Shock Index: A Simple Clinical Parameter for Quick Mortality Risk Assessment in Acute Myocardial Infarction

Background: Primary percutaneous coronary intervention (PCI) has become the preferred reperfusion strategy in patients with ST-segment elevation myocardial infarction and cardiogenic shock. Early identification of patients at risk for developing cardiogenic shock allows rapid decision making to determine reperfusion and transportation to a PCI centre. The aim of this analysis was to evaluate shock index (SI) as a marker for patients at risk of cardiogenic shock. Methods: A total of 644 consecutive patients (73% male) with acute myocardial infarction with ST elevations were analyzed retrospectively. Primary PCI was performed in 92% of patients, and 7% of patients underwent rescue PCI. The SI parameter was defined as the ratio of heart rate to systolic blood pressure at hospital admission. Results: SI (odds ratio [OR], 81.26; 95% confidence interval [CI], 9.76-676.51; P < 0.001), age (OR, 1.17; 95% CI, 1.08-1.26; P < 0.001), and diabetes (OR, 4.94; 95% CI, 1.44-16.97; P < 0.011) were independent predictors of mortality. In the group of patients with SI >= 0.8, 20% died, whereas in the group with SI < 0.8, 4% of patients died (P < 0.01). Conclusions: The proposed clinical parameter SI correlates with patients' prognosis and could therefore be used as a simple indicator of mortality risk of acute myocardial infarction. The simplicity of this proposed index makes its use accessible in large-scale clinical practices for risk stratification during first contact with patients.