UPRIGHT POSTURES AND ISOPROTERENOL INFUSION FOR PROVOCATION OF NEUROCARDIOGENIC SYNCOPE - A COMPARISON OF STANDING AND HEAD-UP TILTING

Head-up tilt testing has proved to be useful in provocation of neuroca rdiogenic syncope. The purpose of this study was to examine whether si mply assuming an upright posture by standing can be an alternative to the head-up tilt testing for diagnosis of neurocardiogenic syncope. Ei ghty-four patients with recurrent unexplained syncope and 22 normal vo lunteers were recruited into the study. Forty-seven patients with sync ope and all normal volunteers received the standing test. Thirty-seven of the patients with syncope received head-up tilt testing (90 degree s). All subjects lay down for 5 minutes and then assumed an upright po sture until syncope or presyncope occurred or until a maximum of 10 mi nutes was reached in each stage of the test. The tests included four s tages: baseline and infusion of 1, 2, or 3 mu g/min isoproterenol in e ach of the successive stages. Five subjects could not tolerate the pro cedure, and further testing was terminated. overall, the standing test was positive in 83% of the patients with syncope, and its specificity was 74%. The head-up tilt testing was positive in 75% of the patients with syncope. The duration of assuming an upright posture before occu rrence of syncope or presyncope was significantly longer in the syncop e-tilting group in the third stage (p < 0.01) and the fourth stage (p < 0.05) compared with the syncope-standing group. However, the curves of the time course for cumulative positive rates were not significantl y different (p = 0.0739) in the two groups. The standing test can serv e as an alternative to head-up tilt testing and can be applied to pati ents with recurrent unexplained syncope for confirmation of the diagno sis.