Abstract 13611: Prognostic Value of Shock Index in Patients Admitted With Non ST-Segment Elevation Myocardial Infarction: The ARIC Study Community Surveillance

Abstract

Introduction: Shock index (SI), defined as the ratio of heart rate (HR) to systolic blood pressure (SBP), is easily obtained and has been reported to predict all-cause mortality in acute myocardial infarction (AMI) hospitalizations, primarily among patients with STEMI. Large-scale investigations examining the prognostic value of SI in patients with NSTEMI are lacking. Methods: Hospitalizations for acute myocardial infarction were sampled from 4 US areas by the ARIC Study and classified by physician review. HR and SBP at first presentation were abstracted from the medical record. Pulseless patients, those with unobtainable SBP, and transfer patients were excluded. An SI value ≥0.7 was considered high. The TIMI risk score for NSTE-ACS was calculated using the established algorithm. Predictions of all-cause 28-day mortality were analyzed using receiver operating characteristics (ROC). Results: From 2000-2014, 18,301 weighted hospitalizations for NSTEMI patients were sampled and had vitals successfully obtained. Of these, 5753 (31%) had high SI (≥0.7). Patients with high SI were more often female (46% vs 39%) and older (65 vs 63 years), with more prevalent chronic kidney disease (40% vs. 32%), pneumonia (16% vs 8%), and complication by acute heart failure (42% vs 30%). However, the TIMI risk score was comparable for the 2 groups (4.3 vs. 4.2). Angiography (36% vs 58%), revascularization (19% vs 41%), and guideline-directed medications were less often administered to patients with high SI, and the 28-day mortality was nearly 3 times higher (13% vs 5%). Continuous values of SI were more predictive of 28-day mortality than the TIMI risk score, both overall (ROC-AUC: 0.68 vs 0.54; P <0.0001) and among the subset of patients who were revascularized (ROC-AUC: 0.72 vs. 0.56; P <0.0001). Conclusion: The SI outperformed the TIMI risk score for prediction of short-term mortality in patients hospitalized with NSTEMI, and may be useful for risk stratification in emergency settings.