Catheter electrical ablation of ventricular tachycardia (VT) was attempted in 31 patients (57 +/- 15 years) who had refractory recurrent VT. Fifteen patients had coronary artery disease, seven had arrhythmogenic right ventricular dysplasia, four had cardiomyopathy and five had no structural heart disease. Ten patients were NYHA class III-IV. Ten patients experienced cardiac arrest or syncope during VT. Twenty-two patients had only one documented morphologic type of spontaneous VT. Whereas nine patients had more than one: the VT was incessant or daily in 17 patients. One to 16 shocks (mean 5.6) of 160 to 240 joules each (1162 +/- 1060 joules) were delivered to the endocardial exit site of VT--as identified by endocardial activation mapping (29 patients) and pacemapping (31 patients)--during one (22 patients) or more than one session (nine patients). Cumulative delivered energy was 840 +/- 558 joules for right ventricular VT (11 patients) and 1362 +/- 1240 joules for left ventricular VT (20 patients). Reversible side effects occurring immediately after shocks included: nonclinical VT (two patients), ventricular fibrillation (two patients), AV block (three patients). Mean CK-MB fraction 6 hours after shocks was 91 +/- 46 IU/1. An electrophysiology study performed 7 to 10 days later demonstrated that the original clinical VT was inducible in seven patients, nonclinical monomorphic VT was inducible in eight patients and no VT was inducible in 13 patients.(ABSTRACT TRUNCATED AT 250 WORDS)