Electrocardiographic markers of cardiac resynchronization therapy response: delayed time to intrinsicoid deflection onset in lateral leads.

Cardiac resynchronization therapy (CRT) has emerged as an important intervention for patients with heart failure (HF) with reduced ejection fraction and delayed ventricular activation. In these patients, CRT has demonstrated to improve quality of life, promote reverse left ventricular (LV) remodeling, reduce HF hospitalizations, and extend survival. However, despite advancements in our understanding of CRT, a significant number of patients do not respond to this therapy.