On Sunday when Medtronic warned physicians to stop using a potentially faulty wire attached to its heart defibrillators, the company also advised patients to consult their doctors. On Monday, anxious patients were doing just that, causing some doctors' offices to be flooded with calls as people tried to determine whether they might have the defective models.
The risk of a defective wire is low. Medtronic said that about 2.3 percent of the estimated 235,000 patients with the defective wire, or 4,000 to 5,000 people, would experience a lead fracture within 30 months of implantation. But learning through tests that one's defibrillator has a faulty lead can create agonizing decisions for patients and doctors.
One decision is whether to remove the wire, a procedure that carries some risks, or leave it in place alongside a replacement.
Removal carries significant risk of damage to the heart and veins through which the wire wends from the defibrillator, a generator implanted under the skin near the collarbone.
When working properly, defibrillators deliver a potentially life-saving shock if the heart beats rapidly and purposelessly in a rhythm known as ventricular fibrillation. A surge from the device can restore a life-supporting heart rhythm.
If the Medtronic lead, called the Sprint Fidelis, were faulty, it could simply signal the patient to check with a doctor about a possible malfunction. Or it could deliver a painful, body-rocking shock when such a jolt is not needed. Or the device could fail to deliver a life-saving shock when it is needed.
The malfunction does not involve conventional pacemakers without defibrillators, Medtronic said.
Dr. David R. Broudy, a cardiologist and electrophysiologist who implants defibrillators in Seattle, said Monday that he was in the habit of telling all patients about potential complications when he implants defibrillators. He said there was a 2 to 3 percent chance of complications, including serious infections and malfunctions in leads and other parts.
He says he has 92 defibrillator patients who have a Sprint Fidelis lead, although on Monday he received calls from only three of them. Like other doctors, he said he would send letters alerting patients who do not call.
Medtronic also said that it would send letters to all Sprint Fidelis patients.
Defibrillator patients generally carry cards that contain the lead's identifying numbers, which in the Medtronic recall are 6930, 6931, 6948 and 6949. Each patient is being asked to come in for computerized testing that could detect abnormalities in resistance and other electrical functions that could signal an impending fracture in the lead.
In Seattle, Dr. Broudy said that in trying to assess what to do for each of his patients with the potentially defective lead, he would check factors like the number of times the device had appropriately delivered shocks and the degree of a patient's anxiety.
"There are different needs for different patients," he said. Those who have had frequent abnormal heart rhythms, he said, may be more dependent on the device than others. Even patients in whom no evidence of possible cracks in the leads is found will need to have their Medtronic defibrillators reprogrammed.
The quandary will be for those found to have a fractured lead.
Doctors can insert a new lead into the vein if there is room for it, attach it to the heart, and then put a cap on the old one.
The risks of surgically removing the lead depend in part on how long it has been in place. Scar tissue forms around the lead after it is implanted. Removal can produce bleeding from torn veins and damage heart muscle. The risk of such complications ranges from 1.4 percent to 7.3 percent.
Dr. John Kassotis, director of cardiac electrophysiology at the State University of New York Downstate Medical Center in Brooklyn, said, "You can definitely take the leads out if they have been in less than six months and usually if it is less than two years."
Patients who do need surgical removal of the lead should go to doctors and medical centers that have extensive experience in performing such procedures, experts interviewed Monday said.