Left ventricular end-diastolic extrasystole with pseudonormalization of a left bundle branch block unmasking inferior ischemia

An electrocardiogram tracing of a patient in conducted sinus rhythm with left bundle branch block is shown, in which occasional pseudonormalization of intraventricular conduction is seen. This event is attributed to ventricular fusions with end-diastolic extrasystoles of the left His-Purkinje system distal to the block site. This type of extrasystole is discussed. In this case, normalization of ventricular activation allowed for diagnosis of inferior subepicardial ischemia.