BackgroundTissue Doppler-derived left ventricular systolic velocity (mitral S’) has shown excellent correlation to left ventricular ejection fraction (LVEF) in non-critically patients. However, their correlation in septic patients remains poorly understood and its impact on mortality is undetermined. We investigated the relationship between mitral S’ and LVEF in a large cohort of critically-ill septic patients.MethodsWe conducted a retrospective cohort study between 01/2011 and 12/2020. All adult patients (≥ 18 years) who were admitted to the medical intensive care unit (MICU) with sepsis and septic shock that underwent a transthoracic echocardiogram (TTE) within 72 h were included. Pearson correlation test was used to assess correlation between average mitral S’ and LVEF. Pearson correlation was used to assess correlation between average mitral S’ and LVEF. We also assessed the association between mitral S’, LVEF and 28-day mortality.Results2519 patients met the inclusion criteria. The study population included 1216 (48.3%) males with a median age of 64 (IQR: 53–73), and a median APACHE III score of 85 (IQR: 67, 108). The median septal, lateral, and average mitral S’ were 8 cm/s (IQR): 6.0, 10.0], 9 cm/s (IQR: 6.0, 10.0), and 8.5 cm/s (IQR: 6.5, 10.5), respectively. Mitral S’ was noted to have moderate correlation with LVEF (r= 0.46). In multivariable logistic regression analysis, average mitral S’ was associated with an increase in both 28-day ICU and in-hospital mortality with odds ratio (OR) 1.04 (95% CI 1.01–1.08,p= 0.02) and OR 1.04 (95% CI 1.01–1.07,p= 0.02), respectively.ConclusionsEven though mitral S’ and LVEF may be related, they are not exchangeable and were only found to have moderate correlation in this study. LVEF is U-shaped, while mitral S’ has a linear relation with 28-day ICU mortality. An increase in average mitral S’ was associated with higher 28-day mortality.Graphical AbstractSupplementary InformationThe online version contains supplementary material available at 10.1186/s40560-023-00678-z.