Implant Electrical Characteristics Predict Response to Cardiac Resynchronization Therapy

Background: The optimal site for left ventricular (LV) lead placement in cardiac resynchronization therapy (CRT) remains uncertain. Intra-procedural measures for predicting response to CRT have shown mixed results. Hypothesis: This study analyzed intracardiac electrogram (IEGM) character-istics at implant and assessed patients ’ response rates (RR) to CRT. Methods: Forty-one consecu-tive patients undergoing CRT were enrolled. Medically optimized patients in sinus rhythm, with ejection fraction (EF) < 35%, and a dyssynchrony index (DI)> 34 were included. Right ventricular (RV) leads were positioned mid-septum. LV leads were targeted to the latest mechanical activation on echocardiography. IEGMs were measured, assessing intrinsic RV-to-LV delay (int RV-LV), RV-paced delay (RVp-LV), and LV-paced delay (LVp-RV). The difference between LVp-RV and RVp-LV was recorded as delta-LV. Response was defined as improvement of EF> 10%, reduction in LVEDD> 15 % and improvement of ≥1 NYHA class. Results: Overall RR was 79%. LV leads were placed in the target location in 91%. Int RV-LV was 101 ± 14 ms in responders; 78 ± 11 ms in non-responders (p < 0.05). Int RV-LV> 100 had a RR of 87%; int RV-LV < 100 had a RR of 68%. LVp-RV and RVp-LV did not differ significantly between responders and non-responders. Delta-LV> 40 m