New Artificial Heart Re-Designed

The maker of the world's first self-contained artificial heart said Wednesday it has removed a piece of the device because of fears it may cause clotting. Deposits that can cause clotting were found on a plastic cage in the artificial hearts of two patients who died. As a result, the cage has been removed, said Edward Berger, spokesman for Danvers-based Abiomed.

A majority of recipients of the AbioCor heart have had clots called hematomas removed, Berger said. In addition, one of the patients who died had suffered a devastating stroke, apparently caused by a blood clot, but doctors attributed his death to other causes. Doctors are concerned the plastic cage is touching the tissue and restricting the flow of blood, which could lead to clotting, though there is no definitive evidence the device causes blood clots, said Dr. David Lederman, Abiomed's chief executive. ``There's no way we can definitively make any conclusion,'' Lederman said. ``Since we don't need it, we removed it.''

The plastic cage was created for early devices that were tested on cows. The cage was meant to prevent heart tissue from obstructing blood flow into the replacement heart. But the cage is not needed on humans because surgeons are attaching the cuff in a place where there is no concern about blockage, Berger said.

The change was announced during a news briefing at which Abiomed officials updated the status of clinical trials of the device. ``The overall design is sound,'' Lederman said. ``It works, and it works well.''

The plastic-and-titanium device has been implanted in six patients who were all dying of heart failure and too sick for heart transplants. Three have died, two of organ failure and one of bleeding during surgery. The first recipient of the device, Robert Tools, suffered a stroke four months after receiving it. The hospital said Tools' death in November was unrelated to the stroke. Doctors had said all along that strokes were among the risks for artificial heart patients. The AbioCor was designed with a smooth plastic lining to decrease the chance of blood clots forming.

Researchers also said Wednesday they are working on a version of the replacement heart that would fit smaller adults. The current heart fits only about half of men and 18 percent of women. The new model would be about 70 percent of the size of the original device. Clinical trials on the new heart could begin in 2004, according to Lederman.