The setting in which the spell occurred, the family history, and the patient's memory of feeling faint may help distinguish the majority of cases. Psychological causes - hysteric faints are unassociated with decreased BP, decreased HR, or pallor. They may occur in the supine position. Fluttering of the eyes behind half-closed eyelids may be noted. Hyperventilation syncope is believed to be the result of cerebral vasoconstriction from self induced hypocapnia.
Frequent symptoms are tachypnea, anxiety, and breathlessness, blurred vision and lightheadedness.
Details of the history are particularly useful to evaluate the cause of syncope. Syncope that occurs with exercise, occurs in an athlete, is recurrent, or that occurs in a patient with a positive family history of syncope, sudden death, or cardiomyopathy should be closely evaluated. Age - gives clues to the most common etiologies Syncope in an infant should always be aggressively investigated. Myocardial tumors, outflow obstructions, myocarditis, cardiomyopathies, long QT syndrome, and seizures are all possible. Syncope in adolescents may be caused by IHSS, mitral valve prolapse, coronary artery abnormalities, pulmonary hypertension, anemia, pregnancy, psychological problems, or drug abuse.