Left-bundle branch block, an alert for cardiac resynchronization therapy

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Medtronic. Background Left bundle branch block (LBBB) might be the first finding of cardiovascular diseases but it is also the target of cardiac resynchronization therapy (CRT) in heart failure (HF) with reduced ejection fraction (HFrEF). LBBB prognosis and the implication of CRT in an unselected real-world setting are of great potential clinical impact. Methods A central ECG database together with national registries has been screened to identify LBBB patients. Cox models were fitted to assess the hazard ratio (HR) of death, cardiovascular death (CVD) and HF hospitalization (HFH) according to gender and CRT use. A subdistribution of the hazard ratio (SHR) was used to account for non-cardiovascular death as a competing risk. Logistic regression was fitted to investigate characteristics associated with CRT use. Results Of 5359 patients with LBBB and QRS duration over 150ms, 36% were female. The median age was 76 years and males had a significantly higher risk of death after 5 years from the LBBB diagnosis. CRT, when indicated, has a large benefit on all-causes of death (HR: 0.53, 95% confidence intervals (CI): 0.42-0.67), CVD (HR: 0.53 CI: 0.39-0.71) and HFH (HR: 0.71 CI: 0.60-0.82), especially in the first 5 years after the indication. These results are consistent with the competing risk analysis. Conclusion In an unselected LBBB population, CRT is underused but extremely beneficial. Therefore it’s crucial to find ways of better implementing and understanding CRT utilization, focusing on characteristics that influence recommendations.