Abstract:
The effects of acute left ventricular heart failure are mitigated by temporary support of the cardiac function through use of either one or both of an expendable temporary one-way valve positioned in the aorta, having a collapsible frame that is expanded upon deployment, and/or a temporary dilation device positioned in the descending aorta for expanding upon deployment to increase the diameter of the associated portion of the aorta. When used together, the dilation device is positioned distal to the temporary one-way valve.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to temporary cardiac assist devices employed to provide functional support to a diseased, traumatized or failing heart for a limited time until the heart recovers sufficiently to perform effectively without support or until a longer-term treatment is provided. In particular, the invention relates to collapsible, non-powered devices that are introduced through percutaneous transluminal techniques to decrease the resistance against which the heart must pump.  
       BACKGROUND OF THE INVENTION  
       [0002]     Acute left ventricular heart failure can occur episodically in a patient suffering from chronic congestive heart failure (CHF) or from a specific acute stress situation. Some typical stress situations include myocardial infarction, unstable angina, cardio-surgery and catheter-based coronary interventions. The condition is characterized by a reduction in cardiac output, increased left ventricular end diastolic pressure and volume, decreased pump efficiency (reduced ejection fraction) and increased after load (outflow resistance). The increase in outflow resistance may arise from several factors including hypertension, aortic stenosis and poor peripheral run-off.  
         [0003]     The therapeutic reduction in after load (the resistance against which the heart contracts) has become an important treatment for heart failure. This has been addressed pharmacologically through the use of antihypertensive drugs and vasodilators. A few medical device systems have been developed that may manage after load as part of the cardiac assist or support function. For example, the intra-aortic balloon pump (IABP) has been used as a temporary mechanical heart assist device in episodes of acute left ventricular failure.  
         [0004]     The IABP comprises a percutaneously introduced balloon catheter that is positioned in the aorta, and a control console that times the inflation/deflation cycle of the balloon to augment cardiac performance. The balloon is deflated during systole to reduce outflow resistance and inflated during diastole to propel blood forward and to augment coronary artery perfusion (counter-pulsation). As the heart recovers from the acute incident the patient is gradually weaned from IABP support. This may be accomplished by reducing the balloon pump volume and/or by reducing the percentage of cardiac cycles during which the IABP is activated. Although this system is widely used, it is expensive, requires careful and nearly continuous adjustment and its use requires frequent monitoring by a skilled medical technologist. The system requires that the balloon inflation/deflation cycle be electronically timed to coincide with the patient&#39;s cardiac cycle.  
         [0005]     A number of prior mechanical device inventions have been made for the treatment of heart failure, particularly left ventricular heart failure. Nearly all of these inventions are dependent on the use of an external power source for operation; and all of the systems that support the function of the heart by augmenting pulsatile flow of blood require that the device operation be timed to coincide with some portion of the natural rhythm of the heart.  
         [0006]     U.S. Pat. No. 4,388,919 (Benjamin) and U.S. Pat. No. 4,881,527 (Lerman) describe systems that support the circulation by external compression means of the torso or peripheral limbs. U.S. Pat. No. 6,254,525 (Levin) describes an inflatable bladder that is positioned around the heart to provide pulsatile support by compressing the heart.  
         [0007]     U.S. Pat. No. 4,902,273 (Choy) and U.S. Pat. No. 5,176,619 (Segalowitz) describe support systems that employ intra-ventricular balloon pump means.  
         [0008]     U.S. Pat. No. 5,800,334 (Wilk) describes a balloon support system that is positioned within the pericardial space; and U.S. Pat. No. 4,902,272 (Milder) describes an intra-aortic balloon pump device.  
         [0009]     U.S. Pat. No. 6,193,648 (Krueger) describes a mesh jacket that is snugly positioned around the heart to prevent continued enlargement due to congestive heart failure. In theory this limits the rate of degradation of cardiac performance. The device is non-powered, does not require a timing mechanism. However, implantation of the device requires a significantly invasive surgical procedure.  
         [0010]     Several prior art devices are directed at replacement of the diseased natural aortic valve (i.e. to treat aortic valve insufficiency). A number of these devices are directed toward percutaneous transluminal introduction of an aortic valve prosthesis that is intended to replace or supplant the function of the natural aortic valve. In order for these devices to perform their intended function the natural heart valve must be removed or rendered non-operative. None of these devices is designed with the intention of use as a temporary treatment for acute heart failure by functioning in concert with a relatively normal natural aortic valve. Also, the known prior art does not provide temporary implantable non-powered devices for the treatment of the failing left ventricle.  
         [0011]     Previously described percutaneously introduced valve inventions are designed to fit within a specific diameter annulus or implant site depending upon the anatomic dimensions of the individual patient. A number of the prior patents that describe percutaneous transluminal introduction of an aortic valve prosthesis are described below to illustrate the existing technology and to assist in providing an understanding of the features that differentiate the present invention from the prior art.  
         [0012]     U.S. Pat. No. 3,671,979 (Moulopoulos) describes percutaneous introduction of a prosthetic heart valve that can be repositioned and removed and is intended to replace the function of a diseased natural aortic valve. This device is inserted into the vessel in a collapsed form and is deployed like an umbrella with the apex of the umbrella (cone) pointing upstream toward the heart. This configuration provides no means for centering the valve within the aorta. In principle, the arrangement allows the valve leaflets to contact the aortic wall during diastole and thus prevent reverse flow. The design does not permit central blood flow; and the area immediately downstream and within the umbrella has no flow or low flow of blood. This design configuration can lead to clot formation and ultimately release of a dangerous clot. This patent also illustrates a percutaneous valve that is introduced as a deflated balloon. The balloon must be externally powered and requires a timing mechanism to synchronize the inflation/deflation cycle with the cardiac rhythm. This concept is also illustrated in International Publication Number WO 00/44313 (Lambrecht, et al.).  
         [0013]     U.S. Pat. No. 4,056,854 (Boretos, et al.) describes percutaneous introduction of a prosthetic heart valve that is intended to replace the function of the natural aortic valve, but may remain tethered to an extension stem so that it can be re-positioned or removed at a later date. The valve annulus is formed by a series of springs connecting the distal ends of outwardly biased support wires. The valving mechanism is a single flexible tubular membrane that surrounds the frame formed by the annulus and the support wires. The entire valve assembly is constrained within a capsule during introduction. This design requires a large vascular access incision due to the size of the capsule and the non-compressible spring components. The design depends upon the random collapse of the tubular membrane to prevent retrograde flow.  
         [0014]     U.S. Pat. No. 6,168,614 (Andersen et al.) and U.S. Pat. No. 5,855,601 (Bessler et al.) describe prosthetic valves that are intended as permanent implants to assume the function of the natural aortic valve. The inventions include mechanisms for fixing the structure that forms the valve annulus to an intravascular site such as the natural valve annulus after the natural valve has been removed.  
         [0015]     It is known in the prior art to provide means for the temporary dilation of a blood vessel. Nearly all of the known devices described for this intended use are related to angioplasty and valvuloplasty balloon catheters. These inventions generally do not provide means to allow for blood flow during the time that the balloon is inflated and dilation is taking place.  
         [0016]     A non-balloon intravascular dilation device that permits blood flow during vessel dilation is described in U.S. Pat. No. 5,653,684 (Laptewicz et al.). This invention incorporates a flexible wire mesh catheter tip that is used to compress flow obstructing material against the interior wall of a vessel and thereby return the diameter of the vessel to a sufficient diameter to allow normal flow in the vessel. This device is intended to remain in the vessel for periods of up to 48 hours. It is not designed for substantially expanding the diameter of a vessel for the purpose of reducing outflow resistance.  
         [0017]     Prior art devices use expandable wire mesh structures to expand the lumen of a generally tubular body structure. Examples of these devices are provided in U.S. Pat. No. 4,347,846 (Dormia) and U.S. Pat. No. 4,590,938 (Segura et al.). These devices are useful primarily for the retrieval of obstructions such as stones from non-vascular ducts. The basket that is expandably formed from the wire mesh is geometrically asymmetrical in some respect to allow for both the capture and retention of the obstructive stone. The devices incidentally dilate the body structure when they are expanded to capture the obstruction, but the devices are not designed for use in dilating blood vessels and do not remain in the body for longer than is required for the retrieval procedure.  
       SUMMARY OF THE INVENTION  
       [0018]     An object of this invention is to provide improved devices and improved treatment methods to effect many of the same therapeutic support functions as current mechanical and electromechanical therapies for acute heart failure, whereby the improved devices and related treatment methods also are significantly less complex than those of the known prior art. The present treatment for one embodiment of the invention, involves percutaneous transluminal introduction and positioning of a temporary one-way valve in series with the patient&#39;s essentially normal natural aortic valve. The valve may be positioned in the ascending aorta near the natural aortic valve, at the beginning of the descending aorta or at a site in between these two positions. The valve is actuated (opened) by the expulsion of blood from the heart, in the same way that the natural aortic valve is opened. The temporary one-way valve of this invention requires no external power source or timing mechanism. The valve closes at the end of systole and relieves much of the systemic back-pressure that affects the natural valve and the left ventricle and thereby improves the performance of the left ventricle. This improvement in performance may be noted by an improvement (increase) in cardiac output and ejection fraction, and a decrease in heart rate and pulmonary capillary wedge pressure. These changes tend to decrease myocardial oxygen demand and thus allow the heart to recover from the episode of acute ventricular failure. The present treatment for a second embodiment of the invention involves percutaneous transluminal placement of a temporary dilatation means in the descending aorta to increase the diameter (and thus the volume) of that portion of the outflow path engaged by the device and thereby decreases the outflow resistance. The valve component and the dilation component of the first and second embodiments may be used alone or together in a given patient.  
         [0019]     The one-way valve assembly embodiment consists of an annulus, a frame or annulus support structure, valve leaflets, and control means to both advance the collapsed valve through the arterial tree to the site of deployment and later to remove the valve, control means to deploy the valve, and a structure to prevent prolapse of the leaflets in some configurations of the valve.  
         [0020]     The temporary vessel dilatation device consists of an expansible frame that may be percutaneously transluminally introduced in a collapsed form from an access site in a peripheral artery, such as the femoral artery. In a preferred embodiment, the temporary dilation device takes the form of a cylindrical cage that can be expanded after being positioned at the desired site to enlarge the diameter of an associated lumen portion of the descending aorta while allowing blood to flow freely through its natural course.  
         [0021]     The present inventive devices, as indicated, include a collapsible valve and a vascular dilation device that are introduced through percutaneous transluminal techniques either as part of a cooperating system or separately. Use of these devices and the disclosed treatment method offers temporary support to the injured heart to allow recovery without the need for a substantially more complex system involving powered pumping and timing mechanisms.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     Various embodiments of the present invention are described in detail below with reference to the drawings, in which like items are identified by the same reference designation, wherein:  
         [0023]      FIG. 1   a  is a perspective view of the distal end of one embodiment of the invention for a temporary valve assembly illustrating the frame in the deployed position with the valve partially open within a cross sectional portion of an aorta;  
         [0024]      FIG. 1   b  is a top view from the distal end of the temporary valve assembly absent the frame below the annulus of  FIG. 1   a;    
         [0025]      FIG. 2   a  is a perspective view of the distal end of an alternative embodiment of the invention for a temporary valve assembly illustrating the frame in the deployed position with the valve partially open within a cross sectional portion of an aorta;  
         [0026]      FIG. 2   b  is a top view from the distal end of the temporary valve assembly absent the frame below the annulus of  FIG. 2   a;    
         [0027]      FIG. 3   a  is a perspective view of the distal end of an alternative embodiment of the invention for a temporary valve assembly illustrating the frame in the deployed position with the valve partially open within a cross sectional portion of the aorta;  
         [0028]      FIG. 3   b  is a top view from the distal end of the temporary valve assembly of  FIG. 3   a;    
         [0029]      FIG. 4  is a perspective view of the distal end of an alternative embodiment of the invention for a temporary valve assembly illustrating the frame in the deployed position with the valve partially open within a cross sectional portion of the aorta;  
         [0030]      FIG. 5   a  is a perspective view of an alternative embodiment of the temporary valve assembly shown in  FIG. 2   a  illustrating the frame in the deployed position with the valve partially open within a cross sectional portion of the aorta;  
         [0031]      FIG. 5   b  is a perspective view of an alternative embodiment of the temporary valve assembly shown in  FIG. 4  illustrating the frame in the deployed position with the valve partially open within a cross sectional portion of the aorta;  
         [0032]      FIG. 5   c  is an enlarged view of a portion of  FIGS. 5   a  and  5   b;    
         [0033]      FIG. 6  is a side view of the valve assembly of  FIG. 1   a  inserted in the aorta in one position consistent with the treatment method of the invention;  
         [0034]      FIG. 7  is a side view of the valve assembly of the present invention inserted in the aorta in an alternate position relative to that of  FIG. 6  consistent with the treatment method of the invention;  
         [0035]      FIG. 8  is a side view of one embodiment of the invention showing the vascular dilation device in an expanded state within a cutaway portion of the descending aorta independently of the valve assembly catheter;  
         [0036]      FIG. 9   a  is a side view of an alternative embodiment of the invention for a vascular dilation device in a partially expanded state and concentrically disposed about a valve assembly catheter within a cutaway portion of the descended aorta;  
         [0037]      FIG. 9   b  is a side view of the vascular dilation device, as illustrated in  FIG. 9   a , but in a fully expanded position; and  
         [0038]      FIG. 10  is of a partial cross sectional view of a valve assembly and a dilatation device of embodiments of the present invention simultaneously deployed in a cutaway portion of the aorta for a treatment method embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0039]     In general, the components of a collapsible valve assembly  100  as inserted in a thoracic aorta  2  are illustrated in  FIG. 1   a , for one embodiment of the invention. It should be noted that not all of the component elements shown are required for each exemplary embodiment illustrated herein. Examples of such possible variations will be described with reference to the various drawings. The components shown include an expandable frame  10  comprising a plurality of radially outwardly biased wires  4  or bands joined together at least at one end  12  to form a cage-like structure that may be open at the end opposite the joining point. Still other frame structures are discussed with respect to other of the present drawings. The collapsed diameter dimension of the valve assembly  100  is between 2 mm and 5 mm, and the expanded diameter dimension of the frame  10  suitable for application in an adult patient is between 20 mm and 35 mm. The wires  4  may be joined by welding or other adhesive means to a hollow cylinder  20  (see  FIG. 5   c ) or directly to each other at the apex  12  of the conic or bulbous frame  10  and to an elongated control element  22  that extends out of the body through the remote percutaneous access site (not shown). The control element  22  may be a wire or a flexible tube that must possess adequate column strength so as to allow the valve assembly  100  to be deployed from the confinement of a guide catheter  24 , (such as the type typically used in vascular access procedures), and adequate tensile strength to allow safe withdrawal of the valve assembly  100  into the guide catheter  24  prior to removal from the body. Upon introduction of the valve assembly  100  into the thoracic aorta  2  the distal end of the guide catheter  24  is positioned at the intended deployment site. The catheter  24  is then retracted while maintaining counter tension on the control element  22 . The radially outwardly biased frame structure  10  is thus allowed to expand so as to cause the greatest diameter of the frame to frictionally engage the interior wall of the thoracic aorta  2 . The wires  4  or bands that form the expandable frame  10  can be of preformed, outwardly biased spring construction, or can be fabricated of shape memory material such as nitinol, or can be radially expandable by means of a control element (as discussed later in this description). The expandable valve frame  10  of the valve assembly  100  embodiment shown in  FIG. 1   a  forms a generally conic or bulbous shape when expanded. The individual frame wires  4  or bands of the valve frame  10  are connected to a valve annulus  14  in the form of a flexible strand at the point that forms the greatest diameter of the expanded frame  10 . When ideally deployed and functioning the plane formed by the annulus  14  is maintained at right angles to the direction of blood flow during systole (see arrow). The annulus  14  can be disposed within or outside of the frame members  10  in a generally circular plane. The annulus  14  may be covered with flexible polymeric material so as to form a seal at its interface with the wall of the aorta. The free ends of the frame wires  4  can terminate at the plane of the annulus  14  or extend beyond the plane of the annulus to provide additional surface contact area with the wall of the thoracic aorta  2 . The multiple valve leaflets  18  (at least 3) are attached to the annulus  14  so as to form a one-way valve that permits a central flow of blood during cardiac systole (see direction of arrow) and to prevent or minimize back flow during diastole. The leaflets  18  are preferable formed of a thin, flexible, clot resistant, biocompatible polymeric material such as polyester or polyurethane and are attached to the annulus by suturing, adhesives or other suitable means. The leaflets  18  either form a conic shape with the apex of the cone located distal to (downstream of) the annulus  14 , when the one-way valve is in the closed position, or close in a plane described by the annulus  14 . When the leaflets  18  are arranged so as to close in a plane they seat against a prolapse prevention element  16 . This component of the valve assembly  100  lays in the plane of the annulus  14  immediately proximal (upstream of) the valve leaflets  18  and is formed by at least four filaments that form a grid within the plane of the circle formed by the annulus  14 , for example. In a preferred form the prolapse prevention component  16  is a metallic or polymeric mesh disc with the open area of the grid accounting for at least 70% of the total area described by the annular space. The valve leaflets  18  may be attached directly to the periphery of the prolapse prevention element  16  rather than to a physical annulus. In this case the periphery of the prolapse prevention element  16  serves as a “virtual” annulus and no separate annular ring is required in the valve assembly  100 . In such an embodiment, the periphery of the prolapse prevention element  16  is reinforced with flexible polymeric material so as to form a seal at its interface with the wall of the thoracic aorta  2 .  
         [0040]     The embodiment of the valve assembly depicted in  FIG. 2   a  differs from the valve assembly shown in  FIG. 1   a  with respect to the construction of the valve frame  10 . This alternate valve frame assembly  100 ′ also assumes a generally conic or bulbous shape upon expansion. However, the individual wires or bands of the valve frame are not only joined at the apex  12  of the cone, but are either continually extended to pass through a point opposite the apex  26  or joined at a point opposite the apex  26  to enclose the annulus plane and thus form a closed bulb shaped cage. This construction adds stiffness to the frame structure, provides increased stability by increasing the area of frame contact with the wall of the thoracic aorta  2 , and provides increased assurance that the plane of the valve annulus  14  remains at right angles to the direction of blood flow during systole (see arrow).  
         [0041]     The valve assembly embodiments illustrated in  FIG. 1   a  and  FIG. 2   a  must be sized for specific aorta diameter dimensions. The thoracic aorta  2  of an adult human ranges in diameter from approximately 19 mm to 31 mm in over 90% of the population. Typical replacement valves used to supplant a diseased non-functional aortic valve are made available in 2 mm increments over this diameter range.  FIG. 3  and  FIG. 4  depict embodiments of the valve assemblies  100  and  100 ′ that are configured to allow a single valve assembly size to be used over most or all of the range of adult aorta diameters. This is accomplished by modifying the location of the plane of the annulus  14  and adding a secondary set of leaflets  30 , for example. The valve assembly  100 ″ of  FIG. 3  is otherwise analogous in design to the valve assembly  100  depicted in  FIG. 1   a ; and the valve assembly  100 ′″ of  FIG. 4  is otherwise analogous in design to the valve assembly  100 ′ shown in  FIG. 2   a . The annulus  14  planes of the valve assemblies  100 ″ and  100 ′″ shown in  FIG. 3  and  FIG. 4 , respectively, have been shifted toward the apex  12  of the frame assembly. In these embodiments the annulus  14  plane is at a point where the diameter described by the members of the frame assemblies  100 ″ and  100 ′″ is typically between 20 mm and 24 mm so that the annulus diameter occupies at least 50% of the aorta diameter. In order to prevent any significant retrograde blood flow during diastole, the periphery of the annulus  14  is fitted with at least three thin, flexible, biocompatible leaflets  30  that are attached at their fixed edges to the annulus  14  or the prolapse prevention element  16  to form a skirt. The leaflets  30  are generally trapezoidal in shape with the lesser length attached to the annulus  14 . These leaflets  30  operate in concert with the central leaflets  18  to open and permit antegrade blood flow during systole and close to prevent retrograde blood flow during diastole. The free edges of the peripheral leaflets  30  engage the wall of the thoracic aorta  2  during diastole to prevent any substantial retrograde flow.  
         [0042]     The embodiments depicted in  FIG. 1  through  FIG. 4  share the characteristic feature that expansion of the valve assembly is accomplished through the action of the radially outwardly biased wire or band members  4  of the frame  10 . The alternative expandable valve assemblies  100 ″″ and  100 ′″″ illustrated in  FIG. 5   a  and  FIG. 5   b , respectively, differ from the valve assembly embodiments  100 ,  100 ′,  100 ″, and  100 ′″ depicted and described previously in this description with respect to the means for expanding the valve frame from its collapsed configuration to its expanded, deployed configuration. The valve assembly  100 ″″ depicted in  FIG. 5   a  is analogous to the valve assembly  100 ′ shown in  FIG. 2   a , and the valve assembly  100 ′″″ depicted in  FIG. 5   b  is analogous to the valve assembly  100 ′″ shown in  FIG. 4  with regard to the respective locations of the annulus  14  planes. In both  FIG. 5   a  and  FIG. 5   b  the wire or band members  4  of the valve frame  10  are joined at a point or apex  26  at one end, and at their opposite ends to one end of a hollow cylinder  20  (see  FIG. 5   c ). There is additionally attached a control member  40  that extends from the point or apex  26  through the longitudinal axis of the respective valve assembly  100 ″″,  100 ′″″, through the hollow cylinder  20 , and thence through the central channel of the flexible catheter  24  to a point outside of the body where it is connected to an actuation means. The flexible wire or band members  4  of the valve frame  10  depicted in  FIG. 5   a  and  FIG. 5   b  are not sufficiently radially outwardly biased to cause deployment of the respective valve assembly  100 ″″,  100 ′″″ upon advancement of the valve assembly from the confinement of the catheter  24  by action of the control wire  21  attached to the cylinder  20  of the respective valve assembly  100 ″″,  100 ′″″. Instead, the alternative valve assemblies  100 ″″,  100 ′″″ of  FIG. 5   a  and  FIG. 5   b  are deployed by positioning the distal end of the catheter  24  at the desired site, retracting the catheter  24  while maintaining the position of the control wire  21 , followed by retraction of the central control member  40 . This combination of actions by the operator releases the respective valve assembly  100 ″″,  100 ′″″ from the confinement of the catheter  24  and then compresses the frame longitudinally to expand the diameter and complete deployment of the valve assembly. In the case of these alternative configurations, the control wire  40  passes through a central point in the plane of the valve annulus  14  without interfering with the functional operation of the valve leaflets  18  and/or  30 .  
         [0043]      FIG. 6  is a generalized overview of one embodiment of the collapsible valve assembly  100 ″ shown in its expanded, deployed configuration within the ascending aorta  80  during cardiac diastole. In this preferred position the valve assembly is placed at a site between the natural aortic valve  60  and the brachiocephalic trunk  66 , the first major arterial branch of the aorta. There is an adequate space  64  and thus, sufficient intraluminal volume to allow normal flow of blood to the coronary arteries  62  during cardiac diastole. In this position the temporary valve assembly  100 ″ bears a great proportion of the systemic blood pressure during diastole; and thus the back-pressure on the natural aortic valve  60  is largely relieved. Upon contraction of the left ventricle and opening of the aortic valve  60  outflow resistance is reduced relative to the situation where the temporary valve  100 ″ is not deployed.  
         [0044]     The valve assembly overview illustrated in  FIG. 7  shows one embodiment of the collapsible valve assembly  100 ′″ in its expanded, deployed configuration within the descending thoracic aorta  90  during cardiac systole. In this position, the valve assembly is placed distal to the left subclavian artery  68 , the third major arterial branch of the aorta. When positioned at this alternative site or at locations in between this site and the location depicted in  FIG. 6  for a valve assembly  100 ″, the temporary valve  100 ′″ will also bear a portion of the systemic blood pressure during cardiac diastole and thus relieve a portion of the back-pressure on the natural aortic valve  60 . By relocating the valve assembly  100 ′″ from the position of the valve assembly  100 ″ shown in  FIG. 6 , toward the position depicted in  FIG. 7 , it is possible to gradually wean the patient from temporary support of cardiac function. If, upon such repositioning, cardiac performance is not acceptable, as determined by such means as electrocardiographic and hemodynamic measurements, the temporary valve assembly  100 ″ or  100 ′″ may be again repositioned at a point nearer the natural aortic valve  60  for an additional period of time. Once satisfied with cardiac performance, the operator can undeploy the temporary valve  100 ″ or  100 ′″ into the catheter  24 , and withdraw the catheter and valve assembly  100 ″ or  100 ′″ as a unit from the body.  
         [0045]      FIG. 8  is a side view of one embodiment of a temporary vascular dilation device assembly  150  of the present invention positioned in the infrarenal abdominal aorta  75  with the dilation device shown in the expanded state. The dilation device assembly  150  is preferably deployed in the infrarenal abdominal aorta (distal to the renal arteries  70 ), but alternatively may be deployed in a more distal portion of the arterial system such as in the iliac or femoral arteries. When the device is deployed the volume of the arterial system may be increased by up to 200 cc, thus decreasing outflow resistance and encouraging an improvement in cardiac output and left ventricular ejection fraction. The temporary vascular dilation device depicted in  FIG. 8  is designed for introduction into the body independently of the temporary valve assembly of this invention. The dilation device may be percutaneously introduced and deployed prior to insertion of the valve assembly catheter  24 , which can be subsequently inserted through the openings in the expandable dilation device assembly  150 .  
         [0046]     Several alternate configurations  150 ,  200 , and  201  of the dilation device assembly are described below with reference to the respective drawings. It should be noted that not all of the component elements shown are required for each exemplary embodiment illustrated herein. Examples of such possible variations will be described with reference to the various drawings. The components shown include a self-expandable frame  150  comprising a plurality of radially outwardly biased wires or bands  105  in the embodiment of  FIG. 8  joined together at top end  102 , and at bottom end  108  to form a generally cylindrical symmetrical cage-like structure  150 . The collapsed diameter dimension of the vascular dilation assembly is ideally between 1 mm and 6 mm and the expanded diameter dimension of the dilation assembly suitable for application in an adult patient is between 25 mm and 50 mm. The wires  105  can be joined together by swaging, welding or other connecting means to a cylindrical ring or directly to each other at each end  102  and  108  of the generally cylindrical cage, for example. The wires or bands  105  that form this cage can be disposed parallel to each other, or alternately disposed in a clockwise/counter clockwise helical fashion or may be formed into a braided structure. The proximal end  108  of the cylindrical cage  150  of  FIG. 8  is connected to an elongated control element  106  that extends through a dedicated guide catheter  124  and thence out of the body through the remote percutaneous access site (not shown). The control element  106  can be a wire or a flexible tube with adequate column strength so as to allow the dilation device to be deployed from the confinement of a guide catheter  124 , (such as the type typically used in vascular access procedures), and adequate tensile strength to allow safe withdrawal of the dilation device into the guide catheter  124  prior to removal from the body, for example. Upon introduction of the dilation device into the abdominal aorta the distal end of the guide catheter  124  is positioned at the intended deployment site. The catheter  124  is then retracted while maintaining counter tension on the control element  106 . The radially outwardly biased cylindrical cage structure  150  is thus allowed to expand so as to cause the expanded diameter of the cage structure  150  to frictionally engage and dilate the wall of the infrarenal abdominal aorta  75 . The wires or bands  105  that form the self-expandable frame  150  can be of preformed, outwardly biased spring construction, and/or fabricated of shape memory material such as nitinol. The embodiments of  FIGS. 9   a  and  9   b  are radially expandable by means of control elements (as discussed below), for example.  
         [0047]     The partially deployed temporary dilation assembly  200  shown in  FIG. 9   a  is slidably mounted concentrically on the guide catheter  24  of the temporary valve assembly  100 , or  100 ′, or  100 ″, or  100 ′″, or  100 ″″. The guide catheter  24  passes through cylindrical rings  102  and  108  at each end of an expandable frame  107 . After the temporary valve assembly  100 , or  100 ′, or  100 ″, or  100 ′″, or  100 ″″ is positioned at the desired location and deployed, the temporary dilation assembly  200  may be positioned at its preferred location by advancing a control element  109  that is attached to either one of the slidable rings  102  or  108 , at an end of the expandable frame  107 . In this example, the cage frame  107  can be expanded to its deployed position by applying opposing forces on two control elements,  109  and  110 , attached respectively to the rings,  108  and  102 , at the proximal and distal ends of the cage assembly  107 . For example, the cage  107  is expanded by applying a retraction force to control element  110  while holding control element  109  in a fixed position, thereby dilating the engaged section of the infrarenal abdominal aorta  75 .  
         [0048]     In another embodiment of the invention, the proximal end (ring  108 ) of a fully deployed dilation assembly  201  depicted on  FIG. 9   b  is fixedly mounted to the guide catheter  24 . In the case where the proximal ring  108  of the dilation assembly  201  is fixed to the guide catheter  24 , the expandable frame  107  is expanded by applying tension (retraction force) to the control element  110  attached to the slidable end  102  of the dilation assembly  201 . In an alternative case, the fixed end and the slidable end are reversed, the cage can then be expanded by fixing the distal end (ring  102 ) of the dilation assembly to the guide catheter  24 , and applying compressive force to (advancing) the control element  109  attached to the slidable (proximal) end  108  of the dilation assembly  201 .  
         [0049]      FIG. 10  is an overview showing the in vivo placement of the temporary valve assembly  100 ′ in position in the ascending aorta  80 , and the temporary dilation assembly  200  in a dilated state positioned in the infrarenal aorta  75 .  
         [0050]     It is believed that the various embodiments of the invention described above may improve cardiac performance as measured by such criteria as any of: reduced outflow resistance, increased ejection fraction, increased cardiac output, decreased diastolic pressure on the natural aortic valve, decreased heart rate and/or decreased pulmonary capillary wedge pressure depending on the status and condition of a specific patient.  
         [0051]     Although various embodiments of the invention have been shown and described, they are not meant to be limiting. Those of skill in the art may recognize certain modifications to these embodiments, which modifications are meant to be covered by the spirit and scope of the appended claims.