The following two articles demonstrate the power of EBCT to predict future cardiovascular events. The first article shows that a calcium score over 160 confers a 20 to 35-fold increase in risk, while the second paper was able to show that patients in the highest age-sex matched quartile of calcium scores had a 59-fold increase in risk compared with those in the lowest quartile. This suggests that the rate of progression of calcium scores is a more powerful predictor than the absolute scores. Patients with mild to moderate scores, but whose scores are above the 50th percentile for their age and sex, should receive aggressive risk factor modification.

1. Predictive Value of Electron Beam Computed Tomography of the Coronary Arteries

Background: Coronary electron beam computed tomography (EBCT) detects atherosclerotic coronary artery disease by measuring calcium deposition in the walls of coronary arteries. EBCT-derived coronary artery calcium (CAC) scores correlate with the severity of underlying coronary artery disease.
Methods and Results: We followed 1173 asymptomatic patients who underwent EBCT between September 1993 and March 1994. During average follow-up of 19 months, 18 subjects had 26 cardiovascular events: 1 death, 7 myocardial infarctions, 8 coronary artery bypass graft procedures, 9 coronary angioplasties, and 1 nonhemorrhagic stroke. For CAC score thresholds of 100, 160, and 680, EBCT had sensitivities of 89%, 89%, and 50% and specificities of 77%, 82%, and 95%, respectively. Odds ratios ranged from 20.0 to 35.4 (p<0.00001 for all).
Conclusions: Coronary EBCT predicts future atherosclerotic cardiovascular disease events in asymptomatic subjects.

2. Identification of Patients at Increased Risk of First Unheralded Acute Myocardial Infarction by Electron Beam Computed Tomography
Background: There is a clear relationship between absolute calcium scores (CS) and severity of coronary artery disease. However, hard coronary events have been shown to occur across all ranges of CS.
Methods and Results: We conducted 2 analyses: in group A, 172 patients underwent EBCT imaging within 60 days of suffering an unheralded myocardial infarction. In group B, 632 patients screened by EBCT were followed up for a mean of 32 +/- 7 months for the development of acute myocardial infarction or cardiac death. The mean patient age and prevalence of coronary calcification were similar in the 2 groups (53 +/- 8 versus 52 +/- 9 years and 96% each). In group B, the annualized event rate was 0.11% for subjects with CS of 0, 2.1% for CS 1 to 99, 4.1% for CS 100 to 400, and 4.8% for CS>400. However, mild, moderate, and extensive absolute CSs were distributed similarly between patients with events in both groups (34%, 35%, and 27%, respectively, in group A and 44%, 30%, and 22% in group B). In contrast, the majority of events in both groups occurred in patients with CS > 75th percentile (70% in each group).
Conclusions: Coronary calcium is present in most patients who suffer acute coronary events. Although the event rate is greater for patients with high absolute CSs, few patients have this degree of calcification on a screening EBCT. Conversely, the majority of events occur in individuals with high CS percentiles. Hence, CS percentiles constitute a more effective screening method to stratify individuals at risk.