A hunt is on for Shiley Inc.'s employee No. 2832 - also known as "the Phantom Welder" of possibly defective heart valves.

His identity evades his employers, worries federal regulators and haunts more than 300 people whose chests contain the heart valves he worked on.The worker in Shiley's Irvine, Calif., plant welded some 550 valves between February 1981 and May 1982, according to Shiley work records.

The U.S. Food and Drug Administration says these valves appear to fail at twice the rate of devices welded at about the same time by other Shiley workers.

Twenty-one of the devices welded by No. 2832 already have failed inside a patient's chest, according to Shiley.

And lawyers suing Shiley over the valves' workmanship say the company has acknowledged 17 deaths among these failures.

Shiley estimates that only 350 people still wear one of the 550 valves, including 130 in the United States and 220 overseas.

It says the group of valves is safe and merits no special attention from regulators. But the company admits it cannot identify the mystery worker who welded them.

Shiley, a subsidiary of Pfizer Inc., says there once was an employee No. 2832, but this worker left prior to 1981 - before the valves in question were produced.