Jenny Simpson, a decorated American middle-distance runner and former 1500m world champion, has officially stepped away from competitive running. The announcement follows a life-threatening medical emergency that occurred in June while Simpson was participating in a track event in North Carolina. According to Simpson, she was serving as a pacer for a mile group when she suffered a cardiac arrest.

Emergency responders performed CPR on-site before transporting her to a hospital, where she was placed on life support to address complications involving her heart and lungs. In a statement shared via Instagram, Simpson revealed that medical professionals diagnosed her with arrhythmogenic right ventricular cardiomyopathy (ARVC), a rare heart condition that affects the heart muscle and can cause dangerous arrhythmias.

Simpson, 39, is widely considered one of the most accomplished female runners in U.S. history, having competed in three Olympic Games and secured multiple world championship medals. Her decision to retire marks the end of a career that spanned nearly two decades at the elite level. While the recovery process has been significant, Simpson’s public disclosure highlights the sudden nature of the condition and the necessity of immediate intervention during her collapse. She has not provided further details regarding her long-term health outlook beyond her decision to leave the sport.