Prevalence of Non-calcified Coronary Plaque on 64-Slice Computed Tomography Coronary Angiography in Patients with Zero and Low Coronary Artery Calcium Scores

Abstract

Objective: To study the prevalence of non-calcified plaque causing significant coronary artery stenosis in patients with zero or low coronary artery calcium scores in a regional hospital in Hong Kong. Methods: Computed tomography reports and clinical records (at least 3 years after computed tomography coronary angiography) of 336 consecutive patients with coronary artery calcium scores and computed tomography coronary angiography performed with a 64-slice multi-detector computed tomography scanner from January 2007 to December 2008 were retrospectively reviewed. Patients with zero and low coronary artery calcium scores were analysed for prevalence of atherosclerotic plaque and degree of arterial luminal stenosis. Results: The records of 194 patients with zero (n = 130; 67.0%) and low (n = 64; 33.0%) coronary artery calcium scores were included. Non-calcified plaque was found in 20 (15.4%) patients with zero coronary artery calcium score and 49 (76.6%) patients with low coronary artery calcium score. Significant coronary artery stenosis (>50% luminal diameter stenosis) by non-calcified plaque was found in five (3.8%) patients with zero coronary artery calcium score and 18 (28.1%) patients with low coronary artery calcium score. Subsequent cardiac catheterization was performed in three patients with zero coronary artery calcium score (mean follow-up, 34.5 months; standard deviation, 6.3 months); the result was in agreement with computed tomography coronary angiography for one patient and two had overestimation of stenosis. Subsequent cardiac catheterizations were performed in 11 patients with low coronary artery calcium score; the results were in agreement with computed tomography coronary angiography for 10 patients and one had overestimation of stenosis. Conclusions: Absence of coronary artery calcium does not exclude obstructive coronary artery disease. Low coronary artery calcium score is not reliable in predicting non-calcified plaque burden.