Coronary Calcification and Predicted Risk of Coronary Heart Disease in Asymptomatic Men with Hypercholesterolaemia

OBJECTIVE: To document the relationship between coronary calcification and coronary risk assessed clinically in asymptomatic patients with hypercholesterolaemia. DESIGN: Prospective observational study. SETTING: Health screening clinic. PATIENTS: A total of 286 asymptomatic men aged 45-64 with plasma cholesterol >or= 6.5 mmol/l. INTERVENTIONS: Electron beam computed tomography to measure coronary calcium score. MAIN OUTCOME MEASURES: The Framingham equation was used to separate subjects into groups with either low 10-year risk of coronary artery disease (<or= 10%) or high 10-year risk (>or= 20%). Coronary calcium score was assessed in each group. RESULTS: The mean log calcium score was significantly higher in the 97 high-risk men than in the 189 low-risk men (1.58 +/- 0.84 versus 1.00 +/- 0.85, < 0.001). Arithmetic means (158 versus 55), and the proportion with a score > 400 (11% versus 2%, p < 0.01) were also greater. However, 27% of the high-risk group had a low calcium score (<or= 10), which is known to be associated with minimal coronary artery disease assessed by angiography. CONCLUSIONS: Approximately one quarter of asymptomatic hypercholesterolaemic men aged 45 to 64 who have an estimated risk of coronary heart disease of >or= 20% in 10 years have minimal coronary calcification. They may therefore represent a subset at lower risk of disease. However, uncertainties about the predictive power of coronary calcification for coronary events must be resolved before electron beam computed tomography can be used to select high-risk patients for primary prevention.