Researchers have discovered a previously unrecognized electrical signal in the heart that could help predict sudden cardiac death before it strikes.

Sudden cardiac death can strike without warning, killing people who appear healthy and have no known history of heart problems. For decades, doctors have struggled to identify who is most vulnerable, even though a potentially lifesaving treatment already exists. Now, researchers have discovered that clues to these fatal events may have been hiding in one of medicine’s most familiar diagnostic tests.

Scientists at the University of California, Berkeley developed an artificial intelligence system that detects subtle electrical patterns in routine electrocardiograms (EKGs) associated with an increased risk of sudden cardiac death. In a study published in Nature, the AI outperformed a standard clinical screening method, raising the possibility that doctors could identify more at-risk patients before their hearts suddenly stop.