Association between Wait Time for Transthoracic Echocardiography and 28-Day Mortality in Patients with Septic Shock: A Cohort Study

Background: the optimal timing of Transthoracic echocardiography (TTE) performance for patients with septic shock remains unexplored. Methods: a retrospective cohort study included patients with septic shock in the MIMIC-Ⅲ database. Risk-adjusted restricted cubic splines modeled the 28-day mortality according to time elapsed from ICU admission to receive TTE. The cut point when a smooth curve inflected was selected to define early and delayed group. We applied propensity score matching (PSM) to ensure our findings were reliable. Causal mediation analysis was used to assess the intermediate effect of fluid balance within 72 h after ICU admission. Results: 3264 participants were enrolled and the risk of 28-day mortality increased until the wait time was around 10 h (Early group) and then was relatively flat afterwards (Delayed group). A beneficial effect of early TTE in terms of the 28-day mortality was observed (HRs 0.73−0.78, all p < 0.05) in the PSM. The indirect effect brought by the fluid balance on day 2 and 3 was significant (both p = 0.006). Conclusion: early TTE performance might be associated with lower risk-adjusted 28-day mortality in patients with septic shock. Better fluid balance may have mediated this effect. A wait time within 10 h after ICU may represent a threshold defining progressively increasing risk.