Artificial valve is positioned using a thin catheter and a balloon
One of the causes of heart failure is aortic stenosisan abnormal narrowing of the valve between the heart's main pumping chamber and the aorta, the major artery supplying blood to your body.
In the past, some people with this serious condition had to go untreated because they were too sick for the standard surgery. But now there's a new option: an implantable valve that doesn't require open-heart surgery.
The most common cause of aortic stenosis in older patients is a buildup of calcium deposits in the valve, akin to the accumulation of arterial plaque in atherosclerosis. That narrowing in the aortic valve means the heart has to work harder to pump enough blood, which eventually weakens the heart muscle and leads to symptoms of heart failure: fatigue and shortness of breath. Chest pain, angina and fainting are also symptoms of aortic stenosis.
Once symptoms develop, people with aortic stenosis need to have the faulty valve replaced or the disease will progress, which may cause worse symptoms and even threaten survival. Valve replacement is aimed at preventing serious complications like heart failure and potentially fatal heart-rhythm disturbances. But open-heart surgery is too risky for some patients, particularly those who are 80 or older and have other chronic health problems like kidney disease or emphysema.
In late 2011, the Food and Drug Administration approved the first artificial aortic valve that can be implanted via minimally invasive surgery. Instead of open-heart surgery, doctors can perform a transcatheter valve implanta procedure in which the new valve is threaded to the patient's heart through a catheter, a flexible tube that's a little wider than a pencil.
Meeting the Criteria
About 300,000 Americans have aortic stenosis. No medication can treat the narrowed aortic valve itself. Some patients can undergo an angioplasty-like procedure called valvuloplasty, where a balloon-tipped catheter is threaded into the aortic valve. Expanding the balloon can widen the diseased valve and help improve blood flow for a time, but any benefit is short-lived.
The new device, called the SAPIEN transcatheter heart valve, was approved specifically for patients too sick to undergo open-heart surgery but well enough to expect that the new heart valve will improve their lives. A list of specific criteria to meet includes:
- The valve narrowing must be caused by calcium deposits. Other, less common causes include damage from rheumatic fever and infection of the lining of the heart and valves, called infective endocarditis.
- The patient's natural aortic valve opening has to fit a certain size range; otherwise it can be too big or too small for the replacement to work.
- The patient must be able to tolerate anti-clotting medication such as clopidogrel (Plavix) afterward.
The transcatheter procedure is performed under general anesthesia. The surgeon makes an incision in the femoral artery in the thigh (or sometimes an artery in the chest), and then threads the very thin catheter through arteries to the heart. That's done with the guidance of fluoroscopy, a type of x-ray imaging that allows the surgeon to view the process in real time on a video screen.
The artificial valve is compressed on a balloon thin enough to be snaked through the catheter to the aortic valve. Once there, the balloon is inflated to expand the new valve within the damaged one. The natural aortic valve has a set of leaflets that open and close to regulate blood flow; those leaflets are used to anchor the artificial valve in place.
The implant itself consists of tissue from a cow's heart that's attached to a stainless steel mesh frame. The procedure takes about one to three hours, and patients generally spend a few days to a week in the hospital. Afterward, doctors will prescribe a recovery plan, which may include dietary changes and possibly an exercise program.