CT Coronary Angiography in ER Patients with Chest Pain

Abstract & Commentary

By Andrew J. Boyle, MBBS, PhD, Assistant Professor of Medicine, Interventional Cardiology, University of California, San Francisco. Dr. Boyle reports no financial relationships relevant to this field of study.

This article originally appeared in the May 2012 issue of Clinical Cardiology Alert. It was edited by Michael H. Crawford, MD, and peer reviewed by Ethan Weiss, MD. Dr. Crawford is Professor of Medicine, Chief of Clinical Cardiology, University of California, San Francisco, and Dr. Weiss is Assistant Professor of Medicine, Division of Cardiology and CVRI, University of California, San Francisco. Dr. Crawford reports no financial relationships relevant to this field of study, and Dr. Weiss is a scientific advisory board member for Bionovo.

Source: Litt HI, et al. CT angiography for safe discharge of patients with possible acute coronary syndromes. N Engl J Med 2012;366:1393-1403.

Patients presenting to the emergency department (ED) with chest pain are often admitted to "rule out" myocardial infarction (MI). Many of the patients are subsequently found to have noncardiac causes of chest pain. The best method to differentiate noncardiac chest pain from acute coronary syndromes (ACS) remains unknown. Early differentiation between these entities would facilitate discharge directly from the ER and has the potential to prevent millions of needless admissions. However, early discharge must be safe. The evolution of computed tomography (CT) now allows visualization of the coronary arteries by coronary CT angiography (CCTA). This technique requires a regular heart rhythm, the ability to receive nitroglycerin and beta-blockers at the time of the scan, and the ability to hold one's breath in order to obtain adequate images. Litt and colleagues performed a multicenter, prospective, randomized trial comparing two strategies of assessing patients who present to the ED with chest pain: One involves the use of CCTA, the other involves usual care. Their results were presented at the recent American College of Cardiology Meeting and were recently published in the New England Journal of Medicine.

Patients older than the age of 30 presenting with symptoms compatible with a possible ACS were considered eligible for the study if they had an initial ECG with no ischemic changes, had a low-to-intermediate clinical risk profile (TIMI Risk Score of 0-2), and the treating physician thought they required further testing or admission to rule out ACS. Exclusion criteria were the need for admission for other reasons regardless of the cause of the chest pain, recent normal CCTA, coronary angiogram, and any contraindication to CCTA. Usual care was at the discretion of the physician. Patients could be randomized before the results of the first troponin were available. CCTAs were reported by experienced clinicians, and were graded as negative (normal or stenosis < 50%) or positive (stenosis ≥ 50%). Importantly, the patients with < 50% stenosis had a follow-up troponin 90-180 minutes after the first, and if it was normal, they could be discharged.

The authors enrolled 1370 patients and randomized them in a 2:1 fashion to CCTA (n = 908) vs. usual care (n = 462). Baseline characteristics were similar in the two groups. Of the 908 patients assigned the CCTA, 767 actually underwent CCTA: 10.4% had a positive result (≥ 50% stenosis), 6.1% had an indeterminate result, and 640 patients (83.4%) had a negative result (< 50% stenosis). Most patients in the usual care group underwent stress testing. MI occurred in 1% of the CCTA group and 0.9% of the usual care group (P = NS) during hospitalization. There were no differences in the rates of invasive coronary angiography or revascularization.

Patients in the CCTA group were more likely to be discharged from the ED (50% vs. 23%) and were more likely to be diagnosed with coronary artery disease (9% vs. 4%). In the 30 days after discharge, MI occurred in 0.1% of the CCTA group and 0.4% of the usual care group (P = NS). There was no difference on the rate of repeat hospitalization. The authors conclude that a CCTA-based strategy for low-to-intermediate-risk patients presenting with possible ACS appears to allow the safe, expedited discharge from the ED in patients who would otherwise be admitted.

Commentary

ED presentations with chest pain are common and costly. There are millions of admissions to rule out MI each year that subsequently turn out to reveal noncardiac causes of chest pain. The CCTA-guided approach outlined by Litt and colleagues resulted in more patients being directly discharged from the ED, but no difference in the rates of invasive angiography, revascularization, or subsequent death or MI. This has the potential to decompress monitored hospital beds and busy EDs, and to realize significant cost savings. Discharge of chest pain patients from the ED is always daunting for ED physicians, as the prospect of missing an MI could result in poor patient outcomes and a potential lawsuit. Litt and colleagues identified 83% of low-to-intermediate risk patients presenting with possible ACS as having negative scans (< 50% coronary stenosis). With a combination of negative troponin and a negative CCTA, they were able to discharge 50% of patients from the ED, and there was a very low rate of MI in these patients in the 30 days after discharge, suggesting this approach is safe.

The results of this study are congruous with prior CCTA studies in the ED, such as the ROMICAT study. In appropriate patients, 64-slice CT scanners are known to be accurate, and several studies have now shown that those with negative scans have very low event rates after discharge directly from the ED. In addition to the clinical information that is relevant for the index admission, CCTA provides valuable insight about the presence of plaque that may guide future preventive strategies, such as aspirin and statin therapy, in appropriate patients. A negative stress test does not provide such information, potentially missing an opportunity for aggressive preventive measures. Thus CCTA provides important information acutely, but also for the long-term follow-up of the patient. There are several limitations to this study. First, a formal cost-effectiveness analysis was not presented and is warranted. Second, we are not told whether the CCTA scans were prospectively or retrospectively gated. Retrospective gating is associated with similar levels of radiation to nuclear testing, but prospective gating significantly reduces the radiation to the patient (by around 70%). Dedicated teams can significantly reduce the radiation to patients by instituting a prospective gating policy. Overall, this study and others like it demonstrate the clinical utility of CCTA as an up-front approach in the assessment of patient with possible ACS.