Electrocardiographic clues to identify nonresponders to cardiac resynchronization therapy

Background: The aim of cardiac resynchronization therapy (CRT) is to restore myocardial electromechanical synchrony. Achieving this in patients with chronic severe heart failure due to poor left ventricular (LV) systolic function and cardiac dyssynchrony on optimal medical therapy, is associated with improved clinical performance and outcomes. Up to one-third of patients undergoing CRT do not benefit from implantation. Ensuring LV capture is essential and can be at times difficult to confirm. Methods: Described herein, are six patients who underwent biventricular pacemaker implantation but failed to experience an improvement in LV systolic function or functional capacity. Results: In each case, the 12-lead electrocardiogram (ECG) was helpful in unmasking loss of LV capture in patients who were presumed to have biventricular pacing. Conclusions: Despite the technical wizardry behind CRT and patient system analyzers, the surface ECG should continue to be an invaluable tool for evaluating patients who have undergone CRT.