Coronary Computed Tomographic Angiography in the Evaluation of Patients with Acute Chest Pain
Emergency room visits for evaluation of acute chest pain are common. Among those patients without known coronary artery disease, after acute coronary syndromes are excluded but disease is still suspected, further patient evaluation is generally indicated. Noninvasive testing prior to discharge, or soon after, is an approach often used to exclude the presence of clinically significant disease. Given its high negative prognostic value and ability to be quickly obtained, coronary CTA has been proposed as an approach in this setting.
The objective of this Assessment is to compare the net health outcomes following a coronary CTA diagnostic strategy to outcomes in other commonly used strategies for evaluating patients with acute chest pain and no known coronary artery disease presenting to the emergency room and found not to have evidence of acute coronary syndromes.
Randomized controlled trials and prospective observational studies reporting prognosis of coronary CTA in the emergency room setting were identified by searching the MEDLINE® (via PubMed) database through September 2011. A separate search was performed to identify studies reporting follow-up of incidental findings in any setting.
Randomized controlled trials conducted in the samples of the target population were included. Prospective observational studies including more than 100 patients reporting prognostic value of coronary CTA were also reviewed.
Two randomized, controlled trials and 2 prognostic studies were identified. The first trial evaluated 197 patients from a single center without evidence of acute coronary syndromes to coronary CTA (n=99) or usual care (n=98). Over 6 months’ follow-up, no cardiac events occurred in either arm. Invasive coronary angiography rates were somewhat higher in the coronary CTA arm (12.1% versus 7.1%). Diagnosis was achieved more quickly following coronary CTA. The second trial (CT-STAT) evaluated a similarly selected sample of 699 randomized patients from 16 centers—361 undergoing coronary CTA and 338 undergoing myocardial perfusion imaging. Over 6 months’ follow-up, there were no deaths in either arm, 2 cardiac events in the coronary CTA arm, and 1 in the perfusion imaging arm. Invasive coronary angiography rates were similar in both arms (7.2% after coronary CTA; 6.5% after perfusion imaging). A second noninvasive test was obtained more often following coronary CTA (10.2% versus 2.1%), but cumulative radiation exposure in the coronary CTA arm (using retrospective gating) was significantly lower—mean 11.5 versus 12.8 mSv. Time to diagnosis was shorter (mean 3.3 hours) and estimated emergency room costs were lower with coronary CTA. Two studies of patients from the target population reported no cardiac events following a negative coronary CTA after 12 months’ (n=481) and 24 months’ (n=368) follow-up.
Author’s Conclusions and Comments
Owing to the negative prognostic value of coronary CTA in this population, the test offers an alternative for patients and providers. Evidence obtained in the emergency setting, similar to more extensive results among ambulatory patients, indicates a normal coronary CTA appears to provide a prognosis as good as other noninvasive tests. Other important outcomes that need be considered in comparing technologies include invasive coronary angiography rates, use of a second noninvasive test, radiation exposure, and follow-up of any incidental lung findings. While there is uncertainty accompanying the limited trial evidence, it is reasonable to conclude that the invasive angiography rate following coronary CTA is similar to that following perfusion imaging. Evidence regarding comparative differences in obtaining a second noninvasive test is limited to CT-STAT and was greater following coronary CTA. Despite that difference, cumulative radiation exposure remained lower in the coronary CTA arm utilizing retrospective gating techniques. Given radiation reduction realized with prospective gating and spiral acquisition, radiation exposure accompanying coronary CTA will continue to decrease. Incidental findings following coronary CTA are common and lead to further testing without evidence for benefit.
While uncertainties exist and should be further studied, considering important outcomes in the patient population, the net health outcome following coronary CTA appears to be as good as that following other strategies.
Based on the available evidence, the Blue Cross and Blue Shield Association Medical Advisory Panel (MAP) made the following judgments about coronary CTA for patients with acute chest pain presenting to the emergency room with no known history of coronary artery disease, and found not to have evidence of acute coronary syndromes.
1. The technology must have final approval from the appropriate governmental regulatory bodies.
Coronary CTA is performed using multidetector-row CT (MDCT), and multiple manufacturers have received U.S. Food and Drug Administration (FDA) 510(k) clearance to market machines. Current machines are equipped with at least 64 detector rows. Intravenous iodinated contrast agents used for coronary CTA have also received FDA approval.
2. The scientific evidence must permit conclusions concerning the effect of the technology on health outcomes.
For patients with acute chest pain presenting to the emergency room with no known history of coronary artery disease, and found not to have evidence of acute coronary syndromes, there is sufficient evidence to permit conclusions concerning the effect of coronary CTA on relevant health outcomes.
3. The technology must improve the net health outcome; and
4. The technology must be as beneficial as any established alternatives.
By avoiding adverse cardiac events, use of coronary CTA in the target population will improve the net health outcome, as well as other strategies currently used in practice.
5. The improvement must be attainable outside the investigational settings.
Coronary CTA is widely available and used outside the investigational setting. The main clinical trial evaluating its use was primarily performed in real-world settings.
Based on the above, for patients with acute chest pain presenting to the emergency room with no known history of coronary artery disease, and found not to have evidence of acute coronary syndromes, coronary CTA meets the TEC criteria.
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chest pain; composite endpoint; Computed Tomography; CTA; diagnostic; dobutamine; echocardiography; ED; electrocardiograms; emergency department; evaluation; exercise; extracardiac; gated; incidental findings; ischemic; MACE; major adverse cardiac events; MPI; multidetector; multislice; myocardial; myocardial perfusion imaging; nondiagnostic; radiation exposure; radionuclide; rule out; SCCT; sestamibi; Society of Cardiovascular; stress; technetium; thrombolytic; transverse; treadmill; triage;