CTA Safe and Effective to Rule Out ACS in Emergency Room for Low- to Moderate-Risk Patients--Cheaper Too

Shelley Wood

May 04, 2009

May 4, 2009 (Washington, DC and Boston, Massachusetts) - Another study looking at the use of coronary computed tomography angiography (CTA) in the emergency room has found that the imaging tool can rule out coronary artery disease (CAD) and acute coronary syndromes (ACS) in 50% of patients with a low to intermediate risk of disease [1]. While other studies have also supported a role for CTA in the ER, authors of this latest study, known as ROMICAT, say their series represents one of the largest studies to date and also extends the findings to a low- to intermediate-risk patient. Most emergency-room series have focused to date on low-risk patients only.

In all, 31 of 368 patients (8%) were found to have ACS on the basis of further testing, the authors, led by Dr Udo Hoffmann (Harvard Medical School, Boston, MA), note. "CT is not a good option in a group with a high prevalence of CAD/ACS, and we do not need to do CT in people who have too low a risk," Hoffman told heartwire . "But most people would agree that in a group like the one we have here, with an 8% event rate--this is exactly the segment in whom imaging should be performed."

The ROMICAT study is published in the May 5, 2009 issue of the Journal of the American College of Cardiology.

Hoffman et al used an observational cohort study design, enrolling only patients with normal initial troponin and a nonischemic electrocardiogram. A 64-slice CT angiogram was done before hospital admission, but patients and physicians were blinded to the CTA results, and any treatment decisions were made on the basis of positive troponin or unstable angina pectoris during hospitalization and/or a positive stress test. Patients were also followed for six months for major adverse cardiac events.

As Hoffman et al report, CTA found that 50% of patients had no CAD, 31% had nonobstructive disease, and 19% had inconclusive results or significant stenosis. When these findings were assessed according to ACS diagnosis by other tests postadmission, sensitivity and negative predictive value for ACS were both 100%--none of the patients without plaque on CTA had ACS. By contrast, specificity and positive predictive value were lower, at 17% and 54%, since some of the patients had plaque but no ACS. However, patients with ACS typically had more plaque than patients without, the authors note.

Average hospital stay for patients was 40 hours, the authors report--a cost and inconvenience to patients that could have been avoided had CT been used to determine patient care, Hoffman said. "If you look at it from the emergency-department point of view, it's important to identify as quickly as possible those whom you can send home. That will save a day in the hospital, as well as the troponin test and nuclear-perfusion imaging. If doctors can clear out those patients, they can spend more time with the people who need it."

Hoffman added that he and his colleagues are currently reviewing the CT angiograms of patients who were found to have CAD, to see whether there is anything CT can detect in terms of plaque morphology that could help determine which patients have ACS vs those who don't. "That's taking these findings from a patient level to a lesion level," he said.

In an accompanying editorial [2], Dr Mark A Hlatky (Stanford University School of Medicine, CA) calls ROMICAT a "promising development" for the use of coronary CTA in the emergency department. "A finding of normal coronary arteries will likely obviate additional tests and speed patient discharge to home and appears to be associated with a good short-term prognosis. A finding of some degree of coronary atherosclerosis might not, however, 'clear the air,' as further investigations are likely with either stress testing or invasive coronary angiography (or both)."

The question of whether hard clinical outcomes are actually changed by the use of CTA will require studies in which CT is actually used to direct the course of care in patients, Hlatky points out. In this study, he points out, 8% of patients were lost to follow-up, potentially because patients who had a poor clinical outcome were more difficult to contact. "Although the low rate of adverse cardiac events in the ROMICAT study is reassuring, larger studies with more complete follow-up will be needed to assess more fully the prognostic implication of a coronary CTA in the emergency department," he concludes.

Cost Savings With CTA?

In other recent CT news, researchers presented a similar, smaller study during the American Roentgen Ray Society 2009 Annual Meeting, in Boston, MA, but also factored in the costs of using CTA to rule out ACS in chest-pain patients vs the costs of standard care--typically cardiac enzyme tests and serial ECGs [3].

In their analysis, 50 out of 53 low-risk patients initially admitted with chest pain were negative on CTA (defined as <30% stenosis in any one coronary segment). These 50 were also found, subsequently, to have negative cardiac enzymes and negative ECGs. Standard-care charges were a mean of $7567 per patient. By comparison, the charges for CTA followed by observation in the hospital were calculated to be $6153, while CTA without observation was calculated at $4251. They also calculated differences in patient length of hospital stay based on diagnostic workup and found that CTA without and with observation would be significantly less than standard care (five hours, 14.3 hours, and 25.4 hours, respectively).

Lead author for the study, Dr Janet May (University of Washington, Seattle), explained that cardiac CT was added to the standard patient "workup," and patients continued through the regular pathway of patient care. As such, she says, "We were able to see the actual savings in both time and charges that would have occurred had we used cardiac CT instead of the standard of care. I do think the savings in length of stay are just as important as the dollars saved. The two go hand in hand."

No patients reported adverse events over six months' postdischarge, researchers noted, although May emphasized to heartwire that safety of using cardiac CT in low-risk emergency-department chest pain requires further documentation.

"We are working on publishing some one-year follow-up data from chest-pain patients who had CT in the emergency department that will show early, rapid discharge is a very safe practice when the CT showed no coronary artery disease," May noted.

Hoffman disclosed receiving research funding from GE Healthcare and Siemens. Hlatky disclosed being a member of a medical advisory panel for Blue Cross/Blue Shield, where he has served as a paid consultant for an as-yet-unpublished analysis of coronary CTA cost-effectiveness. May et al disclosed receiving research funding from GE Healthcare.