Nonsustained ventricular tachycardia arising from the right ventricular outflow tract.
Characteristics of left bundle branch block morphology, inferiorly directed frontal plane QRS axis and repetitive nonsustained salvos were used to define a discrete subgroup of patients with ventricular tachycardia (VT). The origin of this tachycardia was thought to be the right ventricular outflow tract. Twenty-six patients with this definition (group 1) were compared with 29 consecutive patients with all other forms of VT (group 2). When compared with patients in group 2, group 1 patients were younger (average age 37 vs 51 years, p less than 0.005), had less structural heart disease (2 of 26 vs 25 of 29 patients, p less than 0.005) and had a better prognosis (no deaths) after an average follow-up time of 28 months in comparison with 5 deaths after an average follow-up of 35 months (p less than 0.05). Induction of VT was possible using isoproterenol infusion in 14 of 20 group 1 patients, but no VT could be induced in 9 group 2 patients (p less than 0.05). Exercise stress testing induced VT in 11 of 21 group 1 patients and 2 of 9 group 2 patients (p greater than 0.05). Programmed electrical stimulation failed to induce VT in 9 group 1 patients, but did induce it in 15 of 20 group 2 patients (p less than 0.005). Successful therapy in group 1 patients was achieved by beta blockers alone (7 patients), beta blockers plus type 1A antiarrhythmic drugs (9 patients), procainamide alone (2 patients), sotalol (3 patients) and amiodarone (2 patients). Three patients were not treated.(ABSTRACT TRUNCATED AT 250 WORDS)