Source: Siemens Healthcare, image courtesy of Columbia Radiology Imaging, Columbia, Mich.

CHICAGO—Coronary CT angiography (CCTA), as the first test for low- to intermediate-risk patients presenting to emergency departments (ED) with potential acute coronary syndrome, results in safe and expedited discharge from the emergency department of many patients who would otherwise be admitted, according to the late-breaking clinical trial, ACRIN PA, presented March 26 at the American College of Cardiology’s (ACC) 61st annual scientific session.

Of the six million annual visits to U.S. EDs for chest pain, up to 85 percent are not actually caused by cardiac problems. “Although an ACS is ultimately diagnosed in only 10 to 15 percent of patients who present with chest pain, the majority of these patients are admitted to hospitals, at an estimated cost of over $3 billion annually," wrote the study authors in the New England Journal of Medicine, where the study was simultaneously published. While CCTA costs approximately $1,500, costs for those admitted to the hospital for stress testing and monitoring typically total more than $4,000 for each patient, according to the researchers.

Prior ED studies of CCTA have shown low event rate for patients with little or no disease, efficiency compared with SPECT myocardial perfusion imaging (MPI) and potential cost savings compared with SPECT MPI; however, no previous study had sufficient power to demonstrate an acceptable safety endpoint with a less than 1 percent rate of 30-day major adverse coronary event for negative “rule-out.”

In this Phase IV trial, the researchers randomly assigned 1,370 patients at five centers to traditional “rule-out” care (462 patients) or CCTA (908 patients) in a 1:2 ratio. Providers at each site made all decisions about tests and treatment for the traditional care group patients on an individual basis.

During the study’s presentation, the lead investigator, Harold I. Litt, MD, PhD, from the department of radiology at University of Pennsylvania in Philadelphia, said that the groups were “well-matched, and, of note, 60 percent of the patients were black.”

The CCTA group followed a three-part protocol: tests to measure blood levels of two substances associated with heart damage and risk of heart attack or stroke, CCTA and discharge if test results were negative.

Of 640 patients with a negative CCTA examination, none died or had an MI within 30 days. As compared with patients receiving traditional care, patients in the CCTA group had a higher rate of discharge from the ED (49.6 vs. 22.7 percent—a difference of 26.8 percentage points); a shorter length of stay (median, 18 hours vs. 24.8 hours); and a higher rate of detection of CAD (9 vs. 3.5 percent—a difference of 5.6 percentage points). There was one serious adverse event in each group.

Researchers found no significant differences in 30-day resource utilization between the CCTA and traditional care arms—but the percentages were consistently higher for the CCTA arm, including for catheterization (5.1 vs. 4.2 percent), revascularization (2.7 vs. 1.3 percent), repeat ED visit (8 vs. 7.5 percent), rehospitalization (3.1 vs. 2.4 percent) and a cardiologist visit (7.1 vs. 3.8 percent). Litt noted that the researchers are obtaining one-year follow-up on these data.

A true comparative randomized, controlled trial would require approximately 50,000 subjects, and there is a low event rate in population studies. Therefore, one limitation of the trial, which Litt acknowledged, was that it was “powered for a conservative safety goal, allowing ED physicians to feel confident about discharging patients following CCTA.” Also, he added that they only focused on the low to intermediate risk groups, so the results cannot be extrapolated for higher risk groups.

The researchers tracked radiation exposure in the study, but those results were not revealed during the ACC. However, Litt noted that radiation is “very technology dependent, but dose with CCTA is now lower than SPECT MPI.”

In responding to a question from study discussant Thomas C. Gerber, MD, PhD, of Mayo Clinic in Rochester, Minn., about the difference in revascularization rates, Litt said, “Both CCTA and catheterization may be showing patients who have significant CAD, with more than 70 percent stenosis in whom most physicians would intervene, but if those patients had a stress test, it may have been negative. Is that because it’s a false positive catheterization, or is it because it’s a false negative stress test? This reinforces the importance of fractional flow reserve.”

ACRIN PA 4005 is the first cardiovascular study conducted by the American College of Radiology Imaging Network (ACRIN). This project is funded, in part, under a grant with the Pennsylvania Department of Health, and additional funding was obtained from the ACRIN Foundation.