Major adverse cardiac event rates in moderate‐risk patients: Does prior coronary disease matter?

BACKGROUND: Despite negative troponins and nonischemic electrocardiograms (ECGs), patients at moderate risk for acute coronary syndrome (ACS) are frequently admitted. The objective of this study was to describe the major adverse cardiac event (MACE) rate in moderate‐risk patients and how it differs based on history of coronary artery disease (CAD). METHODS: A secondary analysis of the HEART Pathway implementation study was conducted. This prospective interrupted time‐series study accrued adults with possible ACS from three sites (November 2013–January 2016). This analysis excluded low‐risk patients determined by emergency providers' HEART Pathway assessments. Non–low‐risk patients were further classified as high risk, based on elevated troponin measures or ischemic ECG findings or as moderate risk, based on HEAR score ≥ 4, negative troponin measures, and a nonischemic ECG. Moderate‐risk patients were then stratified by the presence or absence of prior CAD (MI, revascularization, or ≥70% coronary stenosis). MACE (death, myocardial infarction, or revascularization) at 30 days was determined from health records, insurance claims, and death index data. MACE rates were compared among groups using a chi‐square test and likelihood ratios (LRs) were calculated. RESULTS: Among 4,550 patients with HEART Pathway assessments, 24.8% (1,130/4,550) were high risk and 37.7% (1715/4550) were moderate risk. MACE at 30 days occurred in 3.1% (53/1,715; 95% confidence interval [CI] = 2.3% to 4.0%) of moderate‐risk patients. Among moderate‐risk patients, MACE occurred in 7.1% (36/508, 95% CI = 5.1% to 9.8%) of patients with known CAD versus 1.4% (17/1,207, 95% CI = 0.9% to 2.3%) in patients without known prior CAD (p < 0.0001). The negative LR for 30‐day MACE among moderate‐risk patients without prior CAD was 0.08 (95% CI = 0.05 to 0.12). CONCLUSION: MACE rates at 30 days were low among moderate‐risk patients but were significantly higher among those with prior CAD.