The Monitored Atherosclerosis Regression Study, a randomized, double- blind, placebo-controlled, 2-year trial of lovastatin monotherapy, found that coronary lesions < 50% diameter stenosis (%S) and coronary lesions < 50%S at baseline had different responses to therapy. We now report on clinical, lipid, and nonlipid risk factors of treatment response in these lesion subsets.Methods and ResultsTwo hundred seventy subjects, 37 to 67 years old, with plasm/ba total cholesterol (TC) 190 to 295 mg/dL (4.91 to 7.63 mmol/L) and total triglyceride < 500 mg/dL (5.65 mmol/L) were randomized to low-fat, low-cholesterol diet and either lovastatin 80 mg/d or placebo. Logistic regression was used to model the association between risk factors and coronary lesion progression in mild/moderate ( < 50%S) and severe ( < 50%S) lesions in 220 angiogram pairs analyzed by computer quantitative coronary angiography. In the placebo group, risk factors (P< .05) for the progression of mild/moderate lesions were triglycerides and TC/high-density lipoprotein cholesterol (HDL-C). Risk factors for the progression of severe lesions were HDL-C (negative), low-density lipoprotein cholesterol (LDL-C)/HDL-C, and TC/HDL-C. TC/HDL-C was the pre-dominant risk factor for both mild/moderate and severe lesions in the multivariate analysis. In the lovastatin group, with aggressive lowering of LDL-C and TC below 85 mg/dL and 156 mg/dL, respectively, risk factors for mild/moderate lesions included triglycerides and very-low-density lipoprotein-LDLassociated apolipoprotein C-Ill (apo C-III-heparin precipitate), a marker of triglyceride-rich lipoprotein particles. Apo C-III-heparin precipitate was the predominant risk factor in the multivariate analysis. Risk factors for severe lesions were LDL-C, LDL-C/HDL-C, TC/HDL-C, and apo B; LDL-C/ HDL-C was the predominant risk factor.ConclusionsThese results indicate that triglyceride-rich lipoproteins and cholesterol-rich lipoproteins have a differential effect on mild/moderate and severe lesion progression, respectively. These results add to the growing evidence of the importance of triglyceride-rich lipoproteins as a risk factor for coronary artery disease and the need for treatment in the progression of atherosclerosis.