Acute changes in electromechanical parameters during different pacing configurations using a quadripolar left ventricular lead
Quadripolar left ventricular (LV) leads allow for several pacing configurations in candidates for cardiac resynchronization therapy (CRT). Whether different pacing configurations may affect LV dyssynchrony and systolic function is not completely known. We aimed to evaluate the acute effects of different pacing vectors on LV electromechanical parameters in patients implanted with a quadripolar LV lead. In this two-centre study, within 1 month of implantation 21 CRT patients (65 ± 8 years, 76 % men, 38 % ischemic) receiving a quadripolar LV lead (Quartet 1458Q, St Jude Medical) underwent LV capture threshold assessment, intracardiac electrogram optimization, and two-dimensional echocardiography during four pacing configurations: D1-P4, P4-RV coil, D1-RV coil, and P4-M2. LV dyssynchrony and contractile function were expressed by septal-to-lateral delay and global longitudinal strain (GLS). LV capture threshold varied between the configurations (P < 0.001), showing higher values in the configurations P4-RV coil and P4-M2. Septal-to-lateral delay decreased in the configurations D1-P4 and D1-RV coil (P = 0.003 and P = 0.033 vs. spontaneous rhythm, respectively). GLS improved significantly vs. spontaneous rhythm only in the configuration D1-P4 (from −8.6 ± 3.5 to −11.0 ± 3.2 %, P = 0.001). Accordingly, an increase in stroke volume and a decrease in mitral regurgitation were observed in the configuration D1-P4 (P ≤ 0.001 vs. spontaneous rhythm). In CRT patients receiving a quadripolar LV lead, significant variations in electromechanical parameters were observed by changing pacing vector. Individually targeting the optimal pacing site may enhance the acute haemodynamic response to CRT.