Quick on-the-field emergency care is widely credited with helping save Damar Hamlin’s life, but it’s unclear if his cardiac arrest could have been prevented with screening. Doctors have said they’re still evaluating what caused Hamlin’s heart to stop after a tackle during Monday night’s Bills-Bengals game. One possibility is a fluke type of chest trauma that is impossible to predict or prevent. Existing heart conditions are the most common cause of sudden cardiac arrest in young athletes. Cardiac testing including EKGs and echocardiograms can sometimes detect them. But these tests can’t detect all heart conditions. And they sometimes miss ones that can be deadly.