Optimization of coronary sinus lead placement targeted to right-to-left delay in patients undergoing cardiac resynchronization therapy.

Aims Anatomical placement of the coronary sinus (CS) lead in basal or mid-ventricular positions of the posterior and lateral walls is associated with a better clinical outcome of cardiac resynchronization therapy (CRT). We hypothesized that optimization of CS lead placement targeted the right-to-left electrical delay (RLD) predicts an additional clinical benefit. Methods and results The CS lead was placed according to current standards in 90 patients (Conventional group) and at the site of the longest RLD in 121 patients (RLD group). Non-responders were defined as those who died or underwent hospitalization for heart failure or did not improve in their Clinical Composite Score within 6 months. There were 67 (32%) non-responders. Compared with Conventional group, the final CS pacing site was more frequently in the basal segments in the RLD group (40% vs. 23%, P = 0.007); moreover, the RLD ratio (% RLD) of the total QRS width was longer (77 +/- 13 vs. 73 +/- 15, P = 0.05) and biventricular QRS shortened more from the baseline (-31 +/- 21ms vs. -21 +/- 26 ms, P = 0.004). Nevertheless, the rate of non-responders was similar in the RLD and Conventional groups (35% vs. 28%, P = 0.30), as was % RLD (76 +/- 16 vs. 75 +/- 13, P = 0.66). QRS width during right ventricular (RV) pacing was an independent predictors of adverse outcome, with a 2% increase in the risk of failure for each 1ms increase in QRS (P = 0.006). Conclusion Optimization of CS lead placement targeted to latest electrical activation does not provide additional clinical benefit to anatomical placement in basal or mid-ventricular positions of the posterior and lateral walls. QRS width during RV pacing was a strong predictor of CRT failure