Therapy failure was defined by the occurrence of the following events : spontaneous recurrence of ventricular tachycardia or ventricular fibrillation , sudden cardiac death , inducibility of sustained ventricular tachycardia or ventricular fibrillation with programmed stimulation of the heart , symptomatic non-sustained ventricular tachycardia requiring therapy or side-effects of antiarrhythmic drugs requiring withdrawal .
