Identifying non-responders to cardiac resynchronization therapy in the non-left bundle branch block.

Background: Non-response to cardiac resynchronization therapy (CRT) is an important issue in the treatment of heart failure with reduced ejection fraction (HFrEF) and non-left bundle branch block (LBBB). Electrocardiogram-gated myocardial perfusion single-photon emission computed tomography imaging (G-MPI SPECT) is typically used to assess left ventricular (LV) dyssynchrony. This study aimed to determine whether G-MPI parameters are associated with non-responsiveness to CRT.

Methods: Between January 2021 and December 2022, 128 patients underwent CRT, of whom 73 with preoperative evaluation using G-MPI were selected. Forty-three patients with non-LBBB (21 and 22 CRT responders and non-responders, respectively) and 30 patients with LBBB were analyzed.

Results: Among patients with non-LBBB, CRT responders and non-responders exhibited no significant differences in baseline characteristics, except for the LV dimension. A receiver operating characteristic curve analysis identified 108° and 27.7° as the optimal cutoff values for the bandwidth and phase standard deviation (SD), respectively, to predict non-responsiveness to CRT (area under the curve [AUC] = 0.762; 95% confidence interval [CI] 0.601-0.923 and AUC = 0.742; 95% CI 0.576-0.909, respectively). A multivariate analysis revealed that a cutoff bandwidth of ≥ 108° and phase SD of ≥ 27.7° are independent predictors of non-responsiveness to CRT in patients with non-LBBB (hazard ratio 5.65; 95% CI 1.53-20.9; P = 0.009). In contrast, there were no significant associations between G-MPI parameters and non-responsiveness to CRT in patients with LBBB.

Conclusions: Preoperative G-MPI might be associated with non-responsiveness to CRT in patients with non-LBBB, indicating that identifying potential non-responders can improve patient management.