Comparison of Traditional Cardiovascular Risk Models and Coronary Atherosclerotic Plaque as Detected by Computed Tomography for Prediction of Acute Coronary Syndrome in Patients With Acute Chest Pain

Early triage of patients presenting to the emergency department (ED) with the chief complaint of chest pain suggestive of acute coronary syndrome (ACS) remains a diagnostic challenge. Elements of the chest pain history are associated with increased or decreased likelihoods of ACS.1 Sensitive troponin assays and initial electrocardiogram (ECG) provide important information in the initial decision.2–4 However, clinical history, a single set of cardiac biomarkers, and the initial ECG alone or in combination cannot identify the group of patients who can be safely discharged without further diagnostic testing. The percentage of patients who present to the ED with ACS and are inappropriately discharged is low (around 2%).5 However, discharged subjects have a two to three times increased risk of dying.5 Therefore, the standard of care for subjects with acute chest pain typically includes serial ECG and cardiac biomarkers followed by a stress test with or without imaging.6–9 The standard work-up decreases the risk of diagnostic errors. However, the complete “rule-out myocardial infarction” protocol is time-consuming and costly. Clinical risk scores (e.g., Thrombolysis in Myocardial Infarction [TIMI],10 Goldman,11 and Sanchis12) and triage algorithms are available to predict adverse cardiac events and facilitate the triage decision.10–14 However, the performance of these tools is not optimal.15 Risk scores used for the prediction of future cardiovascular events (e.g., Framingham Risk Score) and risk factors for coronary artery disease (CAD) have only limited value for the confirmation or exclusion of ACS in the ED.16,17 Coronary computed tomography angiography (CTA) permits detection of coronary stenosis and atherosclerotic plaque with high sensitivity, specificity, and negative predictive value.18–22 In patients who present to the ED with acute chest pain, exclusion of a significant coronary stenosis and plaque by coronary CTA has a high negative predictive value for ACS.23–32 In contrast, patients with a significant coronary stenosis detected by computed tomography (CT) have a high likelihood of ACS. However, there is a significant proportion of patients in whom coronary atherosclerotic plaque is present, without significant stenosis. In the Rule Out Myocardial Infarction Using Computer-Assisted Tomography (ROMICAT) trial, we observed approximately one-third (113 of 368) of patients with nonobstructive plaque.28 The quantitative assessment of coronary plaque and the combination of coronary plaque burden with clinical risk scores could possibly improve the accuracy for the diagnosis as well as the exclusion of ACS. We determined the association of four dichotomized (low- vs. intermediate- to high-risk categories) clinical risk scores and of the coronary atherosclerotic plaque burden as detected by CT with the outcome of ACS in patients who presented to the ED with the chief complaint of chest pain and inconclusive initial evaluation (negative cardiac biomarkers, nondiagnostic ECG changes), and no history of CAD. We hypothesized that the combination of risk scores and plaque burden improves the discriminatory capacity for the diagnosis of ACS.