Long-term prognosis of patients undergoing electrophysiologic studies for syncope of unknown origin.

Long-term prognosis was determined in 70 patients with unexplained syncope who underwent electrophysiologic testing between April 1981 and April 1986. The electrophysiologic study had positive results in 37 patients--31 with ventricular tachycardia, 3 with supraventricular tachycardia and 3 with abnormal conduction. There was no significant difference in the 3-year actuarial recurrence rate between the positive and negative outcomes (32 vs 24%, respectively). At 3 years, patients with positive outcomes had higher rates of sudden death than patients with negative results (48 vs 9%, respectively, p less than 0.002). The 3-year total mortality rate was also markedly higher in patients with positive results than among those with negative outcomes (61 vs 15%, respectively, p less than 0.001). Multivariate analyses showed mortality to be independently associated with unsustained ventricular tachycardia on prolonged electrocardiographic monitoring. It was concluded that patients with electrophysiologically positive results had high rates of sudden death and total mortality that have not been previously well recognized.