Slow conduction within lateral myocardial scar and response to cardiac resynchronization therapy.

Cardiac resynchronization therapy (CRT) improves symptoms and survival in some selected heart failure patients. However, around 30% of patients still do not respond to CRT. In these patients, methodological approach of any potential cause of nonresponse should be reviewed. We describe the case of limited left ventricle (LV) myocardium capture by LV lead during biventricular pacing secondary to a slow conduction from LV lead impulse, located in a scar zone, and the benefit of interventricular delay optimization in this setting. This case emphasizes the interest of considering 12-lead electrocardiogram during management of patients with CRT.