CCTA’s insights on plaque may help track treatment response

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Coronary CT angiography (CCTA) may allow cardiologists to assess the progression or regression of plaque in asymptomatic patients at low to moderate risk who are treated with statins, according to a study published in Radiology on June 2. The study also shed light on predictors of noncalcified plaque.

A team of researchers from the radiology department at the National Institutes of Health Clinical Center in Bethesda, Md., designed the study to assess the relationship between total, calcified and noncalcified plaque and cardiovascular risk factors in asymptomatic patients who are low to intermediate risk for coronary artery disease (CAD). They enrolled 202 participants in the Randomized Trial of Imaging Versus Risk Factor-Based Therapy for Plaque Regression study who were older than 55 years and eligible for statin therapy.

Each participant had undergone CCTA using a 320-detector row scanner, which allowed them to determine coronary artery calcium (CAC) scores and detect noncalcified plaque. They then calculated total plaque volume, total plaque index and noncalcified plaque index for their analysis.

The patients had a mean Framingham risk score of 8.9; a mean American Heart Association 2013 risk score of 12.1; and a median CAC score of 73. Noncalcified plaque accounted for 67 percent of the total plaque in patients with a CAC score higher than 400 and 82 percent of the total plaque in patients with scores between 11 and 100.

The total plaque index was 23 percent greater in men than in women and the noncalcified plaque index was 21 percent greater in men than in women. After adjusting for risk factors, the total plaque index was still higher in men than in women.

The noncalcified plaque index was significantly associated with diabetes, greater systolic blood pressure and higher low-density lipoprotein (LDL) cholesterol levels. After adjusting for CAC score, it was still associated with LDL cholesterol levels.

“These variables were not associated with CAC score, as may have otherwise been expected,” they wrote. “Age was a strong predictor of CAC score but not of noncalcified plaque burden. These results suggest that coronary CT angiography evaluation of coronary plaque burden may provide unique information from the CAC score.”

The researchers pointed out that under the 2013 guidelines for reducing the risk of atherosclerosis, as many as 12.8 million people may become eligible for statin therapy to lower their LDL cholesterol. They wrote that their results highlight the importance of LDL cholesterol levels as a predictor of noncalcified plaque and CCTA’s usefulness for quantifying plaque burden and the progression or regression of CAD.