Medtronic Inc. on Friday said it was voluntarily recalling around 1,900 automated external heart defibrillators used by paramedics and firemen.

The defibrillators being recalled were manufactured in 1997 and display a “connect electrodes” message and may not analyze a patient’s heart rhythm even when the electrodes are properly connected, the company said.

The devices are used to shock a dangerous heartbeat back into normal rhythm.

Medtronic said it had received 54 incident reports with this specific group of LIFEPAK 500 defibrillators, including eight instances where it may have prevented patient resuscitation.

An analysis found that the defect could “theoretically” effect up to 8 percent of patients, according to Medtronic spokesman Rich Fischer.

“This anomaly was noted only with this particular model… the recall has no effect on defibrillators from other years,” he said.

The company said the recall represents about 1 percent of LIFEPAK 500 external heart defibrillators currently in use worldwide.

The defibrillators have a lifespan of about 8 years, but can be upgraded, Fischer said.

Earlier this month, Medtronic said it had warned doctors about some faulty batteries installed in a line of its implantable heart defibrillators.

The problem involves batteries in its Marquis line of implantable cardioverter defibrillators made before December 2003.