Prognostic Utility of Killip Classification in Acute Myocardial Infarction: A Retrospective Cohort Analysis in Contemporary Clinical Practice

Background and Aims The Killip classification is a long-established bedside tool for early haemodynamic risk stratification in ST-elevation myocardial infarction (STEMI). However, its prognostic performance in contemporary STEMI populations treated with primary percutaneous coronary intervention (PCI) remains debated. We aimed to re-evaluate the association between Killip class and in-hospital mortality in a modern STEMI cohort. Methods We conducted a retrospective cohort study including 288 consecutive adults admitted with confirmed STEMI to the Hospital of the Lithuanian University of Health Sciences, Kaunas Clinics, between 1 January 2018 and 31 December 2021. STEMI was diagnosed according to the Fourth Universal Definition of Myocardial Infarction and ESC guidelines. The primary endpoint was in-hospital all-cause mortality. Independent predictors were identified using multivariable logistic regression. Model discrimination was assessed using receiver operating characteristic (ROC) analysis. Results Overall, in-hospital mortality was 18.2% (52/286 evaluable patients). Mortality increased substantially across Killip classes, from 1.0% in class I and 3.0% in class II to 69.6% in class IV (p < 0.001). In multivariable analysis, Killip class IV remained an independent predictor of in-hospital mortality (OR 60.94, 95% CI 15.98–232.46; p < 0.001), together with age, body mass index, troponin level, and asystole. The final model demonstrated excellent discrimination (AUC 0.969, 95% CI 0.945–0.992). Conclusions In this temporary STEMI cohort, Killip class IV was strongly and independently associated with in-hospital mortality. Although lower Killip classes showed limited prognostic separation, the Killip classification remains a rapid and clinically accessible tool for early risk assessment, particularly in haemodynamically unstable patients.