CT Angiography for Safe Discharge of Patients

Published - Written by Lisa Rosenbaum

Chest pain is the second most common reason for Emergency Room visits in this country, and although only 10-15% of patients admitted with chest pain are ultimately diagnosed with an acute coronary syndrome, the majority of patients get admitted. So common, in fact, is this admission diagnosis, that during cardiology rounds the other week, when I asked a resident how the patient was doing, she responded, “Oh fine, we’re just rome-eee-ing him,” (a new twist on the acronym “ROMI” for “Rule out MI”). Sure, on a busy floor, it’s easy enough to deem the “soft” rule-outs as unnecessary. But put yourself in the shoes of the ED docs. GI distress from a bad tuna sandwich can look a lot like the pain of unstable plaque. So how to decide who is safe to go home?

One method that has shown initial promise is Coronary CT Angiography, (CCTA), which in previous trials has demonstrated a robust negative predictive value among patients with low to intermediate risk of CAD. However, previous trials were not statistically powered to really answer the question as to whether CCTA was a safe strategy to effectively triage patients who required some further form of testing*. Thus, in this week’s NEJM, Litt et al present the results of “CT Angiography for Safe Discharge of Patients with Possible Acute Coronary Syndromes,” a “real-world” trial which aims to get at this lingering question.

The study, which included five sites, enrolled low to intermediate risk patients who presented to the ED with chest pain and possible ACS. Patients were 30 years or older, with symptoms possibly representing ACS, TIMI, (Thrombolysis in Myocardial Infarction), scores between 0 to 2, and ECGs that were without evidence of acute ischemia. The study was powered to address the hypothesis that patients without CCTA evidence of coronary-artery stenoses ≥50% would have a 30-day rate of cardiac death or myocardial infarction of less than 1%. Secondary outcomes included rates of discharge from the ED, length of stay if admitted, and 30-day rates of death, myocardial infarction, revascularization, and resource utilization.

Nearly 1400 patients were randomized in a 2:1 fashion to either CCTA, or usual care, (the treating team decided which tests, if any, were warranted). Of the 908 patients assigned to the CCTA strategy, 84% ultimately underwent CCTA, with tachycardia, an impediment to image acquisition, being the most common reason for failure to undergo testing. Notably, 64% of patients in the usual care arm underwent some form of diagnostic testing. Among the 640 patients found to have a negative CCTA, there were no deaths or MIs within 30 days of presentation, thus confirming the study’s primary hypothesis. Regarding secondary outcomes, it was notable that patients in the CCTA group were more likely to be discharged from the ED, had shorter length of stay when admitted, and were more likely to be identified as having coronary disease on invasive angiography.

But does this answer our question: is CCTA a safe strategy to effectively triage low risk chest pain patients in the ED? I think the jury’s still out. What this study suggests is, if your patient in the ED has a negative CCTA, he’s safe to go home. However, the study was not adequately powered to address whether CCTA should be the standard ED strategy to make triage decisions in these low risk chest pain patients. Unfortunately, studies of diagnostic testing among low risk patients are extremely challenging, as event rates are so low that more patients, more time, and more money, are required to really answer whether this strategy, per se, is safe. As we await further trials, I suspect we will continue to do a lot of ro-mee-ing on the floor.

* Goldstein JA, Chinnaiyan KM, Abidov A, et al. The CT-STAT (Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment) trial J Am Coll Cardiol 2011;58:1414-1422