CIMIT Forum: Percutaneous Cardiac Valve Therapy

Percutaneous Cardiac Valve Therapy

In developed countries, aortic stenosis is the most common acquired disorder of the heart valves. Its prevalence increases with age, and in the United States, approximately 50,000 aortic valve replacements are performed each year. Replacing the aortic valve currently requires open heart surgery. For patients unable to undergo open heart surgery, balloon angioplasty is another option, but this procedure is a short-term solution that does not improve survival. In recent years, surgeons and engineers have begun to explore the possibility of replacing the aortic valve without performing open heart surgery. New devices now allow surgeons to replace an aortic valve using only a catheter. This form of aortic valve replacement promises to be a valuable alternative to existing therapies for aortic stenosis.

The typical device used to perform a trans-catheter aortic valve replacement consists of a bovine heart valve mounted on a collapsible stent attached to a catheter. The collapsed stent is moved into place using the catheter, and when the stent is properly positioned, it can be expanded to push the old valve out of the way, allowing the new valve to function.

The best way to deliver the new valve to the appropriate site is a controversial topic. Initially, surgeons attempted to access the aortic valve by running the catheter up the femoral vein and by then cutting a small hole from the right atrium into the left atrium. This approach was eventually abandoned in favor of a retrograde approach in which the catheter is run directly to the aortic valve through the femoral artery. Another approach sometimes used today is to run the catheter through a hole between the ribs and through the apex of the heart. The trans-apical approach is more invasive than the retrograde approach, but it allows the surgeon to avoid running a bulky catheter through twisting vasculature. It is difficult to compare the results of femoral and apical placement because patients undergoing apical placement are usually sicker than those undergoing femoral placement.

Trans-catheter aortic valve replacement has already been approved in Europe, and a clinical study known as the Partners trial is underway to test the efficacy of the technique. At Massachusetts General Hospital, trans-catheter aortic valve replacement has been performed in five patients. In the future, researchers hope to create a device with a narrower catheter, a retrievable stent, and less leakage around the new valve.