Medtronic Inc., the world's biggest maker of devices that help maintain a normal heartbeat, failed to correct manufacturing problems and investigate complaints about its LifePak 12 external defibrillators, regulators said.

The Food and Drug Administration in a June 9 letter cited damaged cable connectors and failures to follow through with preventive action. The agency posted on its Web site its letter to the Minneapolis company yesterday, after inspections of Medtronic's Redmond, Wash., plant.

Medtronic's LifePak 12 external defibrillators, used in hospitals to shock the heart back to a normal rhythm, are similar to the LifePak 500 devices the company recalled in February. Medtronic's cardiac rhythm management business, which also includes pacemakers and implantable defibrillators, accounted for 46 percent of its $2.78 billion in sales in its latest quarter.

"We have been working with the FDA for several months on these issues and believe we are close to getting this resolved," Medtronic spokesman Rob Clark said. The company will meet with agency officials this week to present an update, he said.

About 60,000 LifePak 12 external defibrillators are in use worldwide, Clark said.

In the warning letter, the FDA said Medtronic also did not investigate some complaints about defibrillator malfunctions, including one involving a patient's death. Problems were linked to broken or bent pins in the cable connectors, possibly because the company did not have adequate inspection procedures, the agency said. Failure to correct the problems may result in legal and civil penalties, the FDA said.