LITTLE ROCK, Ark. -- The Wisconsin man who collapsed and died last month after finishing the Little Rock Marathon had a heart condition that would have been undetected in a routine physical exam and was not by itself fatal.

Dr. Stephen J. Erickson, a pathologist with the state crime laboratory, said Monday that Adam Nickel had narrow heart arteries that tended to restrict the flow of blood that caused his death when combined when combined with the electrolyte abnormalities that can result from running long distances.

Nickel, 27, a graduate student at the University of Wisconsin in Madison, collapsed after finishing the 26.2-mile race in 3:02:26 on March 2. He was an experienced long-distance runner and had no known medical problems.

"This was like a lightning bolt out of the blue, very bad luck that he had this unseen silent abnormality in his heart muscle," said Erickson, one of two doctors who conducted the autopsy. "This is a very, very rare kind of event."

Dr. Charles Kokes, chief medical examiner, said if Nickel hadn't been a runner, the heart condition, known as multifocal small coronary artery fibromuscular dysplasia, might not have caused problems for him for some time. Instead, Nickel went from an irregular heartbeat to death without experiencing symptoms that would have caused him to faint, slow down or stop.