Vasovagal fainting: a diphasic response.

VASOVAGAL fainting, also called vasodepressor fainting, is a common and dramatic reaction frequently occurring as a response to an emotionally disturbing event. The pathophysiology of the faint itself has been recently reviewed by Edholm and by Sharpey-Schafer. The cardinal manifestations are low blood pressure and slow heart rate. The cardiovascular events which precede the faint have received very little attention, however, and their importance has not been recognized. The few published protocols showing prefaint events are concerned with such special maneuvers as postural changes, hypoxia, or significant blood loss. Except for the Greenfield and Engel-Romano" reports, there are apparently no published records of data obtained at short intervals preceding the onset of emotionally induced fainting. Even the physiology of the faint seems not to be as familiar as would be expected from its frequency. Many physicians are unaware that asystole is common and that when it occurs convulsions may also develop. It is also not widely known that cardiac arrhythmias may occur as part of the faint, perhaps because few electrocar-