Cardiac arrhythmias in experimental syncope.

The frequency with which a history of one or more syncopal episodes is elicited among aviation cadets in a flying training program was found to depend on the circumstances of the questioning. When anonymity seemed to be assured, 15 out of 50 admitted having had previously undisclosed syncope. Carotid sinus massage and certain breathing maneuvers were used to induce experimental syncope. During these procedures 21 of the 50 had one or more syncopal episodes. Arrhythmias were seen in 15 of the 21 who fainted and in 22 of the 29 who did not faint. Cardiac arrhythmias were not induced in any case by respiratory maneuvers after administration of atropine. The experimental procedures were not able to identify the subjects who had previously experienced syncope. The results argue against the supposition that syncope itself indicates an underlying disease state.