Incremental Value of Computed Tomography in Triaging Emergency Department Patients With Acute Chest Pain

Abstract

In North America, more than 5 million patients per yearpresent to the emergency department (ED) with acute chestpain [1]. Early triage is essential for both prognosis andtreatment; however, current management methods do noteffectively assess those patients in whom initial cardiacbiomarkers and electrocardiogram (ECG) changes areinconclusive. Although 80% of patients admitted to thehospital undergo extensive testing, which often provenoncardiac causes of chest pain, 2%-8% of dischargedpatients inadvertently have acute coronary syndrome(ACS) [2].At the same time, it is important to note that chest painmay result from a broad range of etiologies, includingcardiac, pulmonary, musculoskeletal, and psychologicalorigins. As such, a thorough history and physical examina-tion of the patient should be undertaken to narrow thedifferential diagnosis before imaging is requested. In thisway, clinicians may be able to arrive at a diagnosis withoutthe need for unnecessary imaging studies.Recent advances in multidetector computed tomography(MDCT) and the advent of the triple-rule-out (TRO) protocolprovide noninvasive visualization of coronary and/orpulmonary arteries, thoracic aorta, and the other intrathoracicstructures. By evaluating both coronary and noncoronarydisease, the TRO scan provides a cost-effective diagnosticstudy for acute chest pain [3]. The aim of this article is toprovide an overview of the imaging modalities used in theevaluation of patients presenting with acute chest pain, witha focus on the role and added value of MDCT.Initial AssessmentTraditionally, the initial assessment in the ED entailsa thorough history, physical examination, and ECG, as wellas measurement of cardiac biomarkers. However, up to 28%of patients present with atypical chest pain or delayed find-ings [4], which limit the sensitivity of traditional assess-ments. Up to 20% of patients with ACS have atypical ornonexistent chest pain, and up to 10% of patients initiallydiagnosed with an myocardial infarction are later found tohave normal or nonspecific ECG findings [4]. Moreover, themeasurement of troponin has high specificity but lowsensitivity for an ACS in the initial hours of presentation.Due to these diagnostic errors, the American College ofCardiology (ACC) and American Heart Association (AHA)have published guidelines on risk stratification for patientswith ACS. Patients in the first category (low risk) and secondcategory (high risk) pose no major difficulty to diagnosis andtreat [5]. However, patients in the third category (interme-diate risk) are more difficult to triage [5]. This group consistsof patients often in their fourth through sixth decade of life,with findings that tend to be indeterminate, nonspecific, oratypical, with few if any risk factors. Imaging has thegreatest potential for risk stratification and clinical decisionmaking in this challenging category.Standard Diagnostic TestingCurrent AHA-ACC guidelines recommend a multimodalapproach to diagnostic testing [5]. For early triage, functionaltests are of limited value because of the requirement forserial negative biomarkers, the specific expertise ofpersonnel, and the frequency of nondiagnostic tests [1]. The