Association Between Platelet Count/Lactate Dehydrogenase Ratio and In-Hospital Mortality in the Patients With Sepsis-Induced Myocardial Injury

Background: Sepsis-induced myocardial injury (SIMI) is a severe complication with high mortality, yet effective prognostic prediction tools remain limited. Although platelet-derived indices have been explored in SIMI, these metrics primarily reflect systemic inflammation rather than the extent of myocardial injury or metabolic status. Methods: We retrospectively analyzed 3071 critically ill individuals with SIMI admitted to the intensive care unit (ICU) of the Chinese People’s Liberation Army (PLA) General Hospital between January 2020 and October 2025. The association between the platelet count (PLT)/lactate dehydrogenase (LDH) ratio and in-hospital mortality was assessed using multivariable Cox regression, restricted cubic splines, and receiver operating characteristic (ROC) curve analysis. Subgroup analyses evaluated consistency across clinically relevant strata. Results: The PLT/LDH ratio was independently associated with lower in-hospital mortality (hazard ratio [HR] = 0.44, 95% confidence interval [CI]: 0.34–0.57, p < 0.001). Compared with the lowest tertile, the highest tertile of PLT/LDH ratio was associated with a 67% reduction in risk (HR = 0.33, 95% CI: 0.25–0.43, p < 0.001). The PLT/LDH ratio demonstrated modest, statistically significant incremental discriminative performance over PLT or LDH alone (both p < 0.05). A nonlinear relationship was observed, with an inflection point at approximately 0.306 (p for nonlinearity < 0.0001). Subgroup analyses revealed a consistent association across all subgroups, with significant interactions for sex, hypertension, chronic kidney disease, and liver disease (all p for interaction < 0.05). Conclusions: The PLT/LDH ratio is independently associated with in-hospital mortality in patients with SIMI. It may serve as a simple and practical tool for prognostic prediction in patients with SIMI upon ICU admission.