Health care device maker St. Jude Medical is advising doctors about how to care for patients who were implanted with relatively new Optisure dual-coil defibrillation leads that may stop working because of damage during manufacturing.

Though the number of devices impacted by the problem is relatively small — 447 worldwide — malfunctioning defibrillation leads is a sensitive topic following widely publicized problems with other leads in the past.

An implantable defibrillator monitors a patient's heart beat and can deliver an electric jolt to revive a heart that stops beating. The device uses thin insulated wires called leads to deliver the energy from its batteries to the heart tissue.

On Friday, the U.S. Food and Drug Administration announced that a letter to doctors sent by St. Jude Medical in November disclosing the potential problem with the Optisure leads has been classified as a Class 1 recall — meaning that using one of the affected devices could lead to serious health consequences.

St. Jude said in a news release that it had received no reports that the manufacturing problem led to any malfunctions or injuries.

The company said about 278 of the 447 affected Optisure leads are in the U.S. A company spokesman couldn't comment on how many Optisure leads have been sold since the FDA approved them for sale in February 2014.

The medical device advisory sent to doctors on Nov. 4, archived on a German device regulator website, says a manufacturing process to trim excess medical adhesive may have damaged the protective coating on the leads.

"There is the potential for lead damage to result in loss of defibrillation therapy during attempted shock delivery," the advisory says. It notes that a software feature in the defibrillator called Dynamic TX may prevent the problem, but only if the feature is turned on.

For patients with one of the 447 affected Optisure dual-coil leads, the advisory counseled doctors to double-check whether Dynamic TX is turned on.

Patients with St. Jude Medical Optisure leads connected to a defibrillator made by a different company without the Dynamic TX technology should do a maximum-energy test. If the lead shorts out, it may need to replaced, the advisory says.

A news release from the company Friday said the issue stemmed from a "variation" in the manufacturing process that has been resolved. It noted that St. Jude is working on an updated advisory notice to doctors about the impacted leads.

A company spokesman said Friday that the issue is not related to the 377 adverse event reports regarding Optisure leads that have been filed in the FDA's Manufacturer And User Facility Device Experience (MAUDE) database since July 2014.

Two cardiologists familiar with St. Jude's past problems with leads told the Star Tribune that the issue identified in Friday's FDA recall advisory appeared unrelated to the adverse events reported in MAUDE.

"I think this is a limited manufacturing process control issue and not indicative of a broader problem," Minneapolis Heart Institute cardiologist Dr. Robert Hauser said in an e-mail.

Dr. Edward Schloss, a cardiologist in Cincinnati who has studied past St. Jude defibrillation lead failures, noted that the widely used defibrillation leads from other device companies have similar numbers of adverse events reported to MAUDE.

"St. Jude has said for a number of years that they are really compulsive about their MAUDE reporting … And, 'Don't be deceived, we've got a lot of MAUDE reports but it's just because our field personnel report everything,' " Schloss said by phone. "What they are supposed to do is pretty much just send in a report for just about anything."

In 2011, St. Jude Medical recalled 227,000 Riata or Riata ST model defibrillation leads because of premature erosion of wire insulation. The company agreed to pay up to $14.25 million to settle about 950 Riata patient lawsuits last year.

Joe Carlson • 612-673-4779