Vasovagal Fainting: A Diphasic Response

VASOVAGAL fainting, also called vaso-depressor fainting, is a common and dra-matic reaction frequently occurring as a re-sponse to an emotionally disturbing event. The pathophysiology of the faint itself has been recently reviewed by Edholm7 and by Sharpey-Schafer.19 The cardinal manifesta-tions 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 Greenfield11 and Engel-Romano8" 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 ex-pected 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