The beneficial effect of hydroxymethylglutaryl coenzyme A reductase inhibitors (statins) on the progression of atherosclerosis has been noted in individual studies. This may be a “class effect,” assuming equivalent improvement in lipid abnormalities. Hecht and Harman compared the effects of atorvastatin and simvastatin on the progression of asymptomatic coronary artery disease (CAD) using serial electron beam tomography (EBT) to determine calcified plaque burden.
Through an observational technique that employed serial EBT evaluation, lipid-lowering agents, and dosing (as determined by treating physicians), 149 asymptomatic patients with no history of CAD who had positive evidence of atherosclerotic disease on EBT evaluation were included in the study. Aspirin use and tobacco cessation were recommended to all patients, along with tight control of diabetes and hypertension. Patients were aggressively treated, resulting in optimal improvement in all lipid parameters. About 50 percent of patients in both groups took niacin in addition to a statin.
After 14 months of treatment, comparison of the 46 participants taking simvastatin and the 103 participants taking atorvastatin demonstrated dramatic improvement in all lipid measurements with no significant post-treatment difference in progression rates of the calcium or volume scores. Among untreated patients with asymptomatic atherosclerotic disease based on EBT, the annual rate of progression of subclinical atherosclerosis ranged from 24 to 52 percent. The subjects in this study had an annual increase in EBT values of 7.5 percent in the simvastatin group and 10.8 percent in the atorvastatin group, rates that were not significantly different. Calcium progression has been associated with a worse prognosis and an increase in adverse cardiac events.
The authors conclude that, among patients in these aggressively treated groups, the similar reduction in plaque progression rates in patients with asymptomatic CAD based on EBT measurements demonstrates that this primary prevention effect is a “class effect.” The relative effects of the statins and niacin on plaque development cannot be determined in this study because of the high use of concomitant niacin.