Section 4: Using EBCT to Track Progression or Regression of Coronary Atherosclerosis

Return to the EBT Coronary Calcium Research section

EBCT is the only noninvasive test that can be used to assess response to therapeutic interventions aimed at shrinking coronary plaque. The first article describes a 12-15 month study showing that statin treatment results in stabilization and even shrinkage of plaque burden, while no statin treatment can result in a 50% increase in plaque burden. The second article found that patients whose scores increase over a 12-36 month study period experience a 10-fold increase in risk of coronary events when compared to patients whose scores remain stabilized.

1. Effect of HMG-CoA Reductase Inhibitors on Coronary Artery Disease as Assessed by Electron Beam Computed Tomography

Background: Angiographic studies of the regression of coronary artery disease are invasive and costly, and they permit only limited assessment of changes in the extent of atherosclerotic disease. EBCT is noninvasive and inexpensive. The entire coronary artery tree can be studied during a single imaging session, and the volume of coronary calcification as quantified with this technique correlates closely with the total burden of atherosclerotic plaque.

Methods: We conducted a retrospective study of 149 patients (61% men and 39% women; age range, 32 to 75 years) with no history of coronary artery disease who were referred by their primary care physicians for screening EBCT. All patients underwent baseline scanning and follow-up assessment after a minimum of 12 months (range, 12 to 15), and a volumetric calcium score was calculated as an estimate of the total burden of plaque. Treatment with HMG-CoA inhibitors (statins) was begun at the discretion of the referring physician. Serial measurements of LDL cholesterol were obtained, and the change in the calcium volume score was correlated with average LDL cholesterol levels.

Results: 105 patients (70%) received treatment with statins, and 44 patients (30%) did not. At follow-up, a net reduction in the calcium volume score was observed only in the 65 treated patients whose final LDL cholesterol levels were less than 120 mg/dl (mean change in the score, -7 +/- 23%; p=0.01). Untreated patients had an average LDL cholesterol level of at least 120 and at the time of follow-up had a significant net increase in mean calcium volume score (mean change, +52 +/-36%; p<0.001). The 40 treated patients who had average LDL cholesterol levels of at least 120 had a measurable increase in mean calcium volume score (mean change, +25 +/-22%, p<0.001), although it was smaller than the increase in the untreated patients.

Conclusions: The extent to which the volume of atherosclerotic plaque decreased, stabilized, or increased was directly related to treatment with statins and the resulting serum LDL cholesterol levels. These changes can be determined noninvasively by electron beam CT and quantified with use of a calcium volume score.
Callister,T et al. N Engl J Med 1998;339:1972-78)

2. Cardiac Events in Patients with Progression of Coronary Calcification on Electron Beam Computed tomography

Background: Coronary artery calcification (CAC) is a sensitive marker of coronary artery disease (CAD). We have previously shown that CAC progression can be accurately followed by means of sequential EBCT imaging employing a volumetric calcium score (VCS). In this study we conducted an outcome analysis of patients who underwent 2 sequential EBCT scans at a minimum interval of 12 months, and related the occurrence of cardiac events to the presence of regression/progression of CAC.

Methods: Telephone interviews of 269 asymptomatic individuals (68% men, mean age 54 +/-7) referred by primary care physicians for a screening and follow-up EBCT scan due to the presence or risk factors for CAD. The medical records of patients with self-reported events were reviewed for information accuracy.

Results: The interscan time ranged between 12 and 36 months and 134 (50%) showed progression of CAC (average VCS increase: 24 +/-7%). Events occurred in 22 patients: 7 myocardial infarctions (MI), 2 cardiac deaths, 7 coronary angioplasties (PTCA), and 9 coronary artery bypass surgeries. 20 of 22 events (91%) occurred in patients showing CAC progression with a mean increase in VCS of 41 +/-10% (p<0.05 for comparison with mean progression in the entire cohort). The proportion of patients with VCS progression was larger in the group suffering events than in the cohort at large (91% vs. 50%, p<0.001). 2 events (1 MI and 1 PTCA) occurred in patients with apparent plaque stabilization (VCS change: -0.07% for both cases). The relative risk for a cardiac event in patients with VCS progression was 10 fold greater than that of patients with stabilization of VCS.

Conclusions: EBCT can accurately assess the evolution of CAD as indicated by changes in volumetric calcium scores. This preliminary study shows that progression of CAC detected by this tool may portend a significantly increased risk of cardiac events.
Raggi, P et al. RSNA Annual Meetings, 11/99