True left bundle branch block and long-term mortality in cardiac resynchronisation therapy patients

Background: Left bundle branch block (LBBB) is an important qualification criterion and determinant of prognosis in cardiac resynchronisation therapy (CRT) patients. Aims: Our goal was to investigate the long-term mortality and morbidity in a sizable cohort of patients with CRT with regard to the new strict LBBB definition proposed by Perrin. Methods: We performed a longitudinal cohort study that included consecutive CRT patients. Primary endpoint (all-cause death) and secondary endpoint (all-cause death and hospitalisation for heart failure) were analysed. All preimplantation elec- trocardiograms were categorised as LBBB or non-LBBB according to the new definitions/criteria analysed. Results: The survival analysis comprised 552 patients with CRT. The Perrin criteria, CRT guidelines class I indication criteria, and Strauss criteria were fulfilled in 38.9%, 79.4%, and 62.3% of all LBBB patients, respectively. During the nine-year study period, 232 patients died and the combined endpoint was met by 292 patients. The Perrin “true LBBB” definition criteria were inferior to the Strauss “complete” LBBB definition criteria in predicting survival as reflected by Kaplan-Meier survival curves (C-statistics). Multivariate Cox regression models showed that both LBBB definitions predicted mortality, however, the Perrin definition had a higher hazard ratio (HR 0.67) compared to the Strauss definition (HR 0.51). Conclusions: It seems that the Perrin “true LBBB” criteria are not well-suited for the selection of CRT candidates. Perhaps they do not reflect the presence of a true/complete LBBB or exclude too many patients who, despite some residual conduction in the left bundle branch, responded well to CRT.