ACC 2015: CTA comparable to functional tests to diagnose CAD

Results of a clinical trial reported this past weekend at the American College of Cardiology’s (ACC) annual meeting held in San Diego confirmed what radiologists have long been contending. Not only is a coronary CT angiography (CTA) exam a comparable alternative to stress testing among low- to intermediate-risk patients presenting with chest pain, but the cumulative radiation exposure per patient can be lower.

The Prospective Multicenter Imaging Study for Evaluation of Chest Pain (PROMISE) study was the first randomized control clinical trial to evaluate clinical outcomes in patients who either had a coronary CTA (an anatomical strategy) or underwent exercise electrocardiography (ECG), exercise imaging, or pharmacologic imaging (functional strategies).¹ A total of 10,003 patients with chest pain suspicious for coronary artery disease (CAD) but no history of prior coronary disease with a mean age of 61 years were recruited by 193 community-based health centers. They were followed for a median of two years.

The objective of the study was to compare health outcomes in patients who presented with new symptoms suggestive of CAD that required further evaluation. The primary hypothesis of the study was that the clinical outcomes in patients assigned to anatomical testing with the use of CTA would be superior to those in patients assigned to functional testing, according to lead author Pamela Douglas, M.D., professor of medicine -cardiology at Duke University School of Medicine in Durham, NC and director of the imaging program of the Duke Clinical Research Institute.

The study’s primary end point was a composite of major cardiovascular events that included death from any cause, myocardial infarction, hospitalization for unstable angina, and major complication of cardiovascular procedures or diagnostic testing that occurred within 72 hours for any event over the duration of follow-up. Both groups experienced a statistically comparable number of events. A total of 164 (3.3%) of patients in the CTA group and 151 (3.0%) patients in the functional testing group experienced at least one event. CTA did not improve clinical outcomes during the median 25 month time period. The percentage of events were lower than expected, a factor the authors suggested could be attributed to the use of cardiovascular medications – especially statins – and other improvements in cardiovascular care over the past decade.

“Until this study, we have essentially been guessing on decisions about which initial test to use for this huge population of patients who need evaluation for cardiovascular symptoms,” said Douglas. “Our study shows that the prognostic outcomes are excellent and are similar regardless of what type of test you use, but there are some indications that CTA might be the safer test, with fewer catheterizations without obstructive disease and lower radiation exposure when compared to nuclear testing.”

The study was designed to represent real world care. Coronary CTA was associated with a small but nonsignificant increase in costs, the researchers reported.

The open access article published online March 14 in the New England Journal of Medicine may be accessed here.

REFERENCE

1. Douglas PS, Hoffman U, Patel MR et al. Outcomes of anatomical versus functional testing for coronary artery disease. NEJM Published online March 14, 2015. DOI: 10.1056/NEJMoa1415516.