Continuous electrical activity during sustained monomorphic ventricular tachycardia. Observations on its dynamic behavior during the arrhythmia.

Catheter mapping was performed during sinus rhythm and monomorphic ventricular tachycardia (VT) in 56 consecutive patients with sustained, monomorphic VT. Forty-two patients had an old myocardial infarction (VT-old MI group), 6 patients had right ventricular dysplasia (VT-RV dysplasia group), and 8 patients had idiopathic VT (idiopathic-VT group). Continuous electrical activity was recorded in 15 of 42 patients of the VT-old MI group (36%), 5 of 6 of the VT-RV dysplasia group (83%), and in 0 of 8 patients in the idiopathic VT group (0%). In 17 of 20 patients with continuous electrical activity during VT, observations on the dynamic behavior of continuous electrical activity during VT revealed at least 1 of the following characteristics: spontaneous disappearance and reappearance of continuous electrical activity without changes in rate, morphologic pattern or axis of VT; pacing-induced transient termination of continuous electrical activity without termination of VT; spontaneous disappearance of continuous electrical activity during VT as a rate-dependent phenomenon; Wenckebach-like conduction to other areas resulting in transient and periodic continuous electrical activity; dependence of continuous electrical activity on ventricular activation pattern during VT; pacing-induced change from a noncontinuous electrogram into continuous electrical activity without prevention of termination of VT; and termination of continuous electrical activity after antiarrhythmic drugs without termination of VT. Continuous electrical activity was always recorded in the aneurysm and never over normal heart areas. At the sites where continuous electrical activity was recorded during VT, potentials recorded during sinus rhythm were abnormal. Our observations suggest that several electrophysiologic phenomena can simulate continuous electrical activity during monomorphic VT. Transient, continuous electrical activity is a frequent phenomenon that represents electrical activity from abnormal areas not necessarily required to perpetuate VT.