When a valve wears out
Former First Lady Barbara Bush and actor-comedian Robin Williams this month joined the thousands of Americans who have come to need an artificial valve implanted to regulate the blood flow out of the heart to supply the rest of the body.
Bush, 83, had aortic valve replacement surgery March 4 after experiencing shortness of breath and being diagnosed with a hardened valve. Williams, 57, announced March 5 that he would postpone his 80-city “Weapons of Self-Destruction” tour for the same surgery after having similar symptoms and a faulty-heart valve diagnosis.
Aortic valve replacement, already a common cardiac procedure, is likely to become more frequent as the population ages. More than 140,000 Americans had heart valve procedures such as replacements in 2008, according to the Millennium Research Group, a Toronto-based company that collects data on healthcare products.
The aortic valve, a delicate gate that lets blood out but not back in, tends to wear out with age and can develop leaks or become too tight for the necessary volume of blood to pass through.
The valve can also cause problems in younger people born with an imperfect structure. A worn-out valve forces the heart to work harder and can ultimately cause heart failure.
A new valve -- made of metal and plastic or animal tissue -- can help keep the heart in shape, but some patients are too frail to have open-heart surgery. For those, new technology that doesn’t require a surgeon to open up the chest can be a lifesaver.
“The aortic valve is the gatekeeper,” says Dr. Eugene Grossi, a cardiac surgeon at the New York University School of Medicine. This 1-inch doorway has three inward-facing petals; they are “gossamery,” like chiffon, Grossi says.
The valve acts as a one-way swinging door: Blood leaving the heart pushes the petals apart, but when they swing shut again, they prevent blood from washing back in.
There are three other valves that regulate flow in the heart, but the aortic valve, at the base of the left ventricle, is most likely to fail.
Over time, calcium deposits build up on the valve and can cause it to harden. This can cause a narrowing, or stenosis, of the doorway. Or the petals may become stuck partway open and leak -- what doctors call a regurgitating valve. The blood is pumped out but flows back in again when the muscle relaxes.
Either condition stresses the heart, which struggles to maintain blood pressure. This causes shortness of breath (beyond that caused by strenuous exercise), fatigue and chest pain. A person with a damaged valve may also experience fainting spells and swollen ankles or feet. These symptoms, which may also indicate other kinds of heart or lung problems, require prompt medical attention.
Should a faulty aortic valve be the problem, “if you don’t have it treated, there’s a 50% chance you won’t live half a year,” Grossi says.
Valve problems are not limited to the elderly. Some people are born with only two petals, instead of three. This congenital defect affects 13.7 in 1,000 people, according to the American Heart Assn. Children with a two-flap (known technically as a bicuspid) valve may be perfectly healthy but will require treatment as adults if the channel narrows. Women with bicuspid aortic valves should seek medical advice before becoming pregnant, if possible, because pregnancy will require added effort from the heart.
In addition, some infections, such as rheumatic fever, can damage valves.
Diagnosis is fairly straightforward. A doctor can hear a heart murmur with a stethoscope and confirm the problem with an echocardiogram, which uses sound waves to create an image of the heart. There is no medicine that can protect or mend a damaged valve, so surgery is a common treatment.
“It’s a mechanical disease and it needs a mechanical solution,” says Dr. Raj Makkar, a cardiologist at Cedars-Sinai Medical Center in Los Angeles.
Doctors can occasionally repair a leaky valve, but replacements are more common. Surgeons have been swapping out heart valves since 1960, although the technology has improved since then. The standard technique is to spread apart the breastbone and hook the patient to a heart-lung machine while excising the old valve and inserting the new. Nowadays, some surgeons can do the same thing with smaller incisions, improving patient comfort and recovery time.
There are two basic choices for a new valve: mechanical and biological. Biological valves are crafted from animal tissue or material from human cadavers. They can last for a decade or more, but may calcify and wear out eventually. Mechanical valves, made of metal and plastic, last indefinitely. However, they can cause blood clots, so a person with a mechanical valve has to take blood thinners, which carry their own risks.
Choosing between the two is a very hard decision to make, says Dr. Andrew Hurwitz, a cardiovascular surgeon at Glendale Memorial Hospital. Younger patients often opt for the mechanical valve because a biological one might need to be replaced when they get older and are less able to bounce back from surgery. In elderly patients, the biological valve is likely to last the rest of their lifetime.
Unfortunately, many people in need of a new valve are too elderly or sick to go under the knife. The risk of serious complications or death goes up with age, and patients with valve trouble often have other heart problems as well.
“At the current time, almost half of the patients with aortic stenosis don’t get treated,” Makkar says.
Makkar and Cedars-Sinai are participating in trials of a technique that is less risky for older patients. Edwards Lifesciences in Irvine manufactures a collapsible valve. Surgeons can thread this valve, scrunched down to pencil-width, through the femoral artery in the leg up to the heart. Then they use a balloon to inflate the valve, and the hardened tissue of the old valve holds it tightly in place.
The new valves, first used in 2002, have been approved for use in Europe, and more than 2,000 patients worldwide have received them. The valves are used only in the sickest patients, those who have a greater than 1 in 10 chance of dying within a month of open-heart surgery. They might be available in the U.S. around 2011, says Larry Wood, Edwards vice president for transcatheter valve replacement.
Edwards’ collapsible valves are only appropriate for stenosis, not a leaky valve, because they require the calcified tissue of a stenotic valve to hold them in place. Although Wood ultimately expects the valves to be offered to lower-risk patients, he notes that there are not yet scientific data to justify widespread use.
“Surgery remains the gold standard,” he says. “You’re much better going with surgery that we have 50 years of experience with.”
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