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EDUCATION EXHIBIT |
1 Department of Radiology, University of Maryland, Baltimore, Maryland
Chest pain is among the most common causes for seeking treatment in the emergency room (ER). In a 2003 survey from the Centers for Disease Control and Prevention, chest pain was the second most frequent symptom leading to an ER presentation, after stomach pain; it accounted for approximately 5.8 million (5.1%) of 113 million ER visits in the United States (1).
The paramount challenge in the assessment of a patient with chest pain is to distinguish between life-threatening and comparatively benign causes of pain. Potentially life-threatening conditions include aortic dissection and pulmonary embolism, but by far the most important of them is the acute coronary syndrome (ACS). ACS is defined by the American Heart Association as a spectrum of coronary artery–related ischemic conditions that comprises ST-segment-elevation acute myocardial infarction, non–Q wave or subendocardial infarction, and unstable angina (2).
Patients who present with acute chest pain can be divided into three groups, as a first approximation, based on their initial medical history, electrocardiographic findings, and cardiac enzyme levels. Patients with ACS are at high risk and, according to recommendations by the American College of Cardiology and American Heart Association, are to be referred emergently or urgently for coronary angiography (2). A second group of patients, after the initial assessment, can readily be characterized as having a benign cause of chest pain and usually are discharged early. A third large cohort can be identified in whom the symptoms of chest pain are atypical for ACS or whose initial electrocardiographic tracings and cardiac enzyme levels are either normal or nonspecific. The outcome of triage for patients in this group is uncertain, but the group probably includes many of the 2%–4% of patients who are inappropriately discharged from the ER and later found to have ACS (3).
The limitations of current methods of chest pain evaluation have led to the exploration of other techniques for achieving a more rapid and definitive assessment. Radionuclide perfusion testing and echocardiography are being used increasingly in the ER to assist in the stratification of patients with chest pain. Other investigators have described the potential utility of electron-beam computed tomography (CT) and magnetic resonance imaging for patient triage (4,5).
Recent developments in multidetector CT technology hold forth the possibility that this modality will prove valuable in evaluating chest pain in the ER. The current generation of multidetector CT scanners can produce 64 sections per rotation, with a spatial resolution of 0.5–0.6 mm and temporal resolution of 50–100 msec. These newly achieved specifications permit routine visualization of the major coronary arteries with sensitivity and specificity well above 80% (6). The article by Hoffmann et al in this issue of RadioGraphics provides a cogent perspective from which to view the capabilities and challenges of multidetector CT in the evaluation of chest pain in the ER (7).
The introduction to the article is a review of the current difficulties in diagnosing ACS in the ER, including issues of inappropriate admission and discharge and medicolegal consequences. This review is followed by a description of multi-detector CT protocols and coronary anatomy. In a section about cardiac CT findings, the authors make the important point that while coronary artery stenosis is the most widely accepted finding, it may not be the only relevant finding. Multidetector CT also provides information about myocardial function and perfusion. Coronary artery plaque characterization may eventually prove indispensable for stratifying ER patients according to their risk for ACS (7).
Perhaps the most intriguing issue discussed in this article is the appropriate scope for the use of multidetector CT in the ER triage of patients with chest pain. Two competing strategies have been advocated. One is the so-called "one-stop shop" or "triple rule-out," in which multidetector CT is used to achieve a comprehensive evaluation of potential causes of chest pain, including both ACS and morbid noncoronary diseases such as aortic dissection and pulmonary embolism. The second approach is to restrict the evaluation to cardiac CT and assessment of ACS.
Proponents of the first strategy point to the already widespread use of CT to evaluate the aorta and pulmonary arteries and assert that coronary artery imaging can be achieved with little compromise in regard to accuracy. We recently conducted a pilot study to test this approach. In our "one-stop shop" multidetector CT study of 69 patients with an intermediate risk for ACS, we found overall sensitivity and specificity of 87% and 96%, respectively, for detection of all (cardiac and noncardiac) causes of chest pain (8). The results of our study suggest that negative findings at multidetector CT may help accomplish the earlier discharge of patients from the ER. This study, which must be regarded as preliminary, was limited by the use of 16-section multidetector CT scanners with relatively long imaging times.
Advocates of the use of dedicated cardiac CT to assess ER patients with chest pain caution that a comprehensive protocol will require a larger quantity of intravenous contrast material with a longer duration of injection to optimize opacification of the pulmonary arteries and aorta. A related concern is that the use of a nondedicated or general cardiac CT protocol may compromise the quality of coronary artery depiction. An additional issue cited in the current article is the variable extent of overlap in clinical manifestations between ACS and noncoronary conditions, such that a comprehensive CT angiographic evaluation often may not be necessary.
It is conceivable that if multidetector CT becomes a part of the ER chest pain armamentarium, both approaches may ultimately be validated and used in their respective clinical scenarios, but this conclusion is speculative. It is undeniable, however, that the use of multidetector CT in the ER patient presenting with chest pain is the subject of intense and ongoing evaluation that may lead to a clinical paradigm shift (9–11). The article by Hoffmann and colleagues provides a glimpse into this exciting area of research.
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