Predicting coronary heart disease: from Framingham Risk Score to ultrasound bioimaging

Atherosclerosis is the leading cause of death and disabling disease. Whereas risk factors are well known and constitute therapeutic targets, they are not useful for prediction of risk of future myocardial infarction, stroke, or death. Therefore, methods to identify atherosclerosis itself have been tested and found useful (ie, coronary calcium detection by computed tomography scanning, reduction in ankle-brachial index, and ultrasound scanning of the carotid arteries). This review will focus on the latter technique. Detection of thickened carotid intima-media by ultrasound has been used in many large epidemiological studies, but although it has been found to be associated with increased risk of cardiovascular death, its clinical utility is limited. Detection of carotid plaque has, on the other hand, been found to be associated with a substantial risk of future events. Similarly, detection of plaque in the femoral arteries is associated with increased risk, and plaque in the femoral as well as carotid arteries predicts even higher risk. Furthermore, quantification of plaque size (plaque area), such as quantification of amount of coronary calcium on computed tomography scanning, improves predictability-the larger the plaques, the higher the risk. So far, studies using ultrasound all have been performed with 2-dimensional ultrasound imaging. Recently, 3-dimensional ultrasound imaging has been introduced, which allows for more accurate quantification of atherosclerosis. Small studies pioneering its use have indicated the utility of measuring changes in vessel-wall volume and plaque volume with respect to treatment effect. The High-Risk Plaque Initiative BioImage Study is currently investigating the predictive value of total carotid plaque volume with respect to prediction of future cardiovascular events.