Refining left bundle branch block criteria for improved left bundle branch area pacing response in heart failure.

BACKGROUND: Left bundle branch block (LBBB) on the surface electrocardiogram (ECG) is a key criterion for selecting patients suitable for cardiac resynchronization therapy. However, the diagnostic criteria for LBBB vary across guidelines, and their impact on the efficacy of left bundle branch area pacing (LBBAP) remains unclear. OBJECTIVE: This study aimed to investigate the correlation among different LBBB-related ECG criteria, as well as ECG characteristics, on the efficacy of LBBAP in heart failure (HF). METHODS: Consecutive patients with systolic HF with wide QRS complexes who successfully underwent LBBAP were enrolled. Preoperative standard 12-lead ECG was assessed. This included LBBB-related parameters, including time to notch/slur in lateral leads. The associations among different LBBB criteria (2009 American Heart Association guidelines, 2013 European Society of Cardiology guidelines, 2021 European Society of Cardiology guidelines, Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy, and Strauss criteria) were evaluated. The endpoints were post-LBBAP electrical synchronization, echocardiographic response, and clinical outcomes. RESULTS: Among 149 patients included in the analyses (baseline left ventricular ejection fraction 32.6% ± 7.0%; QRS duration 170.8 ± 20.3 ms), substantial variability in LBBB classification was observed among different criteria. The Strauss criteria demonstrated the highest predictive accuracy for QRS narrowing (area under the curve 0.710) and showed favorable performance for identifying echocardiographic responders (area under the curve 0.631). Patients who met the Strauss LBBB criteria had a significantly lower risk of composite clinical endpoint than those without LBBB (adjusted hazard ratio 0.216; 95% confidence interval 0.057-0.810; P = .023). Combining the Strauss criteria with delayed time to notch/slur in lead V5/V6 (>60 ms) further improved the predictive value of ECG-based assessment. CONCLUSION: LBBAP provides the most clinical benefit among patients with HF with Strauss-defined LBBB. The combination of the Strauss criteria with delayed notch/slur in lead V5/V6 maximizes the predictive value of the ECG.