The HEART Score for Suspected Acute Coronary Syndrome in U.S. Emergency Departments

Acute coronary syndrome (ACS) is a leading cause of morbidity and mortality worldwide, resulting in millions of emergency department (ED) visits and billions in hospital costs each year (1). However, no evidence suggests that the current paradigm of acute care, which includes serial evaluation of electrocardiograms, cardiac biomarkers, and cardiac stress testing, improves patient outcomes (2). Objective risk scores may help clinicians identify which patients require further hospital-based testing, and who could be safely discharged.

HEART (History, Electrocardiogram, Age, Risk factors, Troponin) is a 0- to 10-point scoring system developed and validated in Europe and recommended by the American Heart Association (3). Scores are categorized as low (0 to 3), moderate (4 to 6), and high risk (7 to 10) to inform clinical decision making. However, there are no large prospective studies reporting its accuracy in a U.S. population (4). Our study aims to describe HEART accuracy for prospectively collected HEART scores to report patient outcomes for low-risk, moderate-risk, and high-risk patient encounters in Southern California community EDs.

We conducted a prospective study of all suspected ACS ED encounters at 15 community hospitals. Study sites were operated by Kaiser Permanente Southern California (KPSC). KPSC is an integrated health system that, in May 2016, implemented decision support to capture HEART scores and incorporate this tool into routine ED care. All ED encounters for Kaiser members (≈ 80% of ED visits) with a prospective HEART score documented by the treating emergency physician were included. Encounters were excluded if patients were <18 years of age, died in the ED, transferred to another hospital, had a do not resuscitate/hospice status, or had an ED acute myocardial infarction (MI) diagnosis. All sites use the same troponin laboratory assay (Access AccuTnI+3, Beckman Coulter, Brea, California) to calculate the HEART score. The primary outcome was 30-day all-cause mortality or acute MI. The secondary outcome was 6-week major adverse cardiac event rates, which also included any coronary revascularization procedures. C-statistics were calculated for the HEART score’s ability to predict the primary and secondary outcomes.

A total of 29,196 ED encounters met the study criteria, and most (59%) had low-risk (0 to 3) HEART scores (n = 16,703). The overall frequency of 30-day MI and death was 0.6%, with increasing frequencies related to higher HEART scores (Figure 1). The percent of patients having an adverse event ranged from 0% (0 of 1,794) for encounters with a HEART score of 0 to 11.1% (1 of 9) for a HEART score of 10. ED encounters for patients with low-risk HEART scores (0 to 3) had a primary event that occurred in 35 of 16,703 (0.2%; 95% confidence interval [CI]: 0.1 to 0.3) for patients at low risk, 114 of 11,302 (1.0%; 95% CI: 0.8 to 1.2) for those at moderate to risk (4 to 6), and 36 of 1,191 (3.0%; 95% CI: 2.1 to 4.0) for those at high risk (7 to 10).

Figure 1:

Results validating HEART using prospectively collected scores in a large U.S. patient population. We report 30-day all-cause mortality or acute myocardial infarction (AMI) events after an ED visit stratified HEART score (0–10). Additionally, 6-week major adverse cardiac events (MACE) stratified by low, moderate and high-risk HEART scores.

The C-statistic describing the accuracy of the HEART score for the primary outcome was 0.76 (95% CI: 0.72 to 0.79). In the sensitivity analysis including the ED encounters for patients with an MI, the c-statistic was 0.88 (95% CI: 0.87 to 0.89). Likelihood ratios for low-risk, moderate-risk, and high-risk HEART scores were 0.3, 1.6, and 4.9, respectively. The overall proportion of 6-week major adverse cardiac events was 1.5%, with most events attributable to revascularization (234 of 448; 52.2%) (C-statistic 0.78; 95% CI: 0.77 to 0.80).

Our results demonstrate that the majority of ED patients with suspected ACS fall below the 1% risk threshold of a 30-day adverse event. If a HEART score of 5 or below were chosen as the low-risk threshold (≈ 1% 30-day MI or death risk) (5), this would account for 89% of the ED encounters, representing a large number of visits that might safely avoid hospitalization or noninvasive cardiac stress testing. Given the ever-increasing evidence that questions the benefits of noninvasive testing or hospitalization, using a HEART score of 5 or below as the low-risk threshold appears to be a rational approach that may avoid unnecessary testing and revascularization procedures in-hospital, and could certainly improve the affordability of care.