Early Hemodynamic Instability and Major Adverse Cardiovascular Events Among Acute Coronary Syndrome Patients Presenting to the Emergency Department: A Retrospective Cohort Analysis

Acute coronary syndrome (ACS) remains a major contributor to cardiovascular mortality despite advances in emergency cardiovascular intervention and coronary revascularization strategies. This retrospective cohort study evaluated the association between early hemodynamic instability and major adverse cardiovascular events (MACE) among 1,248 ACS patients admitted between January 2023 and December 2025. Patients were categorized into stable and unstable groups based on early emergency department hemodynamic assessment including blood pressure, lactate level, Killip classification, vasopressor requirement, and cardiac output estimation. The primary outcome consisted of 30-day MACE including cardiovascular mortality, recurrent myocardial infarction, cardiogenic shock, ventricular arrhythmia, and urgent revascularization. A total of 372 patients (29.8%) demonstrated early hemodynamic instability and experienced significantly higher rates of cardiogenic shock, ventricular arrhythmia, mechanical ventilation, ICU admission, and 30-day mortality compared with stable patients. Multivariable regression analysis identified serum lactate >4 mmol/L (adjusted OR 3.42; 95% CI 2.10-5.11), systolic blood pressure <90 mmHg (adjusted OR 2.96; 95% CI 1.88-4.47), and left ventricular ejection fraction <35% (adjusted OR 2.71; 95% CI 1.77-4.09) as independent predictors of MACE. Early hemodynamic instability was strongly associated with poor short-term cardiovascular outcomes, suggesting that integrated emergency hemodynamic profiling may improve early risk stratification and facilitate timely cardiovascular intervention.