Background: The predominant cause of coronary artery calcification is atherosclerosis. Although fast x-ray computed tomography (CT) has been demonstrated to be a sensitive technique to detect coronary calcification, the increasing prevalence of calcification with age has been associated with a low specificity for identifying obstructive atherosclerosis. We hypothesized that the specificity of this test would be improved in a younger patient population, making it more useful in the diagnosis of coronary artery disease.
Methods and results: We compared fast CT-detected calcification with coronary angiography in 106 patients under the age of 50 years. Nonenhanced fast CT scans consisting of 20 contiguous 3-mm tomograms of the proximal coronary arteries were obtained during a single breath hold. A positive scan was defined as 4 contiguous voxels (> or = 1 mm2) of density > 130 Hounsfield units in the region of the epicardial coronary arteries. Calcification detected by fast CT had an 85% sensitivity to predict patients with significant coronary artery disease (> or = 50% diameter stenosis), with a specificity of 45%. Although the sensitivity to detect multivessel disease was 94%, the sensitivity to detect single-vessel disease was 75%. Changing the threshold for defining a positive fast CT scan from 4 to 2 contiguous voxels produced a small improvement in sensitivity, to 88%, but reduced specificity to 36%.
Conclusions: Although the specificity to detect angiographically significant coronary disease with fast CT improves in a younger patient population, it continues to be relatively low. In contrast to older patient populations, a small but significant number of patients < 50 years old with angiographically significant coronary artery disease do not have coronary calcification demonstrated by fast CT. Thus, caution should be used in excluding significant coronary artery disease on the basis of a negative fast CT study.