Coronary calcium scoring can be trusted to guide cardiac test selection

Coronary artery calcium scanning predicts the risk of myocardial infarction and sudden death accurately enough to guide the selection of diagnostic tests for symptomatic patients, according to a multicenter prospective study.

The Early Identification of Subclinical Atherosclerosis by Noninvasive Imaging Research (EISNER) study, led by Leslee J. Shaw, Ph.D., at Emory University in Atlanta, also indicates the multislice CT-based calcium tests can be used without triggering unnecessary exams or expense.

Researchers at Cedars-Sinai Medical Center and Harbor-UCLA Medical Center, both in Los Angeles, St. Luke’s-Roosevelt Hospital and Weill Cornell Medical College, both in New York City, and the University of California at Irvine participated in the study. Findings appeared in the Sept. 29 issue of the Journal of the American College of Cardiology.

The findings of the EISNER study provide the first direct evidence that coronary artery calcium scanning could be an acceptable, cost-effective screening test for coronary artery disease, since it is able to identify high-risk subgroups in need of aggressive medical treatment, according to senior investigator Dr. Daniel S. Berman, chief of cardiac imaging at Cedars-Sinai.

“Over half of patients who suffer heart attacks have no warning that they have heart disease until the heart attack occurs. If we knew the patients were at risk, current treatments could prevent the majority of these unnecessary events. We had to address the concerns about unnecessary testing and costs related to this potentially lifesaving procedure,” he said in a release.

Coronary calcium scans were performed on 1361 volunteers at intermediate risk for coronary artery disease. Instances of cardiac death and myocardial infarction were then tracked from May 2001 to June 2005. The objective was to determine the relationship between coronary artery calcium scores, subsequent cardiac events, and the frequency and cost of cardiac diagnostic tests. Coronary artery calcium scores of 0 indicate no plaque and scores greater than 1000 signal very extensive plaque (1 to 9 = minimal, 10 to 99 = mild, 100 to 399 moderate, 400 to 999 = extensive plaque).

Shaw and colleagues found coronary artery calcium scores varied widely, but more than half, 56.7% of subjects, had scores of less than 10, and only 8.2% had scores higher than 400.

A strong correlation was established between the scores and the probability of a patient receiving noninvasive testing. Noninvasive testing was infrequent and associated medical costs were low for subjects with low coronary calcium scores. The frequency and expense of testing rose progressively with increasing CAC scores (p < 0.001), particularly for the 31 subjects who had scores over 1000.

The probability that a subject would undergo catheter-based x-ray angiography also increased with higher coronary artery calcium scores. Only 19.4% of participants with calcium scores under 1000 underwent cardiac catheterization.

Recent trials have demonstrated that screening with coronary artery calcium scoring is a better prognosticator of risk than the Framingham Risk Score-the traditional way of assessing risk-based patient demographics, blood testing, and blood pressure--in middle-aged and elderly patients. Additional data have been reported from trials showing that coronary artery calcium scans are more effective than standard cholesterol and blood pressure measurements for identifying patients who are most vulnerable to heart disease, according to the authors.

But the scans are not covered by private insurance, in part because of concerns that detection of low levels of cardiovascular disease will lead to unnecessary testing, including exercise imaging and invasive cardiac catheterization procedures, the authors noted.