COMPARISON OF RESPONSES TO ISOPROTERENOL AND EPINEPHRINE DURING HEAD-UP TILT IN SUSPECTED VASODEPRESSOR SYNCOPE

Head-up tilt is known to play an important role in establishing the diagnosis of vasodepressor syncope in patients with syncope of unknown etiology.1-5 Although passive head-up tilt alone may trigger a vasodepressor response, recent studies show that an infusion of isoproterenol significantly increases the sensitivity of head-up tilt in reproducing vasodepressor syncope.1-5 However, isoproterenol is not endogenously produced and the role of endogenous catecholamines, such as epinephrine, in provoking vasodepressor syncope is unknown. Therefore, we compared the responses to isoproterenol and epinephrine during head-up tilt in patients suspected of having vasodepressor syncope. © 1991.