139-06: Impact of mechanical activation and right-to-left ventricular interlead electrical delay on response to cardiac resynchronization therapy

Abstract

Purpose: Prior studies suggest that a LV lead position in the latest mechanically activated segment (mechanically concordant) and a long right-to-left interlead sensed electrical delay (RL-IED) improves cardiac resynchronization therapy (CRT) outcome. We compared the effect of a mechanically concordant LV lead and a long RL-IED on clinical and echocardiographic outcome in patients receiving a CRT device. Methods: We prospectively included 161 patients in NYHA class II-IV and an ECG with a left bundle branch block (age 70 ± 9 years, 39 (24%) female, QRS width 173 ± 21 ms, LV EF 25 ± 6 %, end-systolic (ESV) volume 197 ± 71 ml). The LV lead position was verified by postimplant cardiac CT. The segment with the latest mechanical activation segment was determined by preimplant speckle tracking radial strain echocardiography. The RL-IED was measured during CRT implant and expressed as a percentage of preimplant QRS width. Follow-up was performed after six months. Results: The LV lead was positioned mechanically concordant in 75 (47%) patients, while 82 (51%) and 4 (2%) had the lead in an adjacent or remote segment, respectively. The median RL_IED was 63 (range 1–84) %. The proportion of patients improving in NYHA class, the increase in LV EF, and reduction in ESV was similar in patients with or without a mechanically concordant LV lead (51 vs. 68 %, P = 0.12; 13 ± 9 vs. 11 ± 9 %, P = 0.11; 74 ± 56 vs. 66 ± 53 ml, P = 0.39, respectively). Separated by the median RL-IED, 69 % with a long RL-IED improved in NYHA class compared to 46 % with a short RL-IED (P < 0.01). Patients with a long RL-EID had a larger increase in LVEF and reduction in ESV (13 ± 10 vs. 11 ± 7 %, P = 0.04; 86 ± 54 vs. 54 ± 50 ml, P < 0.001, respectively). Conclusion: A long RL-IED, but not a mechanically concordant LV lead position, is associated with improved clinical and echocardiographic CRT outcome in patients with a high degree of mechanically optimal LV lead positions concordant or adjacent to the segment with latest mechanical activation.