Preoperative LDL-C and mortality after cardiac valve surgery: a retrospective cohort study on the mediating role of inflammatory risk

BACKGROUND: The connection between low-density lipoprotein cholesterol (LDL-C) levels and postoperative outcomes following cardiac valve surgery (CVS) remains controversial. Therefore, this research aimed to study the connection of LDL-C levels with the incidence of adverse clinical outcomes in patients undergoing CVS. METHODS: 1,304 patients undergoing first-time CVS were identified from the MIMIC-IV database. Participants were split into two groups based on admission LDL-C levels: a low LDL-C group (< 1.4 mmol/L, n = 215) as well as a high LDL-C one (≥ 1.4 mmol/L, n = 1,089). The main endpoint was 30-day all-cause mortality (ACM), with secondary endpoints including in-hospital, 90-, 180- and 365-day ACM rates. The connection between preoperative LDL-C levels and clinical outcomes was evaluated via survival analysis, mediation analysis, and subgroup analyses. RESULTS: Multivariable Cox regression analysis demonstrated preoperative LDL-C level served as an independent protective factor against 30-day ACM following cardiac valve surgery (adjusted HR: 0.594; 95% CI: 0.368-0.960). In stratified analysis, patients in the higher LDL-C tertile exhibited a remarkably lower mortality risk (HR: 0.285; 95% CI: 0.134-0.604). Consistent subgroup analyses validated these findings' robustness across all clinically relevant subgroups. Notably, mediation analysis provided mechanistic evidence that the mortality-increasing effect of lower LDL-C levels may be partially mediated through activation of systemic inflammation. CONCLUSION: Lower preoperative LDL-C levels are independently related with higher 30-day mortality following cardiac valve surgery, potentially mediated by the activation of inflammatory pathways.