6. Kucher N. Catheter embolectomy for acute pulmonary embolism. Chest. 2007;132(2):657-663.
7. Initial certification: vascular/interventional. American Board of Radiology Web site. http://www.theabr.org/ic-vir-landing. Accessed September 24, 2013.
Figure 2. Surface shaded display image of a virtual colonoscopy.
Evaluation of Chest Pain in the Emergency Department by Coronary CT Angiography
James K. Min, MD
Dr Min is director of the Institute of Cardiovascular Imaging at New York-Presbyterian Hospital/Weill-Cornell Medical College, New York.
In the United States each year, approximately 6 million patients present with complaints of chest pain suspicious for acute coronary syndromes (ACS), including unstable angina and myocardial infarction.1 Most of these patients are diagnosed with noncardiac conditions, and nearly half are due to noncardiac etiology. There are an array of diagnostic tests to identify and exclude patients with suspected ACS, such as medical history, cardiac enzyme measurements, electrocardiographic changes, and clinical risk scores. For those with nonnegligible risk for ACS for which this condition cannot be definitively diagnosed or excluded, many are often admitted to the hospital for further testing and observation. Among these patients, less than 30% are found to have ACS. And yet, despite these very careful clinical pathways, between 2% and 8% of patients with ACS are unknowingly discharged to home.2
In recent years, coronary computed tomography angiography (CCTA) has emerged as a noninvasive method that permits direct anatomic visualization of coronary atherosclerosis and luminal stenosis.3 Since the introduction of 64-multidetector row CT scanners in 2005, there have been significant advances in CT technology that now allow for reliable performance of CCTA with very low-dose radiation. Pertaining to the former, improvements in spatial resolution, temporal resolution, and volume coverage enable evaluation of coronary arteries at the submillimeter level, and can be performed in approximately 1 to 5 seconds. Concomitant to the progress in CT technology has been the parallel developments in radiation-dose reduction. As compared to the background radiation exposure of an individual living at sea level for 1 year (~3 millisieverts of radiation), current generation CCTA can be performed at doses <1 millisieverts, with doses approximating a screening mammogram now achievable.
 |  |  | ||
Figure. Volume-rendered coronary computed tomographic angiography showing the coronary vascular bed and myocardium (A); normal right coronary artery without evidence of atherosclerosis (B); and (C) left anterior descending artery with mild nonobstructive calcified plaque (white area). | ||||
The diagnostic accuracy of CCTA against invasive coronary angiography has been tested in several prospective multicenter trials.3 For patients without known but suspected coronary artery disease (CAD), the sensitivity and negative predictive value has ranged between 95% to 99%—that is, CCTA can exclude anatomically obstructive CAD with near 100% certainty (Figure). It is these diagnostic performance characteristics that have encouraged several investigators to evaluate the use of CCTA in the diagnostic algorithm of patients presenting to the ED with acute chest pain—the primary intent being to identify sufficiently low-risk patients without significant CAD who can be safely discharged home.
Since 2011, three prospective multicenter randomized controlled trials have evaluated the incorporation of CCTA into a diagnostic chest pain pathway, as compared to standard-of-care algorithms.4-6 Now comprising more than 3,000 patients, these trials have demonstrated remarkably consistent results, with a reduced time-to-diagnosis of 40% to 50%, reduced lengths of stay in the ED of 25%, and reduced ED costs of 20% to 40%. Importantly, these salient effects on resource utilization and economics were underscored by exceptionally safe outcomes, which never exceeded that of the standard of care. Several studies to date have subsequently assessed the duration of safety conferred by a normal CCTA, or its “warranty period.” These studies have shown the warranty period to last at least 7 years for major adverse cardiac events and mortality.7 Moreover, they also engender hope that the chest pain pathways used for millions of Americans annually can indeed be improved, with CCTA playing an essential role.
As its technology continues to iterate, the diagnostic and prognostic performance of CCTA will invariably continue to improve. However, even at present, CCTA is robust and more accurate for exclusion of CAD when compared to other traditional methods of evaluation, and its use for patients presenting to the ED with chest pain improves throughput, reduces costs, and maximizes patient safety.
References
1. Pitts SR, Niska RW, Xu J, Burt CW. National Hospital Ambulatory Medical Care Surviva: 2006 emergency department summary. Natl Health Stat Report. 2008;7:1-38.
2. Pope JH, Aufderheidi TP, Ruthazer R, et al. Missed diagnoses of acute cardiac ischemia in the emergency department. N Engl J Med. 2000;342(16):1163-1170.
3. Min JK, Shaw LJ, Berman DS. The present state of coronary computed tomography angiography: a process in evolution. J Am Coll Cardiol. 2010;55(:957-965.