Background Cardiac resynchronisation therapy (CRT) offers improved morbidity and mortality in patients with left ventricular dysfunction and intraventricular conduction delay. Up to 30% of CRT recipients fail to derive any clinical benefit. Left ventricular (LV) lead placement to the latest areas of activation (concordant LV lead) are associated with better clinical outcomes, greater LV reverse remodelling and lower mortality compared to a discordant lead position. However, there is little known about the effect of the RV lead position on CRT response. We investigated the relationship between the RV lead position and CRT response in patients with and without a concordant LV lead position.

Methods In this prospective non randomised study, a total of 67 patients successfully underwent CRT (69±9 years, EF 23±7%, QRS 157±21 ms, and NYHA III/IV 63/4). The LV lead was positioned preferentially in a lateral or posterolateral vein. The RV lead was positioned according to operator preference to either the RV septum (RVS n=33) or RV apex (RVA, n=34). The latest site of activation was determined with 2D speckle tracking radial strain imaging (pre-implant), and the LV lead position from biplane fluoroscopy. Patients were regarded as having a concordant LV lead position if the LV lead was pacing the latest segment, and discordant if not. Response was defined as >15% reduction in LV end systolic volume (LVESV) at 6 months follow-up.

Results The baseline characteristics between the RVS and RVA groups were similar. The mean reduction in LVESV from baseline at follow up in the RVS group was greater than in the RVA group (22.7% vs 13.5%, p=0.03). Similarly there was a higher rate of responders in the RVS group (69.7% vs 44.1%, p=0.03). In the concordant group (n=28), there were no differences between the RVS (n=17) and RVA (n=11) groups in the extent of LVESV reduction (29.1 vs 26.4%, p =0.91) and CRT response rates (71.3 vs 81.8%, p=0.22) In patients with a discordant LV lead, there were significant differences between the RVS (n=16) and RVA (n=23) groups in the extent of LVESV reduction (15.8 vs 4.7%, p=0.05) and in response rates (28.3 vs 12.8%, p<0.01).

Conclusion In patients with a concordant LV lead position, the RV lead position appears to make no difference in the response to CRT. However in patients with a discordant LV lead position, an RVS lead position is associated with better LV reverse remodelling. These findings suggest an important role for the RV lead position particularly in patients with a suboptimal LV lead position.