During most heart attacks, a blood clot forms and blocks one of the coronary arteries that feed the heart. This kills part of the heart muscle, turning it into scar tissue, which often leads to shortness of breath, weakness and a reduced ability to exercise.
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Today researchers at the Cedars-Sinai Heart Institute in Los Angeles are using a patient's stem cells to transform scar tissue into living heart muscle. The idea is simple: Harvest stem cells from an unaffected part of the heart, multiply them in the laboratory and inject them into the site of the injury, so they can take root and repair the damage.
Eduardo Marbán, M.D., and his colleagues have tested the procedure on 17 patients, and the results are striking. Heart attack survivors treated with their own stem cells within three months of an attack experienced a 50 percent reduction in scar tissue, on average, and all generated new heart tissue. If studies continue to show impressive results, heart patients will benefit from the procedure within four to five years, Marbán says.
The team is also testing the treatment using donor cells, which have worked well in experimental animals, Marbán reports. If donor cells work in humans, patients wouldn't have to undergo biopsies or wait for cells to replicate to receive treatment. The procedure might even work for patients who are in the throes of a heart attack, by preventing scar tissue from forming in the first place.
Marbán's team hopes to complete a study of 270 patients with donor cells by mid-2014. Depending on the results, donor cell treatment could be widely available in about 10 years.
When a donor heart is ready for transplant, it's typically packed in a picnic cooler with a bag of cold saline solution. Cheap and easy, maybe, but also inefficient, since donor hearts begin to deteriorate the moment they're removed from a person's chest.
Bruce Rosengard, M.D., vice president of The Medicines Co. in Parsippany, New Jersey, pushed to make the beating-heart transplant a reality. Here's how it works: A miniature heart-lung machine circulates donor blood through the heart until moments before it's stitched into a recipient's chest. Rosengard's team at Cambridge University's Cardiothoracic Specialty Hospital in England was the first to perform successful transplants using this method in 2006.
Recovery time is promising, too. In a European study, 19 of 20 patients who received beating-heart transplants were out of the intensive care unit in less than 24 hours; the 20th patient was out in under 48 hours. Standard transplants, by comparison, require two to three days in the ICU. To date, more than 140 patients worldwide have received this type of transplant (100 in Europe and 40 in the United States). If clinical trials continue to show impressive results, the technology could be approved by the Food and Drug Administration (FDA) and widely available by 2014.
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