In late March, Medtronic Inc. sent a letter to doctors advising them that the wire leads in a line of widely used heart defibrillators could tear at a "higher than expected" rate.

The "Dear Doctor" letter assured physicians that the performance of the Sprint Fidelis line of leads is consistent with similar products, and it offered suggestions about how to best implant it.

Four months later, several physicians in the Twin Cities have stopped using the leads, and Medtronic is investigating a patient's death in which a model of the Sprint Fidelis lead is "in question."

The lead is still being sold and is being implanted in patients.

The lead is a key component in the defibrillator system - a flexible, insulated wire snaked through a vein, connecting the stopwatch-size battery implanted in the chest to the heart.

Most defibrillators use two or three leads, which help the device shock an errantly beating heart back into rhythm.

Leads have not generated as much attention as defibrillator batteries, several of which were recalled in the past two years by Medtronic, Guidant Corp. (now part of Boston Scientific Corp.) and St. Jude Medical Inc., all with Twin Cities ties.

Those high-profile recalls called into question how physicians and patients are informed of device malfunctions by manufacturers, and whether the U.S. Food and Drug Administration (FDA) is diligently tracking device performance.

Guidant was criticized for continuing to sell several defibrillator models after discovering flaws that could cause some to malfunction. Two months after a Grand Rapids, Minn., man died when his defibrillator failed to revive him, the company issued an alert. Until then, doctors and patients had no idea the devices could malfunction.

A thin and nimble lead

Fridley-based Medtronic's March 21 letter to physicians may be the first major case since the recalls in which the performance of a widely used medical device has been probed in the cardiology community.

Since the FDA approved the Sprint Fidelis leads in September 2004, 169,000 have been used in patients in the United States, and many doctors prefer it because it is thin and nimble. The company says the overall fracture rate is "extremely low."

According to Medtronic's own longevity study of 70,000 leads used over 20 years in the United States, the most widely used Fidelis lead (model 6949) has a 99.2 percent survivability rate two years after being implanted. (Most leads need to be replaced every five to 10 years, though some last longer.)

While Medtronic informed the FDA about the lead fracture problem, it does not consider its letter to doctors an official advisory. The FDA has not recalled the device.

Unlike its February 2005 defibrillator recall, Medtronic did not issue a news release, and a product performance report on its website lists no advisories associated with Sprint Fidelis leads. Patients would likely hear of potential problems through their doctors.

Outside panel review

Medtronic said that it consulted with an independent physician quality panel - five doctors paid by the company for their time and expenses - and decided to write a physician letter reviewing how the lead should be implanted.

Meanwhile, the company continues to "monitor and analyze" why some leads tear.