HEAD-UPRIGHT TILT-TABLE TESTING IN EVALUATION AND MANAGEMENT OF THE MALIGNANT VASOVAGAL SYNDROME

Vasovagally mediated cardiac asystole has been proposed as a potential cause of sudden cardiac death. To assess this possibility and identif y characteristics that define patients with vasovagally mediated asyst ole, head-upright tilt-table testing was performed in 50 consecutive p atients (26 women and 24 men, mean age 42 +/- 10 years) with recurrent unexplained syncope. The upright tilt-table test was performed in the fasting state for 30 minutes, with or without the use of intravenous isoproterenol (1 to 3-mu-g/min). The production of ventricular asystol e lasting > 4 seconds was considered a positive result. All patients w ith tilt-induced asystole received therapy with either beta blockers, disopyramide, transdermal scopolamine or atrioventricular permanent pa cing, the efficacy of which was evaluated with serial tilt-table tests . Reproducible tilt-induced asystole occurred in 10 patients (7 men an d 3 women, mean age 23 +/- 12 years) (7 patients during baseline tilt, and 3 during isoproterenol infusion). Analysis of this group revealed that they had significantly more frequent and severe syncopal episode s (3 patients had episodes needing bystander cardiopulmonary resuscita tion) than did those patients with tilt-induced syncope without asysto le. All patients who had tilt-induced asystole eventually became tilt- table negative with therapy (4 with beta blockers, 2 with disopyramide , and 4 with atrioventricular permanent pacing), and over a mean follo w-up of 21 +/- 6 months no further syncopal episodes occurred. It is c oncluded that patients with recurrent tilt-induced asystole represent a distinct subgroup that has recurrent severe syncope that may mimic o r result in sudden cardiac death. Head-upright tilt-table testing is c linically useful in the diagnosis of this malignant vasovagal syndrome and in the evaluation of prophylactic therapy.