CHICAGO – Cardiac CT angiography in the emergency department safely redirects to home the many patients who would otherwise be admitted for acute chest pain, according to results of the prospective, randomized ACRIN PA 4005 trial.
Low- to intermediate-risk patients who receive cardiac computed tomographic angiography (CCTA) were more likely to be discharged directly from the emergency department (ED), to have shorter hospital stays, and to have more than double the coronary artery disease (CAD) diagnosed than were those receiving a traditional evaluation.
Moreover, none of the 640 patients who had a negative CCTA died or had a myocardial infarction within 30 days after presentation (95% confidence interval, 0-0.57), Dr. Harold Litt, principal investigator of ACRIN (American College of Radiology Imaging Network) PA 4005, said at the annual meeting of the American College of Cardiology.
The upper limit of the confidence interval met the study’s prespecified safety threshold of less than 1%, and may be robust enough to help sway ED physicians who have been unwilling to adopt a CT-based strategy because similar findings from other randomized trials were not sufficiently powered.
"This is a large public health problem," Dr. Litt said, noting that roughly 2%-3% of patients are discharged from the ED with an unrecognized MI.
Conversely, more than 6 million Americans visit the ED for chest pain each year. Only 10%-15% are ultimately diagnosed with acute coronary syndrome (ACS), with most admitted to hospitals at a staggering cost of more than $3 billion annually.
The ACRIN PA 4005 trial randomized 1,370 patients with symptoms consistent with possible ACS from five clinical sites to undergo at least 64-slice CCTA or traditional evaluation, comprising mostly – but not limited to – exercise treadmill test, stress test with imaging, and stress echocardiography. They had an average TIMI (Thrombolysis in Myocardial Infarction) risk score of 0-2 and an electrocardiogram without acute ischemia. Their average age was about 50 years, and 60% were black.
Half of the 908 CCTA patients were discharged directly from the ED, compared with 23% of the 642 traditional-care patients (95% CI, 21.4-32.2).
The overall length of stay was 18 hours and 25 hours, respectively, but decreased even further to 12 hours for the 602 CCTA patients who had a negative scan, said Dr. Litt, chief of cardiovascular imaging at the University of Pennsylvania Health System in Philadelphia.
The CCTA group was also less likely than was the traditional-care group to have negative findings on invasive angiography (29% vs. 53%; 95% CI, –48.8-3.3).
The finding of more incidental CAD diagnoses in the CCTA arm vs. the traditional-care arm (9% vs. 3.5%; 95% CI, 0-11.2) is more problematic to interpret.
"Will this result in better prevention for them as they go on?" he asked. "Will they be encouraged to have lifestyle modifications and be put on statins, etc., resulting in lower future event rates and not showing up in the emergency room? Or will it just result in more testing that won’t be a benefit to them? We don’t know the answer to that."
No significant differences were observed in a 30-day resource utilization that included catheterization, revascularization, repeat ED visit, rehospitalization, and cardiologist visit. A 1-year follow-up is being obtained, and cost modeling will be conducted, he said. The possibility for substantial health care savings exists, however, as low- to intermediate-risk patients account for 50%-70% of cases presenting with possible ACS.
Overall, MI was reported within 30 days after presentation in 10 CCTA patientsand 5 traditional-care patients (1% vs. 11%; CI, –5.6-5.7). One serious adverse event (bradyarrhythmia) occurred in each group. There were no cardiac deaths in the traditional-care group.
Dr. Litt acknowledged that CCTA does increase radiation exposure, but said that radiation dosage is very technology dependent and that current technology has reduced the average radiation dose to less than that from nuclear myocardial perfusion studies. He also cautioned that the ACRIN PA 4005 results should not be extrapolated to groups with a higher risk of clinically significant coronary disease.
Invited discussant Dr. Thomas Gerber, a professor of medicine and radiology at Mayo Clinic in Jacksonville, Fla., asked why the investigators chose to focus on coronary CT angiography instead of the "triple rule-out" CT angiography strategy to evaluate the coronary arteries, pulmonary arteries, and thoracic aorta, and whether there were any patients who had pulmonary embolism or aortic dissection on subsequent evaluation.
Dr. Litt said they did track PE and acute aortic syndromes, and will report these findings in the future. The investigators used CCTA because they wanted to focus on patients in whom exclusion of ACS was the primary diagnostic question. He acknowledged that not all dissections are visible on CT, but added that "we are getting to the point where the radiology dose from a triple rule-out isn’t all that much higher than from a coronary CT. So in light of that new technology, that question may need to be reevaluated."