For a detailed description of the 4G polymorphism, read Kohler et al. PAI-1 and Coronary Artery Disease. NEJM 2000; 342 (24): 1792-1801. In some studies, the 4G allele (four guanine bases) was significantly associated with high plasma PAI-1 concentrations, and was most strongly associated with previous MI, as well as risk of future MI. Studies have shown that subjects who are homozygous for the 4G allele have plasma PAI-1 concentrations approximately 25% higher than those with the 5G allele (5 guanine bases). Similarly, among patients with hypertriglyceridemia, those with the 4G allele also have higher plasma PAI-1 concentrations than those with the 5G allele. There are still conflicting data on the strength of the relation between PAI-1 gene polymorphism and MI, but it is suggested that the 4G allele is more likely to contribute to MI, particularly in the presence of hypertriglyceridemia.