Significance of effective cardiac resynchronization therapy pacing for clinical responses: An analysis based on the effective cardiac resynchronization therapy algorithm

Background: High percent ventricular pacing maximizes cardiac resynchronization therapy (CRT) response. An effective CRT algorithm classifies each left ventricular (LV) pace as effective or ineffective on the basis of the detection of QS or QS-r morphology on the electrogram; however, the relationship between percent effective CRT pacing (%e-CRT) and responses is unclear.

Objective: We aimed to clarify the association between %e-CRT and clinical outcomes.

Methods: Of the 136 consecutive CRT patients, 49 using the adaptive and effective CRT algorithm with percent ventricular pacing > 90% were evaluated. The primary and secondary outcomes were heart failure (HF) hospitalization and prevalence of CRT responders, defined as patients with an improvement in LV ejection fraction of ≥10% or a reduction in LV end-systolic volume of ≥15% after CRT device implantation, respectively.

Results: We divided the patients into the effective group (n = 25) and the less effective group (n = 24) by the median value of %e-CRT (97.4% [93.7%-98.3%]). During the median follow-up period of 507 days (interquartile range 335-730 days), the effective group had a significantly lower risk of HF hospitalization than the less effective group as revealed by Kaplan-Meier analysis (log-rank, P = .016). Univariate analysis revealed %e-CRT ≥ 97.4% (hazard ratio 0.12; 95% confidence interval 0.01-0.95; P = .045) as a predictor of HF hospitalization. The effective group had a higher prevalence of CRT responders than the less effective group (23 [92%] vs 9 [38%]; P < .001). Univariate analysis revealed that %e-CRT ≥ 97.4% (odds ratio 19.20; 95% confidence interval 3.63-101.00; P < .001) was a predictor of CRT response.

Conclusion: High %e-CRT is associated with high CRT responder prevalence and low HF hospitalization risk.