COMPUTED TOMOGRAPHY CORONARY ANGIOGRAPHY: DIAGNOSTIC AND PROGNOSTIC VALUE
Fabiola B. Sozzi, M.D., Ph.D., Cardiology Unit, Policlinico Hospital, Milan, Italy
Coronary multislice computed tomography (CT) is increasingly being used as a tool for non-invasive visualization of the coronary arteries (1). The technique provides information on atherosclerotic plaque burden and to some extent on plaque composition. The diagnostic value of coronary CT scan is high. In the last few year a flourish literature on the prognostic value of coronary CT has been published. Accuracy of coronary CT needs to be assessed in management outcome studies, in which diagnostic and therapeutic strategies would be decided based on CT alone, without reference to any coronary angiography results.
A main point is that plaque composition represents a long-term predictor of cardiac events. In a long-term follow-up study on the predictive value of coronary CT, Sozzi et al (1) demonstrated that non-calcified and mixed plaques carried a worse prognosis compared to calcified plaques. Referring to plaque vulnerability concept, Mann et al (2) studied 31 subjects who died suddenly of CAD. They found that lipid core size and minimal cup thickness, 2 major determinants of plaques vulnerability, were not related to absolute plaque size or degree of stenosis. Accordingly, atherosclerotic plaque growth and destabilization are highly variable. Many serial angiographic studies have demonstrated that most AMI occur due to the occlusion of coronary arteries that did not previously contain significant stenosis; furthermore the coronary artery with the most severe stenosis is usually not the “culprit” one. Thus, plaque progression and clinical outcome are not always closely related, and each is poorly predicted on clinical and angiographic grounds, as most plaques that underlie an AMI are <70% stenosed.
Previously, CT was associated with elevated radiation exposure. Radiation doses are rapidly decreasing with newer acquisition protocols, arriving to an exposure of 2 mSv per exam.
1. Sozzi FB, Civaia F et al. Long-term follow-up of patients with first-time chest pain having 64-slice computed tomography. AJC 2011;15:516-21.
2. Mann JM, Davies MJ. Vulnerable plaque. Relation of characteristics to degree of stenosis in human coronary arteries. Circulation 1996;94:928-931.