WORSENING OF VASOVAGAL SYNCOPE AFTER BETA-BLOCKER THERAPY

Head-up tilt test was done in a 27-year-old man with recurrent syncope of unexplained cause. Severe sinus bradycardia and hypotension accomp anied by lightheadedness, cold sweating, and nausea occurred at 80 deg rees head-up position during 4 mu g/min isoproterenol infusion. Oral p ropranolol, 160 mg/d, in four divided doses, effectively prevented the above-mentioned abnormal vasovagal reflexes; diltiazem was only parti ally effective while disopyramide, aminophylline, or atropine was inef fective in preventing the abnormal vasovagal reflexes induced by head- up tilt with isoproterenol infusion. However, the patient experienced ten episodes of syncope in 2 weeks after he was discharged from the ho spital on a regimen of atenolol, 50 mg/d. His symptoms ameliorated imm ediately after discontinuation of atenolol therapy and he became free of severe symptoms while receiving fludrocortisone. Thus, we have docu mented a patient with worsening of vasovagal syncope after beta-blocke r therapy.