Impact of peak strain dispersion and septal flash on left ventricular myocardial work in patients with complete left bundle branch block.

This study used two‑dimensional speckle‑tracking imaging (2D‑STI) and pressure‑strain loop (PSL) analysis to investigate the impact of peak strain dispersion (PSD) and septal flash (SF) on left ventricular myocardial work in patients with complete left bundle branch block (CLBBB). We enrolled 110 patients with CLBBB, stratified by the presence (n = 69) or absence (n = 41) of SF, and 45 matched controls. Two-dimensional speckle tracking imaging was employed to obtain the PSD (defined as the standard deviation of the time to peak longitudinal strain in all left ventricular segments). PSL analysis quantified global constructive work (GCW), global wasted work (GWW), global work efficiency (GWE), global work index (GWI) and regional myocardial work parameters. The correlations of SF and PSD with work indices were assessed, and multivariate regression identified predictors of left ventricular systolic dysfunction (GWI < 1907 mmHg%). The SF group exhibited significantly higher PSD and GWW, and lower GWE, GWI, and GCW than the non-SF group (all p < 0.05). Both SF and higher PSD were negatively correlated with the work indices of the septum, free wall, and their ratios (all p < 0.01). Multivariate analysis confirmed that SF (OR: 2.717, 95% CI: 1.037-7.119) and PSD (OR: 1.055, 95% CI: 1.019-1.093) are independent risk factors for left ventricular systolic dysfunction. CLBBB patients with SF have greater left ventricular systolic impairment, coupled with septal-to-free wall workload imbalance. PSD, a global dyssynchrony parameter, complements the local visual index SF.