At four U.S. medical centers, surgeons, nurses and anesthesiologists are quietly scrubbing in for the return of one of the most vilified medical devices ever conceived-the artificial heart. Each of the four teams was tapped a year ago by Abiomed, a little-known Danvers, Mass., company whose engineers have worked for more than a decade to build a 900-gram electromechanical pump they call the PulsaCor. Surgeons at the Texas Heart Institute and Massachusetts General Hospital, among others, are now practicing putting the synthetic heart into calves. David Lederman, Abiomed's CEO, says they'll be performing the surgery on a human before 2000 is out.

That first patient will, in all likelihood, already be dead. Lederman confides that Abiomed, moving cautiously, will seek permission to undertake a surgical dry run on a brain-dead individual on total life support. Before the doctors and nurses don their gloves, Abiomed's recently convened board of ethical advisors will have spent months overseeing the selection of candidates. What's more, Lederman has devised a complicated credit-sharing scheme to ensure that no single player steals the limelight of what he believes will be a "very visible" event. Even the decision to grant TR access to Abiomed's engineers and facilities was a carefully considered media "test case."