Higher Killip class at presentation is associated with increased in-hospital mortality in patients with ST-elevation myocardial infarction (STEMI). This retrospective cohort study, published in the European Heart Journal Open, included 288 consecutive adults with STEMI admitted between January 2018 and December 2021 to evaluate the association between Killip class and in-hospital mortality.

STEMI diagnosis followed the Fourth Universal Definition of Myocardial Infarction and European Society of Cardiology (ESC) guidelines. The primary endpoint was in-hospital all-cause mortality. Independent predictors were identified using multivariable logistic regression, and model discrimination was assessed using receiver operating characteristic (ROC) analysis.

Among 286 evaluable patients, in-hospital mortality was 18.2%. Mortality increased 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 independently associated with in-hospital mortality (odds ratio [OR] 60.94; 95% confidence interval [CI], 15.98-232.46; P < 0.001), along with age, body mass index (BMI), troponin level, and asystole. The model demonstrated high discrimination, with an area under the curve (AUC) of 0.969 (95% CI, 0.945-0.992).

Killip Class IV was strongly associated with in-hospital mortality, while lower Killip classes showed limited separation in risk. The classification remains a clinically accessible tool for early risk assessment.