Apolipoprotein E phenotypes in patients with myocardial infarction.

The frequencies of genetic apo E isoforms E2, E3 and E4 were determined in 523 patients with myocardial infarction and compared to those in a control group (1031 blood donors). A significant difference in the frequency of apo E4 was noted between patients and controls (0.05 greater than P greater than 0.025). No differences in the frequencies of isoforms E3 and E2 were observed. In particular, there was no significant difference between the two groups in the frequency of apo E2 homozygosity, a condition that is associated with type III hyperlipoproteinemia. However, all E2 homozygote survivors of myocardial infarction had hyperlipoproteinemia type III (cholesterol 269 +/- 29 mg/dl; triglyceride 419 +/- 150 mg/dl; age 54 +/- 14 years; N = 5). On the contrary, E2 homozygote controls (all apo E-2/2 blood donors and their apo E-2/2 relatives who were from the same age range as the patients) had primary dysbetalipoproteinemia but normal or subnormal plasma cholesterol concentrations (cholesterol 184 +/- 28 mg/dl; triglyceride 151 +/- 52 mg/dl; age 56 +/- 13 years; N = 11). This indicates that E2 homozygotes with hyperlipoproteinemia type III who occur rarely in the population but comprise about 1% of myocardial infarction patients have a markedly increased risk for coronary atherosclerosis, whereas the risk for E2 homozygotes with normal or subnormal plasma cholesterol (= primary dysbetalipoproteinemia) may be considerably lower than for the general population. The data illustrate the complex relationship between apo E genes, lipid levels, and risk for atherosclerosis.