Expert review on coronary calcium

Abstract

While there is no doubt that high risk patients (those with >20% ten year risk of future cardiovascular event) need more aggressive preventive therapy, a majority of cardiovascular events occur in individuals at intermediate risk (10%-20% ten year risk). Accurate risk assessment may be helpful in decreasing cardiovascular events through more appropriate targeting of preventive measures. It has been suggested that traditional risk assessment may be refined with the selective use of coronary artery calcium (CAC) or other methods of subclinical atherosclerosis measurement. Coronary calcification is a marker of atherosclerosis that can be quantified with the use of cardiac CT and it is proportional to the extent and severity of atherosclerotic disease. The published studies demonstrate a high sensitivity of CAC for the presence of coronary artery disease but a lower specificity for obstructive CAD depending on the magnitude of the CAC. Several large clinical trials found clear, incremental predictive value of CAC over the Framingham risk score when used in asymptomatic patients. Based on multiple observational studies, patients with increased plaque burdens (increased CAC) are approximately ten times more likely to suffer a cardiac event over the next 3-5 years. Coronary calcium scores have outperformed conventional risk factors, highly sensitive C-reactive protein (CRP) and carotid intima media thickness (IMT) as a predictor of cardiovascular events. The relevant prognostic information obtained may be useful to initiate or intensify appropriate treatment strategies to slow the progression of atherosclerotic vascular disease. Current data suggests intermediate risk patients may benefit most from further risk stratification with cardiac CT, as CAC testing is effective at identifying increased risk and in motivating effective behavioral changes. This article reviews information pertaining to the clinical use of CAC for assessing coronary atherosclerosis as a useful predictor of coronary artery disease (CAD) in certain population of patients.

Figure 1

The Algorithm recommended by SHAPE (Screening for Heart Attack and Prevention). Patients with higher calcium scores get increasing therapies, as well as more diagnostic workup.

Figure 2

56-year-old male with family history of heart disease, found to have no coronary calcification. This person was subsequently not treated with statin therapy, after being assessed as low risk by CT imaging.

Figure 3

62-year-old sister of patient from Figure 2, found to have moderate calcifications and started on statin and aspirin therapy, in addition to lifestyle modification counseling.

Figure 4

Extensive calcifications, warranting aggressive medical management for atherosclerosis.

Figure 5

Ten-year follow up for all cause mortality. Patients with scores > 1000 had a 26% mortality rate, multiples higher than patients without coronary calcification.