The human heart operates much like an automobile engine. Cells in the upper chamber, or atrium, of the heart emit an electrical impulse that travels along a track that divides into the right and left lower ventricles. As the impulse descends into the two branches at the same speed, the muscle contracts almost simultaneously. But in some people there is a block in one branch that causes a delay in contraction, forcing the electrical impulse to detour slowly through the heart muscle itself. The heart struggles to send blood out to the body, much like a car constantly stalling due to poorly timed pistons. 
| David Kass, with the pacemaker that's now helping heart-failure patients, too. |
But just as a car engine can be tuned-up, so can an out-of-sync heart-thanks to the pacemaker. Originally used to fix electrical abnormalities in people with irregular heart rhythms, notes cardiologist David Kass, the pacemaker is now successfully resynchronizing weak hearts in heart failure patients, whose previous treatment options were only drugs or surgery. "It doesn't require open-heart surgery. It's not a ventricular assist, it's not a transplant," says Kass. "It's an electrical stimulator that coordinates contraction." In a Circulation study of 22 patients with a potentially fatal form of heart failure known as dilated cardiomyopathy, Hopkins researchers led by Kass found that the therapy improved the heart's ability to contract and pump out blood by an average of 35 percent. Those patients whose hearts have the largest amount of timing discord, and whose hearts are often weakest, were the ones who seemed to benefit most from a pacemaker. "These devices are costly, and must be placed inside the body," Kass says. "So we want to be sure we select patients who will respond." - Gary Logan
Hopkins Medical News, Spring 2003
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