The world's first self-contained artificial heart patient suffered a stroke and is back on a ventilator, his surgeons said Wednesday.

Robert Tools, 59, had the stroke Sunday afternoon at Jewish Hospital, said Dr. Laman Gray, one of the surgeons who implanted the plastic-and-titanium AbiorCor heart on July 2.

Dr. Robert Dowling, Tools' other surgeon, characterized the patient's condition as serious.

"His condition is slightly better than someone with a heart because we don't have to worry about the heart," Gray said.

Gray said he believed the stroke was caused by a blood clot. Initially, Tools couldn't move his arms or legs, but he was able to move his legs Tuesday night, Gray said.

Doctors had said early on that strokes were among the risks for the artificial heart patients. The AbioCor was designed with a smooth plastic lining to decrease the chance of blood clots forming.

The doctors don't know how much Tools is going to recover or how long the recovery will take.

Last week, Tools was feeling well enough for an outing with the Louisville mayor to promote dining out. Buoyed by his progress, doctors had said it was possible he could be home for Christmas.

Before receiving the artificial heart, Tools was suffering from congestive heart failure, diabetes and kidney disease. He was given little chance of surviving 30 days without the operation. Four others have received the AbiorCor since Tools.

In Philadelphia, the fifth person to have the surgery is breathing better, though still on a ventilator, and is doing light exercise in his hospital bed, his surgeon said Wednesday.

The man, whose name was not being released, "is fully awake and recognizes family and friends," said Dr. Louis E. Samuels, associate professor at MCP Hahnemann University and director of the transplant team that performed the operation Nov. 5.