Postexercise syncope: Evidence for increased activity of the sympathetic nervous system

This report describes an association of postexertional syncope with increased levels of circulating catecholamines. A 36-year old male who experienced postexercise bradycardia and asystole had higher basal plasma norepinephrine (120 versus 68 ± 6 pg/ml) and epinephrine (18 versus less than 10 pg/ml) but a similar vagal tone (vagal tone index of 5.44 versus 5.81 ± 1.00 U) when compared with 6 closely matched subjects who underwent an uneventful stress test.