Modified shock index: A bedside clinical index for risk assessment of ST-segment elevation myocardial infarction at presentation

Introduction: Prompt identification of higher-risk patients presenting with ST-segment elevation myocardial infarction (STEMI) is crucial to pursue a more aggressive approach. Objective: We aimed to assess whether the modified shock index (MSI), the ratio of heart rate to mean arterial pressure, could predict six-month mortality among patients admitted with STEMI. Methods: A retrospective observational cohort study was performed in a single center including 1158 patients diagnosed with STEMI, without cardiogenic shock on admission, between July 2009 and December 2014. They were divided into two groups: group 1-patients with MSI < 0.93 (72%); group 2-patients with MSI >= 0.93 (28%). The primary endpoint was six-month all-cause mortality. Results: MSI >= 0.93 identified patients who were more likely to have signs of heart failure (p= 0.002), anemia (p< 0.001), renal insufficiency (p= 0.014) and left ventricular systolic dysfunction (p= 0.045). They more often required inotropic support (p< 0.001), intra-aortic balloon pump (p< 0.001) and mechanical ventilation (p< 0.001). Regarding in-hospital adverse events, they had a higher prevalence of malignant arrhythmias (p= 0.01) and mechanical complications (p= 0.027). MSI= 0.93 was an independent predictor of overall six-month mortality (adjusted HR 2.00, 95% CI 1.20-3.34, p= 0.008). Conclusion: MSI was shown to be a valuable bedside tool which can rapidly identify high-risk STEMI patients at presentation. (C) 2018 Sociedade Portuguesa de Cardiologia. Published by Elsevier Espana, S.L.U. All rights reserved.