Continuous Local Electrical Activity A Mechanism of Recurrent Ventricular Tachycardia

SUMMARY Although the mechanism of most episodes of recurrent ventricular tachycardia (VT) is believed to be re-entry, definitive proof of this hypothesis has heretofore been unavailable in man. Using programmed stimulation and ventricular endocardial mapping we studied three patients in whom the initiation of VT was dependent upon developing a critical degree of fractionation and delay in local left ventricular electrograms. When electrical activity spanned diastole, VT ensued. Maintenance of VT was associated THE MECHANISM OF RECURRENT ventricular tachycardia (VT) is thought to be re-entry.' ' While reproducible initiation and termination of VT by programmed stimulation suggests a re-entrant mech-anism,4 similar findings have recently been described for "triggered automatic " tachyarrhythmias.5-i Proof of re-entry therefore requires the demonstration of a tempora