Electrophysiologic evaluation of syncope in patients with bifascicular block.

Thirteen patients with syncope and bifascicular block were evaluated by electrophysiologic study (EPS) including programmed stimulation. The mean age was 62 years. Six patients had coronary artery disease, three had cardiomyopathy, and four showed no evidence of organic heart disease. Holter monitoring and neurologic evaluation were nondiagnostic in all patients prior to EPS. EPS demonstrated inducible ventricular tachycardia (VT) in four patients, an HV interval greater than or equal to 70 msec in four, intra- and infra-His block with atrial pacing in one, and was nondiagnostic in four patients. Four of six patients with an HV interval greater than or equal to 70 msec or pacing-induced infranodal block were treated with permanent pacemakers, four of four patients with VT received antiarrhythmic therapy, and three of four patients with nondiagnostic studies received no therapy (one patient received a permanent pacemaker). During a mean follow-up period of 19 months (range 3 to 60 months) all but three patients have been free of syncope. One patient with VT did not take prescribed antiarrhythmic therapy, another patient with VT died suddenly; the remaining patient had a normal study and basilar migraines were subsequently diagnosed. We conclude that: (1) ventricular tachycardia may be a significant cause of syncope in patients with bifascicular block and was induced by programmed stimulation in approximately one third of patients studied; (2) EPS including programmed stimulation is helpful in delineating both the etiology of syncope and appropriate treatment in patients with bifascicular block. A negative study may also be of prognostic value.