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 accompanied by light-headedness, cold sweating, and nausea occurred at 80 degrees head-up position during 4 micrograms/min isoproterenol infusion. Oral propranolol, 160 mg/d, in four divided doses, effectively prevented the above-mentioned abnormal vasovagal reflexes; diltiazem was only partially effective while disopyramide, aminophylline, or atropine was ineffective 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 hospital on a regimen of atenolol, 50 mg/d. His symptoms ameliorated immediately after discontinuation of atenolol therapy and he became free of severe symptoms while receiving fludrocortisone. Thus, we have documented a patient with worsening of vasovagal syncope after beta-blocker therapy.