Objectives A nonoptimal left ventricular (LV) pacing lead position may be a potential cause for nonresponse to cardiac resynchronisation therapy (CRT). 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) < 35%, and wide QRS complex ≥120 ms were included for implantation of a CRT device. Left ventricular (LV) activating sequence was mapped 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 ischaemic 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 < 0.01). The period after CRT procedure exceeded 3 months in 9 of 10 patients. Eight of these 9 patients were classified as responders to CRT (8/9, 89%) and 3 patients as super responders (3/9, 33%), the other 1 ischaemic 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 P < 0.01). NYHA class was improved (1.6 ± 0.5 vs 3.3 ± 0.5) and the 6-min walk test was increased (405 ± 92 m vs 307 ± 82 m). Echocardiography demonstrated LVEF was improved (0.42 ± 0.06 vs 0.30 ± 0.04), left ventricular end-systolic volume (LVESV) was reduced (121 ± 38 ml vs 153 ± 44 ml) and mitral regurgitation velocity (MRV) was decreased (3.9 ± 1.2 m/s vs 4.5 ± 1.5 m/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 function of heart failure patients during short-term follow-up.