Minimally Invasive Valve Replacement
Heart valves, like joints, break down over time because of wear and tear. And every year about 50,000 patients undergo complex open-heart surgery to receive new ones. Now doctors at Stanford University have developed a procedure to replace ailing valves without cutting open a patient's chest.
The procedure, called transcatheter aortic valve replacement, or TAVR, uses a catheter to guide the artificial valve to the beating heart through a small incision in the leg or between the ribs. "It's far less traumatic than open-heart surgery, especially for patients who are inoperable or high risk," says Alan C. Yeung, M.D., chief of the division of cardiovascular medicine at Stanford. In fact, surgeons can't perform the procedure if the person's heart is young and healthy. "We rely on defects in the heart — spots that are hardened — to hold the valve in place," he explains. The new valve expands and pushes the old valve aside.
The FDA approved the breakthrough procedure in 2011, after a two-year follow-up study showed it reduced the risk of death by more than 40 percent. A bonus: TAVR takes 30 minutes, and patients are awake and talking within a couple of hours.
A Beatless Heart
Each year up to 40,000 patients would benefit from a heart transplant, yet only about 2,200 donor hearts are available. Artificial hearts are a time-tested alternative (they've been available since 1982), but the primary model, the Jarvik-7, requires the use of an external air compressor, and patients need maintenance surgeries.
A team at the Texas Heart Institute in Houston has introduced a new device, called a beatless heart, that pushes blood through the body at a steady rate, like a Jet Ski propeller. With no valves, flexible components or complex machinery, it acts less like a heart than a pair of turbines, says inventor William Cohn, M.D., director of minimally invasive surgical technology at the institute. "Our heart has only two moving parts floating in magnetic fields, spinning rapidly," he says. "So it doesn't burn out as fast as an artificial heart with multiple parts."
One oddity about the procedure: The beatless heart doesn't make a pulse. And without a pulse, doctors can't monitor heart rate. Nevertheless, Cohn's team has successfully implanted continuous-flow devices in more than 70 animals, primarily calves. He has even tested the procedure on one human patient, a man with multiple-organ failure. The device worked flawlessly for almost six weeks even as the man's liver and lung function continued to deteriorate. Family members finally asked Cohn to turn off the device so the man could die.
Plans are under way to test the device (and procedure) in a half-dozen human patients. If the technology shows promise, Cohn's team hopes to begin clinical trials soon after, though it predicts that FDA approval is several years away.
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