Landmark studies of heart failure patients with prolonged QRS duration on electrocardiography (ECG) demonstrated that biventricular pacing (BIVP) was superior to right ventricular pacing (RVP).1 Detrimental long-term effects and unpredictable acute hemodynamic effects due to RVP led to the existing skepticism regarding RVP, and BIVP became favored as the standard of care implementing cardiac resynchronization therapy (CRT).2 However, despite reductions in mortality and morbidity, one-third of eligible patients do not benefit from BIVP, thus demonstrating the shortcoming of QRS duration and morphology in predicting CRT response.