Possibilities of DNA analysis for the detection of predisposition to thrombotic disease

Genetic polymorphisms modify the response of factor VII to oral contraceptive use: an example of gene-environment interaction

Elevated plasma levels of factor VII and fibrinogen are risk factors for cardiovascular disease, especially arterial thrombosis. Oral contraceptive use increases factor VII and fibrinogen plasma levels. It has been described that DNA polymorphisms are associated with the plasma levels of hemostatic variables and their regulation. The R/Q353 polymorphism in the factor VII gene and the -455G/A polymorphism in the fibrinogen beta-gene are associated with plasma levels of factor VII and fibrinogen, respectively. We analysed data of a randomised study (n = 95) in which two types of oral contraceptives were compared with regard to their effect on factor VII and fibrinogen, in which we also determined R/Q353 and -455G/A polymorphisms. Women were allocated randomly to either receiving a monophasic oral contraceptive containing 75 micrograms of gestodene and 20 micrograms of ethinyl estradiol, or 150 micrograms of desogestrel and 20 micrograms of ethinyl estradiol. Blood was taken before treatment and after 3 and 6 months of oral contraceptive use. Factor VII and fibrinogen increased significantly after 3 and 6 months of oral contraceptive use; the increase in factor VII was higher in the desogestrel group than in the gestodene group at 3 and 6 months. For fibrinogen, there were no intergroup differences at 3 and 6 months. At baseline, an association between genotype and plasma factor VII and fibrinogen levels was observed. In multivariate analysis, the R/Q353 polymorphism and the type of oral contraceptive were determinants of the effect on the change in factor VII, with the highest increase in women carrying the Q allele and using the desogestrel-containing oral contraceptive, and the lowest increase in women with the RR genotype who use the gestodene-containing oral contraceptive. For fibrinogen, no interaction among type of oral contraceptive, -455G/A polymorphism, and change in plasma levels was observed. We conclude that an individual's genetic variation may contribute to the response of plasma factor VII to oral contraceptive use.

The effects of cardiopulmonary bypass on fibrin formation and lysis: is a normal fibrinolytic response essential?

Fibrinolytic activity in blood is regulated by a dynamic process that includes control of production, secretion, inhibition, and clearance of fibrinolytic proteins. The concentration of active tissue plasminogen activator (tPA) in the region of the thrombus controls the rate of fibrinolytic activation. We have developed a first-generation kinetic model that can be used to simulate the effects of secretion, inhibition, and clearance reactions on the concentrations of active tPA, active plasminogen activator inhibitor type 1 (PAI-1), and tPA/PAI-1 complex in the circulation. This model was used to estimate the rate and pattern of secretion of tPA and PAI-1 in individual subjects. We also undertook a laboratory evaluation of fibrinolysis in patients with a history of myocardial infarction. Elevated PAI-1 activity in the absence of elevations in other acute-phase proteins suggested an intrinsic increase in PAI-1 secretion in patients post-myocardial infarction. Cardiopulmonary bypass (CPB) results in a major increase in fibrinolytic activity that has been associated with an increased risk for hemorrhage. Fibrinolytic proteins were sampled from patients both during surgery and for 2 days postoperatively. Total tPA antigen rose throughout CPB and returned to baseline in the post-operative period. PAI-1 activity fell during the initial bypass and by the end of bypass had returned to baseline. On the first to second postoperative day there was a large increase in PAI-1 activity and a significant decrease in tPA activity. These data suggest that during this period there is a window of risk for a thromboembolic event. There was, however, a large individual variability in patient response to CPB.