A within-group risk factor analysis was conducted to predict angiographic change in the Cholesterol Lowering Atherosclerosis Study, a randomized, placebo-controlled trial of colestipol plus niacin therapy in men with previous coronary bypass surgery. Global angiographic change, including both native coronary arteries and bypass grafts after 2 treatment years, was the end point. Risk factors included on-trial clinical measures, plasma lipids, lipoproteins, and apolipoproteins. Univariate analysis indicated that risk factors previously observed by others in epidemiologic investigation of ischemic heart disease-total cholesterol, LDL cholesterol, non-HDL cholesterol, triglycerides, apolipoprotein B, and diastolic blood pressure-had significant effects in the placebo-treated group. Univariate analysis indicated significant effects of apolipoprotein C-III in drug-and placebo-treated groups. Multivariate analysis indicated the predominant risk factor predicting the probability of global coronary progression was non-HDL cholesterol in placebo-treated subjects and the content of apolipoprotein C-IlI in high density lipoproteins of drug-treated subjects. Both drug-and placebo-treated group findings point to an important role for triglyceride-rich lipoproteins in progression and regression of human atherosclerosis. (Circulation 1990;81:470-476) T hree controlled clinical trials (the Lipid Research Clinics Coronary Primary Prevention Trial, the Helsinki Heart Study, and the Coronary Drug Project) have shown that the incidence rate of coronary heart disease can be reduced by drugs that lower total plasma cholesterol. [1][2][3] see p 694 Although reduction of total plasma cholesterol was a common feature of these trials, the drugs tested reduced cholesterol levels through different mechanisms and produced widely different patterns of lipoprotein transport. The mechanism(s) of benefit in these trials is believed due to a primary effect of lowering blood lipids or lipoproteins on coronary atherosclerosis at the level of the arterial wall.

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The 2-year therapy effect on femoral atherosclerosis was evaluated in the Cholesterol Lowering Atherosclerosis Study (CLAS), a randomized, placebo-plus-diet-controlled angiographic trial of colestipol-niacin therapy plus diet in men with previous coronary bypass surgery. Different diet compositions were prescribed to enhance the differential in blood cholesterol responses between the two groups. The annual rate of change in computer-estimated atherosclerosis (CEA), a measure of lumen abnormality, was evaluated between treatment groups. A significant per-segment therapy effect was found in segments with moderately severe atherosclerosis (p less than 0.04) and in proximal segments (p less than 0.02). When segmental CEA measures were combined into a per-patient score using an adaptation of the National Heart, Lung, and Blood Institute scoring procedure, a significant therapy effect was observed (p less than 0.02). Total variance of the annual change rate in CEA was as predicted from pilot studies, but measurement variation was larger. The therapy effect observed in femoral arteries, although significant, was less marked than the strong and consistent benefit previously reported for both native coronary arteries and aortocoronary bypass grafts.

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