Medtronic Inc., the world's biggest maker of heart-rhythm devices, was sued by closely held Medgraph Inc., which claims its patent is violated by Medtronic's CareLink monitoring system.

The CareLink system and associated equipment for blood glucose monitoring, which allow doctors to track patients over the Internet, incorporates Medgraph's technology, the company said in the lawsuit filed Dec. 2 in federal court in Rochester, N.Y.

Medgraph, based in Rochester, N.Y., is seeking an order stopping the infringement and is asking for unspecified damages.

A representative for Fridley-based Medtronic didn't immediately return a call seeking comment.

Medgraph provides technology to manufacturers of home-based health monitoring devices.

Medtronic fell 32 cents to $42.47 at 12:01 p.m. in New York Stock Exchange composite trading.