Coronary calcium distribution tied to heart attack risk

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Calcium coverage scoring, which identifies the amount and distribution of calcified plaque build-up in the coronary arteries, may better predict a person's risk of heart attack, according to a new multicenter study published in the June issue of Radiology.

"Now we know that the location of the calcium in the arteries is particularly important in estimating a patient's potential risk," said the study's lead author Elizabeth Brown, ScD, research assistant professor in the department of biostatistics at the University of Washington in Seattle.

The Multi-Ethnic Study of Atherosclerosis (MESA) began in July 2000. The prospective study included 6,814 men and women between the ages of 45 and 84. Researchers compared CT image data for 3,252 participants with calcific plaque to data collected from 3,416 patients without calcific plaque. A calcium coverage score was developed to estimate the percentage of coronary arteries affected by plaque.

The authors noted that 146 additional MESA participants were excluded from the analysis due to lack of sufficient CT image data.

The patient follow-up was for a median period of 41 months to determine whether there was a relationship between the distribution of calcium shown in the CT images and the likelihood of heart attack or other cardiac event, according to the study.

The results showed that diabetes, hypertension and dyslipidemia (abnormal concentrations of lipids [fats] or lipoproteins in the blood) were highly associated with calcium coverage score. The study also found that the calcium coverage score was a better predictor of future cardiac events than currently used measures that gauge only the amount of calcium present.

On average, compared to patients without diabetes, patients with diabetes had 44 percent more of their coronary arteries affected by plaque. A two-fold increase in calcium coverage score indicated a 34 percent increase in risk of heart attack or other serious cardiac event and a 52 percent increase in the risk of any cardiac event, according to the study.

"Currently, physicians only see the result in terms of an overall score designed to measure the amount of calcified plaque," Brown said. “The new approach will provide physicians with a measure of the proportion of the arteries affected.”

She said that the method has the potential to improve estimates of a patient's risk for adverse clinical outcomes, such as heart attack or death.