Coronary artery calcification determined by electron beam computed tomography correlates well with coronary atherosclerosis. Quantitative techniques, most notably the Agatston calcium score (ACS), have been suggested but have limited reproducibility. Serial imaging recently has been recommended by the American College of Cardiology/American Heart Association Task Force to improve the predictive value. The volumetric calcium scoring (VCS) algorithm measures calcium by volume and compares the results with statistics from a population without coronary artery disease (CAD). The VCS algorithm provides minimal interscan variability and allows for monitoring of
CAD progression and regression secondary to medical therapy. Knez and associates used a prospective study of symptomatic patients to determine the positive predictive value of the VCS algorithm and the traditional ACS for significant CAD.
More than 2,000 symptomatic adults with no history of CAD were included in the study. Most of them had chest pain, and some had unexplained exertional dyspnea or congestive heart failure. Coronary angiography was performed on all participants; lumen diameter stenosis of 50 percent or more was defined as significant CAD. Total calcium scores were significantly different in patients with and without CAD. However, the best sensitivity and specificity were obtained with the VCS algorithm, using a cutoff of at least the 75th percentile. The ACS method was not as accurate as the VCS algorithm. Patients with no coronary calcifications had a very low risk of CAD, giving the calcium score a high negative predictive value.
The authors conclude that calcium scoring is a useful screening test for CAD in symptomatic patients, with an accuracy similar to that of exercise/pharmacologic stress scintigraphy or echocardiography. Calcium scores may be useful in predicting high-risk stenosis, including triple-vessel and left-main disease. Calcium scoring eventually may be used to decrease the frequency of invasive procedures that do not lead to intervention.