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Inflamed arteries' effects on nearby adipose tissue can be captured on CT angiography to better uncover vulnerable plaques, research suggested.

Culprit lesions held more noncalcified plaque with low- (12.6% versus 3.6%, P<0.001) and intermediate-attenuation (38.4% versus 19.4%, P<0.001) than did nonculprit lesions in scans of acute coronary syndrome (ACS) patients acquired at Germany's University of Erlangen in 2009-2010.

These high-risk plaque characteristics were also more numerous in culprit lesions than in the highest-grade stenosis lesions in stable coronary artery disease (low-attenuation: 12.6% versus 5.6%, P=0.002; intermediate-attenuation: 38.4% versus 22.1%, P<0.001).

Pericoronary adipose tissue CT attenuation was similarly increased around culprit lesions, Damini Dey, PhD, of Cedars-Sinai Medical Center in L.A., and colleagues reported online in .

The presence of culprit lesions was predicted by low- and intermediate-attenuation non-calcified plaque burden and pericoronary adipose tissue CT attenuation on multivariable analysis.

Low- and intermediate-attenuation plaques signal necrotic core and fibrofatty tissue, respectively, both of which are made of lipid components, Dey's group noted. On CT, they appear different from high-attenuation noncalcified plaque, which is fibrous tissue with densely-packed collagen.

"The association between PCAT [pericoronary adipose tissue] CT attenuation and high-risk plaque characteristics may reflect vascular inflammation causing morphological changes of PCAT and may influence plaque stability. Quantitative PCAT CT attenuation does not require extra protocols within routine CT angiography and may represent a dynamic imaging biomarker of vascular inflammation, enabling a simple, noninvasive identification of both coronary inflammation and from routine CT angiography," they suggested.

The investigators based their retrospective case-control study on 19 consecutive patients who presented with a first ACS and 16 matched controls who had symptomatic stable CAD. The cohort averaged 59.5 years of age, with 86% men.

"These results are potentially exciting in that routine inflammation imaging may be clinically meaningful and informative in a short-term setting, presenting multiple possibilities for enhanced patient care. Further, this metric may serve as a meaningful end point in clinical trials of therapeutic agents," Rory Hachamovitch, MD, MSc, and Venu Menon, MD, both of the Cleveland Clinic, wrote in an .

However, they noted that it was unclear how the patients were matched and that the sample was probably too small for adequate risk adjustment.

"The second, larger-picture challenge is the question of how CT-based identification of coronary inflammation will be positioned within a clinical testing strategy. Can a relatively expensive modality (with associated radiation and contrast exposure) compete with a highly accurate, less expensive biochemical assay (e.g., high sensitivity troponin) in a short-term setting?" they posited.

In patients with suspected ACS, the troponin elevations already trigger catheterization and possible downstream revascularization. Yet even with a negative troponin test, ACS would be excluded and the value of CT negated, Hachamovitch and Menon argued.

"The possible value of CT angiography in this setting may be in patients whose diagnosis remains ambiguous despite serial biomarker tests," they suggested, maintaining that "it appears that the CT identification of culprit lesions is within our sights."