Percutaneous Cardiac Valve Therapy

Aortic stenosis is an under-treated problem in the United States.  For decades, the main method used to treat severe aortic stenosis has been to perform open heart surgery in order to replace the aortic valve.  In 2002, however, doctors successfully replaced for the first time a patient’s aortic valve using only a catheter, thus avoiding open heart surgery.  This new technique seems very promising, although the surgical procedures and the technology are still being perfected. 

One current question is whether it is better to approach the aortic valve through the femoral artery or through an incision in the apex of the heart.  The trans-apical approach allows surgeons to position the new valve more effectively and possibly reduces the risk of stroke.  On the other hand, the trans-apical approach has a higher overall death rate than the trans-femoral approach, possibly because the patients who undergo trans-apical surgery are sicker than those who undergo trans-femoral surgery.

One clinical study currently being conducted to analyze the effectiveness of trans-catheter aortic valve replacement is known as the Partners Trial.  In this study, 97% of procedures have been successful, and 94% of patients have been discharged from the hospital.  The procedure currently takes an average of 128 minutes to perform. 

As researchers attempt to build better devices for trans-catheter aortic valve replacement, they face a number of challenges.  First, it is difficult to access the aortic valve without opening the chest.  The best path to the aortic valve is still uncertain.  Second, it is difficult to accurately place the new valve using only a catheter.  The stents used in today’s devices are not retrievable and could be fatal if misplaced.  Third, devices must be designed so as not to block the coronary arteries, which diverge from the aorta not far from the aortic valve.  Fourth, researchers are still struggling to eliminate perivalvular leakage, which occurs when the new valve fails to fully cover the opening of the aorta.  Finally, questions remain about the durability and stability of the valves and stents in use.

A number of new devices are being designed to overcome these challenges.  Replacement valves being built by companies such as AorTx, Direct Flow, and Sadra are designed to be repositionable and retrievable.  Mechanical valves are also being explored.  Four thousand trans-catheter aortic valve replacements have already been performed, and clinical trials in the United States are ongoing.

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