Time interval from left ventricular stimulation to QRS onset is a novel predictor of nonresponse to cardiac resynchronization therapy

Left ventricular (LV) lead placement at the late activation site (LAS) has been proposed as an optimal LV pacing site (ie, Q-LV interval). However, LAS may be relevant to local electrical conduction, measured as an interval from LV pacing stimulation to QRS onset (S-QRS interval). The purpose of this study was to evaluate the prognostic value of S-QRS for reverse remodeling and the impact of S-QRS on pacing QRS configuration in patients undergoing cardiac resynchronization therapy (CRT). Sixty consecutive heart failure patients with a wide QRS complex underwent CRT. A site with Q-LV ≥95 ms was targeted for LV lead placement. A responder was defined as one with >15% reduction in LV end-systolic volume 6 months after CRT. LV lead placement with Q-LV ≥95 ms was achieved in 52 of 60 patients (86.7%). Thirty-two of 52 patients (61.5%) were responders. S-QRS was significantly shorter in responders than nonresponders (P