Abstract. Background:. Functional mitral regurgitation (FMR) is common in critically ill patients and may cause left atrial (LA) pressure elevation. This study aims to explore the prognostic impact of synergistic LA pressure elevation and FMR in patients with shock. Methods:. We retrospectively screened 130 consecutive patients of 175 patients with shock from April 2016 to June 2017. The incidence and impact of FMR and early diastolic transmitral velocity to early mitral annulus diastolic velocity ratio (E/e’) ≥ 4 within 6 h of shock on the prognosis of patients were evaluated. Finally, the synergistic effect of FMR and E/e’ were assessed by combination, grouping, and trend analyses. Results:. Forty-four patients (33.8%) had FMR, and 15 patients (11.5%) had E/e’ elevation. A multivariate analysis revealed FMR and E/e’ as independent correlated factors for 28-day mortality (P = 0.043 and 0.028, respectively). The Kaplan-Meier survival analysis revealed a significant difference in survival between patients with and without FMR (χ2 = 7.672, P = 0.006) and between the E/e’ ≥ 14 and E/e’ < 14 groups (χ2 = 19.351, P