NEW YORK (AP) -Elite runner Ryan Shay died of an irregular heartbeat due to an enlarged heart after collapsing during the U.S. men's marathon Olympic trials, the New York City medical examiner said.

Shay's heart also had old scarring, but its cause could not be determined, according to Ellen Borakove, a spokeswoman for the medical examiner.

The 28-year-old Shay collapsed in Central Park on Nov. 3, about 5 1/2 miles into the race, and was pronounced dead at a hospital.

His father, Joe Shay, said previously that Ryan was diagnosed with an enlarged heart at age 14. But doctors had repeatedly cleared him for competition, because having a larger than normal heart is not unusual among elite athletes. Training hard in aerobic sports, such as cycling, running or swimming, tends to result in a bigger heart that pumps more blood throughout the body.