title: Narrow QRS complex tachycardia with atrioventricular dissociation.
abstract: We describe the case of a 22-year-old man who had frequent episodes of narrow QRS complex tachycardia with atrioventricular dissociation. The ECG during sinus rhythm showed normal PR and QRS intervals, but it showed a left bundle branch block configuration during atrial pacing or after injection of verapamil. An electrophysiological study demonstrated that the patient had nodoventricular Mahaim fibers. The narrow QRS complex tachycardia was explained by a circuit involving antegrade conduction via the atrioventricular nodo-His axis and retrograde conduction via the nodoventricular bypass tract.
mesh_terms: D000328:Adult; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D008297:Male; D011226:Pre-Excitation Syndromes / Q000503:physiopathology; D013610:Tachycardia / Q000503:physiopathology*; D014700:Verapamil
chemical_list: D014700:Verapamil