Syncope is the temporary loss of consciousness secondary to decreased cerebral blood flow and decreased blood pressure. In a variety of studies, the incidence of vagally mediated (neurocardiogenic) syncope in the teenage years varies from 20% to 50%. Vagally mediated syncope is the result of the normal reflex involving the voluntary and autonomic nervous system controlling heart rate, blood pressure and ultimately cerebral blood flow. Potentially serious causes include primary heart rhythm abnormalities and/or structural abnormalities. An electrocardiogram (ECG) should be normal in vagally mediated syncope. Immediately after a syncopal event, there can be minor T wave changes due to autonomic changes, and these should return to normal within a few hours to days.
