Determination of Shock Index and Age Shock Index Cut-Off Points in Patients with ST-Segment Elevation Myocardial Infarction: SEMI-CI Study

Central Illustration
: Determination of Shock Index and Age Shock Index Cut-Off Points in Patients with ST-Segment Elevation Myocardial Infarction: SEMI-CI Study

Abstract

Background

Shock index (SI) and age shock index (ASI) are less frequently used for assessment of major adverse cardiovascular events (MACE) among patients with ST-segment elevation myocardial infarction (STEMI), and their reported cut-off points are controversial.

Objectives

We aimed to define proper cut-off value of these indices for MACE prediction among Iranian patients with STEMI.

Methods

This study was in the context of the ST-Elevation Myocardial Infarction Cohort in Isfahan (SEMI-CI) study. SI and ASI were calculated by division of heart rate (HR) over systolic blood pressure (SBP) and age multiplied by SI, respectively, in 818 subjects with STEMI. Receiver operating characteristic (ROC) curve analysis was used to determine optimal SI and ASI cut-off values. Chi-square test, independent t test, and analysis of variance were employed for nominal and numerical variables, as appropriate, with consideration of p values < 0.05. MACE was defined as a composite of non-fatal reinfarction, heart failure (HF), recurrent percutaneous intervention (PCI), rehospitalization for cardiovascular diseases, and all-cause mortality.

Results

Mean age was 60.70 ± 12.79 years (males: 81.7%). Area under curve (AUC) values from ROC curve analysis for SI and ASI were 0.613 (95% confidence interval [CI]: 0.569 to 0.657, p < 0.001) and 0.672 (95% CI: 0.629 to 0.715, p < 0.001), respectively. Optimal SI and ASI cut-offs were 0.61 (sensitivity: 61%, specificity: 56%) and 39.5 (sensitivity: 65%, specificity: 66%), respectively. Individuals with SI ≥ 0.61 or within the highest quartile (SI ≥ 0.75) had significantly higher frequency of one-year MACE compared to the reference group (34.7% versus 22.2%, p < 0.001 and 42.4% versus 20.6%, p < 0.05, respectively). Similar relations were observed in terms of ASI values (ASI ≥ 39.5 versus ASI < 39.5: 43.6% versus 17.3%, p < 0.001, ASI Q4 ≥ 47.5 versus ASI Q1 ≤ 28.8: 49% versus 16.6%, p < 0.05).

Conclusions

SI and ASI cut-off values of 0.61 and 39.5 could reliably predict MACE occurrence among Iranian patients with STEMI.

Myocardial Infarction; Sensitivity and Specificity; ROC Curve; Area Under Curve