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Disclaimer: Dr. Vesely, the author of the Patients section is recognized world-wide as an expert in heart valve mechanics and prosthetic valve durability. He is not a physician, however. The information presented on this web site should not be taken as any form of medical advice. Always check with your own physician before deciding which therapy is best for you. Please click here for details of the ValveXchange Website Disclaimers and Notices which apply to all users of this Website. For a simple tutorial on how the heart and valves work, please click here. A more thorough review can be found by clicking here. Additional information can be found at The Patient’s Guide to Heart Valve Surgery.

Signs of Heart Valve Disease:

Heart valve disease often creeps on you without notice. For individuals who are not very active, the first evidence of a disease heart valve can come late in life, along with a host of other types of heart disease, like coronary artery disease. Valve disease can show up as shortness of breath, chest pain and fatigue during moderate exercise. Sometimes the patients are so sick when these signs show up, that they cannot even withstand the surgery to treat the diseased valve. For those patients, non-surgery options can be considered. For all others, physicians usually recommend heart valve repair or heart valve replacement, by way of open-heart surgery, much of which can be done today with a very small incision.

Valve Repair:

When the mitral valve becomes diseased, it can be because it is floppy due to a condition called Myxomatous degeneration, or can be stretched out and leaky because of an underlying condition of the heart itself. The first condition, myxomatous mitral valve prolapse occurs earlier in life, and is believed to be of genetic origin. It manifests as thickened, stretched valve leaflets and the supporting cords (see image right), which often snap, causing the leaflet to flail in the heart untethered. The second condition occurs mainly because of a diseased heart. Because the mitral valve is part of the left ventricle, the valve can become stretched out and leak when the ventricle itself becomes distended due to many types of heart disease that occur later in life.

Both types of valve conditions can be repaired surgically with low complication rates. Mitral valve repair started 20 years ago and today’s surgeons have extensive experience with the various approaches. Repair typically involves excising a portion of the “posterior” leaflet of the mitral valve to correct its geometry, and reducing the diameter of the mitral annulus – the perimeter of the mitral valve. This is done by attaching a “mitral annuloplasty ring” – usually a segment of felt-like material or plastic covered by cloth, to which the annulus is sewn while it is plicated, or puckered up to make the perimeter shorter. For most patients, this surgery will last the rest of their lives. In the western world, repair of the mitral valve is advocated by many doctors as the best solution for the patient – better than replacing the mitral valve with an artificial valve. If the mitral valve cannot be repaired, however, it needs to be replaced with a prosthetic valve.

When an aortic valve becomes diseased, it usually cannot be repaired. Whereas mitral valve leaflets become distended, floppy and leak, the normally thin and pliable aortic valve leaflets slowly turn into little pebbles of bone-like mineral that do not move well and obstruct the flow of blood out of the heart (see images below). These calcified leaflets need to be replaced with an artificial heart valve. TOP

The Patient’s Dilemma:

The long-standing dilemma faced by patients that need their heart valve replaced has always been how to chose between the lesser of two evils – mechanical or tissue valve. Mechanical valve (see image right from St.Jude) are made of metal and/or pyrolitic carbon, a hard ceramic-like material. Tissue valve are made from soft, leather-like biological materials and are intended to mimic the function of the native aortic valve. Neither choice is ideal. Mechanical valve last the life of the patient but require a daily dosage of a powerful anticoagulant called Coumadin®. The active ingredient in Coumadin® is Warfarin, which was initially marketed as rat poison, and still is to this day. Too much or too little Coumadin® is dangerous, and significantly increases the risks of serious brain or intestinal bleeding at one end of the spectrum, or clots and stroke at the other. Being on Coumadin® requires, regular blood-test monitoring and careful attention to all other areas of medical treatment as Coumadin® interacts other drugs. Patients on Coumadin® must follow dietary restrictions (i.e. monitoring vitamin K intake) and cannot participate in physical activities or sports that might cause bleeding. Treating physicians must walk a fine line between life-threatening complications from major bleeding episodes, or blocked blood vessels from clots that break off from the mechanical valve. Besides the immediate change in lifestyle, long-term anticoagulation has complications rates often as high as 4% per year. This essentially guarantees some serious event within a 25-year treatment period. Moreover, recent clinical studies suggest that long-term use of Coumadin® increases the rate of mineralization of other valve and vascular tissues by a factor of two. Many patients thus try to avoid being on Coumadin® at all costs.

The alternative, implantation of an animal tissue-based valve, however, is also not ideal. Although tissue valve do not induce blood clotting and thus do not require the patient to be on Coumadin®, they eventually wear out and need to be replaced surgically. In the best of circumstances, tissue valve last up to 18 years in the elderly patient. In those cases, they outlive the patient. For patients 70 years of age or older, a tissue valve will usually represent a life-long, single-surgery solution. When implanted into younger patients, however, tissue valve tend to wear out sooner and need to be replaced by open-heart surgery, just like the original implant. However, because of the overall high quality of life that tissue valve allow, many patients are now choosing a tissue valve at a younger age, fully expecting at least one redo surgery later in life and possibly more. Fortunately, the first redo surgery these days is becoming safer, with the risk of complications for the first redo surgery being essentially the same as during the first implant surgery. A second redo surgery presents significantly greater challenges and risks. For the patient, the prospect of cutting the chest open again to replace a worn out tissue valve involves the pain, discomfort and down-time of recovery, which can last several weeks. TOP

Transcatheter valve and Minimally Invasive Surgery:

Fortunately, medical technologies continue to evolve towards being less and less invasive. Today, many procedures that used to involve using a heart/lung machine, and stopping the heart can be done by way of catheters that are inserted through a small incision in the groin. More complex procedures can also be done without splitting the breastbone. So called “minimally invasive surgery” (MIS) now allows surgeons to access the heart through an incision between the ribs that can be less than 2” long. There are always compromises, however. The simpler the solution to a disease, the smaller the incision or puncture and the faster the recovery. On the other hand, the more complex the disease and the better the desired outcome, the greater the required exposure of the heart so that the surgeon can do the best possible job.

Transcatheter valve are a good example of this compromise between the level of invasiveness and the quality of the solution. Conventional, surgically implanted tissue valve are very mature devices that can last 18 years. This is because decades of experience in valve design and manufacture eventually ironed out all the known flaws that led to early failure of the first generation devices that were used in the 80’s. Transcatheter valve are the new wave and promise no surgery. However, because they need to be collapsible into tight bundles for catheter delivery through a small incision in the chest or groin, they must depart from these time-proven tenets of valve design and will most likely wear out in about 5 years. Surgically implantable valve thus have the best durability but require more invasive implant. Transcatheter valve can be inserted with a very small incision in the chest or the groin, but will give much shorter service life. That is the compromise. TOP

Features of a long-lived tissue valve:

To better appreciate the reasons for this compromise, one needs to understand the basics of tissue valve function. Although tissue valve may look like the native aortic valve, they are dead tissue that does not have any capacity for repair, like skin and bones. The living and dead pig valve, shown below, demonstrate the primary differences – the far greater degree of leaflet bending or wrinkling in the dead leaflet tissue that makes up one type of tissue-based artificial heart valve (right image). Tissue wrinkling leads to material fatigue and leaflet tearing, and is one of the major causes of valve degeneration and failure. In order to maximize tissue valve longevity, leaflet wrinkling needs to be minimized.

An alternative to fabricating prosthetic valve from pig aortic valve is the “bovine pericardial valve”. Although it has three leaflets, like the pig valve, these leaflets are made from the heart sack of a young cow. The advantage of fabricating a valve from bovine pericardium is the far greater precision to which the valve can be fabricated to minimize leaflet wrinkling. The disadvantage is that any departure from this precision of assembly leads to rapid valve degeneration and failure. When done right, a bovine pericardial valve can last 18 years without failure. When done wrong, it will fail as early as 5 years. Thirty-years worth of experience with valve designs has shown that departure from three main design features leads to diminished durability of tissue valve made of bovine pericardium. These features are:

(i) Flexible stent posts to cushion the closing leaflets
(ii) Central gap to accommodate leaflet extension
(iii) Absolute geometrical precision of 120 leaflet degree symmetry

The anatomy of a typical bovine pericardial valve is shown at right. The valve consists of three leaflets mounted on a frame or “stent” that has a “sewing cuff” at its lower edge so that the surgeon can sew it into the aorta – a tube – after the original diseased aortic valve leaflets have been cut out. Note that the leaflets curve upwards and are mounted on three “stent posts” with 120 degree symmetry, and that there is a little triangular “central gap” between the three leaflets. The two videos shown below demonstrate how a valve opens and closes and what happens if the above three design features are not followed. In each case, the valve is mounted in a chamber filled with clear fluid and the motion is slowed down so that details of valve function can be better appreciated.

The first valve on the right is an old, first-generation valve called the “Ionescu-Shiley”. This valve is no longer used because it failed in about 5 years once implanted into patients. Notice that there is very little inward deflection of the three stent posts when the valve closes, and thus very little leaflet cushioning. Also note the complete absence of the central gap and the resultant wrinkling of the leaflets when they come together. This leaflet wrinkling and “pinwheeling” causes increased stresses in the leaflets and early failure of the valve. In hind sight, this was a poorly designed pericardial valve.

The second video is of another valve that is fabricated from equine pericardium, but without the supporting stent. It is called the “ATS 3F® Aortic Bioprosthesis” It is sewn into the patient aorta by hand, and care must be taken to make sure that it is the right size for the diameter of the aorta and that it is positioned with perfect 120 degree symmetry. As can be seen from this video, obtained from a public display set up by ATS, there is no central gap between the leaflets nor the precise 120 symmetry of leaflet position. Accordingly, the leaflets open asymmetrically and close with considerable central wrinkling, just like in the Ionescu-Shiley valve above.

Compare that with the Edwards Perimount® pericardial valve (image right). Note the smoother leaflet curvature during opening and closing. The Edwards Perimount®, is considered by many surgeons to be the state-of-the-art in bovine pericardial valve. In clinical studies, it has demonstrated 18-year durability when implanted into elderly patients, experiencing 37 million cycles of opening and closure per year, even though it is a piece of dead leather-like tissue about 1/16” thick. Its excellent clinical performance has resulted primarily because of the strict adherence to the three design features listed below. Any compromise in these three design features leads to diminished valve durability. TOP

Design Compromises in Transcatheter Valve:

Unlike the relatively rigid, circular stent structure of surgical valve, the metal cage that supports the leaflets of transcatheter valve is designed to be collapsible. The only way to insert a valve through the leg arteries and up around the aortic arch and into the heart, is to crimp it down tightly over a thin catheter. Example images of the crimped and expanded transcatheter valve are shown at right. The crimped valve is either expanded in place by way of a balloon, just like coronary stents are, or the metal cage is self-expanding. Because delivery of transcatheter valve has the advantage of not requiring surgery, at the same time it has the disadvantage of not being able to remove the diseased, calcified native aortic valve leaflets that have created the obstruction. These leaflets are simply pushed aside by the expanding transcatheter valve. This has the very important disadvantage in that the landing ground for the implanted transcatheter valve cannot be “cleaned out” prior to inserting the new valve.

The consequence is that when a transcatheter valve is deployed inside the calcified native aortic valve, it seldom ends up being circular or of the right diameter. Very often, the deployed metal cage is oval or triangular (as shown below). This is a long-suspected phenomenon that has only recently been demonstrated by way of a clinical study. This distortion occurs because the final diameter and shape of the deployed transcatheter valve is an elastic balance between the outward expansion of the metal frame and the inward contraction of the calcified native valve that has been distended. Because the calcified native valve has hard, irregularly shaped nodules, it usually assumes a non-circular shape when distended.

The deployed valve is thus typically non-circular and of unpredictable diameter. This absence of a precise shape and diameter leads to misshaped leaflets and the absence of the important central gap. Most of the transcatheter valve also do not have stent posts that deflect inward with each cardiac cycle and thus do not cushion the leaflets the way that the long-lived Edwards Perimount® valve does. Transcatheter valve therefore do not have the three important features of a long-lived valve – (i) flexible stent posts for leaflet cushioning, (ii) central gap to accommodate leaflet extension, and (iii) absolute precision in leaflet symmetry. This is the compromise that has been engineered into these devices in order to enable them to fit through the narrow passage of the arteries and be inserted via catheter. Decades of research and the clinical experience with many designs of tissue valve illustrate that such transcatheter valve cannot last more than about 5 years. TOP

Options for dealing with a failed surgical or transcatheter valve:

The risks of re-do surgery are the main reasons why young patients are prescribed mechanical valve. Historically, the risks of re-do surgery to replace a failed tissue valve have been considered worse than the long-term risks and complications of being on Coumadin®. As surgical technique and safety improved over the past decade, the option to have a second surgery to replace a failed tissue valve has become more acceptable to many patients than the prospect of being on Coumadin® for life. However, cutting out a failed tissue valve takes surgical skill and time on the heart-lung machine. The longer one spends on cardiopulmonary bypass, the greater the risk of neurological impairment. Although the mechanism of this is not well understood, it is generally accepted that pumping blood outside the body through an oxygenator damages the blood cells and activates the clotting process. Small blood clots are introduced back into the blood stream, which in turn create partial blockages in the blood vessels of the brain. This leads to the slight cognitive impairment after long periods on cardiopulmonary bypass. The more time on cardiopulmonary bypass, the greater the risk of having transient or permanent neurological deficit.

Replacing a failed tissue valve without having to undergo additional time on cardiopulmonary bypass is thus very attractive. One option is to deploy a transcatheter valve inside a failed, surgically implanted tissue valve. Another is to deploy another transcatheter valve inside a failed transcatheter valve. Both are doable, but not the best solution, as each postpones the inevitable surgery by only 5 years or so - the expected lifespan of transcatheter valve. If the patient is old and frail, with a life expectancy less than 5 years, it is an acceptable solution. For younger, otherwise healthy patients, a valve-in-valve approach reduces the flow area of the prosthetic valve and often leads to an incompetent leaky valve. Neither is good for active individuals who need properly functioning heart valve. Having a leaky valve for many years also overstresses the ventricle and can lead to dilation of the heart and eventually to heart failure. A valve-in-valve approach only postpones the inevitable – another re-do surgery which could be far more difficult and dangerous than if it had been done right the first time.

Transcatheter valve are currently not approved for sale in the US. They have been cleared for use in Europe, but only on only the very sick, inoperable patient who cannot tolerate open heart surgery. They are currently in clinical trials in the US and expect to be approved for use also on the inoperable patient. Because these patients die from their other underlying conditions, no patient has lived long enough to have their transcatheter valve replaced from it wearing out. Because the metal cage is expected to grow over with tissue, digging it out surgically is likely to be far more difficult than re-do surgery for a conventional surgical valve, like the Edwards Perimount® pictured earlier.

For all but the very sick, inoperable patient, choosing a conventional, surgically implantable valve is still the best solution, as it offers the most long-lived valve with good options for replacement. The ValveXchange approach, when available commercially, will take this strategy to the next level of refinement, allowing both the initial implant and the re-do procedure to be done without open chest surgery or cardiopulmonary bypass, AND offer the same longevity as the time-proven surgical valve, plus exchangeable leaflets. Details of the VXi approach can be found in the Products page of the VXi web site. TOP

One Patient’s Decision

It is always interesting to see how patients become informed about their health and how they work through the decision process regarding the type of treatment that they ultimately choose. One such patient, 87-year old Mel Heller, recently shared his experience with us at ValveXchange. Mel Heller is a retired physician, not in the cardiovascular field, who became very interested in the new valve technologies that are available for patients, and educated himself on the topic entirely from the data available on the web. We share his experience with you by way of a letter to his physician that Dr. Heller wrote prior to his procedure.

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