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The relations of high density lipoprotein (HDL) subclasses to severity and rate of progression of coronary atherosclerosis were investigated in 60 men who had survived a myocardial infarction before the age of 45 years and who had subsequently undergone two coronary angjographies, with an intervening time interval of 4-7 years between angiographies. Five HDL subclasses with different particle sizes were determined by gradient gel electrophoresis, and the major serum lipoprotein classes were separated by preparative ultracentrifugation in connection with the second angiography. Highly significant inverse correlations were found between the plasma levels of the largest HDL particles, the HDLa, subclass, and both disease severity as observed on the second coronary angiogram (r=-0.53, p<0.001) and progression of coronary lesions between angiographies (r=-038, /?<0.01). Grouping the patients according to the presence or absence of very low density lipoprotein (VLDL) triglyceride elevation revealed striking differences in the relations of HDL subspecies to coronary atherosclerosis between normotriglyceridemic and hvpertriglyceridemic subjects. There were strong inverse correlations between the plasma HDL^ concentration and both severity of lesions (r=-0.72,p<0.001) and rate of lesion progression (r=-0.58, p<0.01) in the normotriglyceridemic patients, whereas this relation was absent in subjects with hypertriglyceridemia. Although it was retrospective in design, affected by an inherent selection bias due to unavoidable dropouts and exclusions, and limited to young, male, postinfarction patients, the study suggests that the inverse relation between HDL level and coronary heart disease or coronary atherosclerosis seen in previous epidemiological and angiographlc studies is accounted for by the largest HDL particles, the HDLy, subclass. Furthermore, the hvpertriglyceridemic state appears to markedly influence the relations between plasma concentrations of HDL subclasses and coronary atherosclerosis. Prospective studies of unselected patients are needed to corroborate these findings. (Arteriosclerosis and Thrombosis 1991;11:174-182) M ost prospective epidemiological studies have shown an independent inverse relation between high density lipoprotein (HDL) cholesterol concentration and risk of development of coronary heart disease (CHD).

The relations of hemodynamic factors, plasma fibrinogen concentration, serum lipoprotein levels, and clinical risk indicators to coronary atherosclerosis were studied in 56 men who had survived a first myocardial infarction before the age of 45 years and who subsequently underwent two coronary angiographies with an intervening time interval of 4 to 7 years. Presence, severity, and rate of progression of both diffuse lesions and distinct stenoses were determined by means of separate classification systems in 15 proximal coronary arterial segments. High minimum heart rate measured during a 24-hour period in connection with the reangiography was associated with progression of both diffuse lesions and distinct stenoses. High minimum heart rate also correlated positively with angiographic scores of global severity of diffuse atherosclerosis and stenoses. Progression of disease was predicted independently by minimum heart rate and low-density lipoprotein/high-density lipoprotein ratio, whereas lipoprotein A, fibrinogen levels, hypertension, smoking, and beta-adrenergic receptor blockade treatment did not discriminate between patients with and without progression.