Dozens of U.S. patients may have to undergo surgery to replace their Medtronic heart defibrillators following the discovery of a manufacturing problem that could render the devices unable to provide life-saving electric shocks.

Medtronic has recalled 48 implantable cardioverter defibrillators (ICDs) and cardiac resychronization therapy defibrillators (CRT-Ds). On Monday the U.S. Food and Drug Administration classified the move as a Class 1 recall, the highest-severity category involving potentially life-threating problems.

A company spokeswoman said Medtronic has notified the physicians providing care for the 48 patients whose devices are affected by the recall.

"With the support of the Independent Physician Quality Panel, Medtronic has advised that physicians strongly consider explanting these 48 devices," spokeswoman Tracy McNulty said via email.

An implantable defibrillator is a battery-powered device that monitors heart activity and can automatically give low-voltage or high-voltage electric shocks to correct a heartbeat that is too slow, too fast, or dangerously erratic.

There have been no reported deaths as a result of the issue that led to the recall. One patient did need to be rescued with an external defibrillator after their implanted device failed, McNulty wrote. The company has updated its manufacturing processes to prevent the issue from happening in the future.

Medtronic sells many thousands of defibrillators each year. The 48 individual devices are identified by model and serial number in the FDA recall notice, which is available here.