Carotid artery MRI improves risk assessment for cardiovascular disease

For individuals without known cardiovascular disease at baseline, wall thickness measurement by using MRI was more consistently associated with incident cardiovascular disease, particularly stroke, than were carotid intima-media thickness (IMT) by using ultrasound, according to a study published in the journal Radiology.

Bruce A. Wasserman and his associates conducted a prospective study to compare common carotid artery (CCA) wall thickness measured manually by using the US and semiautomatically by using MRI and to examine their associations with incident coronary heart disease and stroke.

Research has shown that plaque buildup in the carotid arteries often mirrors that in the coronary arteries, but the carotids are more easily imaged, making them potentially useful vessels for the assessment of the risk of strokes, heart attacks, and other adverse cardiovascular events.

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"The carotid artery serves as the window into the cardiovascular system," said study lead author Bruce A. Wasserman, M.D., from Johns Hopkins University School of Medicine in Baltimore. "Plaque developing in the carotid artery can contribute directly to a stroke, and its features--which determine its vulnerability to rupture--are closely related to those found in coronary artery plaque in the same patients."

The ultrasound-based carotid intima-media thickness (IMT) test is the most widely used imaging method to assess the level of early-stage carotid atherosclerosis. However, research suggests that IMT offers only minor improvement in cardiovascular disease risk prediction when added to the Framingham risk score, a commonly used measure that takes into account factors like cholesterol, smoking and family history.

Vessel wall MRI is a promising, noninvasive technique that can image the entire carotid wall circumference, in contrast to ultrasound measurements of IMT that are usually based solely on views of the artery's far wall. MRI can also see all three layers of the artery, including the adventitia, the outermost layer not visible on IMT.

"High-resolution MRI can tell us the stage of plaque in the wall and tell us about plaque features that could lead to stroke," Dr. Wasserman said. "It can also see the adventitia, a vessel layer that may have an important role in cardiovascular risk because small vessels proliferate there, leading to thickening of the artery, which may be responsible for early disease development and progression.

The study researchers included 698 men and women aged from 45 to 84 years old with a mean age of 63 at first visit and no known history of cardiovascular disease. The participants underwent ultrasound and MRI between 2000 and 2004 to compare carotid artery wall thickness. During subsequent follow-up, the researchers looked for any correlation between carotid artery wall thickness measurements and coronary heart disease and stroke.

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The researchers found that MRI measures of carotid artery wall thickness were more consistently associated with cardiovascular events than was intima-media thickness using ultrasound which suggests that perhaps MRI could be a better predictor of cardiovascular events, especially stroke. The association between wall thickness and cardiovascular events was stronger with both non-contrast and contrast-enhanced MRI than it was for IMT.

"In our prospective study of individuals without known clinical cardiovascular disease at baseline, wall thickness measured semiautomatically by using MRI was more consistently associated with incident cardiovascular disease, particularly stroke, than was IMT measured manually by using the US", write the authors.

For reference log on to https://doi.org/10.1148/radiol.2018173069