Prolonged seated immobility-associated venous coagulability in a factor V Leiden heterozygote: a case–comparative study
Prolonged sitting and thrombophilia may compound the risk of venous thromboembolism. In order to investigate suspected local lower limb venous procoagulant changes associated with prolonged sitting-induced venous stasis in a man heterozygous for factor V Leiden (participant X), we qualitatively compared venous coagulability in lower and upper limb plasma in this participant and three other male Caucasians over 8 h of sitting. Of the four participants, participant X had the highest baseline values of prothrombin fragments 1 and 2, thrombin–antithrombin III complexes, tissue plasminogen activator, plasminogen activator inhibitor 1, D-dimer and soluble thrombomodulin. Over time, in participant X, venous prothrombin fragments 1 and 2, thrombin–antithrombin III complexes, and soluble thrombomodulin decreased in both limbs; D-dimer decreased in the lower limbs but increased in the upper limbs; the tissue plasminogen activator/plasminogen activator inhibitor 1 molar ratio increased in both limbs; and minimal changes were noted in haematocrit. A foot volume increase was associated with vague symptoms towards the end of the study. Overall, these changes were similar to those observed in other participants. It is concluded from this case comparison that prolonged sitting of 8 h duration under normal atmospheric conditions did not result in local, as well as systemic, procoagulant haemostatic responses in a heterozygote for factor V Leiden when compared with other healthy volunteers. However, this observed, possibly adaptive, response is more likely to be compromised in factor V Leiden subjects during continued or increased venous endothelial stress or in the presence of other venous thromboembolism risk factors.