Prognostic value of CTA-determined plaque morphology in diabetics remains unclear

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CTA showing left-sided cardiac chambers.  

CT angiography could provide prognostic value in evaluating atherosclerotic plaque composition in symptomatic patients with type 2 diabetes mellitus, who are likely to have a higher underlying atherosclerotic burden and higher risk of coronary artery disease, according to a poster presentation at the American Society of Nuclear Cardiology (ASNC) conference.

In a multi-center study evaluating symptomatic patients with type 2 diabetes mellitus (DM), researchers found that those with significant coronary artery disease had a preponderance of mixed plaque versus non-calcified or calcified. They have since designed a follow-up study to determine the prognostic significant of this finding.

While it is commonly accepted that patients with DM have a higher risk of CAD, the atherosclerotic plaque composition in these patients has not been previously studied, according to the researchers.

Uzoma N. Ibebuogu, MD, from the Medical College of Georgia in Augusta, along with colleagues from Massachusetts General Hospital and the Los Angeles Biomedical Research Institute at Habor-UCLA in Torrance, Calif., evaluated the plaque burden, morphology and distribution in type 2 DM patients using CT angiography (CTA) in an ongoing clinical trial.

Researchers evaluated coronary artery segments for the presence or absence of plaques using axial images and curved multiplanar reconstructions on a GE Healthcare workstation. One coronary plaque was assigned per segment. Plaques were classified as nonobstructive ( <50 percent), borderline (50-70 percent) or obstructive ( >70 percent).

Subsequently, the type of plaque was determined as either non-calcified, calcified or mixed, depending on the Hounsfield unit density.

For each patient, investigators determined the number of diseased coronary segments, the number of segments with obstructive and non-obstructive plaques, and the number of each of type of plaque. Researchers defined CTA as abnormal if there were presence of one or more coronary plaques. They further classified abnormal studies into one, two or three vessel disease.

Investigators studied 40 symptomatic diabetic subjects (average age of 63, 55 percent male), who underwent contrast-enhanced CTA. They noted that the enrolled patients had an intermediate pre-test probability of obstructive CAD.

According to the researchers, 83 percent of the subjects had at least one segment with any plaque, 69 percent had detectable coronary artery calcification (CAC) and 36 percent had CAC scores above 400.

Among individuals with any plaque, Ibebuogu and colleagues found that the mean number of segments involved was 5.7; the mean number of segments with exclusively non-calcified, calcified and mixed plaques was 1, 2.7 and 2 segments, respectively.

During his presentation at ASNC, Ibebuogu noted that thin-cap fibroatheromas, an intravascular ultrasound high-risk plaque feature considered as a precursor of coronary plaque rupture, have been shown to occur more frequently in mixed plaques as compared with non-calcified and calcified. He noted that the researchers only used CTA to assess the patients.

Twelve patients had at least one coronary segment with significant stenosis (luminal narrowing ? 50 percent). The researchers found that type 2 DM patients with significant stenosis were more likely to have a mixed plaque composition (39 vs. 28 percent), and less likely to be exclusively non-calcified plaque alone (17 vs. 26 percent) when compared to those without significant stenosis. However, the authors observed no difference in the respective proportion of exclusively calcified plaque (44 vs. 46 percent).

While the prognostic value of the different atherosclerotic plaque morphologies on CTA remains unclear, Ibebuogu told Cardiovascular Business News, “This study may help us identify a subgroup of diabetic patients with high-risk plaques that warrant more aggressive management of their coronary artery disease and more frequent follow up in clinic settings.”

Relative Distribution of Plaque Subtypes (%) in DM Patients According to Presence or Absence of Stenotic Disease ( >50%)
Frequency of Increasing Arterial Luminal Stenosis (%) Among The Study Population