Differences in coronary plaque composition by noninvasive computed tomography angiography in individuals with and without obstructive coronary artery disease.

Background: Coronary CT angiography (CCTA) has emerged as a promising non-invasive tool to detect coronary artery disease (CAD) which provides additional information about atherosclerotic plaque composition. We aimed to assess whether differences in plaque composition and plaque burden exist across patients with more and <50% coronary stenosis.

Methods: 1060 patients (58±11 years, 43% females) with an intermediate risk of CAD referred for 64-slice CCTA were studied. Plaque characteristics and burden was analyzed on CCTA images on a per-segment basis (modified 16-segment AHA classification). Plaques types were classified as: calcified (type 1), mixed (predominantly calcified) (type 2), mixed (predominantly non-calcified) (type 3), and non-calcified (type 4). Plaque types in patients with more and <50% stenosis were compared.

Results: Overall 373 (35.2%) patients had normal coronaries without evidence of plaque. In the remaining 687 patients, 353 (33%) and 334 (31%) were found to have luminal narrowing of <50% and ≥50% in at-least one coronary artery segment, respectively. Those with ≥50% stenotic CAD demonstrated were more likely to have segments with mixed plaque subtype and less likely to be exclusively non-calcified (relative distribution of 58%, 22%, 10%, 11% for type 1-4 respectively) compared to those with <50% stenosis with (59%, 11%, 6% and 24%, respectively (p=0.006). In multivariable adjustment models, individuals with significant CAD were 5-fold more likely to have increased burden type 1 plaque (≥3 coronary segments) as compared to those with non-obstructive CAD (OR: 5.00, 95% CI: 1.05-23.78). The respective odds ratio (95% CI) for ≥3 coronary segments of type 2, 3 and 4 were 8.73 (3.01-25.23), 4.62 (2.99-0.22-1.55), respectively.

Conclusions: Plaque composition is different according to severity of CAD with a higher mixed plaque and lesser non-calcified plaque burden among those patients with ≥50% stenotic CAD. These findings should stimulate further investigations to assess the prognostic value of coronary plaque subtypes according to their underlying composition.