Guidant officials were 'basically playing the statistics' by not disclosing the flaw, said Dr. Douglas P. Zipes, a distinguished professor emeritus at Indiana University School of Medicine.

The FDA wants "to find out all of the elements of this particular situation," agency spokeswoman Kathleen Quinn said. She wouldn't elaborate on the line of questioning, or how long it would take the FDA to investigate.

While Guidant notified the FDA of a flaw in the device, it did not tell doctors until Tuesday. That has prompted some doctors to criticize the Indianapolis medical device maker for withholding information relevant to patient care.

Guidant's one-page "Dear Doctor" advisory, which arrived in doctors' offices Tuesday, reveals that one patient has died and 25 others required replacement implants as a result of the flaw in the Prizm 2 defibrillator.

The flaw is rare but serious. It causes the defibrillator to short-circuit and stop working.

About 37,000 of the devices that might contain the flaw were implanted in heart patients worldwide. Guidant's letter does not call for early replacement of the Prizm 2 models with new units.

Battery-powered defibrillators are used to shock an erratically beating heart back into normal rhythm. The devices typically are replaced about every five years.

Guidant said it sent the advisory partly to respond to an upcoming publication in the medical journal Heart Rhythm that will detail the death of a 21-year-old college student from Minnesota whose defibrillator failed.

The advisory also coincided with an article in The New York Times about the defibrillator problem.

Guidant officials decided that "we need to step in and communicate with our physicians. We realized there was an opportunity for confusion," said Guidant spokeswoman Annette Ruzicka.

Guidant previously did not tell physicians about the flaw because the performance of the Prizm 2 built before 2003 has exceeded expectations, she said.

"The odds of one of them actually containing the flaw is a very, very low number," she said. Prizm 2s built after the flaw was corrected are no more reliable than those with the potential flaw, she said.

Ruzicka said Guidant's reports to the FDA about the 26 incidents and the discovery of the flaw itself are publicly accessible.

Two years ago Guidant was socked with the largest-ever FDA fine against a medical device maker. The agency fined Guidant $92 million for covering up thousands of medical problems related to its aortic graft.

Defibrillator sales totaled $1.8 billion for Guidant last year, or almost half of its total sales. The company's pacemaker and defibrillator division is based in St. Paul, Minn.

Dr. Robert G. Hauser a Minnesota cardiologist who coauthored the upcoming article about the Prizm 2-related death, said he met with Guidant officials this spring and was disappointed they didn't tell doctors earlier about the potential problem with the device.

"I just totally disagreed with it. I'm for full disclosure, and they're for nondisclosure," he said.

Hauser, a senior consulting cardiologist at Abbott Northwestern Hospital in Minneapolis, said while the risk of the device malfunctioning is slight, "It's a serious flaw. It disables the unit entirely."

Dr. Douglas P. Zipes, a distinguished professor emeritus at Indiana University School of Medicine who edits the journal Heart Rhythm, said Guidant officials were "basically playing the statistics" by not disclosing the flaw.

With the death of the student, he said, Guidant's "worst-case scenario" occurred. "A patient who (suffered cardiac arrest and) needed the device . . . happened to have one of the devices that malfunctioned."

At least one of Guidant's competitors notified doctors when its defibrillator was found to have flaws.

Earlier this year, Medtronic took that step at the urging of Zipes, who chairs Medtronic's medical advisory board.

"I think you ought to go public" and let doctors and patients know about defects, the doctor said.

Zipes said he and his IU colleagues were treating 75 patients with the Medtronic defibrillator that had the potential flaw, and they replaced every one of them, despite the small risk of failure.

Medtronic bore the cost of the replacing the devices with new ones, he said. Implantable defibrillators cost $20,000 to $30,000 each.

Guidant is in the latter stages of a pending $25 billion acquisition by Johnson & Johnson.

The New Jersey medical products giant on Tuesday reaffirmed its commitment to buy Guidant. The deal is expected to close in the third quarter, Johnson & Johnson said.

Guidant's stock price slipped 48 cents a share Tuesday, to $73.75.

In a report to investors, Jason Wittes, a stock analyst for Leerink Swann investment firm, said that Guidant's liability to lawsuits in the matter "appears limited to patients in whom there was a malfunction. If the FDA was properly notified of the issue and of the change in manufacturing, regulatory exposure also could be limited."