Help for the heart

Woburn, MA -In 1970, mechanical engineer Victor Poirier began work on an implant to help a damaged heart pump blood. Thirty years later, his invention-HeartMate-has received FDA approval and enabled 2,100 people worldwide to live longer lives.

But for Poirier, now president and chief technical officer of Thermo Cardiosystems, the struggle to gain widespread acceptance for his HeartMate continues. "It's like a child that has reached adolescence," says Poirier. "It still needs a lot of guidance."

While Poirier in the early years had to tackle such issues as designing textured surfaces on the implant to prevent deadly clotting, he now worries more about getting cardiologists to view HeartMate as a valid, proven therapy.

"It's time for our company to take the next step in mass marketing and distribution, but we don't have the size sales force that we need," says Poirier. Thermo Electron, the parent company, wants to sell Thermo Cardiosystems to a firm with a strong presence in the cardiovascular market.

Besides getting more marketing muscle, Thermo Cardiosystems has successfully petitioned the National Institutes of Health to fund a study evaluating the effectiveness of HeartMate versus traditional drug therapy in providing long-term cardiac support for older patients with end-stage heart disease. The study, conducted independently by NIH and New York's Columbia-Presbyterian Medical Center, could provide valuable data showing that HeartMate, rather than being only a temporary solution until a donor heart is available, can be considered as a permanent therapy.

"We've had patients who have been on the device for as long as two years while they await transplants," says Poirier. "But we still need more independent data to convince cardiologists, who tend to be conservative."

Meanwhile, Thermo Cardiosystems engineers continue to work on improvements to HeartMate:

HeartMate II, weighing a third as much as the electric HeartMate I, features a miniature-rotary pump with axial-ceramic bearings. Its small size makes it suit- able for children, who could not receive the earlier device. The new model, scheduled for clinical trials in humans this year in Israel, uses a proprietary transcutaneous energy- transmission system, tubes and wires that extend from the body.

Heartmate III, now in animal trials, pioneers a miniature-centrifugal pump and a magnetically-levitated impeller, developed in collaboration with Sulzer Electronics in Switzerland. Because its moving components do not contact each other, the device could last for many years. (See article in this issue, p. 98)

The design challenges in these new devices are daunting. For example, moving to a rotary-blood pump in HeartMate II raised concerns about destroying blood cells, particularly with the rotor spinning at 10,000 rpm. Engineers relied on computational fluid dynamics soft- ware to design rotor vanes to precise shapes that would prevent pressure drops and resulting blood-cell damage.

Even when such tough design challenges are met, the medical engineer's job is not complete. Despite strong demand for new health care technologies as society ages, Poirier notes that biomedical engineering faces plenty of obstacles, ranging from tough FDA scrutiny to litigation. "If a patient dies in the years following a heart transplant, people accept it as an act of God," he observes. "But put a mechanical device inside the body, and it is a different story. There's a far greater risk of lawsuits."