Shock Index and TIMI Flow as Predictors of 30-Day Major Adverse Cardiovascular Events in Patients with Acute Coronary Syndrome: A Prospective Cohort Study

Background: Rapid risk stratification in acute coronary syndrome (ACS) is crucial, but conventional scores have limitations in emergency settings. We evaluated admission shock index (SI) as a predictor of 30-day major adverse cardiovascular events (MACE) in ACS patients undergoing percutaneous coronary intervention (PCI). Materials and Methods: This prospective cohort study included 172 patients with ACS undergoing PCI. SI was measured on admission in the catheterization laboratory before intervention. The primary endpoint was 30-day MACE, a composite including cardiovascular death, cardiogenic shock, and recurrent myocardial infarction. A receiver operating characteristic curve was used to determine the optimal SI cutoff, and multivariable Cox regression analysis identified independent predictors of MACE. Results: The optimal SI cutoff for predicting MACE was ≥0.8 (area under curve: 0.793, P < 0.001), with a sensitivity of 74.1% (95% CI: 53.7–88.9%) and specificity of 77.9% (95% CI: 70.1–84.5). After multivariable adjustment, an admission SI ≥ 0.8 remained a strong, independent predictor of MACE (adjusted HR: 4.24; 95% CI: 1.67–10.81; P = 0.002). While post-PCI thrombolysis in myocardial infarction (TIMI) flow was not an independent predictor ( P = 0.102), a significant statistical interaction was observed between SI and TIMI flow ( P < 0.001). Conclusion: Admission SI is a simple and strong predictor of 30-day MACE in ACS patients undergoing PCI. Its prognostic value persists even in patients who achieve successful epicardial reperfusion, highlighting a significant interaction where initial systemic hemodynamic compromise is a dominant predictor of poor outcomes.