The Food and Drug Administration classified Abbott Laboratories' recall of certain implantable cardiac devices as class I — the most serious type of recall.

The company initiated the voluntary recall in the U.S. for certain lots of its Ellipse implantable cardioverter defibrillators to prevent the use of faulty devices.

The devices are implanted under the skin in the upper chest area with connecting insulated wires called "leads" that go into the heart. These devices are used to correct abnormal heart rhythms by providing pacing for slow heart rhythms and electrical shock or pacing to stop dangerously fast heart rhythms.

The recall was initiated in June after Abbott identified and determined that electrical failures in some devices were due to a faulty manufacturing process causing some aluminum wires to be partially exposed. The devices with exposed wires are prone to electrical shorting of the capacitor and may not be able to deliver high voltage therapy to patients, the company warned.

The recall covers 108 of Ellipse defibrillators that were manufactured between April 5 and May 29. Of all the recalled devices, 31 have been implanted.

Abbott noted that the affected devices have already been replaced, or are scheduled to be replaced with another device.

The Abbott Park, Ill.-based company said there is no way to determine which of the implanted devices have this issue prior to failure but added that it has not received any reports of the failure occurring in any affected devices.