A federal appeals court on Wednesday revived an earlier patent infringement ruling about pacemakers against St. Jude Medical Inc. (STJ), possibly leaving the medical devices company on the hook for significant damages.

The U.S. Federal Circuit Court of Appeals, which handles patent appeals, sent the case back to the district court so a judge can award damages to Guidant Corp. and Cardiac Pacemakers Inc., which filed the suit against St. Jude in 1996. Guidant is now a unit of Boston Scientific Corp. (BSX).

Cardiac alleged in its original lawsuit that St. Jude infringed on its patent for a pacemaker, an electronic device implanted in someone's chest that gives pulses or shocks to the heart to help it beat. A jury in 2001 awarded Cardiac $140 million in royalties for patent infringement but another court overturned the ruling.

-By Jared A. Favole, Dow Jones Newswires; 202-862-9207; jared.favole@dowjones.com