Percutaneous Mitral Valve Replacement Finally a Reality
This life-saving procedure is approved in Europe, but is still a few years away from being available in the U.S.
Of the estimated 3.7 million Americans with severe mitral regurgitation (MR) and heart failure (HF), as many as 2.5 million have no real treatment options. That’s because they’re too sick or frail to handle open heart surgery to replace their ailing valves.
But the options for inoperable and high-risk surgical candidates are changing after the first successful implantation of a transcatheter prosthetic mitral valve in a human patient earlier this year. Doctors in Denmark implanted the CardiAQ TMVI bioprosthetic valve in an 86-year-old man with severe mitral regurgitation. The procedure is performed by guiding the prosthetic valve at the end of a catheter up through a blood vessel to the location of the defective mitral valve. The CardiAQ valve then self-expands into place over the patient’s own valve and is secured in place by a mechanism that takes advantage of the foreshortening of the frame during diagonal expansion.
The manufacturer refers to the prosthetic tissue valve as “self-conforming and self-anchoring.” Cleveland Clinic cardiac surgeon Patrick Whitlow calls the new device “a milestone.”
“It’s a very big deal because so many older people have severe mitral regurgitation,” he explains. “It’s also a big deal engineering-wise, because you have to fold the valve and then guide it through the atrial septum. Then you open it up.” The atrial septum is the wall separating the heart’s upper two chambers, the atria.
The mitral valve is located between the left atrium and the left ventricle, and allows blood to flow from the atrium to the ventricle, where it is then pumped to the rest of the body. Individuals with MR have a mitral valve that no longer closes tightly and therefore allows blood to seep back into the left atrium from the left ventricle. With less blood flowing to the rest of the body, the heart starts working harder, and congestive heart failure can be the result if there is no intervention.
This new transcatheter mitral valve implant procedure is only available for early clinical evaluation at just one center in Europe and will not progress to multi-center phase-two clinical trials until 2013. Dr. Whitlow suspects it may be at least five years before U.S. patients can take advantage of this new treatment. The U.S. Food and Drug Administration (FDA) requires a rigorous testing program before any new heart valves or other medical devices are approved, and that often means U.S. approvals lag behind Europe.
“It remains to be seen how long it will take to get FDA approval, but I don’t anticipate a lot of problems,” says Dr. Whitlow, adding that valve replacements do carry the risk of blood clots forming and causing blockages in arteries or even strokes. As technology continues to improve and physician experience with these devices and procedures grow, however, such risks are likely to diminish.
And when the transcatheter mitral valve replacement is available in the U.S., the new valve should provide far more options to people with MR. Currently, the primary repair option for MR patients is the MitraClip, which is used to repair defective valve leaflets. But Dr. Whitlow explains that patients can’t have more than two clips, and that the clip has to be centrally located in the valve.
“If it’s on one side of the valve, it’s not as effective,” he says.
Another solution was needed.
Repair vs. Replacement
For many patients with MR, repairing the mitral valve, rather than replacing it entirely is usually the preferred option. Dr. Whitlow explains that repairing the valve is usually better, because you can use more of the body’s natural parts and because there is a limited shelf life for prosthetic devices. However, a severely calcified valve, and one with damage to surrounding tissue, is likely to be in need of total replacement.
Just who makes the ideal candidate for the CardiAQ valve will be determined as more patients are recruited to undergo the procedure. At first, they will be compassionate patients deemed inoperable or at high-risk for surgery. Dr. Whitlow says prosthetic valves are expected to work properly for about 12 to 15 years, but that may change with future versions of the valve.
Valve replacement for patients with severe MR is vital, however, because medical therapy doesn’t prolong life, Dr. Whitlow says. And from the onset of serious symptoms, there is only a 50% survival rate during the next three years, unless a repair or replacement is performed.
MR is also related to heart failure, as about half of the people with HF also have MR. That means poor quality of life characterized by fatigue, frequent lightheadedness, coughing when lying down and shortness of breath, even at rest.
“MR if you have heart failure means extra work that the heart has to do,” Dr. Whitlow says. “Giving people a new valve is a life-changing thing.”