[Histological substrate of ventricular tachycardias of the right bundle-branch block type (sensitive to verapamil)]

Abstract

In order to clarify the anatomic substrate of idiopathic ventricular tachycardia of right bundle-branch block morphology, responsive to verapamil, two patients with this type of arrhythmia were evaluated using hemodynamic studies, right ventricular endomyocardial biopsy as well as electrophysiological and pharmacological studies. Pressures, right and left ventriculography and coronary angiography were normal in both patients. Case 1 showed a prolonged sinus node recovery time and a histological pattern which was compatible with healed myocarditis. Case 2 presented a complete right bundle-branch block, intra-His conduction defects and histological features of aspecific cardiomyopathy. Our results underline the presence of diffuse ventricular histologic changes in patients with idiopathic ventricular tachycardia of right bundle-branch block morphology. These histologic changes seem unable to interfere with cardiac pump function but are sufficient to create significant abnormalities of impulse formation and conduction.