Chen, Chun KaiChun KaiChenLiu, Yen BinYen BinLiuChen, Chu ChihChu ChihChenHUI-CHUN HUANGChien, Kuo LiongKuo LiongChien2026-04-292026-04-292025-05-09https://doi.org/10.1101/2025.05.08.25327272https://scholars.lib.ntu.edu.tw/handle/123456789/737619Background Left bundle branch block (LBBB) adversely affects left ventricular (LV) synchrony and function, resulting in poorer outcomes for patients with systolic heart failure or coronary artery disease (CAD). Recently, LBBB-induced cardiomyopathy was recognized as a potentially reversible condition. Nevertheless, there is a significant knowledge gap regarding how to identify patients with LBBB at risk of reduced LV systolic function, leading to uncertainties in screening strategies. This study aimed to develop and validate a prediction model for detecting reduced LV systolic function among patients with LBBB morphology on electrocardiogram. Methods This study adhered to the Transparent Reporting of a Multivariable Prediction Model for Individual Prognosis or Diagnosis reporting guidelines. We retrospectively enrolled patients with LBBB morphology from the National Taiwan University Hospital between 2010 and 2018. Patients were randomly divided into development and validation sets. Predictors of reduced LV systolic function were identified from medical histories and electrocardiogram features, and a multivariable logistic regression model was developed. Results We enrolled 821 patients with LBBB morphology, divided into development (411 patients) and validation cohorts (410 patients). The final predictive model incorporated several variables, including younger age, male sex, hypertension, CAD, history of congestive heart failure, and discordant LBBB. The model showed good discriminative power with a C-statistic of 0.816 and a bias-corrected C-statistic of 0.807, indicating adequate calibration. Additionally, a clinical scoring system named CCDS65 was developed to categorize patients into groups based on their predicted risk of reduced left ventricular systolic function. Conclusions We developed and internally validated a straightforward predictive model to identify reduced LV systolic function in patients with LBBB morphology simply through history taking and ECG morphology. The CCDS65 scoring system provides a practical tool for quickly detecting reduced LV systolic function in clinical practice, enabling timely management through guideline-directed medical therapy and pacing interventions.posted-content10.1101/2025.05.08.25327272