Study: Adverse events nearly nonexistent after normal cardiac CTA

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A growing body of evidence suggests that emergency department (ED) chest pain patients with normal cardiac CT angiography (CTA) results are at low risk for adverse events and may be discharged after ED evaluation, according to a meta-analysis published online May 4 in the Annals of Emergency Medicine.

J. Adam Oostema, MD, of Michigan State University (MSU) College of Human Medicine in Grand Rapids, and Brady Wilkinson, MD, of the MSU emergency medicine residency program, conducted the meta-analysis using 18 cohort studies which reported major adverse cardiac events in patients undergoing cardiac CTA. A total of 9,514 patients were analyzed, with 37 percent receiving normal CTA results, and the rest demonstrating coronary artery disease (CAD).

Oostema and Wilkinson noted that the population in the analysis must have been fairly high risk, given nearly two-thirds had evidence of CAD. Despite the seemingly high risk of the general population, those with normal cardiac CTA results had a “profoundly low” negative likelihood ratio for major adverse cardiac events of 0.008. Those patients had no myocardial infarctions or readmissions for unstable angina, and had a mortality rate of 0.17 percent.

“Moreover, because many of the adverse events among patients with normal cardiac CT angiography results occurred in an older study using electron beam CT rather than multidetector technology, the sensitivity of cardiac CT angiography with current generation scanners may be even higher than the pooled estimate suggests,” added the authors.

There were a few limitations to the analysis, and the authors noted that the low ratio of adverse cardiac events should be applied with caution. “Revascularization dominated the 'adverse events' in these studies; however, this outcome would be expected to be more common among patients with a documented coronary stenosis by cardiac CT angiography. Thus, the difference in major adverse cardiac events between patients with negative and positive cardiac CT angiography results is primarily driven by their differential treatment, and the clinical utility of the calculated negative likelihood ratio is uncertain.”

They also pointed out that pooled risk estimates should not be applied to patients with known CAD because only four studies in the analysis included these patients and their event rates were not reported.

“Cardiac CT angiography is a promising modality for [ED] chest pain evaluation because it provides rapid, accurate assessment of coronary stenosis and has the potential to evaluate for other emergency causes of chest pain,” wrote Oostema and Wilkinson. “These attractive features must be weighed against the limited availability, need for intravenous contrast administration, radiation exposure and cost associated with cardiac CT angiography.”