whip stitches and includes at least one junction lock-knot  174  around at least one non-apical junction  116 , as will be described in greater detail below. 
     A whip stitch  172  is formed by threading the secondary suture  170  through the primary suture  144  at a penetration point  150 , extending the secondary suture  170  around the strut section  111  and back toward the primary suture  144 , and then threading secondary suture  170  once again through the primary suture  144  at a consecutive penetration point  150 , at which point another whip stitch can be formed in a similar manner. 
     For example, whip stitch  172   b  shown in  FIG.  9 B  is formed by threading the secondary suture  170  radially outward through the primary suture  144  at penetration point  150  (shown in  FIG.  9 B  between loops  172   a  and  172   b ), extending it around the strut segment  111  (in the illustrated example, radially outward over the strut proximal side  190 , then along the strut outer side  193  which is hidden from view, and radially inward over the strut distal side  195 ) back (along strut inner side  192 ) toward the primary suture  144 , threading it through the next sequential penetration point  150  to form the next whip stitch  172   c  in a similar manner. In some embodiments, as in the illustrated example, the primary suture  144  is positioned proximal or adjacent to the strut proximal side  191 . 
     Threading the whip stitches  172  through consecutive penetration points  150  results in a series of angled whip stitches. An angled whip stitch can be defined as a stitch having at least one portion extending between opposite sides of the strut section  111 , oriented at a non-perpendicular angle with respect to a strut section axis defined as tangent to the strut section  111  at the region of the respective stitch. 
     In the example illustrated in  FIGS.  9 A-B , the portion of the whip stitch  172   b  extending along the strut outer side  193  between the strut proximal side  190  and the strut distal side  191  (this portion is hidden from view in  FIG.  9 B ), the portion extending along the strut distal side  191  between the strut outer side  193  and the strut inner side  192 , and the portion extending along the strut inner side  192  (optionally at least partly over the leaflet inner surface  152 ) between the strut distal side  191  and the strut proximal side  190 , are oriented at a non-perpendicular angle relative to a strut section axis which is tangent to the strut  111   a  at the region of whip stitch  172   b . 
     Thus, each angled whip stitch  172  has a portion extending over one axial side of the strut section  111  wrapped thereby, closer to a junction  116  (at the end of the respective strut section) than the opposite portion extending over the opposite axial side of the strut section. In the illustrated example, the portions of whip stitches  172  extending over the proximal side  190  of strut section  111   a  are closer to junction  116   b  than the opposite portions extending over the strut distal side  191 . Alternatively, an opposite orientation of the whip stitches  172  can include the portions extending over the strut distal side  191  being closer to such a junction  116  than the portions extending over the strut proximal side  190 . A series of whip stitches  172  wrapped over a single strut section  111  defined between two junction  116  will generally follow the same angled orientation. 
     Preferably, the diameter of the secondary suture  170  is sufficiently smaller than that of the primary suture  144 , so that threading the secondary suture  170  through the primary suture  144  does not tear or disrupt the primary suture  144 . A secondary to primary sutures diameter ratio with respect to secondary sutures  170  can be defined in the same manner described above with respect to secondary sutures  156 . According to some embodiments, the secondary to primary sutures diameter ratio is less than 0.8. According to some embodiments, the secondary to primary sutures diameter ratio is less than 0.5. According to some embodiments, the secondary to primary sutures diameter ratio is less than 0.3. 
     As shown in  FIG.  9 B , these steps are repeated to form a series of angled whip stitches  172  (such as stitches  172   a ,  172   b ,  172   c ), up to a final whip stitch  172   n  defined as the whip stitch which is closest to the non-apical junction  116  on an end of the strut section  111  (junction  116   b  in  FIG.  9 B ), wherein the final whip stitch  172   n  extends up to a final penetration point  150   n , after which the secondary suture  170  is utilized to form a junction lock-knot  174  over the corresponding non-apical junction  116 . 
     A junction lock-knot  174  includes a transition section  176 , a first loop  178  and a second loop  180 . The transition section  176  extends along one axial side of the junction  116 , in a direction from the junction first lateral side  198  to the junction second lateral side  199 . In the example illustrated in  FIG.  9 B , the secondary suture  170  extend over the outer side  193  of strut section  111   a  from the final penetration point  150   n  at the strut proximal side  190  to the strut distal side  191 , in proximity of the first lateral side  198  of junction  116   b . The transition section  176  is then formed by extending the secondary suture  170  along the junction distal side  195  in a diagonal direction, such as radially inward from the junction outer side  197  toward the junction inner side  196  and laterally from the junction first lateral side  198  to the junction second lateral side  199 . 
     The first loop  178  is then formed by extending the secondary suture  170  around a strut section  111  extending from the junction second lateral side  199 . Struts sections  111   b  and  111   m  are shown to extend from the second lateral side  199  of junction  116   b . In the example illustrated in  FIGS.  9 B-C , the first loop  178  is formed by extending the secondary suture  170  from the transition section  176  around strut section  111   m . 
     The second loop  180  is formed by passing the tail of the secondary suture  170  from the first loop  178 , between the transition section  176  and the junction  116 , and then looping it back to extend through the first loop  178 . In the example illustrated in  FIG.  9 C , the secondary suture  170 , extending from the first loop  178 , is passed, for example in an axial direction (e.g., upward toward outflow end  103 ), and is then folded over itself backward (e.g., in the distal/downward direction), passing through the first loop  178 . The tail of the secondary suture is then forcibly pulled to tighten both loops  178 ,  180  and lock the resulting knot  174 . 
     The procedure can then be repeated by forming a series of whip stitches  172  attaching the leaflet  132  to the subsequent strut section  111  extending from the junction  116 , such as strut section  111   b , and forming similar junction lock-knots  174  over all respective junction  116   along the path of the rounded cusp end portions  134 . Advantageously, this type of stitching pattern facilitates the valve assembly procedure because the knots  174  around the junctions  116  maintain a tight connection between the leaflets and the junctions during assembly. 
     Compared to conventional assembly procedures, during which the assembler is required to maintain tension on the suture while forming each subsequent stitch along the entire circumference of the frame, the junction lock-knots  174  will maintain tight connection of all whip stitches  172  around the strut section  111  leading to the respective junction  116 , relieving the assembler from the need to keep all previous stitches tensioned, and even allowing continuation of the assembly procedure at a later time without the risk of any of the previous loops of knots being loosened. 
     The tight connection of the knot  174  keeps all whip stitches  172  along the strut section  111  leading thereto, tightly connected to the strut section  111  as well, thereby reducing relative motion between the suture  170  and strut sections  111  under normal operation of the valve  100  after implantation. 
     Any junction lock-knot  174  also separates between the series of whip stitches  172  around the strut sections  111  extending from both sides of the junction  116 . Thus, the orientation of angled whip stitches  172  formed subsequent to junction lock-knot  174  are not dependent on the configuration of the whip stitches  172  leading to the knot  174 , and in fact can have a similar or different angular orientation, as well as similar or different stitching density, and so on. This allows the assembler to switch the angular orientation of angled whip stitched in any desired direction that may be convenient during the assembly procedure, which may differ for different strut portion  111  along the circumference of the valve  100 . 
       FIG.  10    shows an example of a portion of a leaflet assembly  130  sutured to the frame  106  (view is from the inside of the valve). As shown, the procedure can be repeated to attach one or more other leaflets  132  to strut sections  111  and junction  116 , including formation of similar junction lock-knots  174  around junctions  116  that interconnect two adjacent leaflets  132 , such as junction  116   d  aligned with commissure  140  between leaflets  132   a  and  132   b  shown in  FIG.  10   . 
     In the illustrated view, the cusp end portion of leaflet  132   a  is sutured to strut sections  111   a ,  111   b  and  111   c , and the cusp end portion of leaflet  132   b  is sutured to strut sections  111   d ,  111   e  and  111   f . As shown, the angular orientation of the whip stitches  172  around strut sections  111   a ,  111   b  and  111   c  is generally similar (having their upper/proximal ends closer to junction  116   d , for example, than their lower/distal ends). After the junction lock-knot  174  around junction  116   d , the orientation of the whip stitches  172  around strut sections  111   d  and  116   e  is reversed to a generally opposite direction, and as shown, after the junction lock-knot  174  around junction  116   f , the orientation of the whip stitches  172  around strut section  111   f  is switched again (to an orientation similar to that of the whip stitches looped over struts section  111   a - c ). The ability to change the orientation of the whip stitches wrapped around each strut segment separately can facilitate the valve assembly process. 
     In some cases, it may be preferable to attach the leaflets  132  to the frame  106  utilizing a secondary suture  156  that does not penetrate through the leaflets  132  and/or through the primary suture  144 .  FIGS.  11 A- 11 D  show an exemplary technique for coupling leaflets  132  along their cusp end portions  134  to strut sections  111 . The views illustrated in  FIGS.  11 A- 11 D  are taken from a bottom view point of a section of a prosthetic valve, such as a section of prosthetic valve  100 ″, similar to the view angle of  FIGS.  9 A- 9 D . 
     A primary suture  144  can be threaded through the cusp end portions  134  in an in-and-out pattern, in the same manner described above in conjunction with  FIG.  4   , forming a plurality of running stitch portions, including inners stitch portions extending over the leaflet inner surface (hidden from view) and outer stitch portions  148  extending over the leaflet outer surface  154  between penetration points  150 , such as outer stitch portions  148   a ,  148   b  and  148   c  shown in  FIG.  11 A . In some embodiments, two primary sutures  144   a  and  144   b  are threaded in opposite direction through penetration point  150 , in a similar manner to that described above in conjunction with  FIG.  8   . Thus, any reference to a primary suture described below in conjunction with  FIGS.  11 A- 11 D  can refer either to a configuration of a single primary suture or to two oppositely threaded sutures, with equal force. 
     As shown in  FIG.  11 A , the cusp end portion  134 , with the primary suture  144  threaded there-through in an in-and-out pattern, is approximated to a strut section  111 , such that the cusp end portion  134  is preferably positioned radially inward (and optionally in contact with) the strut inner side  192 . A secondary suture  170  is looped around the outer stitch portions  148  of the primary suture  144  and around the strut section  111  in a manner that forms a series non-penetrating whip stitches  182  spaced from each other along the length of the strut section  111 . The secondary suture  170  can be similar to any embodiment described above in conjunction with  FIGS.  9 A- 9 D , except that the secondary suture in the embodiments shown in  FIGS.  11 A- 11 D  is utilized to form non-penetrating whip stitches  182  instead of conventional whip stitches  172  that extend from one side of the leaflet to the other side (e.g., from leaflet inner surface  152  to its outer surface  154 ). 
     Unlike whip stitch  172 , the non-penetrating whip-stitch  182  is not threaded through the primary suture  144  at penetration point  150  or any other region of the primary suture  144 , and does not penetrate through the leaflet from one side to the other side. A non-penetrating whip-stitch  182  is formed by looping the secondary suture  170  around the strut section  111 , thereby forming a strut-wrapping section  184 , and then looping the secondary suture around an outer stitch portion  148 , thereby forming a primary-suture-wrapping section  186 . This can be repeated to form a series of following non-penetrating whip stitches  182  in a similar manner along the strut section  111 . 
     For example,  FIG.  11 A  shows two non-penetration whip stitches  182   a  and  182   b , each including a corresponding strut-wrapping section  184  and a corresponding primary-suture-wrapping section  186 . A following non-penetration whip stitch  182   c  is formed by looping the tail of the secondary suture  170 , extending from primary-suture-wrapping section  186   b  (looped around outer stitch portion  148   b ), around the strut section  111 , and back toward the following stitch portion  148   c  of the primary suture  144 , as shown in  FIG.  11 B . 
     In the example shown in  FIGS.  11 A- 11 B , the strut-wrapping section  184   c  is formed by extending the secondary suture  170  across one radial side of the strut section (e.g., strut outer side  193 ) from one axial side to the opposite axial side of the strut (e.g., from strut proximal side  190  to strut distal side  191 ), folding it over the corresponding axial side of the strut (e.g., over strut distal side  191 ), and extending it across the opposite radial side (e.g., strut inner side  192 ) back toward the primary suture  144  (e.g., from strut distal side  191  toward strut proximal side  190 ). 
     As further shown in  FIG.  11 B , the secondary suture  170  is then passed beneath the consecutive outer stitch portion  148   c , between the outer stitch portion and the leaflet  132  (i.e., between outer stitch portion  148  and leaflet inner surface  152 ). As shown in  FIG.  11 C , the secondary suture  170  is then folded over outer stitch portion  148   c , thereby forming primary-suture-wrapping section  186   c . The suture can then pass across the strut section  111  (such as across strut outer side  193  toward strut distal side  191  in the example illustrated in  FIG.  11 C ), repeating these steps to form a following non-penetration whip stitch  182  (such as non-penetration whip stitch  182   d ). 
     As shown in  FIG.  11 D , this procedure can be repeated up to a final non-penetration whip stitch  182   n  defined as the whip stitch which is closest to the non-apical junction  116  on an end of the strut section  111 , wherein the secondary suture  170  can be utilized to form a junction lock-knot  174  following the same steps described above in conjunction with  FIGS.  9 A- 9 D , with the exception that the transition zone  176  of the junction lock-knot  174  extends from the final primary-suture-wrapping section  186   n  of the final non-penetration whip stitch  182   n , instead of from a final penetration point  150   n . 
       FIGS.  12 A- 12 D  shows another exemplary technique for coupling leaflets  132  along their cusp end portions  134  to strut sections  111  via a series of non-penetrating whip stitches  182 , which can be identical to the technique described in conjunction with  FIGS.  11 A- 11 D , except that instead of passing the secondary suture  170  extending from a strut-wrapping section  184  beneath an outer stitch portion  148  and then folding it over the outer stitch portion  148 , to form the primary-suture-wrapping section  186  (as shown in  FIGS.  11 B- 11 C ), the secondary suture  170  is passed over the outer stitch portion  148  (see  FIG.  12 B ) and then folded beneath it (i.e., between outer stitch portion  148  and leaflet inner surface  152 ). All other steps and embodiments can be similar to those described above in conjunction with  FIGS.  11 A- 11 D , and in the interest of brevity will not be further described. 
       FIG.  13    shows another stitching configuration which is similar to that shown in  FIGS.  12 A- 12 D , except that two non-penetration whip stitches  182  pass through each outer stitch portion  148 . In the illustrated example, non-penetrating whip stitch  182   a ′ comprises strut-wrapping section  184   a ′ looped around strut section  111 , and primary-suture-wrapping section  186   a ′ extending therefrom and looped around outer stitch portion  148   a . The secondary suture  170  then extends to form strut wrapping section  184   a ″ of non-penetrating whip stitch  182   a ″, and primary-suture-wrapping section  186   a ′ looped around the same outer stitch portion  148   a . 
     The secondary suture  170  then extends to form subsequent non-penetrating whip stitches  182   b ′ and  182   b ″ in a similar manner, having their primary-suture-wrapping sections  186   b ′ and  186   b ″ looped around outer stitch portion  148   b . It is to be understood that while two non-penetration whip stitches  182  passing through a single outer stitch portion  148  are illustrated in  FIG.  13   , any other number of non-penetration whip stitches  182  can pass through any single outer stitch portion  148  in a similar manner. 
       FIG.  14    shows yet another stitching configuration which is also similar to that shown in  FIGS.  12 A- 12 D , except that each non-penetrating whip stitch  182  further includes a strut-looping section  185  extending from the respective primary-suture-wrapping section  186 , looped solely over the strut section  111 . In the illustrated example, non-penetrating whip stitch  182   a  comprises strut-wrapping section  184   a  looped around strut section  111 , primary-suture-wrapping section  186   a  extending therefrom and looped around outer stitch portion  148   a , and strut-looping section  185   a  extending from the primary-suture-wrapping section  186   a  and looped again around the strut section. 
     In the specific illustrated example, strut-looping section  185   a  is formed by extending the secondary suture  170  from the primary-suture-wrapping section  186   a  across one radial side of the strut section, such as strut outer side  193 , around the strut distal side  191 , over the other radial side, such as strut inner side  192 , toward and over the strut proximal side  190 . The secondary suture is then extended to form the strut-wrapping section  184   b , primary-suture-wrapping section  186   b , and strut-looping section  185   b , together forming the subsequent non-penetrating whip stitch  182   b  in a similar manner. It is to be understood that while a single strut-looping section  185  is illustrated in the example, a non-penetrating whip stitch  182  can similarly include a plurality of single strut-looping sections  185  looped one after the other around the strut section  111 , before forming the subsequent non-penetrating whip stitch  182 . 
     It is to be understood that the configuration described above and illustrated in  FIG.  11 A- 14   , showing the primary-suture-wrapping sections  186  looped around outer stitch portions  148 , is non-binding, and that any primary-suture-wrapping section  186  can be looped around any running stitch portion, including around inner stitch portion  146  of the primary suture  144 . In some embodiments, the cusp end portion  134  can be folded over itself such that the cusp edge  135  is rests over the leaflet outer surface  152  facing outward, such that the outer stitch portions  148  are concealed and the inner stitch portions  146  are facing the strut sections  111 . In such embodiments, the non-penetration whip stitches can be formed in the same manner described above, except that the secondary suture is looped around the inner stitch portions  146  instead of around the outer stitch portions. 
     It is to be understood that various stitching configuration can be combined to attach one or more leaflets  132  to strut sections  111  of the same prosthetic valve  100 . For example, attachment of a leaflet  132  along its rounded cusp end portion  134  to one or more strut section  111  can include a combination of one or more single non-penetrating whip stitches  182  passing through corresponding running stitch portions (as illustrated in  FIGS.  12 A- 12 D ), together with one or more double non-penetrating whip stitches  182  passing through corresponding single running stitch portions (as illustrated in  FIG.  13   ), and/or together with one or more single non-penetrating whip stitches  182  looped twice around the strut section  111  (as illustrated in  FIG.  14   ). Single-pattern or combined-pattern configurations can be implemented along the same strut section  111 , or around different strut section of the same valve. 
     Attachment of the leaflets  132  to the frame  106 , and more specifically, to strut section  111  of the frame  106 , by non-penetrating whip stitches  182 , can advantageously improve long-term durability of the leaflets and their attachment to the frame along the scalloped line, due to the reduced damage to the leaflet material resulting from the fact that the secondary suture  170  does not need to penetrate through the tissue material. 
     While non-penetrating whip stitches  182 , with or without junction lock-knots  174 , are described and illustrated above with respect to attachment of leaflets  132  to the frame  106 , such attachment configurations can be similarly utilized for attachment of other soft components of the valve  100  to the frame  106 , such as skirts  123  that may include any of an inner skirt (not shown) or an outer skirt  124 . 
       FIG.  15    shows a prosthetic valve  100  with an outer skirt  124 , according to some embodiments. The prosthetic valve can be similar in all respects to prosthetic valve  100 ″ described in conjunction with  FIG.  1 B , and in the interest of brevity will not be described further. A skirt  123 , such as outer skirt  124  shown in  FIG.  15   , extends between a skirt proximal end  128  and a skirt distal end  129 , and defines a skirt inner surface  125  facing (and is at least partially in contact with) the frame  106 , and an opposite skirt outer surface  126  facing away from the frame (toward the native anatomy when implanted in a patient’s body). 
     In some embodiments, as further shown in  FIG.  15   , the proximal end of the outer skirt follows a zig-zag pattern, corresponding to a zig-zag pattern of strut section  111  to which it may be sutured. In the specific exemplary embodiment illustrated in  FIG.  15   , the skirt distal end  128  is substantially linear (for example, being straight when the skirt is flattened), meaning that it is retained at the same axial level, disposed circumferentially around the inflow end portion  104  of the valve  100 . 
     In some embodiments, a primary suture  144  (one or more) is sutured along portions of the skirt  123  which are aligned with strut sections  111  of the frame  106  in an in-and-out pattern, and a secondary suture  170  (one or more) formed a plurality of non-penetrating whip stitches  182  to couple the skirt  123  to the strut section  111  of the frame  106 . 
     The primary suture  144  can be stitched through the skirt  123  in an in-and-out pattern according to any of the embodiments disclosed hereinabove, mutatis mutandis. Similarly, any type of non-penetrating whip stitches  182  disclosed above with respect to attachment of leaflets  132  to struts  111 , can be similarly adapted to attach the skirt  123  to struts  111  in the same manner, mutatis mutandis. 
       FIG.  16    shows a partial view or the outer skirt  124  coupled to struts  111  of the frame  106  of the valve  100  shown in  FIG.  15   , from a valve-internal view angle. The leaflet assembly  130  is omitted from view in  FIG.  16    for simplicity. In the illustrated exemplary embodiment, a primary suture  144  is stitched in an in-and-out pattern along the skirt proximal end  129 , for example tracking its zig-zagged shape. In the case of an outer skirt  124 , the primary suture  144  can define a series of running stitch portions that include inner stitch portion  146 , disposed over skirt inner surface  125 , and outer skirt portion  148 , disposed over skirt outer surface  126 . A plurality of non-penetrating whip stitches  182  are then looped around strut sections  111  via strut-wrapping sections  184 , and around running stitch portion of the primary suture  144 , such as over and between inner stitch portions  146  and the skirt inner surface  125 . 
     While a specific embodiment of non-penetrating whip stitches  182 , similar to those described in conjunction with  FIGS.  12 A-D , is illustrated in  FIG.  16   , for example along strut sections  111   m ,  111   n ,  111   o , and  111   p , it is to be understood that the skirt can be sutured to the corresponding strut section  111  by implementing any of the suturing patterns and methods described above in conjunction with  FIG.  11 A- 14   ,  mutatis mutandis . 
     In some embodiments, junction lock-knots  174  are similarly used to attach the skirt  123 , such as outer skirt  124 , to junctions  116  disposed between strut section  111  to which the skirt is sutured via non-penetrating whip stitches  182 , such as junction lock-knots  174   m ,  174   n ,  174   o ,  174   p  and  174   q  formed over respective junctions  116   m ,  116   n ,  116   o ,  116   p  and  116   q  in the illustrated example. The configuration and methods of forming such junction lock-knots  174  is similar to that described hereinabove with respect to attachment of leaflets  132  to junction  116 , mutatis mutandis. 
     In some embodiments, the skirt  123 , such as outer skirt  124 , is coupled to additional junctions  116 , which are not necessarily disposed between strut section  111  around which non-penetrating whip stitches  182  extend, via additional knots, which are not necessarily the junction lock-knots  172  but may be implemented as other knots known in the art, as schematically shown in  FIG.  16    for knots  166   r ,  166   s  and  166   t  around respective junctions  116   r ,  116   s  and  116   t , for example. 
       FIG.  17    shows another valve  100  comprising an outer skirt  124  that can be similar to the valve and skirt of  FIG.  15   , except that the skirt distal end  128  is not linear but rather tracks the shape of the strut sections  111  along the inflow end portion  104  of the valve, which can be undulated or arc-shaped as illustrated in  FIG.  17   , or can otherwise be zig-zagged or otherwise shaped to follow other paths defines by distal strut sections of the valve. 
       FIG.  18    shows a partial view or the outer skirt  124  coupled to struts  111  of the frame  106  of the valve  100  shown in  FIG.  17   , from valve-bottom-internal view angle. The leaflet assembly  130  is omitted from view in  FIG.  18    for simplicity. In the illustrated exemplary embodiment, a primary suture  144  is stitched in an in-and-out pattern along the skirt distal end  129 , for example tracking its undulating shape. This can be in addition to the primary suture  144  stitched along the skirt proximal end  129 , implemented in the same manner described above. 
     A plurality of non-penetrating whip stitches  182  are then looped around the strut sections  111  (of the inflow end portion  104 ) by a series of strut-wrapping sections  184 , and around running stitch portion of the primary suture  144 , such as over and between inner stitch portions  146  and the skirt inner surface  125 . While a specific embodiment of non-penetrating whip stitches  182 , similar to those described in conjunction with  FIGS.  12 A-D , is illustrated in  FIG.  18   , for example along strut sections  111   u  and  111   w , it is to be understood that the skirt can be sutured to the corresponding strut section  111  by implementing any of the suturing patterns and methods described above in conjunction with  FIG.  11 A- 14   , mutatis mutandis. 
     In some embodiments, junction lock-knots  174  are similarly used to attach the outer skirt  124  to junctions  116  along the inflow end portion  104 , such as junction lock-knots  174   r ,  174   s  and  174   t  formed around respective junctions  116   r ,  116   s  and  116   t  in the illustrated example, following the same configuration and methods described hereinabove with respect to attachment of leaflets  132  to junction  116 , mutatis mutandis. 
     In some embodiments, the skirt  123 , such as outer skirt  124 , is attached to additional strut sections  111  disposed between the skirt proximal end  129  and skirt distal end  128  via non-penetrating whip stitches  182  in the same manner and according to all optional embodiments described above. For example, primary suture  144  (one or more) can be sutured in an in-and-out pattern along regions of the skirt aligned with strut sections  111  disposed between the skirt proximal end  129  and skirt distal end  128  (when the skirt is attached to the frame), implemented according to any embodiments of stitching such primary suture  144  described above. A series of non-penetrating whip stitches  182 , implemented according to any of the embodiments described above with respect to  FIG.  11 A- 14   , can be utilized to attached the skirt to the corresponding strut section  111 , as shown for example in  FIG.  18    along strut sections  111   r ,  111   s ,  111   t  and  111   v . 
     In some embodiments, the skirt  123 , such as outer skirt  124 , is attached to additional junctions  116  disposed between the skirt proximal end  129  and skirt distal end  128  via junction lock-knots  174  in the same manner and according to all optional embodiments described above. 
     Some valve are provided with an inner skirt (not shown) disposed around the inner surface of the frame. While outer skirts  124  are illustrated for demonstrating various attachment configurations thereof to the frames throughout  FIGS.  15 - 18   , it is to be understood that the same embodiments described above with respect to outer skirt attachment, may be implemented in a similar manner for attachment of inner skirts to the frame, mutatis mutandis. 
     In some embodiments, junction lock-knots  174  can be utilized for attachment of a skirt  123  (including any of an inner skirt or an outer skirt) to junctions  116  along any of the skirt proximal end  129 , skirt distal end  128 , and/or to junctions  116  disposed between the skirt proximal end  129  and skirt distal end  128  (when the skirt is attached to the frame), without the use of non-penetrating whip stitches  182  around strut sections  111 . 
     For example, a skirt can be sutured to corresponding strut sections  111  along any of the skirt proximal end  129 , skirt distal end  128 , and/or to strut sections  111  disposed between the skirt proximal end  129  and skirt distal end  128  (when the skirt is attached to the frame) via a series of whip stitches  172  that can penetrate through the primary suture  144 , with junction lock-knots  174  formed around junction  116  disposed between such strut sections  111 , in the same manner and following similar methods described above in  FIG.  10 A- 11    for attachment of leaflets  132  to the frame  106 , mutatis mutandis. 
     Additional Examples of the Disclosed Technology 
     In view of the above described implementations of the disclosed subject matter, this application discloses the additional examples enumerated below. It should be noted that one feature of an example in isolation or more than one feature of the example taken in combination and, optionally, in combination with one or more features of one or more further examples are further examples also falling within the disclosure of this application. 
     Example 1. A prosthetic valve comprising: 
     a frame movable between a radially compressed configuration and a radially expanded configuration, wherein the frame comprises a plurality of intersecting struts, and   a leaflet assembly mounted within the frame and comprising a plurality of leaflets configured to regulate flow through the prosthetic valve, wherein each leaflet comprises a rounded cusp end portion defining a cusp edge, a free edge opposite to the cusp edge, and a pair of oppositely-directed tabs separating the cusp edge and the free edge;   wherein each cusp end portion is coupled to at least one strut via at least one primary suture threaded at penetration points therethrough in an in-and-out pattern, and a secondary suture threaded through the primary suture and around at least one section of at least one strut, wherein the secondary suture comprises a plurality of self-tightening constructs, and wherein each self-tightening construct comprises at least one loop configured to constrict under tension around the strut.   

     Example 2. The prosthetic valve of any example herein, particularly example 1, wherein the at least one loop of each self-tightening construct comprises two loops. 
     Example 3. The prosthetic valve of any example herein, particularly any one of examples 1 or 2, wherein each self-tightening construct further comprises a u-shaped section partially extending between the at least one loop and the strut. 
     Example 4. The prosthetic valve of any example herein, particularly any one of examples 1 to 3, wherein the leaflet comprises a leaflet inner surface and a leaflet outer surface, and wherein the primary suture comprises a plurality of inner stitch portions disposed along the leaflet inner surface, and plurality of outer stitch portions disposed along the leaflet outer surface, each inner stitch portion and each outer stitch portion defined between respective penetration points. 
     Example 5. The prosthetic valve of any example herein, particularly example 4, wherein the self-tightening construct is defined between two penetrations points that define at least one outer stitch portion there-between. 
     Example 6. The prosthetic valve of any example herein, particularly any one of examples 4 or 5, wherein the secondary suture further comprises a plurality of suture pull portions extending over the leaflet inner surface. 
     Example 7. The prosthetic valve of any example herein, particularly example 6, wherein at least one of the suture pull portions spans over more than one inner or outer stitch portions. 
     Example 8. The prosthetic valve of any example herein, particularly any one of examples 6 or 7, wherein the suture pull portions are pressed against portions of the at least one primary suture. 
     Example 9. The prosthetic valve of any example herein, particularly any one of examples 1 to 8, wherein the diameter of the secondary suture is smaller than the diameter of the primary suture. 
     Example 10. The prosthetic valve of any example herein, particularly example 9, wherein a secondary to primary sutures diameter ratio is equal to or smaller than 0.8. 
     Example 11. The prosthetic valve of any example herein, particularly example 9, wherein a secondary to primary sutures diameter ratio is equal to or smaller than 0.5. 
     Example 12. The prosthetic valve of any example herein, particularly example 9, wherein a secondary to primary sutures diameter ratio is equal to or smaller than 0.3. 
     Example 13. The prosthetic valve of any example herein, particularly any one of examples 1 to 12, wherein the cusp end portion of each leaflet comprises a series of pre-formed apertures. 
     Example 14. The prosthetic valve of any example herein, particularly example 13, wherein the apertures are dimensioned to accept the at least one primary suture, thereby serving as the penetration points. 
     Example 15. The prosthetic valve of any example herein, particularly any one of examples 13 or 14, wherein the apertures are equally spaced from each other. 
     Example 16. The prosthetic valve of any example herein, particularly any one of examples 13 to 15, wherein the diameter of the apertures is equal to or smaller than the diameter of the primary suture. 
     Example 17. The prosthetic valve of any example herein, particularly any one of examples 13 to 15, wherein the diameter of the apertures is equal to or smaller than the combined diameters of the primary suture and the secondary suture. 
     Example 18. The prosthetic valve of any example herein, particularly any one of examples 1 to 17, wherein the secondary suture is threaded through all successive penetration points. 
     Example 19. The prosthetic valve of any example herein, particularly any one of examples 1 to 18, wherein the at least one primary suture comprises two primary sutures, which are inversely threaded in an in-and-out pattern, through the same penetration points. 
     Example 20. The prosthetic valve of any example herein, particularly any one of examples 13 to 15, wherein the diameter of the apertures is equal to or smaller than the diameter of the two primary sutures. 
     Example 21. The prosthetic valve of any example herein, particularly example 20, wherein the diameter of the apertures is equal to or smaller than the combined diameters of the two primary sutures and the secondary suture. 
     Example 22. The prosthetic valve of any example herein, particularly any one of examples 1 to 21, wherein the at least one primary suture tracks the curvature of the at least one cusp edge. 
     Example 23. The prosthetic valve of any example herein, particularly any one of examples 1 to 22, wherein the primary suture comprises a multi-filament suture. 
     Example 24. The prosthetic valve of any example herein, particularly any one of examples 1 to 23, wherein the secondary suture comprises an ultra-high-molecular-weight polyethylene. 
     Example 25. The prosthetic valve of any example herein, particularly any one of examples 1 to 24, wherein the prosthetic valve is devoid of fabric strips and/or cloth between the cusp end portions of the leaflets and the struts they are attached to. 
     Example 26. A method of assembling a prosthetic valve, the method comprising steps of:
     threading a primary suture in an in-and-out pattern through a cusp end portion of a leaflet;   approximating the cusp end portion with the primary suture threaded there-through to at least one strut of a frame of the prosthetic valve; and   stitching a secondary suture through the primary suture and around the at least one strut, in a manner that forms a plurality of self-tightening constructs, wherein each self-tightening construct is formed to comprise at least one loop configured to constrict under tension around the strut.   

     Example 27. The method of any example herein, particularly example 26, wherein the step of stitching a secondary suture includes threading the secondary suture radially outward through the primary suture at a penetration point, thereby forming the at least one loop around the at least one strut. 
     Example 28. The method of any example herein, particularly example 27, wherein the step of stitching a secondary suture comprises looping the secondary suture again around the at least one strut after forming a first loop, thereby forming two loops for each self-tightening construct. 
     Example 29. The method of any example herein, particularly any one of examples 26 to 28, wherein the step of stitching a secondary suture comprises passing the secondary suture under the at least one loop, between the at least one loop and the at least one strut, to form a u-shaped section. 
     Example 30. The prosthetic valve of any example herein, particularly any one of examples 26 to 29, further comprising a step of extending the secondary suture over a leaflet inner surface, and then threading the secondary suture once again through the primary suture in a radially-outward direction, thereby forming at least one suture pull portion extending over the leaflet inner surface. 
     Example 31. The prosthetic valve of any example herein, particularly any one of examples 26 to 30, wherein the cusp end portion of each leaflet comprises a series of pre-formed apertures, and wherein the step of threading a primary suture comprises threading the primary suture in an in-and-out pattern through the series of pre-formed apertures. 
     Example 32. A prosthetic valve comprising:
     a frame movable between a radially compressed configuration and a radially expanded configuration, wherein the frame comprises a plurality of strut sections intersecting at junctions, and   a leaflet assembly mounted within the frame and comprising a plurality of leaflets configured to regulate flow through the prosthetic valve, wherein each leaflet comprises a rounded cusp end portion defining a cusp edge, a free edge opposite to the cusp edge, and a pair of oppositely-directed tabs separating the cusp edge and the free edge;   wherein each junction is defined between: two opposite axial sides comprising a junction proximal side and a junction distal side; two opposite radial sides comprising a junction inner side and a junction outer side; and two opposite lateral sides comprising a junction first lateral side and a junction second lateral side;   wherein each cusp end portion is coupled to at least one strut section via at least one primary suture threaded at penetration points therethrough in an in-and-out pattern, and a secondary suture threaded through the primary suture and wrapped around the strut section in a series of whip stitches spaced from each other along the length of the strut section;   wherein the cusp end portion is further coupled to at least one junction at an end of the strut section via a junction lock-knot formed by the second suture, and wherein the junction lock-knot is configured to maintain tension on the plurality of the whip stitches wrapped around the corresponding strut section leading to the junction first lateral section.   

     Example 33. The prosthetic valve of any example herein, particularly example 32, wherein each junction lock-knot comprises:
     a transition section extending over one axial side of the junction, in a direction from the junction first lateral side to the junction second lateral side;   a first loop extending from the transition section and around a strut section extending from the junction second lateral side; and   a second loop extending from the first loop, between the transition section and the junction, and folded over itself to extend through the first loop.   

     Example 34. The prosthetic valve of any example herein, particularly example 33, wherein the transition section extends in a diagonal direction from one radial side of the junction toward the opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     Example 35. The prosthetic valve of any example herein, particularly any one of examples 33 or 34, wherein both the first loop and the second loop are tightly tensioned around the junction. 
     Example 36. The prosthetic valve of any example herein, particularly any one of examples 32 to 35, wherein each plurality of whip stitches wrapped around a single strut section are angled whip stitches, oriented in the same direction along the length of the corresponding strut section. 
     Example 37. The prosthetic valve of any example herein, particularly example 36, wherein the cusp end portion is sutured to at least two strut sections extending from both lateral sides of a selected junction, via a plurality of whip stitches wrapped around each of the respective strut sections and a junction lock-knot around the junction positioned there-between, and wherein the plurality of whip stitches around one of the strut sections are angled in a direction opposite to that of the plurality of the whip stitches wrapped around the other strut section. 
     Example 38. The prosthetic valve of any example herein, particularly any one of examples 32 to 37, wherein the diameter of the secondary suture is smaller than the diameter of the primary suture. 
     Example 39. The prosthetic valve of any example herein, particularly example 38, wherein a secondary to primary sutures diameter ratio is equal to or smaller than 0.8. 
     Example 40. The prosthetic valve of any example herein, particularly example 38, wherein a secondary to primary sutures diameter ratio is equal to or smaller than 0.5. 
     Example 41. The prosthetic valve of any example herein, particularly example 38, wherein a secondary to primary sutures diameter ratio is equal to or smaller than 0.3. 
     Example 42. The prosthetic valve of any example herein, particularly any one of examples 32 to 41, wherein the cusp end portion of each leaflet comprises a series of pre-formed apertures. 
     Example 43. The prosthetic valve of any example herein, particularly example 42, wherein the apertures are dimensioned to accept the at least one primary suture, thereby serving as the penetration points. 
     Example 44. The prosthetic valve of any example herein, particularly any one of examples 42 or 43, wherein the apertures are equally spaced from each other. 
     Example 45. The prosthetic valve of any example herein, particularly any one of examples 42 to 44, wherein the diameter of the apertures is equal to or smaller than the diameter of the primary suture. 
     Example 46. The prosthetic valve of any example herein, particularly any one of examples 42 to 44, wherein the diameter of the apertures is equal to or smaller than the combined diameters of the primary suture and the secondary suture. 
     Example 47. The prosthetic valve of any example herein, particularly any one of examples 32 to 46, wherein the at least one primary suture comprises two primary sutures, which are inversely threaded in an in-and-out pattern, through the same penetration points. 
     Example 48. The prosthetic valve of any example herein, particularly any one of examples 42 to 44, wherein the diameter of the apertures is equal to or smaller than the diameter of the two primary sutures. 
     Example 49. The prosthetic valve of any example herein, particularly example 48, wherein the diameter of the apertures is equal to or smaller than the combined diameters of the two primary sutures and the secondary suture. 
     Example 50. The prosthetic valve of any example herein, particularly any one of examples 32 to 49, wherein the at least one primary suture tracks the curvature of the at least one cusp edge. 
     Example 51. The prosthetic valve of any example herein, particularly any one of examples 32 to 50, wherein the primary suture comprises a multi-filament suture. 
     Example 52. The prosthetic valve of any example herein, particularly any one of examples 32 to 51, wherein the secondary suture comprises an ultra-high-molecular-weight polyethylene. 
     Example 53. The prosthetic valve of any example herein, particularly any one of examples 32 to 52, wherein the prosthetic valve is devoid of fabric strips and/or cloth between the cusp end portions of the leaflets and the strut sections and junctions they are attached to. 
     Example 54. A method of assembling a prosthetic valve, the method comprising steps of:
     threading a primary suture in an in-and-out pattern through a cusp end portion of a leaflet;   approximating the cusp end portion with the primary suture threaded there-through to at least one strut section of a frame of the prosthetic valve;   stitching a secondary suture through the primary suture and around the at least one strut section, in a manner that forms a plurality of whip stitches wrapped around the strut section up to a final whip stitch; and   forming a junction lock-knot extending from the final whip stitch around a junction at a respective end of the corresponding strut section, wherein the junction lock-knot is configured to maintain tension on the plurality of whip stitches wrapped around the strut section leading to the junction first lateral section.   

     Example 55. The method of any example herein, particularly example 54, wherein the step of forming a junction lock-knot comprises extending the secondary suture from the final whip stitch disposed at a first lateral side of the junction, over one axial side of the junction, in a direction toward a second lateral side of the junction, thereby forming a transition section of the junction lock-knot. 
     Example 56. The method of any example herein, particularly example 55, wherein the step of forming a junction lock-knot further comprises extending the secondary suture from the transition section around a strut section extending from the second lateral side of the junction, thereby forming a first loop of the junction lock-knot. 
     Example 57. The method of any example herein, particularly example 56, wherein the step of forming a junction lock-knot further comprises extending the secondary suture from the first loop, between the transition section and the junction, folding the secondary suture back over itself and passing it through the first loop, thereby forming a second loop of the junction lock-knot. 
     Example 58. The method of any example herein, particularly example 57, wherein the step of forming a junction lock-knot further comprises forcibly pulling the tail of the second loop to tighten both the first loop and the second loop around the junction. 
     Example 59. The method of any example herein, particularly any one of examples 55 to 58, wherein forming the transition section comprises extending the secondary suture in a diagonal direction from one radial side of the junction toward an opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     Example 60. The method of any example herein, particularly any one of examples 54 to 59, wherein forming the plurality of whip stitches around any single strut section comprises forming a plurality of angled whip stitches oriented in the same direction around the length of the corresponding strut section. 
     Example 61. The method of any example herein, particularly example 60, wherein stitching the secondary suture around the at least one strut section comprises stitching around at least two strut sections separated from each other by a mutual junction, such that all whip stitches around one of the strut sections are formed as angled whip stitches oriented in one direction, while all whip stitches around the other strut section are formed as angled whip stitched oriented in a second direction, opposite to the first direction. 
     Example 62. The method of any example herein, particularly any one of examples 54 to 61, wherein the cusp end portion of each leaflet comprises a series of pre-formed apertures, and wherein the step of threading a primary suture comprises threading the primary suture in an in-and-out pattern through the series of pre-formed apertures. 
     Example 63. A prosthetic valve comprising:
     a frame movable between a radially compressed configuration and a radially expanded configuration, wherein the frame comprises a plurality of strut sections intersecting at junctions, and   a leaflet assembly mounted within the frame and comprising a plurality of leaflets configured to regulate flow through the prosthetic valve, wherein each leaflet comprises a rounded cusp end portion defining a cusp edge, a free edge opposite to the cusp edge, and a pair of oppositely-directed tabs separating the cusp edge and the free edge;   wherein each cusp end portion is coupled to at least one strut section via at least one primary suture threaded therethrough in an in-and-out pattern, and a secondary suture forming a series of non-penetrating whip stitches spaced from each other along the length of the strut section, each non-penetrating whip stitch comprising a strut-wrapping section looped around the strut section and a primary-suture-wrapping section extending therefrom, looped around the primary suture and passing between the primary suture and the leaflet.   

     Example 64. The prosthetic valve of any example herein, particularly example 63, wherein the primary suture defines a series of running stitch portions, and wherein each primary-suture-wrapping section is looped around a corresponding running stitch portion and extends between the running stitch portion and the rounded cusp end portion. 
     Example 65. The prosthetic valve of any example herein, particularly any one of examples 63 or 64, wherein the secondary suture does not penetrate through the leaflet. 
     Example 66. The prosthetic valve of any example herein, particularly any one of examples 63 to 65, wherein the secondary suture does not penetrate through the primary suture. 
     Example 67. The prosthetic valve of any example herein, particularly any one of examples 63 to 66, wherein each junction is defined between: two opposite axial sides comprising a junction proximal side and a junction distal side; two opposite radial sides comprising a junction inner side and a junction outer side; and two opposite lateral sides comprising a junction first lateral side and a junction second lateral side; wherein the cusp end portion is further coupled to at least one junction at an end of the strut section via a junction lock-knot formed by the second suture, and wherein the junction lock-knot is configured to maintain tension on the plurality of the non-penetrating whip stitches wrapped around the corresponding strut section leading to the junction first lateral section. 
     Example 68. The prosthetic valve of any example herein, particularly example 67, wherein each junction lock-knot comprises:
     a transition section extending over one axial side of the junction, in a direction from the junction first lateral side to the junction second lateral side;   a first loop extending from the transition section and around a strut section extending from the junction second lateral side; and   a second loop extending from the first loop, between the transition section and the junction, and folded over itself to extend through the first loop.   

     Example 69. The prosthetic valve of any example herein, particularly example 68, wherein the transition section extends in a diagonal direction from one radial side of the junction toward the opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     Example 70. The prosthetic valve of any example herein, particularly any one of examples 68 or 69, wherein both the first loop and the second loop are tightly tensioned around the junction. 
     Example 71. The prosthetic valve of any example herein, particularly any one of examples 67 to 70, wherein each plurality of non-penetrating whip stitches wrapped around a single strut section are angled non-penetrating whip stitches, oriented in the same direction along the length of the corresponding strut section. 
     Example 72. The prosthetic valve of any example herein, particularly example 71, wherein the cusp end portion is sutured to at least two strut sections extending from both lateral sides of a selected junction, via a plurality of non-penetrating whip stitches wrapped around each of the respective strut sections and a junction lock-knot around the junction positioned there-between, and wherein the plurality of non-penetrating whip stitches around one of the strut sections are angled in a direction opposite to that of the plurality of the non-penetrating whip stitches wrapped around the other strut section. 
     Example 73. The prosthetic valve of any example herein, particularly any one of examples 63 to 72, wherein the at least one primary suture comprises two primary sutures, which are inversely threaded in an in-and-out pattern. 
     Example 74. The prosthetic valve of any example herein, particularly any one of examples 63 to 73, wherein the at least one primary suture tracks the curvature of the at least one cusp edge. 
     Example 75. The prosthetic valve of any example herein, particularly any one of examples 63 to 74, wherein the primary suture comprises a multi-filament suture. 
     Example 76. The prosthetic valve of any example herein, particularly any one of examples 63 to 75, wherein the secondary suture comprises an ultra-high-molecular-weight polyethylene. 
     Example 77. The prosthetic valve of any example herein, particularly any one of examples 63 to 76, wherein the prosthetic valve is devoid of fabric strips and/or cloth between the cusp end portions of the leaflets and the strut sections they are attached to. 
     Example 78. A method of assembling a prosthetic valve, the method comprising steps of:
     threading a primary suture in an in-and-out pattern through a cusp end portion of a leaflet;   approximating the cusp end portion with the primary suture threaded there-through to at least one strut section of a frame of the prosthetic valve; and   looping a secondary suture around the at least one strut section and around the primary suture, in a manner that forms a plurality of non-penetrating whip stitches wrapped around the strut section up to a final non-penetrating whip stitch, each non-penetrating whip stitch comprising a strut-wrapping section looped around the strut section and a primary-suture-wrapping section extending therefrom, passing between the primary suture and the leaflet and looped around the primary suture.   

     Example 79. The method of any example herein, particularly example 78, wherein forming each non-penetration whip stitch comprises forming the strut-wrapping section by: extending the secondary suture across one radial side of the strut section, folding it over an axial side of the strut section, and extending it backward across the opposite radial side of the strut section. 
     Example 80. The method of any example herein, particularly example 79, wherein forming each non-penetration whip stitch further comprises forming the primary-suture-wrapping section by: passing the secondary suture between a running stitch portion of the primary suture and the cusp end portion of the leaflet, and folding it over the running stitch portion. 
     Example 81. The method of any example herein, particularly example 79, wherein forming each non-penetration whip stitch further comprises forming the primary-suture-wrapping section by: passing the secondary suture over a running stitch portion of the primary suture, and looping it back over the running stitch portion and between the running stitch portion and the cusp end portion of the leaflet. 
     Example 82. The method of any example herein, particularly any one of examples 80 or 81, wherein the running stitch portion is an outer stitch portion of the primary suture. 
     Example 83. The method of any example herein, particularly any one of examples 78 to 82, further comprising a step of forming a junction lock-knot extending from the final non-penetrating whip stitch around a junction at a respective end of the corresponding strut section, wherein the junction lock-knot is configured to maintain tension on the plurality of non-penetrating whip stitches wrapped around the strut section leading to the junction first lateral section. 
     Example 84. The method of any example herein, particularly example 83, wherein the step of forming a junction lock-knot comprises extending the secondary suture from the final non-penetrating whip stitch disposed at a first lateral side of the junction, over one axial side of the junction, in a direction toward a second lateral side of the junction, thereby forming a transition section of the junction lock-knot. 
     Example 85. The method of any example herein, particularly example 84, wherein the step of forming a junction lock-knot further comprises extending the secondary suture from the transition section around a strut section extending from the second lateral side of the junction, thereby forming a first loop of the junction lock-knot. 
     Example 86. The method of any example herein, particularly example 85, wherein the step of forming a junction lock-knot further comprises extending the secondary suture from the first loop, between the transition section and the junction, folding the secondary suture back over itself and passing it through the first loop, thereby forming a second loop of the junction lock-knot. 
     Example 87. The method of any example herein, particularly example 86, wherein the step of forming a junction lock-knot further comprises forcibly pulling the tail of the second loop to tighten both the first loop and the second loop around the junction. 
     Example 88. The method of any example herein, particularly any one of examples 84 to 87, wherein forming the transition section comprises extending the secondary suture in a diagonal direction from one radial side of the junction toward an opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     Example 89. The method of any example herein, particularly any one of examples 83 to 88, wherein forming the plurality of whip stitches around any single strut section comprises forming a plurality of angled whip stitches oriented in the same direction around the length of the corresponding strut section. 
     Example 90. The method of any example herein, particularly example 89, wherein forming the plurality of whip stitches around the at least one strut section comprises forming a plurality of whip stitches around at least two strut sections separated from each other by a mutual junction, such that all whip stitches around one of the strut sections are formed as angled whip stitches oriented in one direction, while all whip stitches around the other strut section are formed as angled whip stitched oriented in a second direction, opposite to the first direction. 
     Example 91. A prosthetic valve comprising:
     a frame movable between a radially compressed configuration and a radially expanded configuration, wherein the frame comprises a plurality of strut sections intersecting at junctions;   a leaflet assembly mounted within the frame and comprising a plurality of leaflets configured to regulate flow through the prosthetic valve; and   a skirt disposed around the frame, the skirt comprising a skirt proximal end and a skirt distal end;   wherein each junction is defined between: two opposite axial sides comprising a junction proximal side and a junction distal side; two opposite radial sides comprising a junction inner side and a junction outer side; and two opposite lateral sides comprising a junction first lateral side and a junction second lateral side;   wherein the skirt proximal end is coupled to at least one strut section via at least one primary suture threaded at penetration points therethrough in an in-and-out pattern, and a secondary suture threaded through the primary suture and wrapped around the strut section in a series of whip stitches spaced from each other along the length of the strut section;   wherein the skirt proximal end is further coupled to at least one junction at an end of the strut section via a junction lock-knot formed by the second suture, and wherein the junction lock-knot is configured to maintain tension on the plurality of the whip stitches wrapped around the corresponding strut section leading to the junction first lateral section.   

     Example 92. The prosthetic valve of any example herein, particularly example 91, wherein the skirt proximal end follows a zig-zag pattern. 
     Example 93. The prosthetic valve of any example herein, particularly example 92, wherein the at least one primary suture tracks the zig-zag pattern of the skirt proximal end. 
     Example 94. The prosthetic valve of any example herein, particularly any one of examples 91 to 93, wherein each junction lock-knot comprises:
     a transition section extending over one axial side of the junction, in a direction from the junction first lateral side to the junction second lateral side;   a first loop extending from the transition section and around a strut section extending from the junction second lateral side; and   a second loop extending from the first loop, between the transition section and the junction, and folded over itself to extend through the first loop.   

     Example 95. The prosthetic valve of any example herein, particularly example 94, wherein the transition section extends in a diagonal direction from one radial side of the junction toward the opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     Example 96. The prosthetic valve of any example herein, particularly any one of examples 94 or 95, wherein both the first loop and the second loop are tightly tensioned around the junction. 
     Example 97. The prosthetic valve of any example herein, particularly any one of examples 91 to 96, wherein each plurality of whip stitches wrapped around a single strut section are angled whip stitches, oriented in the same direction along the length of the corresponding strut section. 
     Example 98. The prosthetic valve of any example herein, particularly example 97, wherein the skirt proximal end is sutured to at least two strut sections extending from both lateral sides of a selected junction, via a plurality of whip stitches wrapped around each of the respective strut sections and a junction lock-knot around the junction positioned there-between, and wherein the plurality of whip stitches around one of the strut sections are angled in a direction opposite to that of the plurality of the whip stitches wrapped around the other strut section. 
     Example 99. The prosthetic valve of any example herein, particularly any one of examples 91 to 98, wherein the skirt distal end is coupled to at least one strut section at an inflow end portion of the valve via at least one additional primary suture threaded at penetration points therethrough in an in-and-out pattern, and an additional secondary suture threaded through the primary suture and wrapped around the strut section at the inflow end portion in a series of whip stitches spaced from each other along the length of the strut section, and wherein the skirt distal end is further coupled to at least one junction at an end of the strut section at the inflow end portion via an additional junction lock-knot. 
     Example 100. The prosthetic valve of any example herein, particularly example 99, wherein the additional primary suture tracks the shape of the strut sections disposed around the inflow end portion. 
     Example 101. The prosthetic valve of any example herein, particularly any one of examples 91 to 100, wherein the diameter of the secondary suture is smaller than the diameter of the primary suture. 
     Example 102. The prosthetic valve of any example herein, particularly example 101, wherein a secondary to primary sutures diameter ratio is equal to or smaller than 0.8. 
     Example 103. The prosthetic valve of any example herein, particularly example 101, wherein a secondary to primary sutures diameter ratio is equal to or smaller than 0.5. 
     Example 104. The prosthetic valve of any example herein, particularly example 101, wherein a secondary to primary sutures diameter ratio is equal to or smaller than 0.3. 
     Example 105. The prosthetic valve of any example herein, particularly any one of examples 91 to 104, wherein the skirt proximal end comprises a series of pre-formed apertures. 
     Example 106. The prosthetic valve of any example herein, particularly example 105, wherein the apertures are dimensioned to accept the at least one primary suture, thereby serving as the penetration points. 
     Example 107. The prosthetic valve of any example herein, particularly any one of examples 105 or 106, wherein the apertures are equally spaced from each other. 
     Example 108. The prosthetic valve of any example herein, particularly any one of examples 105 to 107, wherein the diameter of the apertures is equal to or smaller than the diameter of the primary suture. 
     Example 109. The prosthetic valve of any example herein, particularly any one of examples 105 to 107, wherein the diameter of the apertures is equal to or smaller than the combined diameters of the primary suture and the secondary suture. 
     Example 110. The prosthetic valve of any example herein, particularly any one of examples 91 to 109, wherein the at least one primary suture comprises two primary sutures, which are inversely threaded in an in-and-out pattern, through the same penetration points. 
     Example 111. The prosthetic valve of any example herein, particularly any one of examples 105 to 107, wherein the diameter of the apertures is equal to or smaller than the diameter of the two primary sutures. 
     Example 112. The prosthetic valve of any example herein, particularly example 111, wherein the diameter of the apertures is equal to or smaller than the combined diameters of the two primary sutures and the secondary suture. 
     Example 113. The prosthetic valve of any example herein, particularly any one of examples 91 to 112, wherein the primary suture comprises a multi-filament suture. 
     Example 114. The prosthetic valve of any example herein, particularly any one of examples 91 to 113, wherein the secondary suture comprises an ultra-high-molecular-weight polyethylene. 
     Example 115. The prosthetic valve of any example herein, particularly any one of examples 91 to 114, wherein the skirt is an outer skirt, disposed around an outer surface of the frame. 
     Example 116. A method of assembling a prosthetic valve, the method comprising steps of:
     threading a primary suture in an in-and-out pattern through a skirt proximal end of a skirt;   approximating the skirt proximal end with the primary suture threaded there-through to at least one strut section of a frame of the prosthetic valve;   stitching a secondary suture through the primary suture and around the at least one strut section, in a manner that forms a plurality of whip stitches wrapped around the strut section up to a final whip stitch; and   forming a junction lock-knot extending from the final whip stitch around a junction at a respective end of the corresponding strut section, wherein the junction lock-knot is configured to maintain tension on the plurality of whip stitches wrapped around the strut section leading to the junction first lateral section.   

     Example 117. The method of any example herein, particularly example 116, wherein the step of forming a junction lock-knot comprises extending the secondary suture from the final whip stitch disposed at a first lateral side of the junction, over one axial side of the junction, in a direction toward a second lateral side of the junction, thereby forming a transition section of the junction lock-knot. 
     Example 118. The method of any example herein, particularly example 117, wherein the step of forming a junction lock-knot further comprises extending the secondary suture from the transition section around a strut section extending from the second lateral side of the junction, thereby forming a first loop of the junction lock-knot. 
     Example 119. The method of any example herein, particularly example 118, wherein the step of forming a junction lock-knot further comprises extending the secondary suture from the first loop, between the transition section and the junction, folding the secondary suture back over itself and passing it through the first loop, thereby forming a second loop of the junction lock-knot. 
     Example 120. The method of any example herein, particularly example 119, wherein the step of forming a junction lock-knot further comprises forcibly pulling the tail of the second loop to tighten both the first loop and the second loop around the junction. 
     Example 121. The method of any example herein, particularly any one of examples 117 to 120, wherein forming the transition section comprises extending the secondary suture in a diagonal direction from one radial side of the junction toward an opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     Example 122. The method of any example herein, particularly any one of examples 116 to 121, wherein forming the plurality of whip stitches around any single strut section comprises forming a plurality of angled whip stitches oriented in the same direction around the length of the corresponding strut section. 
     Example 123. The method of any example herein, particularly example 122, wherein stitching the secondary suture around the at least one strut section comprises stitching around at least two strut sections separated from each other by a mutual junction, such that all whip stitches around one of the strut sections are formed as angled whip stitches oriented in one direction, while all whip stitches around the other strut section are formed as angled whip stitched oriented in a second direction, opposite to the first direction. 
     Example 124. The method of any example herein, particularly any one of examples 116 to 123, wherein the skirt proximal end comprises a series of pre-formed apertures, and wherein the step of threading a primary suture comprises threading the primary suture in an in-and-out pattern through the series of pre-formed apertures. 
     Example 125. The method of any example herein, particularly any one of examples 116 to 124, wherein the skirt is an outer skirt, disposed around an outer surface of the frame. 
     Example 126. A prosthetic valve comprising:
     a frame movable between a radially compressed configuration and a radially expanded configuration, wherein the frame comprises a plurality of strut sections intersecting at junctions;   a leaflet assembly mounted within the frame and comprising a plurality of leaflets configured to regulate flow through the prosthetic valve; and   a skirt disposed around the frame, the skirt comprising a skirt proximal end and a skirt distal end,   wherein the skirt proximal end is coupled to at least one strut section via at least one primary suture threaded therethrough in an in-and-out pattern, and a secondary suture forming a series of non-penetrating whip stitches spaced from each other along the length of the strut section, each non-penetrating whip stitch comprising a strut-wrapping section looped around the strut section and a primary-suture-wrapping section extending therefrom, looped around the primary suture and passing between the primary suture and the leaflet.   

     Example 127. The prosthetic valve of any example herein, particularly example 126, wherein the skirt proximal end follows a zig-zag pattern. 
     Example 128. The prosthetic valve of any example herein, particularly example 127, wherein the at least one primary suture tracks the zig-zag pattern of the skirt proximal end. 
     Example 129. The prosthetic valve of any example herein, particularly any one of examples 126 to 128, wherein the primary suture defines a series of running stitch portions, and wherein each primary-suture-wrapping section is looped around a corresponding running stitch portion and extends between the running stitch portion and the skirt proximal end. 
     Example 130. The prosthetic valve of any example herein, particularly any one of examples 126 to 129, wherein the secondary suture does not penetrate through the skirt. 
     Example 131. The prosthetic valve of any example herein, particularly any one of examples 126 to 130, wherein the secondary suture does not penetrate through the primary suture. 
     Example 132. The prosthetic valve of any example herein, particularly any one of examples 126 to 131, wherein each junction is defined between: two opposite axial sides comprising a junction proximal side and a junction distal side; two opposite radial sides comprising a junction inner side and a junction outer side; and two opposite lateral sides comprising a junction first lateral side and a junction second lateral side; wherein the skirt proximal end is further coupled to at least one junction at an end of the strut section via a junction lock-knot formed by the second suture, and wherein the junction lock-knot is configured to maintain tension on the plurality of the non-penetrating whip stitches wrapped around the corresponding strut section leading to the junction first lateral section. 
     Example 133. The prosthetic valve of any example herein, particularly example 132, wherein each junction lock-knot comprises:
     a transition section extending over one axial side of the junction, in a direction from the junction first lateral side to the junction second lateral side;   a first loop extending from the transition section and around a strut section extending from the junction second lateral side; and   a second loop extending from the first loop, between the transition section and the junction, and folded over itself to extend through the first loop.   

     Example 134. The prosthetic valve of any example herein, particularly example 133, wherein the transition section extends in a diagonal direction from one radial side of the junction toward the opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     Example 135. The prosthetic valve of any example herein, particularly any one of examples 133 or 134, wherein both the first loop and the second loop are tightly tensioned around the junction. 
     Example 136. The prosthetic valve of any example herein, particularly any one of examples 132 to 135, wherein each plurality of non-penetrating whip stitches wrapped around a single strut section are angled non-penetrating whip stitches, oriented in the same direction along the length of the corresponding strut section. 
     Example 137. The prosthetic valve of any example herein, particularly example 136, wherein the skirt proximal end is sutured to at least two strut sections extending from both lateral sides of a selected junction, via a plurality of non-penetrating whip stitches wrapped around each of the respective strut sections and a junction lock-knot around the junction positioned there-between, and wherein the plurality of non-penetrating whip stitches around one of the strut sections are angled in a direction opposite to that of the plurality of the non-penetrating whip stitches wrapped around the other strut section. 
     Example 138. The prosthetic valve of any example herein, particularly any one of examples 126 to 137, wherein the skirt distal end is coupled to at least one strut section at an inflow end portion of the valve via at least one additional primary suture threaded at penetration points therethrough in an in-and-out pattern, and an additional secondary suture threaded through the primary suture and wrapped around the strut section at the inflow end portion in a series of whip stitches spaced from each other along the length of the strut section, and wherein the skirt distal end is further coupled to at least one junction at an end of the strut section at the inflow end portion via an additional junction lock-knot. 
     Example 139. The prosthetic valve of any example herein, particularly example 138, wherein the additional primary suture tracks the shape of the strut sections disposed around the inflow end portion. 
     Example 140. The prosthetic valve of any example herein, particularly any one of examples 126 to 139, wherein the primary suture comprises a multi-filament suture. 
     Example 141. The prosthetic valve of any example herein, particularly any one of examples 126 to 140, wherein the secondary suture comprises an ultra-high-molecular-weight polyethylene. 
     Example 142. The prosthetic valve of any example herein, particularly any one of examples 126 to 141, wherein the skirt is an outer skirt, disposed around an outer surface of the frame. 
     Example 143. A method of assembling a prosthetic valve, the method comprising steps of:
     threading a primary suture in an in-and-out pattern through a skirt proximal end of a skirt;   approximating the skirt proximal end with the primary suture threaded there-through to at least one strut section of a frame of the prosthetic valve; and   looping a secondary suture around the at least one strut section and around the primary suture, in a manner that forms a plurality of non-penetrating whip stitches wrapped around the strut section up to a final non-penetrating whip stitch, each non-penetrating whip stitch comprising a strut-wrapping section looped around the strut section and a primary-suture-wrapping section extending therefrom, passing between the primary suture and the skirt proximal end around the primary suture.   

     Example 144. The method of any example herein, particularly example 143, wherein forming each non-penetration whip stitch comprises forming the strut-wrapping section by: extending the secondary suture across one radial side of the strut section, folding it over an axial side of the strut section, and extending it backward across the opposite radial side of the strut section. 
     Example 145. The method of any example herein, particularly example 144, wherein forming each non-penetration whip stitch further comprises forming the primary-suture-wrapping section by: passing the secondary suture between a running stitch portion of the primary suture and the skirt proximal end, and folding it over the running stitch portion. 
     Example 146. The method of any example herein, particularly example 144, wherein forming each non-penetration whip stitch further comprises forming the primary-suture-wrapping section by: passing the secondary suture over a running stitch portion of the primary suture, and looping it back over the running stitch portion and between the running stitch portion and the skirt proximal end. 
     Example 147. The method of any example herein, particularly any one of examples 145 or 146, wherein the skirt is an outer skirt and the running stitch portion is an inner stitch portion of the primary suture. 
     Example 148. The method of any example herein, particularly any one of examples 143 to 147, further comprising a step of forming a junction lock-knot extending from the final non-penetrating whip stitch around a junction at a respective end of the corresponding strut section, wherein the junction lock-knot is configured to maintain tension on the plurality of non-penetrating whip stitches wrapped around the strut section leading to the junction first lateral section. 
     Example 149. The method of any example herein, particularly example 148, wherein the step of forming a junction lock-knot comprises extending the secondary suture from the final non-penetrating whip stitch disposed at a first lateral side of the junction, over one axial side of the junction, in a direction toward a second lateral side of the junction, thereby forming a transition section of the junction lock-knot. 
     Example 150. The method of any example herein, particularly example 149, wherein the step of forming a junction lock-knot further comprises extending the secondary suture from the transition section around a strut section extending from the second lateral side of the junction, thereby forming a first loop of the junction lock-knot. 
     Example 151. The method of any example herein, particularly example 150, wherein the step of forming a junction lock-knot further comprises extending the secondary suture from the first loop, between the transition section and the junction, folding the secondary suture back over itself and passing it through the first loop, thereby forming a second loop of the junction lock-knot. 
     Example 152. The method of any example herein, particularly example 151, wherein the step of forming a junction lock-knot further comprises forcibly pulling the tail of the second loop to tighten both the first loop and the second loop around the junction. 
     Example 153. The method of any example herein, particularly any one of examples 149 to 152, wherein forming the transition section comprises extending the secondary suture in a diagonal direction from one radial side of the junction toward an opposite radial side of the junction, as well as from one lateral side of the junction to the opposite lateral side of the junction. 
     Example 154. The method of any example herein, particularly any one of examples 148 to 153, wherein forming the plurality of whip stitches around any single strut section comprises forming a plurality of angled whip stitches oriented in the same direction around the length of the corresponding strut section. 
     Example 155. The method of any example herein, particularly example 154, wherein forming the plurality of whip stitches around the at least one strut section comprises forming a plurality of whip stitches around at least two strut sections separated from each other by a mutual junction, such that all whip stitches around one of the strut sections are formed as angled whip stitches oriented in one direction, while all whip stitches around the other strut section are formed as angled whip stitched oriented in a second direction, opposite to the first direction. 
     It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. No feature described in the context of an embodiment is to be considered an essential feature of that embodiment, unless explicitly specified as such. 
     In view of the many possible embodiments to which the principles of the disclosure may be applied, it should be recognized that the illustrated embodiments are only preferred examples and should not be taken as limiting the scope. Rather, the scope is defined by the following claims. We therefore claim all that comes within the scope and spirit of these claims.