Impaired left ventricular transmural strain gradient linked to septal flash in complete left bundle branch block

This study used layer-specific speckle-tracking imaging (LS-STI) to investigate alterations in the left ventricular transmural contractile gradient and its correlation with septal flash (SF) parameters in patients with complete left bundle branch block (CLBBB). This study included 116 CLBBB patients (37 without SF, 79 with SF) and 40 matched controls. Using LS-STI, we measured the left ventricular global longitudinal systolic peak strain (GLS) and the longitudinal systolic peak strain of the endocardial, mid-myocardial, and epicardial layers (GLS-Endo, GLS-Mid, and GLS-Epi). The strain gradient through the left ventricular wall (transmural gradient, TG) was subsequently calculated. Spearman correlation analysis was used to determine the correlations of SF amplitude and SF duration with systolic strain parameters, particularly the TG. Compared with the non-SF group, the SF group had lower myocardial systolic longitudinal strain in all layers (GLS-Endo: -16.83 ± 4.89% vs. -20.88 ± 3.24%; GLS-Mid: -14.71 ± 4.38% vs. -18.24 ± 2.80%; GLS-Epi: -12.77 ± 3.84% vs. -15.82 ± 2.44%) and transmural gradient (TG: 4.05 ± 1.19 vs. 5.06 ± 1.09) (all P < 0.05). TG was negatively correlated with both SF amplitude and SF duration (r = -0.25, P = 0.027 for amplitude; r = -0.47, P < 0.001 for duration). In CLBBB patients with SF, the left ventricular transmural contractile gradient was more severely impaired, and SF duration was moderately correlated with layer‑specific strain and the transmural gradient. However, its independent or incremental predictive value needs to be further validated.