Patent Publication Number: US-2023144613-A1

Title: Delivery systems with telescoping capsules for deploying prosthetic heart valve devices and associated methods

Description:
This application is a continuation of U.S. patent application Ser. No. 16/870,012, filed May 8, 2020, which is a continuation of U.S. patent application Ser. No. 15/611,823, filed on Jun. 2, 2017, the entire contents of both which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present technology relates generally to systems for delivering prosthetic heart valve devices. In particular, several embodiments of the present technology are related to delivery systems with telescoping capsules for percutaneously delivering prosthetic heart valve devices and associated methods. 
     BACKGROUND 
     Heart valves can be affected by several conditions. For example, mitral valves can be affected by mitral valve regurgitation, mitral valve prolapse and mitral valve stenosis. Mitral valve regurgitation is abnormal leaking of blood from the left ventricle into the left atrium caused by a disorder of the heart in which the leaflets of the mitral valve fail to coapt into apposition at peak contraction pressures. The mitral valve leaflets may not coapt sufficiently because heart diseases often cause dilation of the heart muscle, which in turn enlarges the native mitral valve annulus to the extent that the leaflets do not coapt during systole. Abnormal backflow can also occur when the papillary muscles are functionally compromised due to ischemia or other conditions. More specifically, as the left ventricle contracts during systole, the affected papillary muscles do not contract sufficiently to effect proper closure of the leaflets. 
     Mitral valve prolapse is a condition when the mitral leaflets bulge abnormally up in to the left atrium. This can cause irregular behavior of the mitral valve and lead to mitral valve regurgitation. The leaflets may prolapse and fail to coapt because the tendons connecting the papillary muscles to the inferior side of the mitral valve leaflets (chordae tendineae) may tear or stretch. Mitral valve stenosis is a narrowing of the mitral valve orifice that impedes filling of the left ventricle in diastole. 
     Mitral valve regurgitation is often treated using diuretics and/or vasodilators to reduce the amount of blood flowing back into the left atrium. Surgical approaches (open and intravascular) for either the repair or replacement of the valve have also been used to treat mitral valve regurgitation. For example, typical repair techniques involve cinching or resecting portions of the dilated annulus. Cinching, for example, includes implanting annular or peri-annular rings that are generally secured to the annulus or surrounding tissue. Other repair procedures suture or clip the valve leaflets into partial apposition with one another. 
     Alternatively, more invasive procedures replace the entire valve itself by implanting mechanical valves or biological tissue into the heart in place of the native mitral valve. These invasive procedures conventionally require large open thoracotomies and are thus very painful, have significant morbidity, and require long recovery periods. Moreover, with many repair and replacement procedures, the durability of the devices or improper sizing of annuloplasty rings or replacement valves may cause additional problems for the patient. Repair procedures also require a highly skilled cardiac surgeon because poorly or inaccurately placed sutures may affect the success of procedures. 
     Less invasive approaches to aortic valve replacement have been implemented in recent years. Examples of pre-assembled, percutaneous prosthetic valves include, e.g., the CoreValve Revalving® System from Medtronic/Corevalve Inc. (Irvine, Calif., USA) and the Edwards-Sapien® Valve from Edwards Lifesciences (Irvine, Calif., USA). Both valve systems include an expandable frame and a tri-leaflet bioprosthetic valve attached to the expandable frame. The aortic valve is substantially symmetric, circular, and has a muscular annulus. The expandable frames in aortic applications have a symmetric, circular shape at the aortic valve annulus to match the native anatomy, but also because tri-leaflet prosthetic valves require circular symmetry for proper coaptation of the prosthetic leaflets. Thus, aortic valve anatomy lends itself to an expandable frame housing a replacement valve since the aortic valve anatomy is substantially uniform, symmetric, and fairly muscular. Other heart valve anatomies, however, are not uniform, symmetric or sufficiently muscular, and thus transvascular aortic valve replacement devises may not be well suited for other types of heart valves. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on illustrating clearly the principles of the present disclosure. Furthermore, components can be shown as transparent in certain views for clarity of illustration only and not to indicate that the illustrated component is necessarily transparent. The headings provided herein are for convenience only. 
         FIG.  1    is a schematic, cross-sectional illustration of the heart showing an antegrade approach to the native mitral valve from the venous vasculature in accordance with various embodiments of the present technology. 
         FIG.  2    is a schematic, cross-sectional illustration of the heart showing access through the inter-atrial septum (IAS) maintained by the placement of a guide catheter over a guidewire in accordance with various embodiments of the present technology. 
         FIGS.  3  and  4    are schematic, cross-sectional illustrations of the heart showing retrograde approaches to the native mitral valve through the aortic valve and arterial vasculature in accordance with various embodiments of the present technology. 
         FIG.  5    is a schematic, cross-sectional illustration of the heart showing an approach to the native mitral valve using a trans-apical puncture in accordance with various embodiments of the present technology. 
         FIG.  6    is an isometric view of a delivery system for a prosthetic heart valve device configured in accordance with an embodiment of the present technology. 
         FIG.  7 A  is an enlarged side isometric view of a distal portion of the delivery system of  FIG.  6    configured in accordance with embodiments of the present technology. 
         FIG.  7 B  is an exploded view of a delivery capsule of the delivery system of  FIG.  7 A . 
         FIGS.  8 A- 8 D  are a series of illustrations showing a distal portion of the delivery system of  FIGS.  6 - 7 B  deploying and resheathing a prosthetic heart valve device in accordance with embodiments of the present technology. 
         FIG.  9 A  is a side isometric view of a distal portion of a delivery system configured in accordance with embodiments of the present technology. 
         FIG.  9 B  is a side isometric view of a distal portion of a delivery system configured in accordance with embodiments of the present technology. 
         FIG.  10 A  is a partial cut-away isometric view of a distal portion of a delivery system configured in accordance with a further embodiment of the present technology. 
         FIG.  10 B  is a cross-sectional view of the distal portion of the delivery system of  FIG.  10 A . 
         FIGS.  10 C and  10 D  are isometric views of inner housing configurations for use with the delivery system of  FIGS.  10 A and  10 B . 
         FIG.  11 A  is an isometric view of a distal portion of a delivery system configured in accordance with yet another embodiment of the present technology. 
         FIG.  11 B  is a cross-sectional view of the distal portion of the delivery system of  FIG.  11 B . 
         FIG.  12 A  is an isometric view of a distal portion of a delivery system configured in accordance with a still further embodiment of the present technology. 
         FIG.  12 B  is a cross-sectional view of the distal portion of the delivery system of  FIG.  12 B . 
         FIG.  13 A  is a cross-sectional side view and  FIG.  13 B  is a top view schematically illustrating a prosthetic heart valve device in accordance with an embodiment of the present technology. 
         FIGS.  14 A and  14 B  are cross-sectional side views schematically illustrating aspects of delivering a prosthetic heart valve device in accordance with an embodiment of the present technology. 
         FIG.  15    is a top isometric view of a prosthetic heart valve device in accordance with an embodiment of the present technology. 
         FIG.  16    is a side view and  FIG.  17    is a bottom isometric view of the prosthetic heart valve device of  FIG.  15   . 
         FIG.  18    is a side view and  FIG.  19    is a bottom isometric view of a prosthetic heart valve device in accordance with an embodiment of the present technology. 
         FIG.  20    is a side view and  FIG.  21    is a bottom isometric view of the prosthetic heart valve device of  FIGS.  18  and  19    at a partially deployed state with respect to a delivery device. 
         FIG.  22    is an isometric view of a valve support for use with prosthetic heart valve devices in accordance with the present technology. 
         FIGS.  23  and  24    are side and bottom isometric views, respectively, of a prosthetic heart valve attached to the valve support of  FIG.  22   . 
         FIGS.  25  and  26    are side views schematically showing valve supports in accordance with additional embodiments of the present technology. 
     
    
    
     DETAILED DESCRIPTION 
     The present technology is generally directed to delivery systems with telescoping capsules for deploying prosthetic heart valve devices and associated methods. Specific details of several embodiments of the present technology are described herein with reference to  FIGS.  1 - 26   . Although many of the embodiments are described with respect to devices, systems, and methods for delivering prosthetic heart valve devices to a native mitral valve, other applications and other embodiments in addition to those described herein are within the scope of the present technology. For example, at least some embodiments of the present technology may be useful for delivering prosthetics to other valves, such as the tricuspid valve or the aortic valve. It should be noted that other embodiments in addition to those disclosed herein are within the scope of the present technology. Further, embodiments of the present technology can have different configurations, components, and/or procedures than those shown or described herein. Moreover, a person of ordinary skill in the art will understand that embodiments of the present technology can have configurations, components, and/or procedures in addition to those shown or described herein and that these and other embodiments can be without several of the configurations, components, and/or procedures shown or described herein without deviating from the present technology. 
     With regard to the terms “distal” and “proximal” within this description, unless otherwise specified, the terms can reference relative positions of portions of a prosthetic valve device and/or an associated delivery device with reference to an operator and/or a location in the vasculature or heart. For example, in referring to a delivery catheter suitable to deliver and position various prosthetic valve devices described herein, “proximal” can refer to a position closer to the operator of the device or an incision into the vasculature, and “distal” can refer to a position that is more distant from the operator of the device or further from the incision along the vasculature (e.g., the end of the catheter). With respect to a prosthetic heart valve device, the terms “proximal” and “distal” can refer to the location of portions of the device with respect to the direction of blood flow. For example, proximal can refer to an upstream position or a location where blood flows into the device (e.g., inflow region), and distal can refer to a downstream position or a location where blood flows out of the device (e.g., outflow region). 
     Overview 
     Several embodiments of the present technology are directed to delivery systems and mitral valve replacement devices that address the unique challenges of percutaneously replacing native mitral valves and are well-suited to be recaptured in a percutaneous delivery device after being partially deployed for repositioning or removing the device. Compared to replacing aortic valves, percutaneous mitral valve replacement faces unique anatomical obstacles that render percutaneous mitral valve replacement significantly more challenging than aortic valve replacement. First, unlike relatively symmetric and uniform aortic valves, the mitral valve annulus has a non-circular D-shape or kidney-like shape, with a non-planar, saddle-like geometry often lacking symmetry. The complex and highly variable anatomy of mitral valves makes it difficult to design a mitral valve prosthesis that conforms well to the native mitral annulus of specific patients. As a result, the prosthesis may not fit well with the native leaflets and/or annulus, which can leave gaps that allows backflow of blood to occur. For example, placement of a cylindrical valve prosthesis in a native mitral valve may leave gaps in commissural regions of the native valve through which perivalvular leaks may occur. 
     Current prosthetic valves developed for percutaneous aortic valve replacement are unsuitable for use in mitral valves. First, many of these devices require a direct, structural connection between the stent-like structure that contacts the annulus and/or leaflets and the prosthetic valve. In several devices, the stent posts which support the prosthetic valve also contact the annulus or other surrounding tissue. These types of devices directly transfer the forces exerted by the tissue and blood as the heart contracts to the valve support and the prosthetic leaflets, which in turn distorts the valve support from its desired cylindrical shape. This is a concern because most cardiac replacement devices use tri-leaflet valves, which require a substantially symmetric, cylindrical support around the prosthetic valve for proper opening and closing of the three leaflets over years of life. As a result, when these devices are subject to movement and forces from the annulus and other surrounding tissues, the prostheses may be compressed and/or distorted causing the prosthetic leaflets to malfunction. Moreover, a diseased mitral annulus is much larger than any available prosthetic aortic valve. As the size of the valve increases, the forces on the valve leaflets increase dramatically, so simply increasing the size of an aortic prosthesis to the size of a dilated mitral valve annulus would require dramatically thicker, taller leaflets, and might not be feasible. 
     In addition to its irregular, complex shape, which changes size over the course of each heartbeat, the mitral valve annulus lacks a significant amount of radial support from surrounding tissue. Compared to aortic valves, which are completely surrounded by fibro-elastic tissue that provides sufficient support for anchoring a prosthetic valve, mitral valves are bound by muscular tissue on the outer wall only. The inner wall of the mitral valve anatomy is bound by a thin vessel wall separating the mitral valve annulus from the inferior portion of the aortic outflow tract. As a result, significant radial forces on the mitral annulus, such as those imparted by an expanding stent prostheses, could lead to collapse of the inferior portion of the aortic tract. Moreover, larger prostheses exert more force and expand to larger dimensions, which exacerbates this problem for mitral valve replacement applications. 
     The chordae tendineae of the left ventricle may also present an obstacle in deploying a mitral valve prosthesis. Unlike aortic valves, mitral valves have a maze of cordage under the leaflets in the left ventricle that restrict the movement and position of a deployment catheter and the replacement device during implantation. As a result, deploying, positioning and anchoring a valve replacement device on the ventricular side of the native mitral valve annulus is complicated. 
     Embodiments of the present technology provide systems, methods and apparatus to treat heart valves of the body, such as the mitral valve, that address the challenges associated with the anatomy of the mitral valve and provide for repositioning and removal of a partially deployed device. The apparatus and methods enable a percutaneous approach using a catheter delivered intravascularly through a vein or artery into the heart, or through a cannula inserted through the heart wall. For example, the apparatus and methods are particularly well-suited for trans-septal and trans-apical approaches, but can also be trans-atrial and direct aortic delivery of a prosthetic replacement valve to a target location in the heart. Additionally, the embodiments of the devices and methods as described herein can be combined with many known surgeries and procedures, such as known methods of accessing the valves of the heart (e.g., the mitral valve or triscuspid valve) with antegrade or retrograde approaches, and combinations thereof. 
     The systems and methods described herein facilitate delivery of a prosthetic heart valve device using trans-septal delivery approaches to a native mitral valve and allow resheathing of the prosthetic heart valve device after partial deployment of the device to reposition and/or remove the device. The delivery systems can include a telescoping delivery capsule that has a first housing and a second housing slidably disposed within at least a portion of the first housing. During deployment, the first housing moves in a distal direction over the second housing to release a portion of the prosthetic heart valve device, and then the first and second housings move together in a distal direction to fully deploy the prosthetic heart valve device. This telescoping arrangement of the first and second housings requires the delivery capsule to traverse a short overall longitudinal distance relative to the device positioned therein for device deployment and, therefore, facilitates deployment within the constraints of native anatomy surrounding the mitral valve. In addition, when in the initial delivery state, the disclosed telescoping delivery capsules can have a short overall length relative to the length of the prosthetic heart valve device stored therein, which facilitates delivery along tightly curved paths necessary to access the native mitral valve via trans-septal delivery. The disclosed delivery systems can also be used to delivery other medical devices to other target sites with native anatomy that benefits from a compact delivery capsule and reduced longitudinal translation for deployment. 
     Access to the Mitral Valve 
     To better understand the structure and operation of valve replacement devices in accordance with the present technology, it is helpful to first understand approaches for implanting the devices. The mitral valve or other type of atrioventricular valve can be accessed through the patient&#39;s vasculature in a percutaneous manner. By percutaneous it is meant that a location of the vasculature remote from the heart is accessed through the skin, typically using a surgical cut down procedure or a minimally invasive procedure, such as using needle access through, for example, the Seldinger technique. The ability to percutaneously access the remote vasculature is well known and described in the patent and medical literature. Depending on the point of vascular access, access to the mitral valve may be antegrade and may rely on entry into the left atrium by crossing the inter-atrial septum (e.g., a trans-septal approach). Alternatively, access to the mitral valve can be retrograde where the left ventricle is entered through the aortic valve. Access to the mitral valve may also be achieved using a cannula via a trans-apical approach. Depending on the approach, the interventional tools and supporting catheter(s) may be advanced to the heart intravascularly and positioned adjacent the target cardiac valve in a variety of manners, as described herein. 
       FIG.  1    illustrates a stage of a trans-septal approach for implanting a valve replacement device. In a trans-septal approach, access is via the inferior vena cava IVC or superior vena cava SVC, through the right atrium RA, across the inter-atrial septum IAS, and into the left atrium LA above the mitral valve MV. As shown in  FIG.  1   , a catheter  1  having a needle  2  moves from the inferior vena cava IVC into the right atrium RA. Once the catheter  1  reaches the anterior side of the inter-atrial septum IAS, the needle  2  advances so that it penetrates through the septum, for example at the fossa ovalis FO or the foramen ovale into the left atrium LA. At this point, a guidewire replaces the needle  2  and the catheter  1  is withdrawn. 
       FIG.  2    illustrates a subsequent stage of a trans-septal approach in which guidewire  6  and guide catheter  4  pass through the inter-atrial septum IAS. The guide catheter  4  provides access to the mitral valve for implanting a valve replacement device in accordance with the technology. 
     In an alternative antegrade approach (not shown), surgical access may be obtained through an intercostal incision, preferably without removing ribs, and a small puncture or incision may be made in the left atrial wall. A guide catheter passes through this puncture or incision directly into the left atrium, sealed by a purse string-suture. 
     The antegrade or trans-septal approach to the mitral valve, as described above, can be advantageous in many respects. For example, antegrade approaches will usually enable more precise and effective centering and stabilization of the guide catheter and/or prosthetic valve device. The antegrade approach may also reduce the risk of damaging the chordae tendinae or other subvalvular structures with a catheter or other interventional tool. Additionally, the antegrade approach may decrease risks associated with crossing the aortic valve as in retrograde approaches. This can be particularly relevant to patients with prosthetic aortic valves, which cannot be crossed at all or without substantial risk of damage. 
       FIGS.  3  and  4    show examples of a retrograde approaches to access the mitral valve. Access to the mitral valve MV may be achieved from the aortic arch AA, across the aortic valve AV, and into the left ventricle LV below the mitral valve MV. The aortic arch AA may be accessed through a conventional femoral artery access route or through more direct approaches via the brachial artery, axillary artery, radial artery, or carotid artery. Such access may be achieved with the use of a guidewire  6 . Once in place, a guide catheter  4  may be tracked over the guidewire  6 . Alternatively, a surgical approach may be taken through an incision in the chest, preferably intercostally without removing ribs, and placing a guide catheter through a puncture in the aorta itself. The guide catheter  4  affords subsequent access to permit placement of the prosthetic valve device, as described in more detail herein. Retrograde approaches advantageously do not need a trans-septal puncture. Cardiologists also more commonly use retrograde approaches, and thus retrograde approaches are more familiar. 
       FIG.  5    shows a trans-apical approach via a trans-apical puncture. In this approach, access to the heart is via a thoracic incision, which can be a conventional open thoracotomy or sternotomy, or a smaller intercostal or sub-xyphoid incision or puncture. An access cannula is then placed through a puncture in the wall of the left ventricle at or near the apex of the heart. The catheters and prosthetic devices of the invention may then be introduced into the left ventricle through this access cannula. The trans-apical approach provides a shorter, straighter, and more direct path to the mitral or aortic valve. Further, because it does not involve intravascular access, the trans-apical approach does not require training in interventional cardiology to perform the catheterizations required in other percutaneous approaches. 
     Selected Embodiments of Delivery Systems for Prosthetic Heart Valve Devices 
       FIG.  6    is an isometric view of a delivery system  100  for a prosthetic heart valve device  102  (“device  102 ”; shown schematically in broken lines) configured in accordance with an embodiment of the present technology. The delivery system  100  includes a catheter  104  having an elongated catheter body  106  (“catheter body  106 ”) with a distal portion  106   a  carrying a delivery capsule  108  and a proximal portion  106   b  coupled to a control unit or handle assembly  110 . The delivery capsule  108  can move between a containment configuration for holding the device  102  in an unexpanded state during delivery of the device  102  and a deployment configuration in which the device  102  is at least partially expanded from the capsule  108 . As described in further detail below, the delivery capsule  108  includes a first housing  112  and a second housing  114  slidably disposed within at least a portion of the first housing  112 . During a first deployment stage, the first housing  112  moves in a distal direction over the second housing  114  to release a first portion of the device  102  from the delivery capsule  108 , and during a second deployment stage the second housing  114  and the first housing  112  move together in a distal direction to release a second portion of the device  102  from the delivery capsule  108  (e.g., fully release the device  102  from the delivery capsule  108 ). After partial deployment of the device  102 , the telescoping delivery capsule  108  can optionally resheathe at least a portion of the device  102  by urging the first housing  112  and/or the second housing  114  in a proximal direction back over at least a portion of the device  102 . The partial or full resheathing of the device  102  allows for repositioning of the device  102  relative to the native mitral valve after a portion of the device  102  has been expanded and contacted tissue of the native valve. 
     The handle assembly  110  can include a control assembly  126  to initiate deployment of the device  102  from the telescoping delivery capsule  108  at the target site. The control assembly  126  may include rotational elements, buttons, levers, and/or other actuators that allow a clinician to control rotational position of the delivery capsule  108 , as well as the deployment and/or resheathing mechanisms of the delivery system  100 . For example, the illustrated control assembly  126  includes a first actuator  130  operably coupled to the first housing  112  via the catheter body  106  to control distal and proximal movement of the first housing  112  and a second actuator  132  operably coupled to the second housing  114  via the catheter body  106  to control proximal and distal movement of the second housing  114 . In other embodiments, a single actuator, more than two actuators, and/or other features can be used to initiate movement of the first and second housings  112  and  114 . The handle assembly  110  can also include a steering mechanism  128  that provides steering capability (e.g., 360 degree rotation of the delivery capsule  108 , 180 degree rotation of the delivery capsule  108 , 3-axis steering, 2-axis steering, etc.) for delivering the delivery capsule  108  to a target site (e.g., to a native mitral valve). The steering mechanism  128  can be used to steer the catheter  104  through the anatomy by bending the distal portion  106   a  of the catheter body  106  about a transverse axis. In other embodiments, the handle assembly  110  may include additional and/or different features that facilitate delivering the device  102  to the target site. In certain embodiments, the catheter  104  can be configured to travel over a guidewire  124 , which can be used to guide the delivery capsule  108  into the native mitral valve. 
     As shown in  FIG.  6   , the system  100  can also include a fluid assembly  116  configured to supply fluid to and receive fluid from the catheter  104  to hydraulically move the first and second housings  112  and  114  and thereby deploy the device  102 . The fluid assembly  116  includes a fluid source  118  and a fluid line  120  fluidically coupling the fluid source  118  to the catheter  104 . The fluid source  118  may include a flowable substance (e.g., water, saline, etc.) contained in one or more reservoirs. The fluid line  120  can include one or more hoses, tubes, multiple fluid lines within a hose or tube, or other components (e.g., connectors, valves, etc.) through which the flowable substance can pass from the fluid source  118  to the catheter  104  and/or through which the flowable substance can drain from the catheter  104  to the fluid source  118 . The fluid assembly  116  can also include one or more pressurization devices (e.g., a pump), fluid connectors, fittings, valves, and/or other fluidic components that facilitate moving the fluid to and/or from the fluid source  118 . As explained in further detail below, the movement of the flowable substance to and from the fluid assembly  116  can be used to deploy the device  102  from the delivery capsule  108  and/or resheathe the device  102  after at least partial deployment. In other embodiments, mechanical means, such as tethers and springs, can be used to move the delivery capsule  108  between the deployment and containment configurations. In further embodiments, both fluidic and mechanical means can initiate deployment and resheathing. 
     In certain embodiments, the fluid assembly  116  may comprise a controller  122  that controls the movement of fluid to and from the catheter  104 . The controller  122  can include, without limitation, one or more computers, central processing units, processing devices, microprocessors, digital signal processors (DSPs), and/or application-specific integrated circuits (ASICs). To store information, for example, the controller  122  can include one or more storage elements, such as volatile memory, non-volatile memory, read-only memory (ROM), and/or random access memory (RAM). The stored information can include pumping programs, patient information, and/or other executable programs. The controller  122  can further include a manual input device (e.g., a keyboard, a touch screen, etc.) and/or an automated input device (e.g., a computer, a data storage device, servers, network, etc.). In still other embodiments, the controller  122  may include different features and/or have a different arrangement for controlling the flow of fluid into and out of the fluid source  118 . 
     The delivery capsule  108  includes the first housing  112  and the second housing  114 , which can each contain at least a portion of the device  102  in the containment configuration. The second housing  114  can have an opening  134  at its distal end portion through which the guidewire  124  can be threaded to allow for guidewire delivery to the target site. As shown in  FIG.  6   , the distal end portion of the second housing  114  may also have an atraumatic shape (e.g., a partially spherical shape, a frusto-conical shape, blunt configuration, rounded configuration, etc.) to facilitate atraumatic delivery of the delivery capsule  108  to the target site. In certain embodiments, the delivery capsule  108  includes a proximal cap  136  that extends proximally from the first housing  112  to seal or enclose the device  102  within the delivery capsule  108 . In some embodiments, the proximal cap  136  is omitted and the proximal portion of the delivery capsule  108  is left open. In these embodiments, the proximal end portion of the delivery capsule  108  (e.g., the proximal end portion of the first housing  112 ) can include rounded proximal edges, a tapered portion, and/or a soft or pliable material (e.g., a polymer) positioned at the proximal end to facilitate atraumatic retraction of the delivery capsule  108  through the body. The first housing  112 , the second housing  114 , and/or the proximal cap  136  can be made of metal (e.g., stainless steel), polymers, plastic, composites, combinations thereof, and/or other materials capable of holding the device  102  during trans-septal and/or trans-apical delivery to the target site (e.g., the mitral valve). 
     As discussed above, the first housing  112  slides or otherwise moves relative to the second housing  114  in a telescoping manner to release a portion of the device  102  from the delivery capsule  108  and, optionally, resheathe the device  102  after partial deployment. In certain embodiments, the first and second housings  112  and  114  are hydraulically actuated via the handle assembly  110  and/or the fluid assembly  116 . In hydraulically-actuated embodiments, the delivery capsule  108  includes a first fluid chamber configured to receive a flowable material from the fluid assembly  116  to move the first housing  112  relative to the second housing  114 . The delivery capsule  108  can further include a second fluid chamber configured to receive a flowable material from the fluid assembly  116  to move the first and second housing  112  and  114  as a unit. During the first deployment stage, a clinician can use the first actuator  130  and/or other suitable control means to deliver fluid (e.g., water or saline) from the fluid source  118  to the first fluid chamber to move the first housing  112  in a distal direction over the second housing  114  to release a first portion of the device  102  from the delivery capsule  108 . During the second deployment stage, the clinician can use the second actuator  132  and/or other suitable control means to deliver fluid from the fluid source  118  to the second fluid chamber such that the first and second housings  112  and  114  move together in the distal direction to release a second portion of the device  102  from the delivery capsule  108  until the device  102  is partially or fully unsheathed from the delivery capsule  108 . The first actuator  130 , the second actuator  132 , and/or other features can also be used to remove fluid from the first and second fluid chambers to allow for resheathing of the device  102  or close the delivery capsule  108 . In other embodiments, the first housing  112  and/or the second housing  114  can be moved distally and proximally for unsheathing and resheathing using mechanical means, such as wire tethers. 
     The ability of the first housing  112  to move relative to the second housing  114  in a telescoping manner to deploy the device  102  results in a delivery capsule  108  that is relatively compact in length (e.g., a length of 40 mm or less) and that requires relatively short overall longitudinal translation (e.g., 50 mm or less, 40 mm or less, etc.) to deploy the device  102 . For example, the telescoping delivery capsule  108  inherently requires less longitudinal translation for deployment than if the delivery capsule  108  were defined by a single housing that moves distally or proximally to deploy the device  102 , or two separate housings that move in opposite directions to deploy the device  102 . This shorter longitudinal translation in solely the distal direction facilitates trans-septal delivery of the device  102  to a native mitral valve of a human patient. For a typical patient with functional mitral valve regurgitation (“FMR”), the distance across the left atrium is estimated to be about 50 mm and the length of the left ventricle is estimated to be about 70 mm. During trans-septal delivery of the device  102 , the delivery capsule  108  can extend through the opening in the septal wall between the right and left atria and be positioned in or proximate to the mitral valve annulus by bending the distal portion  106   a  of the catheter body  106  from the left atrium into the mitral valve. The compact size of the delivery capsule  108  facilitates positioning the delivery capsule  108  into the left atrium and making the turn into the native mitral valve without being limited by the anatomical sizing of the right atrium. During device deployment, the telescoping delivery capsule  108  does not require any portion of the delivery capsule  108  to extend in a proximal direction into the left atrium of the heart, and the telescoping arrangement of the first and second housings  112  and  114  results in a short overall longitudinal translation (relative to the axial length of the device  102 ) of the housings  112 ,  114  into the left ventricle of the heart, much less than typical length of the left ventricle. Thus, the telescoping delivery capsule  108  avoids the typical constraints associated with trans-septal delivery and the associated anatomy proximate to the target site in the mitral valve. 
       FIG.  7 A  is an enlarged side isometric view of the delivery capsule  108  of the delivery system  100  of  FIG.  6    configured in accordance with embodiments of the present technology, and  FIG.  7 B  is an exploded view of the delivery capsule  108  of  FIG.  7 A . The delivery capsule  108  includes the first housing  112  partially overlapping and movable relative to the second housing  114 . The first and second housings  112  and  114  are shown as transparent for illustrative purposes in  FIGS.  7 A and  7 B ; however, the first and second housings  112  and  114  may be made from opaque materials, including metals, polymers, plastics, composites, and/or combinations thereof. In certain embodiments, the first housing  112  has a length of about 20-30 mm, the second housing has a length of about 20-30 mm, and the first and second housings  112  and  114  overlap in such a manner that the overall longitudinal length of the delivery capsule  108  is 50 mm or less (e.g., 45 mm, 40 mm, etc.) when in the initial containment or delivery state. In various embodiments, such as when the delivery capsule  108  is configured to retain a prosthetic mitral valve device, the first housing  112  may have an outer diameter of about 11.58 mm and an inner diameter of about 10.82 mm, and the second housing  114  may have an outer diameter of about 9.53 mm and an inner diameter of about 9.02 mm. In other embodiments, the first and second housings  112  and  114  have different dimensions suitable for storing and delivering the medical device contained therein. 
     The delivery capsule  108  further includes a plurality of sealing members (identified individually as first through third sealing members  140   a - c , respectively; referred to collectively as “sealing members  140 ”), such as sealing sleeves and/or O-rings, that can fluidically seal portions of the delivery capsule to define a first fluid chamber  142 , a second fluid chamber  144 , and/or portions thereof. The sealing members  140  can be sleeves, O-rings, O-rings positioned within sleeves, and/or other sealing features that are fixedly attached to the first housing  112 , the second housing  114 , and/or other portions of the delivery capsule  108  via bonding, laser welding, and/or other mechanisms for securing the sealing members  140  in position on portions of the delivery capsule  108 . In certain embodiments, for example, the first and second housings  112  and  114  can include sleeves or flanges formed in or on the surfaces of the housings  112 ,  114  (e.g., using 3D printing) and configured to receive O-rings and/or other sealing features. As shown in  FIGS.  7 A and  7 B , the first sealing member  140   a  can be fixedly attached to the first housing  112 , extend between an inner surface of a distal portion  146  of the first housing  112  and an outer surface of the second housing  114 , and be slidable relative to the second housing  114 . The second sealing member  140   b  can be fixedly attached to the second housing  114  and extend between an outer surface of a proximal portion  148  of the second housing and the inner surface of the first housing  112 . Thus, the first fluid chamber  142  can be defined at a distal end by the first sealing member  140   a , at a proximal end by the second sealing member  140   b , and the portions of an inner surface of the first housing  112  and an outer surface of the second housing  114  that extend between the first and second sealing members  140   a  and  140   b . During deployment, the first sealing member  140   a  slides distally along the outer surface of the second housing  114  as the first fluid chamber  142  is pressurized with fluid to move the first housing  112  in a distal direction over a portion of the second housing  114 . 
     The second fluid chamber  144  is positioned within the second housing  114  and can be defined at a proximal end by the third sealing member  140   c . As shown in  FIG.  7 A , for example, the delivery capsule  108  can further include a platform  150  that extends outwardly from the distal end portion of the elongated body  106  and/or other shaft extending into the delivery capsule  108 , and the third sealing member  140   c  can extend from the platform  150  (e.g., from a surface on or a recess within the platform  150 ) to the inner surface of the second housing  114  to fluidically seal the second fluid chamber  144  at a proximal end from other portions of the delivery capsule  108 . In other embodiments, the platform  150  can itself seal against the inner surface of the second housing  114  to fluidically seal the proximal end of the second fluid chamber  144 . As further shown in  FIG.  7 A , the second fluid chamber  144  can be defined at its distal end by a distal end feature  152  (e.g., a nose cone) at a distal end portion  154  of the second housing  114 , or by another portion of or within the second housing  114 . Thus, the second fluid chamber  144  is defined at its proximal end by a distal-facing portion of the platform  150  and/or the third sealing member  140   c , at a distal end by the distal end feature  152  or (if the end feature  152  is omitted) an interior distal end of the second housing  114 , and the wall of the second housing  114  extending therebetween. During deployment, the third sealing member  140   c , in conjunction with the platform  150 , slides along the inner surface of the second housing  114  as the second fluid chamber  144  is pressurized with fluid to move the second housing  114 , together with the first housing  112  as a unit, in a distal direction. 
     The platform  150  is fixed relative to the body  106  and/or another shaft extending therethrough, and can be configured to support a distal end portion of a prosthetic heart valve device (e.g., the device  102  of  FIG.  6   ) during delivery. For example, the platform  150  can be configured to maintain the device in a substantially constant axial position relative to the native anatomy (e.g., the mitral valve) as the first and second housings  112  and  114  move in a distal direction to unsheathe the device. In other embodiments, the platform  150  can be pulled or otherwise moved in a proximal direction to further unsheathe the device. The platform  150  can be formed integrally with the body  106 , or the body  106  and the platform  150  can be separate components made from metal, polymers, plastic, composites, combinations thereof, and/or other suitable materials. 
     The end feature  152  at the distal portion  154  of the second housing  114  can be a nose cone or other element that provides stability to the distal end of the delivery capsule  108  and/or defines an atraumatic tip to facilitate intraluminal delivery of the capsule  108 . The end feature  152  can be integrally formed at the distal end portion  154  of the second housing  114 , a separate component fixedly attached thereto, or defined by the distal end of the second housing  114 . As shown in  FIGS.  7 A and  7 B , the end feature  152  may include a channel  155  extending through its length and in communication with the distal opening  134  through which various components of the system  100  can extend beyond the distal end portion  154  of the delivery capsule  108 . For example, the channel  155  can be used to carry a guidewire (e.g., the guidewire  124  of  FIG.  6   ), a fluid lumen (discussed in further detail below), and/or a small shaft through which the guidewire, fluid lumen, and/or other system components can extend. O-rings, valves or other sealing members can be positioned in or around the channel  155  and the components extending therethrough to fluidically seal the second chamber  144  at the distal end from the external environment. In other embodiments, the end feature  152  can include multiple channels that extend to separate distal openings. 
     As further shown in  FIG.  7 A , the delivery capsule  108  also includes a separate compartment  156  fluidically sealed from the first and second fluid chambers  142  and  144  and configured to house a prosthetic heart valve device (e.g., the device  102  of  FIG.  6   ) in the unexpanded, containment state. The compartment  156  can be defined at a distal end by a proximal-facing surface of the platform  150 , at a proximal end by the proximal cap  136  or the proximal end of the first housing  112 , and the interior walls of the first and second housings  112  and  114  extending therebetween. In embodiments where the proximal cap  136  is omitted, the proximal portion of the compartment  156  is open to the surrounding environment (e.g., the vasculature). In various embodiments, the platform  150  can include engagement features that releasably couple to portions of the device to facilitate loading of the device into the delivery capsule  108  and secure the device to the delivery capsule  108  until final deployment to allow for resheathing. During deployment, the compartment  156  is opened to the native environment at the target site by the distal movement of the first and second housings  112  and  114  relative to the platform  150 , and, optionally, by proximal movement of the proximal cap  136 . 
     The delivery system  100  further includes fluid lines (identified individually as a first fluid line  158   a  and a second fluid line  158   b ; referred to collectively as “fluid lines  158 ”) in fluid communication with the first and second fluid chambers  142  and  144  via fluid ports (identified individually as a first fluid port  160   a  and a second fluid port  160   b ; referred to collectively as “fluid ports  160 ”). As shown in  FIG.  7 A , the first fluid line  158   a  is in fluid communication with the first fluid chamber  142  via the first fluid port  160   a , and the second fluid line  158   b  is in fluid communication with the second fluid chamber  144  via the second fluid port  160   b . The fluid ports  160  can include valves or other features with openings that regulate fluid to flow into and/or out of the fluid chambers  142 ,  144 . The fluid lines  158  extend from the first and second fluid chambers  142  and  144  through the elongated catheter body  106 , and are placed in fluid communication with a fluid source (e.g., the fluid assembly  116  of  FIG.  6   ) at the proximal portion  106   b  ( FIG.  6   ) of the catheter body  106  such that the fluid lines  158  can deliver fluid to and, optionally, remove fluid from the first and second fluid chambers  142  and  144  independently of each other. In several embodiments, the first and second fluid chambers  142  and  144  each have a dedicated fluid line  158  extending through or defined by portions of the catheter body  106 , or a single fluid line may extend through the catheter body  106  and a valve assembly can be used to selectively deliver fluid to the first and second fluid chambers  142  and  144 . 
     At the distal portion  106   a  of the catheter body  106 , the first fluid line  158   a  extends in a distal direction from the main catheter body  106 , through the distal end of the second housing  114  (e.g., through the channel  155  of the end feature  152  and through the opening  134 ), outside the second housing  114 , and into the first fluid port  160   a  in fluid communication with the first fluid chamber  142 . In the embodiment illustrated in  FIG.  7 A , the first fluid line  158   a  extends through the first sealing member  140   a  and the first fluid port  160   a  is positioned on a proximal-facing surface of the first sealing member  140   a  in fluid communication with the first fluid chamber  142 . In other embodiments, the first fluid line  158   a  can extend through the wall of the first housing  112  and/or another portion of the delivery capsule  108  to fluidly communicate with the first fluid chamber  142 . The portion of the first fluid line  158   a  that extends beyond the distal end of the main catheter body  106  and outside of the second housing  114  can be an umbilical cord-type tube or lumen. Although  FIG.  7 A  illustrates the tube spaced apart from the outer surface of the second housing  114 , the fluid lumen can run tightly along the distal end feature  152  and the outer surface of the second housing  114 . In other embodiments, the distal portion of the first fluid line  158   a  can be a corrugated tube that coils or otherwise retracts when it is not filled with fluid, and/or another type of tube or structure configured to transport fluid to the first fluid chamber  142 . 
     As further shown in  FIG.  7 A , the second fluid line  158   b  can terminate at the second fluid port  160   b  positioned at the distal end of the main catheter body  106  to place the second fluid port  160   b  in fluid communication with the second fluid chamber  144 . In other embodiments, the second fluid line  158   b  can terminate at a distal-facing surface of the platform  150  in fluid communication with the second fluid chamber  144 , or the second fluid line  158   b  may extend in a distal direction beyond the distal end of the main catheter body  106  into the second fluid chamber  144 . In further embodiments, the distal portion of the second fluid line  158   b  includes a tube (e.g., a corrugated tube, an umbilical cord-type lumen, etc.) that extends beyond the distal end of the main catheter body  106 , through the distal end of the second housing  114 , and loops back into fluid communication with the second fluid chamber  144  via a fluid port in the wall of the second housing  112  and/or another portion of the delivery capsule  108  in fluid communication with the second fluid chamber  144 . 
       FIGS.  8 A- 8 D  are a series of illustrations showing the distal portion of the delivery system  100  of  FIGS.  6 - 7 B  deploying and resheathing the device  102  via hydraulic actuation provided by filling and draining of the first and second fluid chambers  142  and  144 . Although the following description is specific to deployment of prosthetic heart valve devices at a native mitral valve, the delivery capsule  108  can be used to deploy prosthetic valves, implants, and/or other medical devices in other portions of the body that may benefit from the short overall longitudinal translation and compact sizing provided by the telescoping delivery capsule  108 .  FIG.  8 A  illustrates the delivery capsule  108  in the initial delivery state with the device  102  constrained within the compartment  156  to allow for trans-luminal delivery of the device  102  to the target site. For a trans-septal approach to the native mitral valve, a clinician accesses the mitral valve from the venous system (e.g., via the transfemoral vein), navigates the delivery capsule  108  through the inferior vena cava into the right atrium, and passes the delivery capsule  108  through an aperture formed in the atrial septal wall into the left atrium. From the septal aperture, the clinician steers the distal portion of the delivery capsule  108  from its initial orientation, directed generally transverse to the inlet of the native mitral valve into axial alignment with the native mitral valve (e.g., a 90° turn) such that the distal portion of the delivery capsule  108  can pass through the native mitral annulus partially into the left ventricle. The compact axial length of the delivery capsule  108  (e.g., less than 50 mm) facilitates this turn from the septal wall into the native mitral valve within the anatomical constraints of the left atrium, which typically has a width of about 50 mm. Once the delivery capsule  108  is positioned at the desired site relative to the native mitral valve, the clinician can begin deployment of the device  102 . 
       FIG.  8 B  illustrates the delivery capsule  108  during the first deployment stage during which the first fluid line  158   a  delivers fluid from the fluid assembly  116  ( FIG.  6   ) to the first fluid chamber  142  via the first fluid port  160   a . As fluid is added to the first fluid chamber  142 , the increase in pressure within the first fluid chamber  142  causes the first sealing member  140   a  and the first housing  112  attached thereto to slide in a distal direction along the outer surface of the second housing  114  (as indicated by arrow  101 ). In certain embodiments, for example, the first sealing member  140   a  can be configured to move relative to the second housing  114  when the pressure within the first fluid chamber  142  exceeds a predetermined threshold, such as 4 atm to 8 atm. The total travel length of the first housing  112  in the distal direction during this first deployment stage can be at least 20 mm. In other embodiments, the first housing  112  may move smaller or greater distances depending on the size of the delivery capsule  108  and/or the device  102  positioned therein. The distal movement of the first housing  112  unsheathes a first portion of the device  102 , such as a brim or atrial portion, allowing it to expand against surrounding native tissue and/or provide visualization for proper seating within the native valve. When the delivery capsule  108  includes a proximal cap, such as the proximal cap  136  shown in  FIGS.  8 A and  8 B  (not shown in  FIGS.  8 C and  8 D  for illustrative purposes), the distal movement of the first housing  112  separates the first housing  112  from the proximal cap  136  to expose the device  102 . In other embodiments, the proximal cap  136  can be pulled in a proximal direction away from the first housing  112  before or during the first deployment stage. 
       FIG.  8 C  illustrates the delivery capsule  108  during the second deployment stage during which the second fluid line  158   b  delivers fluid from the fluid assembly  116  ( FIG.  6   ) to the second fluid chamber  144  via the second fluid port  160   b . When the pressure within the second fluid chamber  144  exceeds a threshold level (e.g., 4-8 atm), the second housing  114  moves in a distal direction (as indicated by arrow  103 ) relative to the platform  150  and the associated third sealing member  140   c  as more fluid enters the second fluid chamber  144 . Because the first fluid chamber  142  and the second fluid chamber  144  operate independently of each other, the first housing  112  moves with the second housing  114  as fluid fills or drains from the second fluid chamber  144 . This distal movement of the second housing  114  partially or fully unsheathes the device  102  from the delivery capsule  108 , while maintaining the brim or atrial portion of the device  102  at substantially the same axial position relative to the native annulus. In certain embodiments, the second housing  114  can translate 20-30 mm in the distal direction depending upon the length of the device  102 . In other embodiments, filling the second fluid chamber  144  pushes platform  150  in proximal direction such that the platform  150  slides proximally along the inner surface of second housing  114  to deploy the remainder of the device  102 . In this embodiment, the device  102  does not maintain its axial position during deployment. During the deployment procedure, the first and second deployment stages can be performed in separate and distinct time intervals as illustrated in  FIGS.  8 B and  8 C  to allow for dual-stage deployment of the device  102 . In other embodiments, however, the first and second deployment stages can be simultaneous or at least partially overlapping such that the first and second fluid chambers  142  and  144  receive fluid at the same time. 
     In various embodiments, the delivery capsule  108  can also be configured to partially or fully resheathe the prosthetic heart valve device after partial deployment from the delivery capsule  108 .  FIG.  8 D , for example, illustrates the delivery capsule  108  during a resheathing stage in which the delivery capsule  108  is driven back towards the delivery state by evacuating fluid from the first fluid chamber  142  via the first fluid line  158   a  and applying a proximally directed force on the first housing  112 . For example, as shown in  FIG.  8 D , the first housing  112  may be operably coupled to a biasing device  137  (e.g., a spring) housed in the handle assembly  110  via a tether  135  and/or other coupling member that extends through the catheter body  106 . The biasing device  137  can act on the first housing  112  (e.g., via the tether  135 ) to drive the first housing  112  in the proximal direction when fluid is removed from the first fluid chamber  142 . In some embodiments, the biasing device  137  is omitted and the tether  135  itself can be manipulated at the handle assembly  110  (e.g., via an actuator) to retract the tether  135  in the proximal direction and draw the first housing  112  proximally. In various embodiments, the biasing device  137  can be positioned within the catheter body  106  (e.g., at the distal portion  106   a  of the catheter body  106 ) and/or associated with the delivery capsule  108  (e.g., as described in further detail below with respect to  FIG.  9 B ) such that the biasing device  137  drives the first housing  112  proximally upon fluid removal. With the fluid evacuated from the first fluid chamber  142 , the first sealing member  140   a  is allowed to slide in a proximal direction (as indicated by arrow  105 ) over the outer surface of the second housing  114  and move the first housing  112  back over at least a portion of the device  102  to place the resheathed portion of the device  102  back into the constrained, delivery state. For example, the first sealing member  140   a  can move in the proximal direction a desired distance and/or until the first sealing member  140   a  contacts the second sealing member  140   b  (e.g., about 20 mm). In some embodiments, resheathing can be initiated by removing fluid from the second fluid chamber  144 , or removing the fluid from both the first and second fluid chambers  142  and  144  to allow the first housing  112  and/or second housing  114  to move back over the device  102 . Similar to the first housing  112 , the second housing  114  can be operably coupled to a mechanism that drives the second housing  114  in a proximal direction when fluid is evacuated from the second chamber  144 , such as a tether, spring, and/or other biasing device. In some embodiments, a vacuum can be applied to the first fluid chamber  142  and/or the second fluid chamber  144  after the fluid has been evacuated from the chambers  142 ,  144  to facilitate moving the first housing  112  and/or the second housing  114  in the proximal direction. This resheathing ability allows the clinician to re-position the prosthetic heart valve device, in vivo, for redeployment within the mitral valve MV or remove the prosthetic heart valve device from the patient after partial deployment. Once the device  102  is fully deployed at the desired location, the first and second housings  112  and  114  can be drawn in a proximal direction through the deployed device  102 , and the elongated catheter body  106  can be pulled proximally along the access path (e.g., through the aperture in the septal wall into the vasculature) for removal from the patient. After removing the catheter  104  ( FIG.  6   ), the catheter  104  and the delivery capsule  108  can be discarded, or one or both components can be cleaned and used to deliver additional prosthetic devices. 
     The telescoping delivery capsule  108  and the delivery system  100  described above with respect to  FIGS.  6 - 8 D  facilitate delivery via the trans-septal delivery approach due to the capsule&#39;s compact length, which can accommodate the turn from the aperture in the atrial septal wall into the native mitral valve necessary to position the device  102  in the native mitral valve without contacting the left atrial wall. In addition, the telescoping deployment provided by the first and second housings  112  and  114  results in short overall axial displacement of the delivery capsule  108  (relative to the length of the device  102 ) into the left ventricle during device deployment, and is thereby expected to avoid contact with portions of the left ventricle wall during deployment. By avoiding contact with the walls of the left ventricle and left atrium, the delivery system  100  also reduces the likelihood of arrhythmia during valve deployment. The hydraulic-actuation of the delivery capsule  108  provides controlled movement of the first and second housings  112  and  114  as the device  102  expands during unsheathing, and in certain embodiments allows the clinician to selectively suspend distal movement of the housings  112 ,  114  during any point of the deployment process to allow for repositioning and/or visualization. Further, the delivery capsule  108  may also be configured to at least substantially inhibit axial translation of the device  102  during deployment and resheathing (e.g., as shown in  FIGS.  8 A- 8 B ) to facilitate accurate delivery to the target site. 
     In other embodiments, the telescoping delivery capsule  108  can operate in the opposite manner with respect to the distal portion  106   a  of the catheter body  106  such that the telescoping housings  112 ,  114  are configured to retract in a proximal direction to deploy the device  102  from the delivery capsule  108  and move in a distal direction to resheathe the device  102 . Such an embodiment would be suitable to deliver the device  102  to the mitral valve from the left ventricle using a trans-apical approach (e.g., via an opening formed in the apical portion of the left ventricle). For example, the hydraulic actuation mechanism can move the first and second housings  112  and  114  in a proximal direction in a telescoping manner toward the distal portion  106   a  of the catheter body  106  to unsheathe the device  102 . Once the device  102  is fully deployed within the mitral valve, the retracted delivery capsule  108  (with the first housing  112  at least partially overlapping the second housing  114 ) can be pulled in a proximal direction through the left ventricle and the apical aperture to remove the delivery system  100 . 
       FIG.  9 A  is a side isometric view of a distal portion of a delivery system  200   a  configured in accordance with embodiments of the present technology. The delivery system  200   a  includes various features at least generally similar to the features of the delivery system  100  described above with reference to  FIGS.  6 - 8 D . For example, the delivery system  200   a  includes two telescoping housings  112 ,  114  that are hydraulically driven distally and proximally between a delivery state and a deployment state by moving fluid to and/or from the first fluid chamber  142  and the second fluid chamber  144 . The delivery system  200   a  further includes a third or proximal fluid chamber  243  positioned in the annular space between the first and second housings  112  and  114 . As shown in  FIG.  9 A , the delivery capsule  108  includes the first sliding sealing member  140   a  fixedly attached to the distal portion of the first housing  112 , the internal second sealing member  140   b  fixedly attached to the second housing  114  between the first and second housings  112  and  114 , and a proximal or fourth sliding sealing member  240   d  fixedly attached to the proximal portion of the first housing  112 . Accordingly, the first fluid chamber  142  is between the distal-most or first sealing member  140   a  and the internal second sealing member  140   b , and the third fluid chamber  243  is between the second sealing member  140   b  and the proximal sealing member  240   d . The third fluid chamber  243  can be placed in fluid communication with a third fluid line  258   c  via a tube or other fluid-carrying features that extend outside of the second housing  114  and through the wall of the first housing  112  via a third fluid port  260   c  into fluid communication with the third fluid chamber  243  (e.g., similar to the distal portion of the first fluid line  158   a ). In other embodiments, the first fluid chamber  142  and/or the third fluid chamber  243  can be placed in fluid communication with the corresponding third fluid line  258   c  using other suitable means, such as fluid channels within the body of the delivery capsule  108 . 
     During device deployment, the first fluid chamber  142  is pressurized with fluid, thereby causing the first sealing member  140   a  and the first housing  112  to slide distally until the proximal sealing member  240   d  comes into contact with the internal second sealing member  140   b  (e.g., about 20 mm). This unsheathes at least a portion of the device  102  from the delivery capsule  108 . Further unsheathing can be performed by pressurizing the second fluid chamber  144  with fluid to hydraulically move the telescoped first and second housings  112  and  114  together in the distal direction to partially or completely unsheathe the device  102 . In other embodiments, the telescoped first and second housings  112  and  114  are moved together in the distal direction using mechanical means. To retract the first housing  112 , the first fluid chamber  142  is evacuated of fluid and the third fluid chamber  243  is pressurized with fluid via the third fluid line  258   c . This causes the proximal sealing member  240   d  and the first housing  112  to slide proximally, e.g., until the first sealing member  140   a  stops against the internal second sealing member  140   b . Accordingly, the supplemental third fluid chamber  243  can be used to facilitate resheathing of the device  102  and/or retraction of the delivery capsule  108  back to its delivery state. In some embodiments, the delivery capsule  108  can include additional fluid chambers that further facilitate device deployment and recapture, and/or the fluid chambers can be defined by different portions of the delivery capsule  108 , while still being configured to hydraulically drive the first and second housings  112  and  114  distally and/or proximally relative to each other. 
       FIG.  9 B  is a side isometric view of a distal portion of a delivery system  200   b  in a delivery state configured in accordance with some embodiments of the present technology. The delivery system  200   b  includes various features at least generally similar to the features of the delivery system  100  described above with reference to  FIGS.  6 - 8 D . For example, the delivery system  200   b  includes two telescoping housings  112 ,  114  that are hydraulically driven distally and proximally between a delivery state and a deployment state by moving fluid to and from the first fluid chamber  142  and the second fluid chamber  144 . The delivery system  200   b  further includes at least one biasing device (identified individually as a first biasing device  262   a  and a second biasing device  262   b ; referred to collectively as “biasing devices  262 ”) that urges the first housing  112  and/or the second housing  114  toward the delivery state in the absence of fluid within the first and second fluid chambers  142  and  144 . The biasing devices  262  can be springs (e.g., as shown in  FIG.  9 B ) or other components that apply force on the housings  112 ,  114  when compressed or extended during device deployment. 
     As illustrated in  FIG.  9 B , the first biasing device  262   a  extends around a portion of the second housing  114  and acts on the distal end portion  146  of the first housing  112  when the first housing  112  moves toward the deployment state. An end stop component  263  or other feature can secure the distal end of the first biasing device  262   a  in place on the second housing  114 . The first biasing device  262   a  compresses as the first housing  112  moves in the distal direction toward the deployment state, thereby applying a force on the first housing  112  in the proximal direction. In certain embodiments, the first biasing device  262   a  applies a constant proximally-directed force on the first housing  112  when the delivery capsule  108  is in the delivery state, and that force increases as the first housing  112  moves in the distal direction. In other embodiments, the first biasing device  262   a  is in a neutral state when the delivery capsule  108  is in the delivery state, and then applies a proximally-directed force to the first housing  112  as the first biasing device  262   a  compresses. This proximally-directed force may not be great enough to urge the first housing  112  closed when fluid is in the first fluid chamber  142 , but after fluid removal from the first fluid chamber  142 , the first biasing device  262   a  can push the first housing  112  in a proximal direction to resheathe a prosthetic device (e.g., the device  102  of  FIGS.  6  and  8 A- 8 D ) positioned within the delivery capsule  108  and/or close the delivery capsule  108  for removal from the patient&#39;s body. 
     As further shown in  FIG.  9 B , the second biasing device  262   b  is positioned within the second housing  114  (e.g., within the second fluid chamber  144 ) such that it acts on the second housing  114  when the second housing  114  moves toward the deployment state. The second biasing device  262   b  can be coupled to the platform  150  at a proximal end of the second biasing device  262   b , and to a distal portion of the second housing  114  or components therein (e.g., the distal end feature  152 ) at a distal end of the second biasing device  262   b . When the second fluid chamber  144  fills with fluid and drives the distal end of the second housing  114  apart from the platform  150 , the second biasing device  262   b  expands, thereby applying force on the first housing  112  and the platform  150  to pull the two components closer together. In certain embodiments, the second biasing device  262   b  applies a continual proximally-directed force on the second housing  114  when the delivery capsule  108  is in the delivery state, and that force increases as the second housing  114  moves in the distal direction. In other embodiments, the second biasing device  262   b  is in a neutral state when the delivery capsule  108  is in the delivery state, and then applies a proximally-directed force to the second housing  114  as the second biasing device  262   b  expands. When fluid is in the second fluid chamber  144 , the biasing force is not of a magnitude to urge the second housing  114  toward the delivery state. However, after draining fluid from the second fluid chamber  144 , the second biasing device  262   b  can pull the second housing  114  in a proximal direction and/or pull the second housing  114  and the platform  150  closer together (depending on the force required to slide the platform  150  relative to the second housing  114 ) to resheathe a device and/or close the delivery capsule  108 . 
     The biasing devices  262  can also limit or substantially prevent distal movement of the housings  112 ,  114  attributable to the forces produced by an expanding prosthetic heart valve device (e.g., the device  102  of  FIGS.  8 A- 8 D ). For example, hydraulic actuation can move the first housing  112  and/or the second housing  114  to unsheathe a portion of a prosthetic heart valve device, allowing the device to expand outwardly. Meanwhile, the biasing devices  262  can urge the housings  112 ,  114  toward the delivery state to counteract the distally-directed expansion forces of the device on the delivery capsule  108 , and thereby prevent axial jumping. One, two, or more biasing devices  262  can be incorporated in any of the delivery capsules disclosed herein to urge the telescoping housings toward the deployment state. In some embodiments, the biasing devices  262  can be positioned elsewhere with respect to the delivery capsule  108  and/or the delivery system  200   b  and operably coupled to the first housing  112  and/or the second housing  114  to bias the housings  112 ,  114  toward the delivery configuration. For example, the second biasing device  262 b can be positioned in a proximal portion of the delivery capsule  108  and operably coupled to the second housing  114  via a tether or other connector such that the second biasing device  262   b  acts on the second housing  114 . As another example, the first biasing device  262   a  and/or the second biasing device  262   b  can be positioned in portions of the catheter body  106  and/or a handle assembly (the handle assembly  110  of  FIG.  6   ), and connected to the first and second housings  112  and  114  via tethers or other connectors extending through the catheter body  106 . 
       FIGS.  10 A and  10 B  are a partial cut-away isometric view and a cross-sectional view, respectively, of a distal portion of a delivery system  300  configured in accordance with some embodiments of the present technology. The delivery system  300  includes various features at least generally similar to the features of the delivery systems  100 ,  200   a ,  200   b  described above with reference to  FIGS.  6 - 9   . For example, the delivery system  300  includes a telescoping delivery capsule  308  having a first housing  312 , a second housing  314  slidably disposed within a portion of the first housing  312 , and two fluid chambers (identified individually as a first fluid chamber  342  and a second fluid chamber  344 ) defined at least in part by sealing members  340  (identified individually as first through third sealing members  340   a - c , respectively). More specifically, the first fluid chamber  342  is defined by the annular space between the first and second sealing members  340   a  and  340   b , and the second fluid chamber  344  is defined by the portion of the second housing  314  between a platform  350  (including the third sealing member  340   c ) and a distal end portion  352 . The first and second fluid chambers  342  and  344  are placed in fluid communication with a fluid source (e.g., the fluid assembly  116  of  FIG.  6   ) via dedicated fluid lines  358  (identified individually as a first fluid line  358   a  and a second fluid line  358   b ). 
     In the embodiment illustrated in  FIGS.  10 A and  10 B , the second fluid line  158   b  is a tube or shaft that extends through an elongated catheter body (not shown; e.g., the catheter body  106  of  FIGS.  6 - 9   ) and affixes to the platform  350  where it terminates at a second fluid port  360   b  to deliver fluid to and/or remove fluid from the second fluid chamber  344  (as indicated by arrows  309 ). The first fluid line  358   a  includes a tube or channel that extends through the length of the second fluid line  358   b , projects in a distal direction beyond the second port  358   b  and the platform  350 , and then extends distally into the second fluid chamber  344  where the first fluid line  358   a  connects to one or more lumens  370  defined by the annular space in the wall of the second housing  114 . The lumen  370  extends through the wall of the second housing  314  to the first fluid port  360   a , which allows fluid to be delivered to and/or removed from the first fluid chamber  342  (as indicated by arrows  307 ). The portion of the first fluid line  358   a  that extends between the second fluid line  358   b  and the lumen  370  can be a flexible tube or corrugated lumen bonded to or otherwise sealed to the inlet of the lumen  370 . Such flexible tubes or corrugated lumens allow the first fluid line  358   b  to bend, flex, and extend to maintain the connection with the lumen  370  as the platform  350  and the second housing  314  move relative to each other when the second fluid chamber  344  is filled or drained. In other embodiments, the first fluid line  358   a  and the second fluid line  358   b  run alongside each other, rather than concentrically, within an elongated catheter body or defined by separate portions of the catheter body. 
     In operation, fluid is delivered to the first fluid chamber  342  via the first fluid line  358   a , which causes the first housing  312  to move in a distal direction over the second housing  314  to unsheathe a portion of a prosthetic heart valve device (e.g., the device  102  of  FIGS.  7 A- 8 D ). In a subsequent or simultaneous step, fluid is delivered to the second fluid chamber  344  via the second fluid line  358   b , causing the second housing  314  to move in the distal direction to further unsheathe the prosthetic heart valve device. During an optional resheathing stage, fluid can be removed from the first fluid chamber  342  via the first fluid line  358   a  and, optionally, the first fluid chamber  342  can be pressurized to move the first housing  312  in a proximal direction back over the prosthetic heart valve device. Further resheathing can be performed by draining and, optionally, applying a vacuum to the second fluid chamber  344 . 
       FIGS.  10 C and  10 D  are cutaway isometric views of housing configurations for use with the delivery system  300  of  FIGS.  10 A and  10 B . More specifically,  FIGS.  10 C and  10 D  illustrate different configurations of a second housing  414 ,  514  having lumens within the housing wall such that the second housing  414 ,  514  can define an end portion of a first fluid line (e.g., the first fluid line  358   a  of  FIGS.  10 A and  10 B ) in fluid communication with a first fluid chamber (e.g., the first fluid chamber  342  of  FIGS.  10 A and  10 B ). In some embodiments as illustrated in  FIG.  10 C , the second housing  414  includes four oblong or oval-shaped lumens (identified individually as first through fourth lumens  470   a - b , respectively; referred to collectively as lumens  470 ) spaced equally about the circumference of the second housing  414  and extending through at least a portion of the wall of the second housing  414 . In some embodiments as illustrated in  FIG.  10 D , the second housing  514  includes four circular lumens (identified individually as first through fourth lumens  570   a - b , respectively; referred to collectively as lumens  570 ) spaced equally about the circumference of the second housing  514  and extending through at least a portion of the wall of the second housing  514 . In some embodiments, each lumen  470 ,  570  has a first end coupled to a portion of the first fluid line (e.g., the first fluid line  358   a  of  FIGS.  10 A and  10 B ) extending from a proximal portion of a catheter body (e.g., the catheter bodies  106 ,  306  of  FIGS.  6 ,  10 A and  10 B ) via a flexible tube or other feature, and a second end that is placed in fluid communication with a first fluid chamber (e.g., the first fluid chamber  342  of  FIGS.  10 A and  10 B ) via individual fluid ports. In some embodiments, only one of the lumens  470 ,  570  is coupled to a portion of the first fluid line (e.g., the first fluid line  358   a  of  FIGS.  10 A and  10 B ) extending from a proximal portion of a catheter body (e.g., the catheter bodies  106 ,  306  of  FIGS.  6 ,  10 A and  10 B ) via a flexible tube or other feature, and the second housing  414 ,  514  includes additional internal lumens that connect the other lumens  470 ,  570  to each other such that the lumens  470 ,  570  can be placed in fluid communication with a first fluid chamber (e.g., the first fluid chamber  342  of  FIGS.  10 A and  10 B ) via individual fluid ports. In some embodiments, the second housing  414 ,  514  includes one, two, three, or more than four lumens  470 ,  570  spaced equidistance or at other desired locations around the circumference of the second housing  414 ,  514 . In still further embodiments, the lumens  470 ,  570  may have different cross-sectional shapes suitable for carrying fluid. Any of the configurations of the second housings  314 ,  414 ,  514  described with reference to  FIGS.  10 A- 10 D  can also replace the second housing  114  in the delivery systems  100 ,  200   a ,  200   b  described above with reference to  FIGS.  6 - 9   . 
       FIGS.  11 A and  11 B  are isometric and cross-sectional views of a distal portion of a delivery system  600  configured in accordance with some embodiments of the present technology. The delivery system  600  includes various features at least generally similar to the features of the delivery systems  100 ,  200   a ,  200   b ,  300  described above with reference to  FIGS.  6 - 10 D . For example, the delivery system  600  includes an elongated catheter body  606  and a telescoping delivery capsule  608  at a distal end portion  606   a  of the catheter body  606 . The delivery capsule  608  includes a first housing  612  and a second housing  614  slidably disposed within a portion of the first housing  612  such that, during deployment, the first housing  612  moves in a distal direction over the second housing  614  to release at least a portion of a prosthetic heart valve device (e.g., the device  102  of  FIGS.  6  and  8 A- 8 D ) from the delivery capsule  608 . 
     Rather than the hydraulically-actuated first and second housings described with reference to  FIGS.  6 - 10 D , the delivery capsule  608  of  FIGS.  11 A and  11 B  moves the first and second housings  612  and  614  using non-fluidic means. For example, the delivery system  600  includes a plurality of tether elements (identified individually as a first tether element  664   a  and a second tether element  664   b ; referred to collectively as “tether elements  664 ”) coupled to a distal portion and/or other portion of the first housing  612  at corresponding attachment features  666  and configured to move the first housing  612  relative to the second housing  614 . The tether elements  664  can be can be wires, sutures, cables, and/or other suitable structures for driving movement of the first housing  612 , and the attachment features  666  can include adhesives, interlocking components, hooks, eyelets, and/or other suitable fasteners for joining one end portion of the tether elements  664  to the first housing  612 . Although two tether elements  664  are shown in  FIGS.  11 A and  11 B , the delivery system  600  can include a single tether element and/or more than two tether elements to drive movement of the first housing  612 . 
     The tether elements  664  extend from the first housing  612  in a distal direction over a distal end portion  654  of the second housing  614  (e.g., a nose cone), into a distal opening  634  of the second housing  614 , and in a proximal direction through the catheter body  606 . At a proximal portion of the delivery system  600 , proximal end portions of the tether elements  664  can be attached to actuators of a handle assembly (e.g., the handle assembly  110  of  FIG.  6   ) and/or otherwise accessible to allow a clinician to pull or otherwise proximally retract the tether elements  664  (as indicated by the arrows associated with the proximal ends of the tether elements  664 ). During this proximal retraction of the tether elements  664 , the distal end portion  654  of the second housing  614  serves as a pulley to change the direction of motion, and thereby move the first housing  612  in a distal direction (as indicated by arrows  611  of  FIG.  11 B ). This causes the first housing  612  to slide over the second housing  614  such that at least a portion of the second housing  614  is telescoped within the first housing  612  and the prosthetic heart valve device is unsheathed from the first housing  612 . 
     The remainder of the prosthetic heart valve device can be unsheathed from the delivery capsule  608  in a subsequent deployment step by moving the second housing  614  (together with the first housing  612 ) in a distal direction. For example, the second housing  614  can be driven in the distal direction using mechanical means (e.g., rods or pistons) to push the second housing  614  distally, or the second housing  614  can move via hydraulic means by moving fluid to one or more fluid chambers (e.g., similar to the fluid chambers described above with reference to  FIGS.  6 - 10 D ). In other embodiments, a piston device and/or other feature can be used to push the prosthetic heart valve device in a proximal direction out from the second housing  614 . Similar to the telescoping delivery capsules described above, the mechanically-activated delivery capsule  608  can have a compact size and a relatively short overall longitudinal translation to deploy the prosthetic heart valve device to facilitate trans-septal delivery of the prosthetic heart valve device to the mitral valve. In other embodiments, the delivery capsule  608  can be used to facilitate the delivery of other types of devices to regions of the body that benefit from the short axial deployment paths provided by the telescoping housings  612 ,  614 . 
     In various embodiments, the delivery capsule  608  can further be configured to allow for resheathing a partially deployed device and/or otherwise moving the delivery capsule  608  back toward its initial delivery state. A clinician pushes or otherwise moves the tether elements  664  in the distal direction (e.g., via an actuator on a proximally-positioned handle assembly), thereby moving the first housing  612  in a proximal direction. To accommodate such distal movement of the tether elements  664 , each tether element  664  can be routed through an individual tube or channel that extends through the catheter body  606  and allows the clinician to both pull and push the tether elements  664 , while inhibiting the tether elements  664  from buckling along the length of the catheter body  606  during proximal movement. In other embodiments, the tether elements  664  and/or portions thereof can be made from semi-rigid and/or rigid materials that avoid buckling when the tether elements  664  are not placed in tension. 
       FIGS.  12 A and  12 B  are isometric and cross-sectional views, respectively, of a distal portion of a delivery system  700  configured in accordance with some embodiments of the present technology. The delivery system  700  includes various features at least generally similar to the features of the mechanically-driven delivery system  600  described above with reference to  FIGS.  11 A and  11 B . For example, the delivery system  700  includes an elongated catheter body  706 , a delivery capsule  708  with telescoping first and second housings  712  and  714  at a distal end portion  706   a  of the catheter body  706 , and a plurality of tether elements (identified individually as a first through fourth tether element  764   a - 764   d , respectively; referred to collectively as “tether elements  764 ”) coupled to portions of the first housing  712 . The tether elements  764  mechanically drive the first housing  712  in both a distal direction to move the delivery capsule  708  toward an unsheathing or deployment state and a proximal direction to move the delivery capsule  708  back toward its initial delivery state (e.g., for resheathing the device). As described in further detail below, the delivery system  700  includes four tether elements  764 —two dedicated unsheathing tether elements  764  that move the first housing  712  in the distal direction and two dedicated resheathing tether elements  764  that move the first housing  712  in the proximal direction. In other embodiments, however, the delivery system  700  can include a single tether element  764  or more than two tether elements  764  to initiate distal movement of the first housing  712 . In further embodiments, the delivery system  700  can include a single tether element or more than two tether elements  764  to initiate proximal movement of the first housing  712 . 
     The first and second tether elements  764   a  and  764   b  are configured to drive the first housing  712  in the distal direction to at least partially unsheathe a proximal heart valve device and/or other device stored within the delivery capsule  708 . Similar to the tether elements  664  of  FIGS.  11 A and  11 B , distal end portions of the first and second tether elements  764   a  and  764   b  are coupled to the first housing  712  at two corresponding attachment features  766 , from which the first and second tether elements  764   a  and  764   b  extend in a distal direction over a distal end portion  754  of the second housing  714  (e.g., a nose cone), into a distal opening  734  of the second housing  714 , and then in a proximal direction through the catheter body  706 . At a proximal portion of the delivery system  700 , a clinician can pull or otherwise proximally retract the first and second tether elements  764   a  and  764   b  (e.g., via actuators on the handle assembly  110  of  FIG.  6   ) to move the first housing  712  in a distal direction over the second housing  714  and unsheathe at least a portion of the device from the first housing  712 . The remainder of the device can be unsheathed from the delivery capsule  708  in a separate deployment step by moving the second housing  714  (together with the first housing  712 ) in a distal direction via mechanical or hydraulic actuation means and/or urging the device in a proximal direction out from the second housing  714  (e.g., via a piston device). 
     The third and fourth tether elements  764   c  and  764   d  are used to mechanically drive the first housing  712  in the proximal direction to at least partially resheathe the device and/or close the delivery capsule  708  for removal from the patient. Distal end portions of the third and fourth tether elements  764   c  and  764   d  are coupled to a distal end portion of the first housing  712  at two corresponding attachment features  770 , such as adhesives, interlocking components, hooks, eyelets, and/or other suitable fasteners for joining one end portion of the tether elements  764  to the first housing  712 . As shown in  FIGS.  12 A and  12 B , the third and fourth tether elements  764   c  and  764   d  extend from the attachment features  770  in a proximal direction between the first and second housings  712  and  714  until they are routed around an arched feature (identified individually as a first arched feature  768   a  and a second arched feature  768   b ; referred to collectively as “arched features  768 ”) of the second housing  714 . The arched features  768  can be protrusions or channels projecting from the outer surface of the second housing  714  and/or in the wall of the second housing  714 , and have a U-shaped or V-shaped surface that reverses the direction of the third and fourth tether elements  764   c  and  764   d . In the illustrated embodiment, the second housing  714  includes two arched features  768  corresponding to the two tether elements  764   c - d , but in other embodiments the second housing  714  can include a single arched feature  768  and/or more than two arched features  768  that are configured to reverse the direction of one or more tether elements  764 . After reversing direction via the arched features  768 , the third and fourth tether elements  764   c  and  764   d  extend in a distal direction over the distal end portion  754  of the second housing  714 , into the distal opening  734 , and then in a proximal direction through the catheter body  706 . At the proximal portion of the delivery system  700 , proximal end portions of the third and fourth tether elements  764   c  and  764   d  can be attached to actuators of a handle assembly (e.g., the handle assembly  110  of  FIG.  6   ) and/or otherwise accessible to allow the clinician to pull or otherwise proximally retract the third and fourth tether elements  764   c  and  764   d , which in turn moves the first housing  712  in the proximal direction. In this embodiment, the arched features  768  of the second housing  714  serve as pulleys to change the direction of motion of the third and fourth tether elements  764   c  and  764   d , thereby moving the first housing  712  in the proximal direction when the third and fourth tether elements  764   c  and  764   c  are proximally retracted. 
     In operation, the clinician can at least partially unsheathe the device by proximally retracting the first and second tether elements  764   a  and  764   b  to move the first housing  712  in the distal direction toward the unsheathing state. The clinician can further unsheathe the device by moving the second housing  714  in the distal direction. If resheathing is desired to adjust position or remove the device from the patient, the clinician can proximally retract the third and fourth tether elements  764   c  and  764   d  to move the first housing  712  back over the device in the proximal direction to resheathe a portion of the device within the first housing  712 . After full deployment of the device at the target site, proximal retraction of the third and fourth tether elements  764   c  and  764   d  can again be used to move the first housing  712  proximally such that the delivery capsule  708  is placed back into the delivery state for removal from the patient. Accordingly, the delivery system  700  uses proximal retraction of the tether elements  764  to mechanically drive the first housing  712  in both the distal and proximal directions. Similar to the telescoping delivery capsules described above, the delivery capsule  708  of  FIGS.  12 A and  12 B  provides deployment procedures that require only short overall longitudinal translation relative to the device size to facilitate trans-septal delivery of a prosthetic heart valve device to the mitral valve and/or deployment of medical devices to other target sites having constrained anatomical dimensions. 
     Selected Embodiments of Prosthetic Heart Valve Devices 
     The telescoping delivery systems  100 ,  200   a ,  200   b ,  300 ,  600  and  700  described above with reference to  FIGS.  6 - 12 B  can be configured to deliver various prosthetic heart valve devices, such as prosthetic valve devices for replacement of the mitral valve and/or other valves (e.g., a bicuspid or tricuspid valve) in the heart of the patient. Examples of these prosthetic heart valve devices, system components, and associated methods are described in this section with reference to  FIGS.  13 A- 26   . Specific elements, substructures, advantages, uses, and/or other features of the embodiments described with reference to  FIGS.  13 A- 26    can be suitably interchanged, substituted or otherwise configured with one another. Furthermore, suitable elements of the embodiments described with reference to  FIGS.  13 A- 26    can be used as stand-alone and/or self-contained devices. 
       FIG.  13 A  is a side cross-sectional view and  FIG.  13 B  is a top plan view of a prosthetic heart valve device (“device”)  1100  in accordance with an embodiment of the present technology. The device  1100  includes a valve support  1110 , an anchoring member  1120  attached to the valve support  1110 , and a prosthetic valve assembly  1150  within the valve support  1110 . Referring to  FIG.  13 A , the valve support  1110  has an inflow region  1112  and an outflow region  1114 . The prosthetic valve assembly  1150  is arranged within the valve support  1110  to allow blood to flow from the inflow region  1112  through the outflow region  1114  (arrows BF), but prevent blood from flowing in a direction from the outflow region  1114  through the inflow region  1112 . 
     In the embodiment shown in  FIG.  13 A , the anchoring member  1120  includes a base  1122  attached to the outflow region  1114  of the valve support  1110  and a plurality of arms  1124  projecting laterally outward from the base  1122 . The anchoring member  1120  also includes a fixation structure  1130  extending from the arms  1124 . The fixation structure  1130  can include a first portion  1132  and a second portion  1134 . The first portion  1132  of the fixation structure  1130 , for example, can be an upstream region of the fixation structure  1130  that, in a deployed configuration as shown in  FIG.  13 A , is spaced laterally outward apart from the inflow region  1112  of the valve support  1110  by a gap G. The second portion  1134  of the fixation structure  1130  can be a downstream-most portion of the fixation structure  1130 . The fixation structure  1130  can be a cylindrical ring (e.g., straight cylinder or conical), and the outer surface of the fixation structure  1130  can define an annular engagement surface configured to press outwardly against a native annulus of a heart valve (e.g., a mitral valve). The fixation structure  1130  can further include a plurality of fixation elements  1136  that project radially outward and are inclined toward an upstream direction. The fixation elements  1136 , for example, can be barbs, hooks, or other elements that are inclined only in the upstream direction (e.g., a direction extending away from the downstream portion of the device  1100 ). 
     Referring still to  FIG.  13 A , the anchoring member  1120  has a smooth bend  1140  between the arms  1124  and the fixation structure  1130 . For example, the second portion  1134  of the fixation structure  1130  extends from the arms  1124  at the smooth bend  1140 . The arms  1124  and the fixation structure  1130  can be formed integrally from a continuous strut or support element such that the smooth bend  1140  is a bent portion of the continuous strut. In other embodiments, the smooth bend  1140  can be a separate component with respect to either the arms  1124  or the fixation structure  1130 . For example, the smooth bend  1140  can be attached to the arms  1124  and/or the fixation structure  1130  using a weld, adhesive or other technique that forms a smooth connection. The smooth bend  1140  is configured such that the device  1100  can be recaptured in a capsule or other container after the device  1100  has been at least partially deployed. 
     The device  1100  can further include a first sealing member  1162  on the valve support  1110  and a second sealing member  1164  on the anchoring member  1120 . The first and second sealing members  1162 ,  1164  can be made from a flexible material, such as Dacron® or another type of polymeric material. The first sealing member  1162  can cover the interior and/or exterior surfaces of the valve support  1110 . In the embodiment illustrated in  FIG.  13 A , the first sealing member  1162  is attached to the interior surface of the valve support  1110 , and the prosthetic valve assembly  1150  is attached to the first sealing member  1162  and commissure portions of the valve support  1110 . The second sealing member  1164  is attached to the inner surface of the anchoring member  1120 . As a result, the outer annular engagement surface of the fixation structure  1130  is not covered by the second sealing member  1164  so that the outer annular engagement surface of the fixation structure  1130  directly contacts the tissue of the native annulus. 
     The device  1100  can further include an extension member  1170 . The extension member  1170  can be an extension of the second sealing member  1164 , or it can be a separate component attached to the second sealing member  1164  and/or the first portion  1132  of the fixation structure  1130 . The extension member  1170  can be a flexible member that, in a deployed state ( FIG.  13 A ), flexes relative to the first portion  1132  of the fixation structure  1130 . In operation, the extension member  1170  guides the device  1100  during implantation such that the device  1100  is located at a desired elevation and centered relative to the native annulus. As described below, the extension member  1170  can include a support member, such as a metal wire or other structure, that can be visualized via fluoroscopy or other imaging techniques during implantation. For example, the support member can be a radiopaque wire. 
       FIGS.  14 A and  14 B  are cross-sectional views illustrating an example of the operation of the smooth bend  1140  between the arms  1124  and the fixation structure  1130  in the recapturing of the device  1100  after partial deployment.  FIG.  14 A  schematically shows the device  1100  loaded into a capsule  1700  of a delivery system in a delivery state, and  FIG.  14 B  schematically shows the device  1100  in a partially deployed state. Referring to  FIG.  14 A , the capsule  1700  has a housing  1702 , a pedestal or support  1704 , and a top  1706 . In the delivery state shown in  FIG.  14 A , the device  1100  is in a low-profile configuration suitable for delivery through a catheter or cannula to a target implant site at a native heart valve. 
     Referring to  FIG.  14 B , the housing  1702  of the capsule  1700  has been moved distally such that the extension member  1170 , fixation structure  1130  and a portion of the arms  1124  have been released from the housing  1702  in a partially deployed state. This is useful for locating the fixation structure  1130  at the proper elevation relative to the native valve annulus A such that the fixation structure  1130  expands radially outward into contact the inner surface of the native annulus A. However, the device  1100  may need to be repositioned and/or removed from the patient after being partially deployed. To do this, the housing  1702  is retracted (arrow R) back toward the fixation structure  1130 . As the housing  1702  slides along the arms  1124 , the smooth bend  1140  between the arms  1124  and the fixation structure  1130  allows the edge  1708  of the housing  1702  to slide over the smooth bend  1140  and thereby recapture the fixation structure  1130  and the extension member  1170  within the housing  1702 . The device  1100  can then be removed from the patient or repositioned for redeployment at a better location relative to the native annulus A. Further aspects of prosthetic heart valve devices in accordance with the present technology and their interaction with corresponding delivery devices are described below with reference to  FIGS.  15 - 26   . 
       FIG.  15    is a top isometric view of an example of the device  1100 . In this embodiment, the valve support  1110  defines a first frame (e.g., an inner frame) and fixation structure  1130  of the anchoring member  1120  defines a second frame (e.g., an outer frame) that each include a plurality of structural elements. The fixation structure  1130 , more specifically, includes structural elements  1137  arranged in diamond-shaped cells  1138  that together form at least a substantially cylindrical ring when freely and fully expanded as shown in  FIG.  15   . The structural elements  1137  can be struts or other structural features formed from metal, polymers, or other suitable materials that can self-expand or be expanded by a balloon or other type of mechanical expander. 
     In several embodiments, the fixation structure  1130  can be a generally cylindrical fixation ring having an outwardly facing engagement surface. For example, in the embodiment shown in  FIG.  15   , the outer surfaces of the structural elements  1137  define an annular engagement surface configured to press outwardly against the native annulus in the deployed state. In a fully expanded state without any restrictions, the walls of the fixation structure  1130  are at least substantially parallel to those of the valve support  1110 . However, the fixation structure  1130  can flex inwardly (arrow I) in the deployed state when it presses radially outwardly against the inner surface of the native annulus of a heart valve. 
     The embodiment of the device  1100  shown in  FIG.  15    includes the first sealing member  1162  lining the interior surface of the valve support  1110 , and the second sealing member  1164  along the inner surface of the fixation structure  1130 . The extension member  1170  has a flexible web  1172  (e.g., a fabric) and a support member  1174  (e.g., metal or polymeric strands) attached to the flexible web  1172 . The flexible web  1172  can extend from the second sealing member  1164  without a metal-to-metal connection between the fixation structure  1130  and the support member  1174 . For example, the extension member  1170  can be a continuation of the material of the second sealing member  1164 . Several embodiments of the extension member  1170  are thus a malleable or floppy structure that can readily flex with respect to the fixation structure  1130 . The support member  1174  can have a variety of configurations and be made from a variety of materials, such as a double-serpentine structure made from Nitinol. 
       FIG.  16    is a side view and  FIG.  17    is a bottom isometric view of the device  1100  shown in  FIG.  15   . Referring to  FIG.  16   , the arms  1124  extend radially outward from the base portion  1122  at an angle α selected to position the fixation structure  1130  radially outward from the valve support  1110  ( FIG.  15   ) by a desired distance in a deployed state. The angle α is also selected to allow the edge  1708  of the delivery system housing  1702  ( FIG.  14 B ) to slide from the base portion  1122  toward the fixation structure  1130  during recapture. In many embodiments, the angle α is 15°-75°, or more specifically 15°-60°, or still more specifically 30°-45°. The arms  1124  and the structural elements  1137  of the fixation structure  1130  can be formed from the same struts (i.e., formed integrally with each other) such that the smooth bend  1140  is a continuous, smooth transition from the arms  1124  to the structural elements  1137 . This is expected to enable the edge  1708  of the housing  1702  to more readily slide over the smooth bend  1140  in a manner that allows the fixation structure  1130  to be recaptured in the housing  1702  of the capsule  1700  ( FIG.  14 B ). Additionally, by integrally forming the arms  1124  and the structural elements  1137  with each other, it inhibits damage to the device  1100  at a junction between the arms  1124  and the structural elements  1137  compared to a configuration in which the arms  1124  and structural elements  1137  are separate components and welded or otherwise fastened to each other. 
     Referring to  FIGS.  16  and  17   , the arms  1124  are also separated from each other along their entire length from where they are connected to the base portion  1122  through the smooth bend  1140  ( FIG.  16   ) to the structural elements  1137  of the fixation structure  1130 . The individual arms  1124  are thus able to readily flex as the edge  1708  of the housing  1702  ( FIG.  14 B ) slides along the arms  1124  during recapture. This is expected to reduce the likelihood that the edge  1708  of the housing  1702  will catch on the arms  1124  and prevent the device  1100  from being recaptured in the housing  1702 . 
     In one embodiment, the arms  1124  have a first length from the base  1122  to the smooth bend  1140 , and the structural elements  1137  of the fixation structure  1130  at each side of a cell  1138  ( FIG.  15   ) have a second length that is less than the first length of the arms  1124 . The fixation structure  1130  is accordingly less flexible than the arms  1124 . As a result, the fixation structure  1130  is able to press outwardly against the native annulus with sufficient force to secure the device  1100  to the native annulus, while the arms  1124  are sufficiently flexible to fold inwardly when the device is recaptured in a delivery device. 
     In the embodiment illustrated in  FIGS.  15 - 17   , the arms  1124  and the structural elements  1137  are configured such that each arm  1124  and the two structural elements  1137  extending from each arm  1124  formed a Y-shaped portion  1142  ( FIG.  17   ) of the anchoring member  1120 . Additionally, the right-hand structural element  1137  of each Y-shaped portion  1142  is coupled directly to a left-hand structural element  1137  of an immediately adjacent Y-shaped portion  1142 . The Y-shaped portions  1142  and the smooth bends  1140  are expected to further enhance the ability to slide the housing  1702  along the arms  1124  and the fixation structure  1130  during recapture. 
       FIG.  18    is a side view and  FIG.  19    is a bottom isometric view of a prosthetic heart valve device (“device”)  1200  in accordance with another embodiment of the present technology. The device  1200  is shown without the extension member  1170  ( FIGS.  15 - 17   ), but the device  1200  can further include the extension member  1170  described above. The device  1200  further includes extended connectors  1210  projecting from the base  1122  of the anchoring member  1120 . Alternatively, the extended connectors  1210  can extend from the valve support  1110  ( FIGS.  13 A- 17   ) in addition to or in lieu of extending from the base  1122  of the anchoring member  1120 . The extended connectors  1210  can include a first strut  1212   a  attached to one portion of the base  1122  and a second strut  1212   b  attached to another portion of the base  1122 . The first and second struts  1212   a - b  are configured to form a V-shaped structure in which they extend toward each other in a downstream direction and are connected to each other at the bottom of the V-shaped structure. The V-shaped structure of the first and second struts  1212   a - b  causes the extension connector  1210  to elongate when the device  1200  is in a low-profile configuration within the capsule  1700  ( FIG.  14 A ) during delivery or partial deployment. When the device  1200  is fully released from the capsule  1700  ( FIG.  14 A ) the extension connectors  1210  foreshorten to avoid interfering with blood flow along the left ventricular outflow tract. 
     The extended connectors  1210  further include an attachment element  1214  configured to releasably engage a delivery device. The attachment element  1214  can be a T-bar or other element that prevents the device  1200  from being released from the capsule  1700  ( FIG.  14 A ) of a delivery device until desired. For example, a T-bar type attachment element  1214  can prevent the device  1200  from moving axially during deployment or partial deployment until the housing  1702  ( FIG.  14 A ) moves beyond the portion of the delivery device engaged with the attachment elements  1214 . This causes the attachment elements  1214  to disengage from the capsule  1700  ( FIG.  14 A ) as the outflow region of the valve support  1110  and the base  1122  of the anchoring member  1120  fully expand to allow for full deployment of the device  1200 . 
       FIG.  20    is a side view and  FIG.  21    is a bottom isometric view of the device  1200  in a partially deployed state in which the device  1200  is still capable of being recaptured in the housing  1702  of the delivery device  1700 . Referring to  FIG.  20   , the device  1200  is partially deployed with the fixation structure  1130  substantially expanded but the attachment elements  1214  ( FIG.  18   ) still retained within the capsule  1700 . This is useful for determining the accuracy of the position of the device  1200  during implantation while retaining the ability to recapture the device  1200  in case it needs to be repositioned or removed from the patient. In this state of partial deployment, the elongated first and second struts  1212   a - b  of the extended connectors  1210  space the base  1122  of the anchoring member  1120  and the outflow region of the valve support  1110  ( FIG.  13 A ) apart from the edge  1708  of the capsule  1700  by a gap G. 
     Referring to  FIG.  21   , the gap G enables blood to flow through the prosthetic valve assembly  1150  while the device  1200  is only partially deployed. As a result, the device  1200  can be partially deployed to determine (a) whether the device  1200  is positioned correctly with respect to the native heart valve anatomy and (b) whether proper blood flow passes through the prosthetic valve assembly  1150  while the device  1200  is still retained by the delivery system  1700 . As such, the device  1200  can be recaptured if it is not in the desired location and/or if the prosthetic valve is not functioning properly. This additional functionality is expected to significantly enhance the ability to properly position the device  1200  and assess, in vivo, whether the device  1200  will operate as intended, while retaining the ability to reposition the device  1200  for redeployment or remove the device  1200  from the patient. 
       FIG.  22    is an isometric view of a valve support  1300  in accordance with an embodiment of the present technology. The valve support  1300  can be an embodiment of the valve support  1110  described above with respect to  FIGS.  13 A- 21   . The valve support  1300  has an outflow region  1302 , an inflow region  1304 , a first row  1310  of first hexagonal cells  1312  at the outflow region  1302 , and a second row  1320  of second hexagonal cells  1322  at the inflow region  1304 . For purposes of illustration, the valve support shown in  FIG.  22    is inverted compared to the valve support  1110  shown in  FIGS.  13 A- 21    such that the blood flows through the valve support  1300  in the direction of arrow BF. In mitral valve applications, the valve support  1300  would be positioned within the anchoring member  1120  ( FIG.  13 A ) such that the inflow region  1304  would correspond to orientation of the inflow region  1112  in  FIG.  13 A  and the outflow region  1302  would correspond to the orientation of the outflow region  1114  in  FIG.  13 A . 
     Each of the first hexagonal cells  1312  includes a pair of first longitudinal supports  1314 , a downstream apex  1315 , and an upstream apex  1316 . Each of the second hexagonal cells  1322  can include a pair of second longitudinal supports  1324 , a downstream apex  1325 , and an upstream apex  1326 . The first and second rows  1310  and  1312  of the first and second hexagonal cells  1312  and  1322  are directly adjacent to each other. In the illustrated embodiment, the first longitudinal supports  1314  extend directly from the downstream apexes  1325  of the second hexagonal cells  1322 , and the second longitudinal supports  1324  extend directly from the upstream apexes  1316  of the first hexagonal cells  1312 . As a result, the first hexagonal cells  1312  are offset from the second hexagonal cells  1322  around the circumference of the valve support  1300  by half of the cell width. 
     In the embodiment illustrated in  FIG.  22   , the valve support  1300  includes a plurality of first struts  1331  at the outflow region  1302 , a plurality of second struts  1332  at the inflow region  1304 , and a plurality of third struts  1333  between the first and second struts  1331  and  1332 . Each of the first struts  1331  extends from a downstream end of the first longitudinal supports  1314 , and pairs of the first struts  1331  are connected together to form first downstream V-struts defining the downstream apexes  1315  of the first hexagonal cells  1312 . In a related sense, each of the second struts  1332  extends from an upstream end of the second longitudinal supports  1324 , and pairs of the second struts  1332  are connected together to form second upstream V-struts defining the upstream apexes  1326  of the second hexagonal cells  1322 . Each of the third struts  1333  has a downstream end connected to an upstream end of the first longitudinal supports  1314 , and each of the third struts  1333  has an upstream end connected to a downstream end of one of the second longitudinal supports  1324 . The downstream ends of the third struts  1333  accordingly define a second downstream V-strut arrangement that forms the downstream apexes  1325  of the second hexagonal cells  1322 , and the upstream ends of the third struts  1333  define a first upstream V-strut arrangement that forms the upstream apexes  1316  of the first hexagonal cells  1312 . The third struts  1333 , therefore, define both the first upstream V-struts of the first hexagonal cells  1312  and the second downstream V-struts of the second hexagonal cells  1322 . 
     The first longitudinal supports  1314  can include a plurality of holes  1336  through which sutures can pass to attach a prosthetic valve assembly and/or a sealing member. In the embodiment illustrated in  FIG.  22   , only the first longitudinal supports  1314  have holes  1336 . However, in other embodiments the second longitudinal supports  1324  can also include holes either in addition to or in lieu of the holes  1336  in the first longitudinal supports  1314 . 
       FIG.  23    is a side view and  FIG.  24    is a bottom isometric view of the valve support  1300  with a first sealing member  1162  attached to the valve support  1300  and a prosthetic valve  1150  within the valve support  1300 . The first sealing member  1162  can be attached to the valve support  1300  by a plurality of sutures  1360  coupled to the first longitudinal supports  1314  and the second longitudinal supports  1324 . At least some of the sutures  1360  coupled to the first longitudinal supports  1314  pass through the holes  1336  to further secure the first sealing member  1162  to the valve support  1300 . 
     Referring to  FIG.  24   , the prosthetic valve  1150  can be attached to the first sealing member  1162  and/or the first longitudinal supports  1314  of the valve support  1300 . For example, the commissure portions of the prosthetic valve  1150  can be aligned with the first longitudinal supports  1314 , and the sutures  1360  can pass through both the commissure portions of the prosthetic valve  1150  and the first sealing member  1162  where the commissure portions of the prosthetic valve  1150  are aligned with a first longitudinal support  1314 . The inflow portion of the prosthetic valve  1150  can be sewn to the first sealing member  1162 . 
     The valve support  1300  illustrated in  FIGS.  22 - 24    is expected to be well suited for use with the device  1200  described above with reference to  FIGS.  18 - 21   . More specifically, the first struts  1331  cooperate with the extended connectors  1210  ( FIGS.  18 - 21   ) of the device  1200  to separate the outflow portion of the prosthetic valve  1150  from the capsule  1700  ( FIGS.  12 A and  12 B ) when the device  1200  is in a partially deployed state. The first struts  1331 , for example, elongate when the valve support  1300  is not fully expanded (e.g., at least partially contained within the capsule  1700 ) and foreshorten when the valve support is fully expanded. This allows the outflow portion of the prosthetic valve  1150  to be spaced further apart from the capsule  1700  in a partially deployed state so that the prosthetic valve  1150  can at least partially function when the device  1200  ( FIGS.  18 - 21   ) is in the partially deployed state. Therefore, the valve support  1300  is expected to enhance the ability to assess whether the prosthetic valve  1150  is fully operational in a partially deployed state. 
       FIGS.  25  and  26    are schematic side views of valve supports  1400  and  1500 , respectively, in accordance with other embodiments of the present technology. Referring to  FIG.  25   , the valve support  1400  includes a first row  1410  of first of hexagonal cells  1412  and a second row  1420  of second hexagonal cells  1422 . The valve  1400  can further include a first row  1430  of diamond-shaped cells extending from the first hexagonal cells  1412  and a second row  1440  of diamond-shaped cells extending from the second hexagonal cells  1422 . The additional diamond-shaped cells elongate in the low-profile state, and thus they can further space the prosthetic valve  1150  (shown schematically) apart from a capsule of a delivery device. Referring to  FIG.  26   , the valve support  1500  includes a first row  1510  of first hexagonal cells  1512  at an outflow region  1502  and a second row  1520  of second hexagonal cells  1522  at an inflow region  1504 . The valve support  1500  is shaped such that an intermediate region  1506  (between the inflow and outflow regions  1502  and  1504 ) has a smaller cross-sectional area than that of the outflow region  1502  and/or the inflow region  1504 . As such, the first row  1510  of first hexagonal cells  1512  flares outwardly in the downstream direction and the second row  1520  of second hexagonal cells  1522  flares outwardly in the upstream direction. 
     EXAPLES 
     Several aspects of the present technology are set forth in the following examples. 
     1. A system for delivering a prosthetic heart valve device into a heart of a patient, the system comprising:
         an elongated catheter body; and   a delivery capsule carried by the elongated catheter body and configured to move between a delivery state for holding the prosthetic heart valve device and a deployment state for at least partially deploying the prosthetic heart valve device, wherein the delivery capsule comprises—
           a first housing configured to contain at least a first portion of the prosthetic heart valve device;   a second housing slidably associated with at least a portion of the first housing, wherein the second housing is configured to contain a second portion of the prosthetic heart valve device,   wherein, during a first deployment stage, the first housing moves in a distal direction with respect to the second housing to release the first portion of the prosthetic heart valve device from the delivery capsule, and   wherein, during a second deployment stage, the second housing and the first housing together move in a distal direction to release the second portion of the prosthetic heart valve device from the delivery capsule.   
               

     2. The system of example  1  wherein the delivery capsule further comprises:
         a first sealing member between a distal portion of the first housing and the second housing,   wherein the first sealing member is slidable along the second housing;   a second sealing member between a proximal portion of the second housing and the first housing;   a first fluid chamber between the first and second sealing members; and   a second fluid chamber defined at least in part by an inner surface of the second housing,   wherein, during the first deployment stage, fluid is delivered to the first chamber to slide the first sealing member in the distal direction over the second housing, and   wherein, during the second deployment stage, fluid is delivered to the second chamber such that the first and second housings move together in the distal direction.       

     3. The system of example 2, further comprising a platform extending from the elongated catheter body into the second housing, wherein the platform includes a distal end portion slidably sealed against an inner wall of the second housing and defines a proximal end of the second fluid chamber. 
     4. The system of example 2 or 3 wherein the first sealing member is a first sleeve extending inwardly from the first housing, and the second sealing member is a second sleeve extending outwardly from the second housing. 
     5. The system of any one of examples 2-4 wherein, after the second deployment stage, the first fluid chamber is configured to be evacuated of fluid while the second fluid chamber remains pressurized with fluid such that the first housing moves in a proximal direction. 
     6. The system of any one of examples 2-5, further comprising:
         a first fluid lumen extending through the elongated catheter body and in fluid communication with the first fluid chamber; and   a second fluid lumen extending through the elongated catheter body in fluid communication with the second fluid chamber.       

     7. The system of example 6 wherein the first fluid lumen passes through the second housing and into a port in the first housing, wherein the port is in fluid communication with the first fluid chamber. 
     8. The system of example 6 wherein second housing has an inner channel in a wall of the second housing, and wherein the inner channel is in fluid communication with the first fluid chamber and defines a portion of the first fluid lumen. 
     9. The system of any one of examples 1-8 wherein the delivery capsule has an overall length of at most 50 mm. 
     10. The system of any one of examples 1-9 wherein the delivery capsule has an overall length of at most 40 mm. 
     11. The system of any one of examples 1-10 wherein the first housing and the second housing each have a length of at most 30 mm. 
     12. The system of any one of examples 1-11, further comprising:
         a first spring biasing the first housing toward the delivery state; and   a second spring biasing the second housing toward the delivery state.       

     13. The system of example 1 wherein the second housing includes an arched feature on an outer surface of the second housing and positioned between the first and second housings,
         wherein the system further comprises:   a first tether element attached to a first portion of the first housing, wherein the first tether element extends from the first housing, over a distal end portion of the second housing, into the second housing, and through the elongated catheter body;   a second tether element attached to a second portion of the first housing, wherein the second tether element extends in a proximal direction around the arched feature, over the distal end portion of the second housing, into the second housing, and through though the elongated catheter body,   wherein proximal retraction of the first tether element slides the first housing over the second housing in the distal direction to unsheathe at least a portion of the prosthetic heart valve device from the delivery capsule, and   wherein proximal retraction of the second tether element slides the first housing over the second housing in a proximal direction to resheathe the prosthetic heart valve device.       

       14 . A system for delivering a prosthetic heart valve device into a heart of a patient, the system comprising:
         an elongated catheter body; and   a delivery capsule carried by the elongated catheter body and configured to be hydraulically driven between a delivery state for holding the prosthetic heart valve device and a deployment state for at least partially deploying the prosthetic heart valve device, wherein the delivery capsule comprises—
           a first housing configured to contain at least a first portion of the prosthetic heart valve device;   a second housing slidably disposed within at least a portion of the first housing, wherein the second housing is configured to contain a second portion of the prosthetic heart valve device;   a first fluid chamber defined at least in part by an inner surface of the first housing and an outer surface of the second housing; and   a second fluid chamber defined at least in part by an inner surface of the second housing,   wherein, during a first deployment stage, the first fluid chamber is configured to receive fluid that moves the first housing in a distal direction over the second housing to release the first portion of the prosthetic heart valve device from the delivery capsule, and   wherein, during a second deployment stage, the second chamber is configured to receive fluid such that the first and second housings move together in the distal direction to release the second portion of the prosthetic heart valve device from the delivery capsule.   
               
     15. The system of example 14 wherein the delivery capsule further comprises:
         a first sealing member between a distal portion of the first housing and the second housing, wherein the first sealing member is slidable along the second housing; and   a second sealing member between a proximal portion of the first housing and the second housing,   wherein the first fluid chamber extends between the first and second sealing members.       

     16. The system of example 14 or 15, further comprising a platform extending from the elongated catheter body into the second housing, wherein the platform includes a distal end portion slidably sealed against an inner wall of the second housing, and wherein the distal end portion of the platform defines a proximal end of the second fluid chamber. 
     17. The system of any one of examples 14-16 wherein, during a resheathing phase, the first fluid chamber is configured to be evacuated of fluid while the second fluid chamber remains pressurized with fluid to allow the first housing to slide in a proximal direction over the second housing. 
     18. The system of any one of examples 14-17, further comprising:
         a first fluid lumen extending through the elongated catheter body and in fluid communication with the first fluid chamber; and   a second fluid lumen extending through the elongated catheter body in fluid communication with the second fluid chamber.       

     19. The system of example 18 wherein the first fluid lumen passes into the second housing, outside the first and second housings, and into a port in the first housing, wherein the port is in fluid communication with the first fluid chamber. 
     20. The system of example 18 wherein the first lumen is defined in part by an inner channel of the second housing. 
     21. The system of any one of examples 14-20 wherein the first and second housings each have a length of 20-30 mm. 
     22. The system of any one of examples 14-21, further comprising:
         a first spring configured to urge the first housing toward the delivery state when the first fluid chamber is evacuated of fluid; and   a second spring configured to urge the second housing toward the delivery state when the second fluid chamber is evacuated of fluid.       

     23. A method for delivering a prosthetic heart valve device to a native mitral valve of a heart of a human patient, the method comprising:
         positioning a delivery capsule at a distal portion of an elongated catheter body within the heart, the delivery capsule carrying the prosthetic heart valve device;   delivering fluid to a first fluid chamber of the delivery capsule to slide a first housing in a distal direction over a portion of a second housing, thereby releasing a first portion of the prosthetic heart valve device from the delivery capsule; and   delivering fluid to a second fluid chamber of the delivery capsule to move the second housing together with the first housing in the distal direction to release a second portion of the prosthetic heart valve device from the delivery capsule.       

     24. The method of example 23, further comprising evacuating fluid from the first fluid chamber while the second fluid chamber remains pressurized with fluid such that the first housing slides in a proximal direction over the second housing. 
     25. The method of example 23 or 24 wherein positioning the delivery capsule within the heart comprises delivering the delivery capsule across an atrial septum of the heart to a left atrium. 
     26. A method for delivering a prosthetic heart valve device to a native mitral valve of a heart of a human patient, the method comprising:
         delivering a delivery capsule at a distal portion of an elongated catheter body across an atrial septum of the heart to a left atrium of the heart, the delivery capsule having a first housing and a second housing slidably disposed within at least a portion of the first housing, wherein the first and second housing contain the prosthetic heart valve device in a delivery state;   positioning the delivery capsule between native leaflets of the native mitral valve;   moving the first housing in a distal direction over the second housing to release a first portion of the prosthetic heart valve device from the delivery capsule; and   moving a second housing in the distal direction to release a second portion of the prosthetic heart valve device from the delivery capsule.       

     CONCLUSION 
     The above detailed descriptions of embodiments of the technology are not intended to be exhaustive or to limit the technology to the precise form disclosed above. Although specific embodiments of, and examples for, the technology are described above for illustrative purposes, various equivalent modifications are possible within the scope of the technology as those skilled in the relevant art will recognize. For example, although steps are presented in a given order, alternative embodiments may perform steps in a different order. The various embodiments described herein may also be combined to provide further embodiments. 
     From the foregoing, it will be appreciated that specific embodiments of the technology have been described herein for purposes of illustration, but well-known structures and functions have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments of the technology. Where the context permits, singular or plural terms may also include the plural or singular term, respectively. 
     Moreover, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in reference to a list of two or more items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of the items in the list. Additionally, the term “comprising” is used throughout to mean including at least the recited feature(s) such that any greater number of the same feature and/or additional types of other features are not precluded. It will also be appreciated that specific embodiments have been described herein for purposes of illustration, but that various modifications may be made without deviating from the technology. Further, while advantages associated with certain embodiments of the technology have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the technology. Accordingly, the disclosure and associated technology can encompass other embodiments not expressly shown or described herein.