In brief Something as benign as a vasovagal reflex or as serious as hypertrophic cardiomyopathy can cause cardiovascular syncope. A thorough medical history and physical examination often provide clues to the underlying etiology. Laboratory tests such as a head-up tilt test, an event recorder, or a signal-averaged ECG can provide further diagnostic information. Treatment may include such simple measures as recommending that the patient avoid the sight of blood, or it may mean prescribing drug therapy or correcting a heart defect. Usually, an athlete can resume exercise after a syncopal episode, but sometimes modifications of activities are necessary.