Screening low- to intermediate-risk acute chest pain patients in the emergency department (ED) with coronary computed tomographic angiography (CTA) is safe and may reduce time spent in the hospital and overall cost compared with conventional testing methods. However, CTA-evaluated patients are more likely to undergo invasive angiography and revascularization, according to a meta-analysis of randomized trials published online February 6, 2013, ahead of print in the Journal of the American College of Cardiology.

Investigators led by Edward Hulten, MD, MPH, of Brigham and Women’s Hospital (Boston, MA), analyzed pooled data from 4 randomized trials involving 3,266 patients who presented to the ED with acute chest pain and were evaluated with CTA (n = 1,869) or standard test methodologies (n = 1,397).

No Harm in CTA Screening

During hospitalization and post-discharge follow-up, there were no deaths in either group and few MIs. Most of the latter occurred during the index hospitalization and were unrelated to the type of diagnostic testing received.

In addition, after discharge, the groups showed similar rates of ED visits for recurrent chest pain or rehospitalization for ACS (table 1).

Table 1. Post-Discharge Safety Events^a

^a Pooled weighted incidence.

However, the pooled weighted incidence of invasive angiography was higher after CTA than standard care. With an absolute increase of 21 angiographies per 1,000 patients, the number needed to scan to result in 1 additional invasive procedure was 48. The same pattern was seen for revascularization, by either PCI or CABG. With an absolute increase of 20 interventions per 1,000 patients, the number needed to scan to result in 1 additional revascularization was 50 (table 2).

Table 2. Outcomes During Hospitalization and Post-Discharge^a

^a Pooled weighted incidence.

No evidence of significant heterogeneity among the individual trials was seen for any of the endpoints.

Although pooled analyses of hospital length of stay and costs were not performed due to differences in protocols among the underlying trials, all 4 individually reported reductions in average hospital stay with CTA, ranging from 3.4 to 11.6 hours, while 3 studies showed cost savings, ranging from $286 to $1,321.

The authors note some important differences in trial methodology, including:

• Definitions of standard care (routine myocardial perfusion imaging vs. testing at the physicians’ discretion, which led to a lower rate of stress testing)
• When CTA results should trigger invasive angiography
• When angiography should lead to revascularization

Dr. Hulten and colleagues also observe that because invasive angiography as well as PCI and CABG profoundly affect the overall cost of CAD care—and not all revascularizations are beneficial—“the pivotal question is whether their increase after [coronary CTA] represents an overuse of [invasive coronary angiography] and PCI/CABG after [coronary CTA] or an underuse in patients undergoing [usual care].”

Clinical Impact of CTA Unclear

In an accompanying editorial, William Guy Weigold, MD, of MedStar Washington Hospital Center (Washington, DC), points out that more than 90% of patients in the meta-analysis did not undergo either invasive angiography or revascularization, underlining the fact that diagnostic workup in the ED is the more common source of hospital cost for chest pain patients.

Moreover, the higher rate of invasive angiography after CTA is likely due to the fact that the sensitive testing method produces a higher ‘diagnostic yield,’ or proportion of patients who need revascularization, than does conventional screening, he continued. Therefore, CTA may reduce the number of unnecessary catheterizations.

“On the other hand, 94% of patients in the [standard care] group never had their coronary arteries ‘looked at,’” Dr. Weigold writes, adding that some may have been sent home with undiagnosed CAD. The trials were underpowered to look at the bigger picture, he notes, adding that larger studies will be required to determine whether such patients ultimately have higher morbidity and mortality than those whose disease is detected and treated. 

CTA Ready for Prime Time 

In a telephone interview with TCTMD, Matthew J. Budoff, MD, of Harbor-UCLA Medical Center (Torrance, CA), praised the meta-analysis for highlighting that there are now 4 randomized trials all showing the appropriateness of CTA for screening acute chest pain patients. The pooled data reinforce the individual trial results and “reassure us that we’re on the right track,” he observed, adding, “I think we’ve achieved a sufficient evidence base to move toward a class I indication for CTA.

“To me, the most important question is whether you can stratify these patients correctly and discharge them safely,” Dr. Budoff continued. With a generally accepted threshold for downstream events of no more than 1%, CTA meets that bar, he added.

“With tens of millions of people going to emergency departments for chest pain every year, we need a safe and fast and cost-effective algorithm for triaging them and getting them out of the system, and it looks like CTA qualifies on all 3 criteria,” he commented.

While CTA with its high negative predictive value is the best triage tool, Dr. Budoff said, “the downside is you find more disease. And then the question becomes whether these people should undergo stenting.” In this context, interventional cardiologists can and should take advantage of FFR to determine whether individual lesions are functionally significant and thus warrant intervention, he said, citing the benefit of this strategy in the FAME and FAME II trials.

The impact of CTA screening on long-term outcomes remains an open issue, Dr. Budoff acknowledged, “but I don’t think we need to show that, for example, CTA is twice as good as nuclear perfusion testing at keeping people alive. We just have to show that it’s safe and faster and less expensive.”

Study Details 

Patients’ mean age was 51 years, and 47% were male. Baseline risk factors did not differ between those screened with CTA or standard testing methods. 

 

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Sources:
1. Hulten E, Pickett C, Bittencourt MS, et al. Outcomes after coronary computed tomography angiography in the emergency department: A systematic review and meta-analysis of randomized, controlled trials. J Am Coll Cardiol. 2013;Epub ahead of print.

2. Weigold WG. Coronary computed tomography angiography in the emergency department. J Am Coll Cardiol. 2013;Epub ahead of print.

 

 

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