A regular ventricular tachycardia with variable QRS morphologies originating from the interventricular septum: what is the mechanism?

摘要

A 48-year-old man with coronary artery disease, a left ventricular ejection fraction of 35%, and New York Heart Association Class III heart failure was referred for catheter ablation of sustained ventricular tachycardia (VT). Sustained VT with a constant cycle length was reproducibly induced by programmed ventricular stimulation from the right ventricle (RV) during an isoproterenol infusion and exhibited variable QRS morphologies with a left bundle branch block and left superior axis pattern (Fig. 1). During the VT, the local ventricular activation in the His bundle (HB) region was simultaneous with the QRS onset (Fig. 1). During the VT, the cycle length of the local ventricular activations recorded from the RV was constant, whereas that of the local ventricular activations recorded from the coronary sinus (CS) became altered (Fig. 1). What is the mechanism?