Patent Publication Number: US-2016220367-A1

Title: Balloon valvuloplasty delivery system

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to a dilation balloon and prosthetic heart valve delivery system. 
     2. Background Art 
     Unhealthy Cardiac valves can exhibit two types of pathologies: regurgitation and stenosis. Regurgitation is the more common of the two defects. Either defect can be treated by a surgical repair. In addition, stenosis can be treated through balloon dilation, also known as valvuloplasty, by placing a balloon catheter inside the valve and inflating the balloon in an effort to increase the opening size of the valve and thus improve blood flow. 
     Under certain conditions, the cardiac valve must be replaced. Standard approaches to valve replacement require cutting open the patient&#39;s chest and heart to access the native valve. Such procedures are traumatic to the patient, require a long recovery time, and can result in life threatening complications. Therefore, many patients requiring cardiac valve replacement are deemed to pose too high a risk for open heart surgery due to age, health, or a variety of other factors. These patient risks associated with heart valve replacement are lessened by the emerging techniques for minimally invasive valve repair, but still many of those techniques require arresting the heart and passing the blood through a heart-lung machine. 
     Efforts have been focused on percutaneous transluminal delivery of replacement cardiac valves to solve the problems presented by traditional open heart surgery and minimally-invasive surgical methods. In such methods, a valve prosthesis is compacted for delivery in a catheter and then advanced, for example, through an opening in the femoral artery and through the descending aorta to the heart, where the prosthesis is then deployed in the aortic valve annulus. Often in the case of a stenosed valve, valvuloplasty is performed prior to delivery of the valve prosthesis. In addition, after deployment of the valve prosthesis, balloon dilation can be performed to post dilate the valve prosthesis and ensure that the valve prosthesis is adequately seated in the native valve annulus. 
     Balloon valvuloplasty is typically carried out prior to a TAVI (Transcatheter Aortic Valve Implantation) procedure in order to open out the calcified tissue leaflets. Some physicians will also do a second balloon valvuloplasty procedure after the valve has deployed in order to ensure that the valve has fully opened out. This means going in with a balloon catheter, retracting it, going in with the valve delivery system, retracting it, then going back in with the balloon catheter. This adds to procedure time, which adds more potential risk to the patient and can be very laborious for a physician. What is needed is a delivery system that not only gives the physician the choice of using a balloon catheter or to use the valve delivery system, but also allows the physician to select and attach the preferred balloon size for each patient. 
     BRIEF SUMMARY OF THE INVENTION 
     Provided herein is a valve prostheses delivery system that generally includes a delivery system having a capsule at a distal end. The capsule surrounds a compressed valve prosthesis and a balloon is provided on a distal end of the delivery system. Such configurations achieve numerous goals. For example, such a configuration allows for a reduction in the number of devices used to treat a stenosed valve through balloon dilation and to deliver a valve prosthesis. In addition, different types of balloons are interchangeable on the delivery device thereby expanding the treatment options. 
     In view thereof, disclosed herein are aspects of an balloon dilation and valve prosthesis delivery system which is generally designed to include an inner shaft assembly including an intermediate portion providing a coupling structure configured to selectively engage a prosthetic valve, and an outer shaft assembly including a delivery sheath capsule, and expandable balloon removably coupled to a base tip on a distal end of the outer shaft assembly, and an inflation lumen extending along the length of the outer shaft assembly. 
     In another exemplary embodiment, disclosed herein are aspects of a balloon dilation and valve prosthesis delivery system including an inner shaft assembly including an intermediate portion providing a coupling structure configured to selectively engage a prosthetic heart valve and an outer shaft assembly including a delivery sheath capsule at a distal end of the outer shaft assembly, the capsule being slidably disposed over the inner shaft assembly and configured to compressively contain a prosthetic heart valve engaged with the coupling structure, an expandable balloon removeably coupled to a distal end of the outer shaft, and an inflation lumen. The inflation lumen extending along the length of the outer shaft assembly, configured to transmit fluid into the balloon for expansion. The inner shaft telescopically slidable within the inflation lumen of the outer shaft assembly, such that a distal end of the inner shaft is extendible forwardly past the distal end of the outer shaft to dispose the inner member within the balloon. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
       The accompanying figures, which are incorporated herein, form part of the specification and illustrate embodiments of a valve prosthesis. Together with the description, the figures further serve to explain the principles of and to enable a person skilled in the relevant art(s) to make, use, and implant the valve prosthesis described herein. In the drawings, like reference numbers indicate identical or functionally similar elements. 
         FIG. 1  is a sectional view of a valve prosthesis delivery system according to an aspect of this disclosure. 
         FIG. 2  is a side view of a valve prosthesis delivery system according to an aspect of this disclosure. 
         FIG. 3  is a perspective view of a valve prosthesis delivery system according to an aspect of this disclosure. 
         FIG. 4  is a perspective view of a valve prosthesis delivery system with a tip removed according to an aspect of this disclosure. 
         FIG. 5  is a perspective view of a valve prosthesis delivery system with an inner member extending forwardly according to an aspect of this disclosure. 
         FIG. 6  is a perspective view of a valve prosthesis delivery system with an inner member extending forwardly according to an aspect of this disclosure. 
         FIG. 7  is a perspective view of a valve prosthesis delivery system and dilation balloon according to an aspect of this disclosure. 
         FIG. 8  is a perspective view of a valve prosthesis delivery system and dilation balloon according to an aspect of this disclosure. 
         FIG. 9  is a perspective view of a valve prosthesis delivery system and dilation balloon according to an aspect of this disclosure. 
         FIG. 10  is a perspective view of a valve prosthesis delivery system and dilation balloon in a collapsed configuration according to an aspect of this disclosure. 
         FIG. 11  is a perspective view of a handle to a valve prosthesis delivery system and dilation balloon according to an aspect of this disclosure. 
         FIG. 12  is a perspective view of a handle to a valve prosthesis delivery system and dilation balloon according to an aspect of this disclosure. 
         FIG. 13  is a perspective view of a valve prosthesis delivery system with a tip removed and a collet portion drawn in phantom lines to show an inner member disposed within a middle member according to an aspect of this disclosure. 
         FIG. 14  is a perspective view of a valve prosthesis delivery system with a tip drawn in phantom lines to show a collet portion and an inner member extending forwardly from the collet portion according to an aspect of this disclosure. 
         FIG. 15  is a schematic view of a stenosed aortic valve and a guide wire for a valve prosthesis delivery system and dilation balloon according to an aspect of this disclosure. 
         FIG. 16  is a schematic view of a stenosed aortic valve and a valve prosthesis delivery system and dilation balloon according to an aspect of this disclosure. 
         FIG. 17  is a schematic view of a stenosed aortic valve and a valve prosthesis delivery system and an expanded dilation balloon according to an aspect of this disclosure. 
         FIG. 18  is a schematic view of a stenosed aortic valve and a valve prosthesis delivery system and a collapsed dilation balloon according to an aspect of this disclosure. 
         FIG. 19  is a schematic view of a valve prosthesis and valve prosthesis delivery system and dilation balloon according to an aspect of this disclosure. 
         FIG. 20  is a schematic view of a valve prosthesis and valve prosthesis delivery system and dilation balloon according to an aspect of this disclosure. 
         FIG. 21  is a schematic view of a valve prosthesis and valve prosthesis delivery system and an expanded dilation balloon according to an aspect of this disclosure. 
         FIG. 22  is a schematic view of a valve prosthesis after deployment according to an aspect of this disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Specific embodiments of the present invention are now described with reference to the figures, wherein like reference numbers indicate identical or functionally similar elements. The terms “distal” and “proximal” are used in the following description with respect to a position or direction relative to the treating clinician when describing an object or device manipulated by the clinician. “Distal” and “distally” are positions distant from or in a direction away from the clinician. “Proximal” and “proximally” are positions near or in a direction toward the clinician. The terms “distal” and “proximal”, when used with respect to a position in a vessel refer to a position or direction relative to the direction of blood flow. Accordingly, “distal” and “distally” are positions downstream of a reference position, and “proximal” and “proximally” are positions upstream of the reference position. 
     The following detailed description of a valve prosthesis delivery system refers to the accompanying figures that illustrate exemplary embodiments. Other embodiments are possible. Modifications can be made to the embodiments described herein without departing from the spirit and scope of the present invention. Therefore, the following detailed description is not meant to be limiting. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
     The present invention is directed to a heart valve prosthesis delivery system including a balloon onto a distal portion of the delivery system capsule. The delivery system is a single device that allows a practitioner to perform balloon dilation on native valve leaflets and to deliver a valve prosthesis percutaneously to the heart to replace the function of a native valve. For example, the valve prosthesis can replace a bicuspid or a tricuspid valve such as the aortic, mitral, pulmonary, or tricuspid heart valve. 
     Typically, balloon dilation, also known as valvuloplasty, is performed using a device separate from the valve prosthesis delivery system. The practitioner first percutaneously inserts the balloon dilation device into the patient, expands the dilation balloon against a native stenosed valve to dilate the valve, deflates the dilation balloon and then removes the balloon dilation device from the patient. At this point, the practitioner can percutaneously insert the valve prosthesis delivery system into the patient to deliver and deploy the valve prosthesis. Occasionally, after the valve prosthesis is deployed, post dilation with the balloon dilation device is required in order to adequately seat the valve prosthesis in the native valve annulus, to prevent valve prosthesis leakage, and/or to remove residual calcification. In this case, the balloon dilation device must be reinserted into the patient after removal of the valve prosthesis delivery system. 
     An introducer is typically used for a procedure involving balloon dilation and valve prosthesis delivery. The introducer allows for the exchange of the balloon dilation device and valve prosthesis delivery system into and out of the patient. However, the introducer also increases the total size and profile that is inserted into the patient. The profile of a device is the total diameter that must be passed into the patient&#39;s vasculature. 
     Valve prostheses typically have eyelets to attach the valve prostheses to a delivery system. The eyelets attach to tabs which retain the valve prosthesis. In addition, valve prosthesis delivery systems typically include an outer sheath or capsule that surrounds the collapsed valve prosthesis during delivery to the implantation site. During deployment, the capsule is withdrawn over the valve prosthesis. 
     Referring now to  FIGS. 1-2 , an exemplary delivery system for valve prosthesis  202  includes delivery system  10  that includes an outer sheath  102 , a pusher tube or middle member  112 , and a central tube or inner member  122 , each of which can be concentrically aligned and permit relative motion with respect to each other. At a distal end of middle member  112  is a capsule  142 . Middle member  112  also includes an inflation lumen  154 . In one aspect of the invention, inflation lumen  154  extends along the length of middle member  112  and is defined by a space between the middle member  112  and a wall  158 . In one aspect, inflation lumen  154  is an annular inflation lumen defined by the annular space between wall  158  and middle member  112 . In a further aspect, wall  158  is located within middle member  112  such that inflation lumen  154  extends along the interior of middle member  112 . In an alternate aspect, wall  158  can surround middle member  112  such that inflation lumen  154  extends along the exterior of middle member  112 . In an alternate aspect of the invention, delivery system  10  can include a non-annular inflation lumen and can include one or more single point inflation lumens that extend along the length of middle member  112 . The one or more single point inflation lumens can extend along the interior of middle member  112  or along the exterior of middle member  112 . 
     Inner member  122  includes guide wire lumen  164  which passes over guide wire  162 . At a distal end of inner member  122  is plunger assembly  132 . Capsule  142  surrounds plunger assembly  132  and collapsed valve prosthesis  202  and restrains valve prosthesis  202  in the radial direction during delivery of valve prosthesis  202 . In one aspect of the invention, valve prosthesis  202  is self-expandable. In an alternate aspect of the invention, valve prosthesis can be balloon expandable. Plunger assembly  132  includes hub  134  at a proximal end and a tip  138  at a distal end. Tip  138  facilitates the advancement of delivery system  10  through the patient&#39;s vasculature. Hub  134  includes one or more tabs  136  for retaining valve prosthesis  202  on plunger assembly  132 . Tabs  136  also prevent the pre-release of valve prosthesis  202  and assist in retaining valve prosthesis  202  during recapture. The top surface of tabs  136  interact with the inner surface of capsule  142  to form an interference fit. 
     Inflation port  170  is connected to inflation lumen  154  and is provided to transmit inflation fluid into balloon  250  to expand balloon  250 . Balloon  250  can be manufactured by a person skilled in the art and can utilize common materials including but not limited to Pebax, Grilimid, nylon in various grades, and latex. In one aspect, balloon  250  is a double wall balloon. The double wall thickness of balloon  250  can range from approximately 0.001 inches to approximately 0.005 inches and will be dictated by material and inflation pressure. 
       FIG. 3  is an embodiment of delivery system  10  including tip  138  at a distal end thereof, middle member  112 , a spindle  220  coupled to middle member  112  and an inner member  122  disposed within middle member  112 . Tip  138  includes a base tip  232  adjacent middle member  112  and tip end  234  coupled to base tip  232 . Spindle  220  permits inner member  122  to move independently of middle member  112  allowing for telescopic movement of inner member  122  within middle member  112 . 
       FIG. 4  shows tip end  234  removed from distal end of outer sheath  102 . In one embodiment, base tip  232  has threads  236  and has a threaded relationship with tip end  234 . In another embodiment, base tip  232  and tip end  234  are removably coupled together by an interference fit. A collet portion  238  extends distally from base tip and includes a plurality of fingers  240  adjacent threads  236 . Fingers  240  are deformable in a radial direction when either an axial or radial force is applied to the fingers  240 . 
       FIG. 5  has inner member  122  telescopically extending forwardly (in a direction indicated by arrow A) from a distal end of middle member  112 . In one embodiment, inner member  122  has a threaded portion  242  on a distal end thereof.  FIG. 6  shows a collet sleeve  244  coupled to base tip  232 . In one embodiment, collet sleeve  244  and base tip  232  have a threaded relationship. In another embodiment, collet sleeve  244  and base tip  232  are coupled together by an interference fit (or any other form of locking mechanism that does not have negative impact on profile or outer diameter). As described above, when collet sleeve  244  is coupled to base tip  232 , collet sleeve  244  applies axial and radial forces to fingers  240  of collet portion  238 , thereby compressing fingers  240  onto inner member  122 . 
       FIG. 7  shows an inflated balloon  250  coupled to the distal end of delivery system  10 . Balloon  250  has a first end  252 , a second end  254  and a middle inflatable portion  256  disposed therebetween. Inner member  122  telescopically extends forwardly from middle member  112  and disposed within balloon  250 . In one embodiment, the unexpanded or wrapped balloon  250  having a first end  252  with an opening which provides access to the interior space of balloon  250  is placed over threaded portion  242  of the forwardly extended inner member  122 . Balloon  250  is advanced over inner member  122  until first end  252  is coupled to middle member  112 . Notably, a soft cap can be placed at the distal end of inner member  122  to protect the interior of the balloon from the threaded portion  242  as the balloon  250  is advanced over inner member  122 . 
     In the embodiment shown in  FIG. 7 , threaded portion  242  of inner member  122  passes through an opening in second end  254  and a cap  258  is disposed over second end  254  and is threadedly secured to threaded portion  242  such that second end  254  of balloon  250  is disposed between threaded portion  242  and cap  258  in order to seal second end  254  allowing balloon  250  to be inflated. In one embodiment, cap  258  has a guidewire lumen in fluid communication with guidewire lumen  164  of inner member  122 . In another embodiment, cap  258  is a fastener and secured to the exterior surface of threaded portion  242  of inner member  122 . Cap  258  is not limited to a threaded relationship with distal end of inner member  122  and other ways to secure cap  258  to inner member  122  are possible, such as an interference fit. In another embodiment, threaded portion  242  of inner member  122  does not pass through second end  254  of balloon  250  and remains disposed within balloon  250 . In this embodiment, cap  258  is disposed over threaded portion  242  such that second end  254  of balloon  250  is disposed between threaded portion  242  and cap  258  when cap  258  is securedly coupled to inner member  122 . 
     Integrating balloon onto distal end of shaft allows for the balloon dilation procedure and the valve delivery procedure to be performed using a single device. In addition, post dilation of the valve prosthesis and native valve can be performed with the same delivery device. Because both procedures can be performed with a single device, devices no longer must be exchanged into and out of the body. Therefore, with the delivery system an introducer is no longer necessary thus decreasing the overall device profile that must be inserted into the body to perform the procedures. Reducing the overall profile allows for a smaller insertion hole into the body which leads to a reduction in vessel closure complications. In addition, reducing the number of devices used in the valve repair procedure also decreases the total procedure time. A typical balloon dilation and valve implantation procedure typically requires approximately 20 to approximately 30 minutes of procedure time. Integrating the balloon dilation device into the valve delivery device could save approximately 5 to approximately 10 minutes of total procedure time because a practitioner does not need to exchange a different balloon dilation device and valve prosthesis delivery device. Thus, a patient undergoing the procedure has less time on anesthesia and also has less risk of bleeding. In addition, since balloon  250  is removably coupled to the distal end of delivery system  10 , different balloon sizes and types are interchangeable allowing the operator to choose a specific balloon for a procedure. Integrating the balloon dilation device into the valve prosthesis delivery system is beneficial for any access method, including transfemoral, transeptal, transapical, transradial, transsubclavian, or transatrial. 
     As shown in  FIG. 8 , collet sleeve  244  is removed to show how a portion of middle member  112  may extend forwardly past base tip  232  such that first end  252  of balloon  250  is disposed between collet portion  238  and middle member  112 . In this embodiment, balloon  250  is inflated, airflow travels (as shown by arrow B) through lumen  154  of middle member  112  and into balloon  250 . 
     Once first and second ends  252 ,  254  of unexpanded balloon  250  are secured to middle and inner members  112 ,  122 , respectively, collet sleeve  244  is disposed over balloon  250  and threadedly secured to collet portion  238 . Collet sleeve  244  (shown in phantom lines in  FIG. 9 ) secures first end  252  to middle member  112  by compressing fingers  240  of collet portion  238  onto first end  252  of balloon  250 . Thus, first end  252  of balloon  250  is disposed between middle member  112  and fingers  240  of collet portion  238 . Collet sleeve  244  not only tightens collet portion  238  onto balloon  250 , but also reduces leading edges when tracking through a patient&#39;s vasculature. In addition, collet sleeve  244  prevents twisting of balloon  250  that might otherwise be happen if collet sleeve  244  is required to be turned in order to secure collet sleeve  244  to collet portion  238 . In an optional embodiment, first end  252  of balloon  250  could have a collet sleeve  244  coupled thereto, which avoid the need to preload collet sleeve  244  in a separate step. 
       FIG. 10  shows inner member  122  retracting rearwardly within middle member  112  (in the direction of arrow C) thereby collapsing a deflated balloon  250  into a folded configuration. Collapsing balloon  250  into a folded configuration is advantageous because the ventricles have a reduced amount of space so the need to minimize the length of delivery system  10  is critical. In another embodiment, balloon  250  can be collapsed radially onto inner member  122  and inner member  122  does not need to be retracted rearwardly within middle member  112 . 
       FIG. 11  shows a handle  260  coupled to a proximal end of outer sheath  102 . Handle  260  having at least one mechanism  262  for operating delivery system  10  and at least one flushing port  264  for providing a fluid to expand and collapse balloon  250 . In one embodiment, inner member  112  has an inner member handle  266  at a proximal end thereof. As shown in  FIG. 11 , inner member handle  266  is positioned exterior to handle  260  at a proximal end thereof. With the inner member handle  266  disposed on handle  260  this way, a user may grasp inner member handle  266  and telescopic manipulate inner member  122  forwardly and rearwardly within middle member  112 . As shown in  FIG. 12 , inner member  122  is retracted rearwardly within middle member  112  in the direction of arrow D. 
       FIG. 13  is a perspective view of distal end of middle member  112  having an opening  268  allowing inner member  122  to telescopically extend forwardly from middle member  112  (as shown in  FIG. 5 ) or retract rearwardly within lumen  154  of middle member  112  (as shown in  FIG. 10 ). Base tip  232  and collet portion  238  are shown in phantom lines to show inner member  122  disposed within middle member  112  such that a distal end of threaded portion  242  is substantially axially aligned with opening  268  of middle member  112 . In  FIG. 14 , tip  138  has tip end  234  shown in phantom lines to exemplify how tip end  234  is secured to base tip  232 . In the embodiment shown in  FIG. 14 , inner member  122  is shown extended forwardly past opening  268  of middle member  112  and further extending within the interior of tip end  234  until inner member  122  abuts distal end of tip end  234 . 
     Balloon dilation and implantation of the valve prosthesis will now be described with respect to  FIGS. 15-22 . As discussed above, in one aspect of the invention the valve prosthesis comprises a self-expanding frame that can be compressed to a contracted delivery configuration onto hub  134  on plunger assembly  132 . The self-expanding frame design requires a loading system to crimp valve prosthesis  202  to the delivery size, while allowing the proximal end of valve prosthesis  202  to protrude from the loading system so that the proximal end can be attached to tabs  136 . 
     The valve prosthesis and plunger assembly can then be loaded into capsule  142 . In the transfemoral approach, the delivery system and valve prosthesis are advanced into the patient&#39;s descending aorta. The delivery system then is advanced, under fluoroscopic guidance, over the aortic arch, through the ascending aorta  302  and into the aortic annulus  306 , mid-way across aortic valve  304 . In the transsubclavian approach, the delivery system and valve prosthesis are advanced through the subclavian artery into the ascending aorta  302  and into the aortic annulus  306 , mid-way across the aortic valve  304 . 
     Once positioning of the delivery system in the aortic annulus  306  is confirmed, balloon dilation can be performed by inflating balloon  250  into the native valve leaflets to dilate aortic valve  304  and to treat calcium buildup  308  by deforming the valve leaflets against the aortic wall adjacent aortic valve  304 , as shown in  FIG. 17 . Balloon  250  is expanded by passing fluid through inflation lumen  154  into balloon  250 . After balloon dilation is performed, the fluid is removed deflating balloon  250  and inner member  122  is retracted within middle member  112  axially compressing balloon, as shown in  FIG. 18 . 
     As shown in  FIG. 19 , after deflation of balloon  152 , capsule  142  is withdrawn proximally, thereby permitting valve prosthesis  202  to self-expand. As valve prosthesis  202  expands, it traps the leaflets of the patient&#39;s defective aortic valve against the valve annulus, retaining the native valve in a permanently open state. The outflow section of the valve prosthesis expands against and aligns the prosthesis within the ascending aorta, while the inflow section becomes anchored in the aortic annulus of the left ventricle, so that the valve prosthesis skirt reduces the risk of perivalvular leaks, as shown in  FIG. 20 . 
     Referring now to  FIG. 21 , in certain cases, dilation of the prosthetic valve is required after valve delivery in order to properly seat the valve prosthesis, prevent leakage, and/or to remove residual calcification on the native valve. This post valve prosthesis delivery dilation procedure can also be performed using balloon  250  on delivery system  10  after valve prosthesis  202  is delivered and expanded into aortic annulus  306 . After deployment of valve prosthesis  202 , tip  138  of integrated delivery system  10  is withdrawn proximally to abut the distal end of capsule  142 . The integrated delivery system  10  is then advanced into valve prosthesis  202 , across replacement valve  212 . Once positioning of the delivery system  10  is confirmed, post deployment balloon dilation is performed by inflating balloon  250  into valve prosthesis  202  and aortic annulus  306 .  FIG. 22  shows the valve prosthesis  202  deployed and expanded into aortic annulus  306  and delivery system  10  is removed from the patient&#39;s ascending aorta  302 . 
     Alternatively, the delivery system and valve prosthesis can be advanced through a transapical procedure. In a transapical procedure, a trocar or overtube is inserted into the left ventricle through an incision created in the apex of a patient&#39;s heart. A dilator is used to aid in the insertion of the trocar. In this approach, the native valve (e.g. the mitral valve) is approached from the downstream relative to the blood flow. The dilation balloon is attached to an exterior surface of a distal end of the trocar. Balloon dilation is performed by expanding the balloon into the native valve. Then the trocar is retracted sufficiently to release the self-expanding valve prosthesis. The dilator is preferably presented between the valve leaflets. The trocar can be rotated and adjusted as necessary to properly align the valve prosthesis. The dilator is advanced into the left atrium to begin disengaging the proximal section of the valve prosthesis from the dilator. In an alternate aspect of the invention, the delivery system can function as a trocar, thus eliminating the need for an overtube or dilator. In this aspect, tip  138  functions as a trocar to penetrate the incision. 
     In an alternate aspect of the invention, the valve prosthesis can be delivered through a transatrial procedure. In this procedure, the dilator and trocar are inserted through an incision made in the wall of the left atrium of the heart. The dilator and trocar are advanced through the native valve and into the left ventricle of heart. The dilator is then withdrawn from the trocar. A guide wire is advanced through the trocar to the point where the valve prosthesis comes to the end of the trocar. Balloon dilation is performed by expanding the balloon into the native valve. Then the valve prosthesis is advanced sufficiently to release the self-expanding frame from the trocar. The trocar can be rotated and adjusted as necessary to properly align the valve prosthesis. The trocar is completely withdrawn from the heart such that the valve prosthesis self-expands into position and assumes the function of the native valve. In an alternate aspect of the invention, the delivery system can function as a trocar, thus eliminating the need for an overtube or dilator. In this aspect, tip  138  functions as a trocar to penetrate the incision. 
     The foregoing description has been presented for purposes of illustration and enablement, and is not intended to be exhaustive or to limit the invention to the precise form disclosed. Other modifications and variations are possible in light of the above teachings. The embodiments and examples were chosen and described in order to best explain the principles of the invention and its practical application and to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention.