CT Measures Possible Hazardous Arterial Plaque in Diabetic Patients

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Based on a new study, imaging of the coronary arteries with computed tomography (CT) angiography provides an accurate evaluation of arterial plaque and could have a significant effect on the management of diabetic patients who face a high risk of heart attacks and other adverse cardiovascular events.

The study has since been published online in the journal Radiology.

Plaque that forms in the arterial walls can confine blood flow and, in some cases, rupture, leading to possibly fatal heart attacks. There is substantial evidence that calcified, or stable, plaque, is less prone to rupture than non-calcified, or soft, plaque. Intravascular ultrasound can measure non-calcified and calcified coronary artery plaque, however it is invasive and incompatible for screening purposes, and coronary artery calcium (CAC) scoring with CT, a common noninvasive option, has limitations.

"Calcium scoring measures how much calcified plaque a person has, but it doesn't measure the component that's not calcified, and that's the component that tends to be dangerous," said João A. C. Lima, M.D., from the cardiology division at Johns Hopkins University in Baltimore, Md.

Quantitative plaque analysis with coronary computed tomography angiography (CCTA) has come into view as a feasible screening option. CCTA can capture the full anatomic map of the coronary arteries in a single heartbeat with low radiation dose. CCTA can offer a picture of the total amount of plaque throughout the arteries of the heart.

Researchers from three centers: the National Institutes of Health (NIH) in Bethesda, Md., Johns Hopkins, and the Intermountain Medical Center Heart Institute in Salt Lake City; recently worked in partnership to assess CCTA in 224 asymptomatic diabetic patients.

"Obese people with diabetes have a propensity for extensive and premature development of coronary artery plaque, making them an ideal study group for plaque assessment," they noted.

The researchers employed measurements of coronary artery wall volume and length to determine a coronary plaque volume index (PVI) for each patient. The method provided information well beyond the presence or absence of coronary stenosis, or narrowing. PVI was linked to age, male gender, body mass index (BMI) and duration of diabetes. Younger individuals with a shorter duration of diabetes had a greater percentage of soft plaque.

"Coronary plaque volume index by CCTA is not only clinically feasible and reproducible in patients with diabetes. It provides a more complete picture of the coronary arteries that could be routinely applied in at-risk patients " said David A. Bluemke, M.D., Ph.D., from the NIH Clinical Center.

"These findings represent a very important step in the ability to quantify plaque, particularly non-calcified plaque," added Lima.

BMI, a measure of body fat based on weight and height, was the principal modifiable risk factor connected to total and soft coronary plaque as determined by CCTA.

"The results reinforce how important it is to evaluate BMI as a potential driver of overall diabetes. As the only modifiable risk factor, obesity is an important target for managing diabetic patients," said Bluemke.

Only about one-third of the coronary plaque in patients showed calcification, underscoring the widespread presence of non-calcified plaque. The ability to distinguish between calcified and non-calcified plaque is important because treatment may vary based on plaque composition.

"People with soft plaque respond better to interventions, particularly medical therapy like statins," said Lima.

The researchers will press on monitoring the patients from the study to better understand the worth of coronary artery plaque evaluation in predicting future adverse cardiovascular events and to further highlight and define the role of plaque volume index versus CAC score. A clinical trial would be required to determine if risk factor reduction would result in reduced PVI.

"Now that we have baseline indices of plaque in the study patients, we can look for people who, despite optimal management, experience a cardiovascular disease event like a heart attack," Bluemke noted.

CCTA is likely to be valuable for other groups of patients at high risk for cardiovascular events, the researchers said, and may one day enable physicians to predict plaque development and treat it aggressively before PVI increases significantly.