CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser. No. 12/502,164, filed Jul. 13, 2009, which is a continuation of U.S. patent application Ser. No. 11/112,847, filed Apr. 22, 2005, now U.S. Pat. No. 7,641,686, which claims priority under 35 U.S.C. §119(e) to (1) U.S. Provisional Patent Application No. 60/564,708, filed Apr. 23, 2004, (2) U.S. Provisional Patent Application No. 60/568,402, filed May 5, 2004, (3) U.S. Provisional Patent Application No. 60/572,561, filed May 19, 2004, (4) U.S. Provisional Patent Application No. 60/581,664, filed Jun. 21, 2004, (5) U.S. Provisional Patent Application No. 60/586,054, filed Jul. 7, 2004, (6) U.S. Provisional Patent Application No. 60/586,110, filed Jul. 7, 2004, (7) U.S. Provisional Patent Application No. 60/586,005, filed Jul. 7, 2004, (8) U.S. Provisional Patent Application No. 60/586,002, filed Jul. 7, 2004, (9) U.S. Provisional Patent Application No. 60/586,055, filed Jul. 7, 2004, (10) U.S. Provisional Patent Application No. 60/586,006, filed Jul. 7, 2004, (11) U.S. Provisional Patent Application No. 60/588,106, filed Jul. 15, 2004, U.S. Provisional Patent Application No. 60/603,324, filed Aug. 20, 2004, (12) U.S. Provisional Patent Application No. 60/605,204, filed Aug. 27, 2004 and (13) U.S. Provisional Patent Application No. 60/610,269 filed Sep. 16, 2004, the entire contents of which are hereby expressly incorporated by reference herein.
BACKGROUND OF THE INVENTION
According to recent estimates, more than 79,000 patients are diagnosed with aortic and mitral valve disease in U.S. hospitals each year. More than 49,000 mitral valve or aortic valve replacement procedures are performed annually in the U.S., along with a significant number of heart valve repair procedures.
Although mitral valve repair and replacement can successfully treat many patients with mitral valvular insufficiency, techniques currently in use are attended by significant morbidity and mortality. Most valve repair and replacement procedures require a thoracotomy, usually in the form of a median sternotomy, to gain access into the patient's thoracic cavity. A saw or other cutting instrument is used to cut the sternum longitudinally, allowing the two opposing halves of the anterior or ventral portion of the rib cage to be spread apart. A large opening into the thoracic cavity is thus created, through which the surgical team may directly visualize and operate upon the heart and other thoracic contents. Alternatively, a thoracotomy may be performed on a lateral side of the chest, wherein a large incision is made generally parallel to the ribs, and the ribs are spread apart and/or removed in the region of the incision to create a large enough opening to facilitate the surgery.
Surgical intervention within the heart generally requires isolation of the heart and coronary blood vessels from the remainder of the arterial system, and arrest of cardiac function. Usually, the heart is isolated from the arterial system by introducing an external aortic cross-clamp through a sternotomy and applying it to the aorta to occlude the aortic lumen between the brachiocephalic artery and the coronary ostia. Cardioplegic fluid is then injected into the coronary arteries, either directly into the coronary ostia or through a puncture in the ascending aorta, to arrest cardiac function. The patient is placed on extracorporeal cardiopulmonary bypass to maintain peripheral circulation of oxygenated blood.
A need therefore remains for methods and devices for treating mitral valvular insufficiency, which are attended by significantly lower morbidity and mortality rates than are the current techniques, and therefore would be well suited to treat patients with dilated cardiomyopathy. Optimally, the procedure can be accomplished through a percutaneous, transluminal approach, using simple, implantable devices.
The circulatory system is a closed loop bed of arterial and venous vessels supplying oxygen and nutrients to the body extremities through capillary beds. The driver of the system is the heart providing correct pressures to the circulatory system and regulating flow volumes as the body demands. Deoxygenated blood enters heart first through the right atrium and is allowed to the right ventrical through the tricuspid valve. Once in the right ventrical, the heart delivers this blood through the pulmonary valve and to the lungs for a gaseous exchange of oxygen. The circulatory pressures carry this blood back to the heart via the pulmonary veins and into the left atrium. Filling of the left ventricle occurs as the mitral valve opens allowing blood to be drawn into the left ventrical for expulsion through the aortic valve and on to the body extremities. When the heart fails to continuously produce normal flow and pressures, a disease commonly referred to as heart failure occurs.
Heart failure simply defined is the inability for the heart to produce output sufficient to demand. Mechanical complications of heart failure include free-wall rupture, septal-rupture, papillary wall rupture or dysfunction aortic insufficiency and tamponade. Mitral, aortic or pulmonary valve disorders lead to a host of other conditions and complications exacerbating heart failure further. Other disorders include coronary disease, hypertension, and a diverse group of muscle diseases referred to as cardiomyopothies. Because of this syndrome establishes a number of cycles, heart failure begets more heart failure.
Heart failure as defined by the New York Heart Association in a functional classification.
Patients with cardiac disease but without resulting limitations of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, dyspnea, or anginal pain.
Patient with cardiac disease resulting in slight limitation of physical activity. These patients are comfortable at rest. Ordinary physical activity results in fatigue, palpitation, dyspnea, or anginal pain.
Patients with cardiac disease resulting in marked limitation of physical activity. These patients are comfortable at rest. Less than ordinary physical activity causes fatigue palpitation, dyspnea, or anginal pain.
Patients with cardiac disease resulting in inability to carry on any physical activity without discomfort. Symptoms of cardiac insufficiency or of the anginal syndrome may be present even at rest. If any physical activity is undertaken, discomfort is increased.
Congestive heart failure is described as circulatory congestion including peripheral edema. The major factor in cardiac pulmonary edema is the pulmonary capillary pressure. There are no native valves between the lungs and the left atrium therefore fluctuations in left atrial pressure are reflected retrograde into the pulmonary vasculature. These elevations in pressure do cause pulmonary congestion. When the heart, specifically the mitral valve, is operating normally correct flow and pressures throughout the circulatory system are maintained. As heart failure begins these pressures and flow rates decrease or increase depending upon the disease and vascular location.
Placement of valves between the lung and the left atrium will prevent retrograde flow and undesired pressure fluctuations to the pulmonary vasculature. Mechanical valves may be constructed of conventional materials such as stainless steel, nickel-titanium, cobalt-chromium or other metallic based alloys. Other materials used are biocompatible-based polymers and may include polycarbonate, silicone, pebax, polyethylene, polypropylene or floropolymers such as Teflon. Mechanical valves may be coated or encapsulated with polymers for drug coating applications or favorable biocompatibility results.
There are many styles of mechanical valves that utilize both polymer and metallic materials. These include single leaflet, double leaflet, ball and cage style, slit-type and emulated polymer tricuspid valves. Though many forms of valves exist, the function of the valve is to control flow through a conduit or chamber. Each style will be best suited to the application or location in the body it was designed for.
Bioprosthetic heart valves comprise valve leaflets formed of flexible biological material. Bioprosthetic valve or components from human donors are referred to as homografts and xenografts are from non-human animal donors. These valves as a group are known as tissue valves. This tissue may include donor valve leaflets or other biological materials such as bovine pericardium. The leaflets are sewn into place and to each other to create a new valve structure. This structure may be attached to a second structure such as a stent or cage for implantation to the body conduit.
Description of the Related Art
The concept of placing a percutaneous valve in the pulmonary veins was first disclosed by Block et all in U.S. Pat. No. 5,554,185. A specific windsock valve for this application was later described by Shaknovich in U.S. Pat. No. 6,572,652.
SUMMARY OF THE INVENTION
There is provided in accordance with one aspect of the present invention, a flow controlled device dimensioned for implantation in a human pulmonary vein. The device comprises an inflatable support structure in at least one movable occluder that controls the flow of blood into and out of the pulmonary veins. Implantation of the valve between the left atrium and the lung within the pulmonary vein reduces the likelihood and/or the severity of regurgitant flow increasing the pulmonary pressure which may lead to pulmonary edema and congestion.
In accordance with a further aspect of the present invention, a method of monitoring a patient comprises monitoring blood flow through the pulmonary veins during the implantation of the device of Claim 1. In accordance with a further aspect of the present invention, there is provided a method of monitoring blood pressure comprising monitoring blood pressure through the pulmonary veins during the implantation of the pulmonary vein valve.
In accordance with a further aspect of the present invention, there is provided a method of treating a patient comprising rerouting blood flow from the pulmonary veins into a prosthetic chamber, and then back into a portion of the heart. The prosthetic chamber may include at least one valve, and may serve as a manifold for combining the flow of the pulmonary veins into a single return conduit, which may be placed into communication with the left ventrical.
Further features and advantages of the present invention will become apparent to those of skill in the heart in view of the detailed description of preferred embodiments which follows, when considered together with the attached drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational schematic view of an axially actuated deployment device in accordance with the present invention.
FIG. 2 is a side elevational schematic view of a rotationally actuated deployment device in accordance with the present invention.
FIG. 3 is a fragmentary cut-away view of a distal end of a deployment catheter having an implantable device therein.
FIG. 4 is a fragmentary view as in FIG. 3, having a different embodiment illustrated therein.
FIG. 5 is a simplified top view of a section through the heart, illustrating a first valve at a first location in a first pulmonary vein, and a second valve at a second location in a second pulmonary vein.
FIG. 6 is a schematic representation of a stent supported valve in a pulmonary vein.
FIG. 7 is a simplified back view of the heart, illustrating the location of the left superior pulmonary vein, left inferior pulmonary vein, right superior pulmonary vein and right inferior pulmonary vein.
FIG. 8 is a simplified view of the lungs and left atrium, illustrating the orientation of the pulmonary veins with respect to the lungs.
FIG. 9A is a perspective schematic view of a Starr-Edwards ball and cage valve.
FIG. 9B is a perspective schematic view of a single leaflet valve.
FIG. 9C is a schematic perspective view of a bi-leaflet valve.
FIG. 9D is a schematic perspective view of a Reed style or duckbill valve.
FIG. 9E is a schematic perspective view of a poly-leaflet valve.
FIG. 9F is a schematic perspective view of a tri-leaflet valve having an inflatable support structure.
FIG. 9G is a schematic perspective view of a tri-leaflet valve having an alternative inflatable support structure.
FIG. 9H is an elevational cross-sectional view through the valve of FIG. 9G.
FIG. 10 is a schematic representation of the heart and pulmonary venous circulation following redirection of the pulmonary venous flow into the left ventrical.
FIG. 11 is a cross-sectional view of a ball valve that can be used to control inflation of the inflatable support structure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Implantation of valves into the body has been accomplished by a surgical procedure or via percutaneous method such as a catheterization or delivery mechanism utilizing the vasculature pathways. Surgical implantation of valves to replace or repair existing valves structures include the four major heart valves (tricuspid, pulmonary, mitral, aortic) and some venous valves in the lower extremities for the treatment of chronic venous insufficiency. Implantation includes the sewing of a new valve to the existing tissue structure for securement. Access to these sites generally include a thoracotomy or a sternotomy for the patient and include a great deal of recovery time. An open-heart procedure can include placing the patient on heart bypass to continue blood flow to vital organs such as the brain during the surgery. The bypass pump will continue to oxygenate and pump blood to the body's extremities while the heart is stopped and the valve is replaced. The valve may replace in whole or repair defects in the patient's current native valve. The device may be implanted in a conduit or other structure such as the heart proper or supporting tissue surrounding the heart. Vessels entering or departing the heart have an attachment or connection interface where the two components join in transition. This transition may provide a secure tissue zone to attach a valve body to. Attachments methods may include suturing, hooks or barbs, interference mechanical methods or an adhesion median between the implant and tissue. Access to the implantation site may require opening the wall of the heart to access the vessel or heart tissue for attachment. It is also possible to implant the device directly into the vessel by slitting in the longitudinal direction or cutting circumferentially the vessel and suturing the vessel closed after insertion. This would provide a less invasive method to implant the device surgically.
Other methods include a catheterization of the body to access the implantation site. Access may be achieved under fluoroscopy visualization and via catheterization of the internal jugular or femoral vein continuing through the vena cava to the right atrium and utilizing a transeptal puncture enter the left atrium. Once into the left atrium conventional and new catheterization tools will help gain access to the pulmonary veins. Engagement of each of the pulmonary veins may require a unique guiding catheter to direct device or catheter placement. Monitoring of hemodynamic changes will be crucial before, during and after placement of the device. Pressure and flow measurements may be recorded in the pulmonary veins and left atrium. Right atrial pressures may be monitored separately but are equally important. Separate catheters to measure these values may be required.
Valve delivery may be achieved by a pushable deployment of a self expanding or shaped memory material device, balloon expansion of a plastically deformable material, rotational actuation of a mechanical screw, pulling or pushing force to retract or expose the device to the deployment site. To aid in positioning the device, radiopaque markers may be placed on the catheter or device to indicate relative position to known landmarks. After deployment of the devices the hemodynamic monitoring will allow the interventional cardiologist to confirm the function of the valves. It is possible to place and remove each valve independently as valves may not be required in all pulmonary veins.
Entry to the body with a catheter may include the internal jugular or femoral vein. This will allow the user to enter the right atrium either superior or inferiorly and complete a transeptal puncture for access into the left atrium. Another approach would be to enter the femoral, brachial or radial artery where the user could access the aortic valve entering the left ventrical. Advancing the device through the left ventrical and past the mitral valve the left atrium can be entered. Utilizing normal cath-lab tools such as guidewires and guide catheters the delivery system or catheter can be advanced to the deployment site. Guidewires may measure 0.010-0.035 inches in diameter and 120-350 centimeters in length. Slippery coatings may aid in the navigation to the implantation site due to the vast number of turns and the tortuerosity of the vasculature. A guide catheter may be used to provide a coaxial support system to advance the delivery catheter through. This guiding catheter may be about 60-180 cm in length and have an outer diameter of 0.040-0.250 inches. It would have a proximal and distal end with a connection hub at the proximal end and may have a radiopaque soft tip at the distal end. It may have a single or multilumen with a wall thickness of 0.005-0.050 inches and may include stiffening members or braid materials made from stainless steel, nickel-titanium or a polymeric strand. The catheter material may include extruded tubing with multiple durometer zones for transitions in stiffness and support. The inner diameter may have a Teflon lining for enhanced coaxial catheter movement by reducing the friction coefficient between the two materials.
As illustrated in FIG. 1, the delivery catheter 10 would be constructed by normal means in the industry utilizing extruded tubing, braiding for stiffening means and rotational torqueability. The delivery catheter 10 has a proximal end 12 and distal end 14 where the proximal end 12 may have a connection hub to mate other cath-lab tools to. The distal end 14 may have a radiopaque marker to locate under fluoroscopy. The outer diameter would measure about 0.030-0.200 inches and have a wall thickness from about 0.005-0.060 inches. The overall length would range from about 80-320 centimeters and have a connection hub or hubs at the proximal end 12 to allow wires, devices and fluid to pass. The connection hub would be compatible with normal cath-lab components and utilize a threaded end and a taper fit to maintain seal integrity. The inner diameter of the catheter 10 would allow for coaxial use to pass items such as guidewires, devices, contrast and other catheters. An inner lining material such as Teflon may be used to reduce friction and improve performance in tortuous curves. In addition a braided shaft of stainless steel or Nitinol imbedded into the catheter shaft 16 may improve the torqueability and aid in maintaining roundness of the catheter lumen.
Multidurometer materials would help soften the transition zones and add correct stiffness for pushability in the body. These zones may be achieved through an extrusion process know as bump tubing. Where the material inner and outer diameter change during the extrusion process. The entire catheter shaft can be produced in one piece. Another method for producing such a catheter shaft is to bond separate pieces of tubing together by melting the two components together and forming a single tube with multiple diameters and or stiffness. The application of heat can be applied by laser or heated air that flows over the shaft material or other methods of heat application sufficient to flow the materials together.
The shaft material may also consist of stiffening members for transition zones or bump extrusions to reduced diameter and maintain correct pushability. Lumen characteristics may include single or multi portals for guidewire or device entry. Conventional guidewire passage through the catheter such as “over-the-wire” may be used or technology such as “rapid-exchange” may aid in procedure ease and catheter exchanges. Since multiple devices may be placed in a single catheterization, rapid-exchange may be preferred but not essential. Other features that may aid in ease of use include a slippery coating on the outer and or inner diameter such as MDX (silicone) or a hydrophilic layer to allow easy access to tortuous anatomy. It may be necessary to utilize a balloon to radially expand the device to its final diameter and location so an inflation lumen and balloon placed distal to the hub could be used. This balloon could be used to pre-dilate the vessel or ostium where the valve may be implanted. Finally elements to transmit signals externally could be imbedded into the catheter for pressure and flow readings or Doppler information. These may include electrical wires, pressure portal or lumens optical fibers.
As illustrated in FIGS. 1-4, delivery of the device 18 via catheterization of the implantation site will include a mechanism to deploy or expel the device 18 into the vessel or atrium. This mechanism may include push or pull members 20 and 21 to transmit forces to the distal portion of the catheter 10. These forces may be applied externally to the body and utilize a handle 22 at the proximal end 12 of the catheter. Means to transmit forces to the distal end 14 may also include a rotational member 24 to loosen or tighten, convert a torque 26 into a translational force such as a threaded screw 28 and nut or to add or subtract stiffness to the catheter 10 or device 18. The handle 22 mechanism may also include a port for hydraulic pressures to be transmitted to the distal portion of the catheter 10 or have the ability to generate hydraulic forces directly with the handle 22. These forces may include a pushing or pulling transmitted to the device 18 or catheter 10, an exposure of the device 18 to allow for implantation or to expel the device 18 from the catheter. Further forces may include a radial or longitudinal expansion of the device 18 or catheter 10 to implant or size the location of implantation. The handle 22 may also include connections to electrical signals to monitor information such as pressures, flow rates, temperature and Doppler information. Another important use of the handle 22 and catheter 10 is the deployment mechanism for the device 18. As the device 18 is navigated to the site, attachment between the device 18 and catheter 10 is essential. Many detachment methods have been used to deploy devices 18 such as stents and embolic coils through balloon expansion and simple pushable coils expelled from the distal end 14 of a catheter 10. The valve device can utilize many different methods to implant at the selected site such as an expulsion out the end of the catheter 10, a mechanical release mechanism such as a pin joint, unscrewing the device 18 from the catheter delivery system, a tethered link such as a thread or wire, a fusible link as used in a GDC coil deployment, a cutting tool to sever a attachment of the device 18 from the catheter 10, a threaded knot to tether the catheter 10 to the device 18 where the as the knot could be untied or cut, a hydraulic mechanism to deploy, expand or fracture a link between the catheter 10 and the device 18. All above mentioned concepts may be enhanced be the utilization of a flexible tip to allow acute articulation of the device 18 and delivery catheter 10 to gain access to the implantation site.
After the device has been temporarily deployed or positioned, it may be advantageous to recapture or reposition the device for optimal results. This may include a rotational or translation of the implant of a complete removal and exchange for a different diameter, length or style device. Capture of an implanted device may require a second catheter to reengage the device to remove or reposition to a proper location.
As illustrated in FIGS. 5-8, in the preferred embodiment the device, such as a valve 30, would be located between the right lung 31a and/or left lung 31b and the left atrium 32 in the right superior pulmonary vein 34a, the right inferior pulmonary vein 34b, the left superior pulmonary vein 34c, the left inferior pulmonary vein 34d and/or in the wall of the left atrium 32. Preferably the valve 30 described above is located to affect the flow and pressure of blood between the pulmonary veins 34a-d and the left atrium 32 or a portion of the left atrium 32 and to lessen the symptoms of mitral regurgitation from a dysfunctional mitral valve 36 including elevations and fluctuations in the pulmonary circulation. The device 30 may be viewed as a one-way valve limiting or restricting retrograde flow into the pulmonary circulation. Having a substantial fatigue life to withstand cyclical operation for a given period of implantation duration will be a factor in selection of both materials and construction. This may include heat treatments to certain portions or all components of the device 30 and analysis of construction and manufacturing techniques to optimize device 30 life. Additionally a coating may be required to maintain patency of the device 30 during normal operation. This may be a surface modification or treatment, a coating added to the device 30 such as heparin or and albumin layer.
The valve could be a valve of any design including bioprosthetic, mechanical or tissue valves. Examples of commonly used prosthetic valves include a ball valve 40 illustrated in FIG. 9A such as a Starr-Edwards, a single leaflet valve 50 illustrated in FIG. 9B such as a Bjork-Shiley valve, a bileaflet or bi-disk valve 60 illustrated in FIG. 9C or an artificial tricuspid valve such as a Magna or Cribier, a reed style valve 70 illustrated in FIG. 9D, a slit in a membrane of material, a duckbill style or many other styles unmentioned here but apparent to one skilled in the art. To facilitate delivery of the valve and to improve hemodynamics other mechanical valve designs may be utilized, including the poly-leaflet valve and flexible leaflet valves as described below. The valves may be deformable to allow for percutaneous delivery or rigid to enable structural integrity. They may include one of the below mentioned features or a combination of a plurality thereof to add performance and or reduce size.
As illustrated in FIG. 9A, the early valve implants began in the early 1960\'s with ball valves 40 such as the Starr-Edwards. This valve 40 includes a base 42 and mechanical structure 44 where a ball 46 is captured and allowed to travel longitudinally sealing flow in one direction and allowing flow in the other. The movement of the ball 46 is driven by flow.
As illustrated in FIG. 9B, disk style valves 50, known as Bjork-Shiley, entered the market in the 1970\'s and began with a single disk 52 supported in a ring 54 where the disk 52 was allowed to pivot within the ring 54 allowing flow in one direction and sealing flow in the other. The tilt angle ranged from about 60-80 degrees.
As illustrated in FIG. 9C, bi-disk valves 60 include two tilting disks to allow for greater flow and less turbulence. These valves 60 were introduced in the 1980\'s and seem to be the standard choice.
As illustrated in FIG. 9E, also disclosed is a poly-leaflet valve 80 for implantation in the body. The valve 80 would contain four or more leaflets 82 free to pivot near the annulus 84 of the valve 80. Increasing the number of leaflets 82 allows the valve 80 to collapse to a smaller diameter, for percutaneous or minimally invasive delivery, while also providing good hemodynamics, and allowing the leaflets 82 to be made from a rigid material ideally one that has clinically proven good biocompatibility in valve applications.
Also disclosed is a flexible leaflet valve for implantation in the body. A mechanical prosthetic valve manufactured from a flexible material such as a polymer or tissue material that allows the leaflets to be substantially deformed during delivery if the valve. The leaflets could also consist of metal or a polymeric coated sub straight. If metallic the leaflet material could be a super elastic alloy such as Nitinol or an alloy with a relatively high yield stress and relatively low modulus of elasticity such as certain titanium alloys. Someone skilled in the art will understand the relationship between elastic modulus and yield stress; in order to select materials with a maximum amount of strain available before yielding begins. This would allow for recoverable deformation during delivery and may enhance fatigue characteristics.
A valve that functions as an iris could also be utilized as a prosthetic valve. The iris could be opened and closed by an internal or external force, a differential in pressure or by the flow of blood.
There are several types of tissue valves that have been previously implanted as replacement valves in the human coronary system. These include valves from human cadavers, and valves from other mammals such as pigs horses and cows utilizing sometimes pericardial tissue to build a valve by sewing techniques. Any of these types of valves could be implanted as described both in a surgical procedure or a catheterization. Additionally other valves such as from the larger venous vessels from smaller animals could be utilized because of the smaller size and reduced flow requirements of the pulmonary veins.
A valve from the patient may also be used, by transplanting the valve into a pulmonary vein. Many native valves could be used such as a venous valve from the lower extremities. The preferred embodiment is to use a native valve from a large peripheral vein.
The flow control device could be an orifice of fixed or adjustable diameter that limits the amount of blood that flows through the pulmonary veins. The orifice diameter could be adjusted remotely or by some hemodynamic mechanism such as pressure or flow differential or pressure change.
The flow control device could consist of one or more flaps located within the atrium to prevent the back flow of blood into the pulmonary veins. The flow control device could be a pivoting or flexible flap that moves to block the ostium of one or more pulmonary veins or it could be a rigid or semi rigid flap or flaps that control the bloods flow path reducing or eliminating the backwards flow of blood in to the pulmonary veins.
In the preferred embodiment the flow through the valve is flow controlled. To the extent possible flow is allowed only in a first direction and not in a second direction. The first direction is intended to be away from the lungs and towards the heart.
The valve may function such that it is pressure controlled that is it opens at a preset pressure differential. The pressure control could be implemented in several ways. The one-way valve could allow flow in the backward or restricted direction at a certain pressure differential. This may be advantageous in preventing the overloading of the atrium. Alternatively the valve could be designed to open in its normal flow direction at a preset pressure differential.
The valve or flow control device may be manufactured partially or completely from metallic components. Depending on the mechanical properties required various biocompatible metals might be chosen. These include, but are not limited to various stainless steel alloys, cobalt-chrome-nickel-alloys, super-elastic alloys such as Nitinol, Tantalum and titanium and its alloys. The device could be self-expanding in nature if desired.
The valve or flow control device may be manufactured partially or completely from polymeric components. Various biocompatible polymers may be used depending on the desired mechanical properties. Some examples of biocompatible polymers include silicone, polyethylene and, flouropolymers such as Teflon.
All or part of the flow control device may attach to the outside of the pulmonary vein by applying external force to the vein the device affects the flow through the vein. Both compressive or expansive forces could be applied to change the vessel geometry. An external portion of the device located around the vein may also help to secure a second portion of the device within the vein.
Valves may be actuated to synchronize with the proper opening and closing times through an internal or external device such as a pacemaker. There may require an actuation device to drive the motion of the valve open and closed. Pressure gradients could be used to sense when actuation is necessary.
The flow control device may include a vane that introduces a swirling motion to the blood. The vane may be used to improve hemodynamic flow through another portion of the flow control device or it may be used alone to improve the hemodynamics of the native anatomy. The vane may additionally function or rotate in a single direction only to limit flow.
In one embodiment the flow control device located between a portion of the pulmonary veins and the heart consists of a pump. The pump may be powered externally, internally or by the biological movement of the heart. The pump may be located inside the pulmonary vein inside the atrium outside the heart or, outside the body.
Inflatable Support Structure
As illustrated in FIGS. 9F, 9G, 9H and 11, certain pulmonary vein valves in accordance with the present invention include an inflatable support structure 90, as is disclosed, for example, in the context of an atrial valve, in the provisional applications incorporated by reference above.
As illustrated in FIGS. 9F and 11, the inflatable support structure 90 comprises at least one annular ring 92, such as an annulus for a valve, which is releasably carried by a deployment catheter having at least one inflation lumen extending therethrough. Following positioning of the valve in the pulmonary vein, the annulus is inflated to the desired size and/or pressure, and thereafter decoupled from the deployment catheter. A one way valve 102 on the inflatable support structure 90 prevents escape of the inflation media and/or allows inflation of the inflatable support structure 90. The one way valve 102 can be a ball valve, as illustrated in FIG. 11, or another type of valve such as a duck bill valve, pinch or flap valve. The flow control valve 102 illustrated in FIG. 11 has a spring 103 actuated check ball 104 that seals off the inflation lumen 105. A push wire 106 in the delivery catheter 107 can be used to displace the check ball 104 from the default sealing position, thereby unsealing the inflation lumen 105 and permitting the inflatable support structure 90 to be inflated. Release tangs 108 can be used to secure and align the delivery catheter 107 with the flow control valve 102.