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Can Carotid Plaque Assessment Rule Out Significant Coronary Artery Disease? A Comparison of Plaque Quantification by 2D and 3D Ultrasound

Title: P1-172 - Can Carotid Plaque Assessment Rule Out Significant Coronary Artery Disease? A Comparison of Plaque Quantification by 2D and 3D Ultrasound
Authors: Amer M. Johri1, David Chitty1, Paul Malik1, Murray Matangi2, Parvin Mousavi1, Andrew Day1, Chris Simpson1. 1Queen's University, Kingston, ON, Canada; 2Kingston Heart Clinic, Kingston, ON, Canada
Abstract Body:

Background: The development of non-invasive, rapid screening tools for early detection of coronary artery disease (CAD) is of considerable interest in the face of sky-rocketing cardiac risk factors in our population. Carotid intima media thickness (CIMT) measured by 2D-carotid ultrasound has been shown to help predict risk. Newer studies suggest that carotid plaque also has an important and overlooked role in risk prediction; however, assessment is hampered by the difficulty of quantifying the irregular 3D architecture of carotid plaque. We investigated the utility of a novel 3D ultrasound-based carotid plaque volume quantification technique as a negative predictor of CAD.

Methods: In a cohort of 70 consecutive patients referred for angiography, 2 and 3D carotid ultrasound scans were conducted using a vascular ultrasound system (iU22, Philips Medical Systems, Markham ON) equipped with a VL13-5 mechanical volume transducer for 3D imaging and L9-3 transducer for 2D imaging. 3D plaque volumes were quantified using the stacked contour method (QLAB GI 3DQ Plug-in Philips Healthcare, Markham, ON). 2D plaque thickness was measured in its maximal dimension, as visualized in the carotid bulb. Luminal narrowing of coronary arteries was analyzed using the established 16-segment model for coronary arteries to produce an overall angiogram score. Receiver operator characteristic (ROC) curves, negative predictive value (NPV), sensitivity, and inter-observer variability (IOV) of 3D and 2D plaque quantification related to the score were determined.

Results: From the ROC curve, the threshold value for plaque volume of 0.09 ml by 3D quantification gave the best NPV (93.3%) for ruling out significant CAD. The threshold value for plaque thickness of 1.35 mm by 2D quantification provided a significantly lower NPV of 75%. Using these thresholds, the sensitivity for significant CAD among patients increased from 93.9% using 2D methods to 98.0% using 3D methods.

Conclusion: The sensitivity and NPV of carotid plaque volume by 3D to rule out significant CAD was high, and greater than plaque thickness determined by 2D ultrasound. 3D ultrasound carotid plaque quantification may serve as an important clinical screening tool to identify patients without significant CAD.