One member of St. Jude’s lead safety panel, Dr. Bruce Wilkoff of the Cleveland Clinic, said in an e-mail that he did not “have specific recollections of how many patient scenarios” had been presented but added that he was aware of the conditions that could result in a patient’s death. Four other specialists on that board either did not respond to repeated requests for comment or declined to comment on the number of patient deaths St. Jude officials had presented to the panel.

In a telephone interview last week, the company’s chief medical officer, Dr. Mark D. Carlson, said that some patient deaths were inevitable because defibrillators occasionally fail; he added that the types of insulation problems with the Riata were common.

However, other heart device specialists said they were disturbed by St. Jude’s explanations, adding that the number of Riata-related deaths appeared unusually high compared with other leads and pointed to a troubling pattern.

“I would hope that anybody looking at that data would say, hey, something is not right here,” said Dr. Edward J. Schloss of Cincinnati, “I think if you saw 20 high-voltage fatalities with a pretty clear pattern of insulation abrasion, that should get your attention.”

It was not supposed to be this way. The safeguards that the major defibrillator makers — Medtronic, St. Jude and Boston Scientific, which acquired Guidant’s heart unit in 2006 — adopted in recent years were supposed to arm doctors with facts rather than opinions.

St. Jude is not the first producer to have encountered product problems since then. In 2007, Medtronic recalled a widely used lead called the Sprint Fidelis after reports emerged that it was cracking and failing in patients.