Background A nonoptimal left ventricular (LV) pacing lead position may be a potential cause for nonresponse to cardiac resynchronization therapy (CRT).
Objective The aim of the current study was to investigate the feasibility and curative effect of CRT by targeted LV lead placement to the latest ventricular electrical activating site mapped in the coronary sinus (CS) branches.
Methods Ten patients with moderate to severe congestive heart failure, depressed left ventricular ejection fraction (LVEF) in the CS branchs, and the latest ventricular electrical activating site was considered as the target site for LV lead placement. The feasibility and curative effect of this kind of CRT were observed. The clinical variables assessed in this study included QRS duration, NYHA class, 6-min walk test and echocardiography index.
Results Seven patients were diagnosed as dilated cardiomyopathy and 3 patients as ischemic cardiomyopathy. Electrophysiological mapping were performed in 28 CS branches which were considered as a possible site for LV lead placement and LV lead was successfully placed at the latest LV electrical activating site in all 10 patients. There were 116 ± 28ms activating time delay at the latest LV electrical activiating site than the QRS onset of ECG. QRS complex were significantly narrowed immediately after CRT than before CRT (121 ± 17ms vs 153 ± 30ms, P(8/9, 89%) and 3 patients as super responders (3/9, 33%), the other 1 ischemic cardiomyopathy patient who died of acute myocardial infarction 2 months after CRT procedure was classified as non-responder to CRT (1/9, 11%). The following clinical variables 3 months after CRT procedure were markedly improved than variables before CRT in these 8 responders (all PNYHA class was improved (1.6 ± 0.5 vs 3.3 ± 0.5) and the 6-min walk test was increased (405 ± 92m vs 307 ± 82m). Echocardiography demonstrated LVEF was improved (0.42 ± 0.06 vs 0.30 ± 0.04), left ventricular end-systolic volume (LVESV) was reduced (121 ± 38ml vs 153 ± 44ml) and mitral regurgitation velocity (MRV) was decreased (3.9 ± 1.2m/s vs 4.5 ± 1.5m/s).
Conclusions Targeted left ventricular lead placement to the latest venticular electrical activating site guided by electrophysiological mapping in the CS branches was feasible. This CRT method was effective for improving heart founction of heart failure patients during short-term follow-up.