PLEASANTON, Calif. — A medical device company has ordered the recall of certain batches of a small mechanical heart pump, saying five people have died while using the device.

Thoratec Corp. urged patients to have their implants checked after confirming 27 reports of cases in which wear and fatigue to an electrical wire required the devices to be replaced, the company said in a statement Friday.

The reports occurred over five years of clinical experience with 1,972 implants, the company said. In five cases, the device could not be replaced and the patients died.

The recall affects devices with catalog numbers 1355 and 102139, which have been distributed to 153 hospitals and distributors throughout the United States and other countries since the beginning of clinical studies in November 2003.

A Thoratec spokeswoman did not immediately respond to a call seeking additional comment Sunday.

The HeartMate II pump was approved in April as a temporary treatment for patients awaiting heart transplants, but analysts had said the larger market for the product is in "destination therapy," or patients with end-stage heart failure who are too ill for a transplant.