LONG-TERM EFFECTS OF PHARMACOLOGICAL THERAPY FOR VASOVAGAL SYNCOPE ONTHE BASIS OF REPRODUCIBILITY DURING HEAD-UP TILT TESTING

The purpose of this study was to determine the efficacy of long-term p harmacological therapy selected on the basis of a head-up tilt test (H UT) in patients in whom reproducibility of the HUT response was demons trable in the initial study. The HUT (80 degrees upright) was performe d for 15 min with or without an infusion of isoproterenol (0.01-0.03 m u g/kg per min) in 54 patients with recurrent unexplained syncope, Whe n vasovagal syncope was induced (positive response), the HUT was repea ted to examine the test reproducibility. Vasovagal syncope was induced in 24 patients during HUT alone, and in 30 patients during the HUT wi th isoproterenol. Acute reproducibility was observed in 49/54 (91%) pa tients. In the tilt-positive patients, HUT was repeated after an intra venous administration of propranolol (0.1 mg/kg) or disopyramide (1 mg /kg) (acute test). Propranolol proved effective in 21 (80%) of 26 pati ents, and disopyramide in 13 (56%) of 23 patients. Thereafter, evaluat ion was done on the long-term clinical follow-up of the pharmacologica l intervention selected on the basis of the acute test in the 34 patie nts in whom the HUT could not induce vasovagal syncope after the oral administration of the pharmacological agent (propranolol 60 mg/day, di sopyramide 300 mg/day). Thirty-two of 34 patients (94%) did not develo p syncopal attacks during a 44+/-12-month period. Thus, in patients wi th unexplained syncope, HUT appears to have a high degree of acute rep roducibility, and the acute drug response guided by HUT may be used to develop an effective long-term pharmacological therapy.