News:Coronary Calcium Coverage Score is Associated with an Increase in the Risk of Coronary Artery Disease

May 29, 2008 By Vijayalakshmi Kunadian MBBS MD MRCP [mailto:vkunadian@perfuse.org]

Calcium within coronary arteries can be detected using imaging modalities such as coronary angiography, intravascular ultrasound and computed tomography (CT). High resolution CT determines the precise regions of calcification within coronary arteries using Agatston and mass scores. Brown and colleagues in a recent study published in Radiology developed a new score called the Calcium Coverage Score (CCS) which measures the percentage of coronary arteries affected by calcium using unenhanced cardiac CT and correlated the CCS with risk factors and cardiovascular events. This score is different to the Agatston score which measures the presence and amount of calcific plaque in the coronary arteries.

The data for this study was obtained from the Multi-Ethnic Study of Atherosclerosis (MESA) consisting of 6,814 patients without known cardiovascular disease aged 45 to 84 years. CT image data was available in 3252 of the 3398 patients with calcific plaque demonstrated on at least one CT image and the remaining 3416 participants did not have calcific plaque on CT. CCS was determined on the CT images using the following formula: Number of absolute subdivisions in which calcific plaque was present/Total number of absolute subdivisions in the coronary arteries x 100. The presence of calcific plaque in short intervals along the arteries were called subdivisions. Patients were followed up for a median of 41 months.

The investigators identified that diabetic patients have 44% more of their coronary artery tree affected by calcific plaque compared with patients who did not have diabetes. The CCS for participants with diabetes, dyslipidemia and hypertension was 1.44 (p<0.001), 1.30 (p<0.001) and 1.22 (p<0.001) respectively compared with those who did not have these risk factors.

CCS and Agatston and mass scores were significantly associated with coronary heart disease events (p<0.05). The hazard ratio adjusted for age and gender for all coronary heart disease events for a 2-fold increase in CCS was 1.52 (95% CI 1.34 to 1.72), p<0.001. When Agatston and mass scores were added in a Cox model for coronary heart disease events with the CCS, the CCS score remained significantly associated with events.

Among patients who underwent 2 scans, the CCS scores were reproducible (intraclass correlation coefficients=0.962). However, CCS is ovecome by limitations because it depends on the accurate tracing of the arteries along their entire length.

The investigators conclude that spatial distribution of calcified plaque is an important component for the development of coronary atherosclerosis above and beyond the overall amount of calcium and the calcium density and contributes to the risk of coronary heart disease events.