Hundreds of injuries linked to a brand of heart defibrillator wires were reported to the government by last winter, a consumer advocate said Tuesday in asking why the wires weren't recalled until this week. Medtronic Inc. pulled its Sprint Fidelis defibrillation wires off the market Monday, after identifying five patient deaths in which broken wires may have played a role.

These wires, officially called leads, connect patients' hearts to a device that sends an electrical shock if it senses a life-threatening abnormal heart rhythm. A fractured lead can leave the defibrillator unable to send a lifesaving shock, or prompt it to deliver painful unnecessary shocks. The Food and Drug Administration had received 599 reports of malfunctions and injuries associated with the Fidelis leads as of Jan. 10, including 204 where patients had been inappropriately shocked, according to a count by the consumer group Public Citizen.

The FDA began monitoring the Fidelis in February, when a prominent cardiologist _ Dr. Robert Hauser of the Minneapolis Heart Institute _ brought concerns to the agency. Leads are fragile, and the new trend in defibrillator technology is to make them increasingly thin for easier insertion. The Fidelis was a popular thin version. Hauser's hospital quit using it earlier this year. In a published review of leads implanted there and of reports to FDA's injury database through February, Hauser wrote that the thinner model was "significantly less reliable" than Medtronic's own thicker predecessor.