Last week, the Indianapolis-based company told doctors that the defibrillator had failed in a small number of cases because of an electrical flaw. It also said that it had fixed the flaw in devices made after mid-2002.

But data provided by Guidant to a Minnesota hospital suggests that from May to September 2002, nine patients at Abbott Northwestern Hospital received implants of defibrillators that were made before April 2002, the Times said.

Changed Its Manufacturing Process

The company first changed its manufacturing process to eliminate the risk of short-circuiting in April 2002. A senior company official has said that Guidant has not received reports of such failures in Ventak Prizm 2 DR Model 1861 units made after April 2002.

The defibrillator is implanted under the skin in the chest to shock a chaotically beating heart back into normal rhythm.

In response to questions from the Times, Guidant said late Wednesday that it had continued to sell units out of inventory made before the fixes because it believed that the devices were reliable.

Sold Product Manufactured Before the Improvements

"After making these improvements, Guidant sold product manufactured before the improvements because the reliability data showed that the original Prizm 2 DR, like the enhanced version, was a highly reliable life-saving product," Guidant said in a statement. "Current data continues to support the reliability of this product."

The Food and Drug Administration said in a statement Wednesday that "We are now in the process of reviewing information from our meeting with Guidant to determine whether further regulatory action may be warranted," The Wall Street Journal reported Thursday.