MedWire News: Athletes who fly to participate in marathon races have greater increases in D-dimer levels after the race than local runners, US researchers report.
These results might explain the reports of deep vein thrombosis and pulmonary embolism in otherwise healthy endurance athletes who have traveled by car or plane to and from endurance events, say Beth Parker (Hartford Hospital, Connecticut) and colleagues.
"Although strenuous endurance exercise such as a marathon activates both coagulation and fibrinolysis, extended car, bus, train, or air travel also activates coagulation, making it possible that the combination of endurance exercise and travel could shift the hemostatic balance in athletes toward activation of the coagulatory system," note the researchers.
To test this hypothesis, Parker and team measured coagulatory markers in 41 participants of the 2010 Boston Marathon who lived either more than a 4-hour plane flight (travelers, n=23) or less than a 2-hour car journey (controls, n=18) from Boston. All study participants were nonsmokers, aged 20 to 51 years, and free from known cardiovascular, metabolic, and coagulatory disease.
The researchers obtained venous blood samples the day before, immediately after, and the day after returning home from the marathon. They tested the samples for soluble D-dimer levels and microparticle procoagulant activity, both of which are venous thrombotic risk markers, and for p-selectin levels, which can be associated with the risk for thrombotic and cardiovascular events.
As reported in the American Journal of Cardiology, travelers experienced a significantly greater increase in D-dimer levels from before to immediately after the race than did controls. Specifically, there was a mean 245-ng/mL increase observed in the travelers (from 142 to 387 ng/mL) compared with an increase of 148 ng/mL in the controls (from 85 to 233 ng/mL).
Furthermore, six of the travelers had D-dimer values above the clinical threshold for excluding venous thrombosis (>500 ng/mL) upon returning home the day after the marathon, whereas none of the controls did.
Parker et al remark that "the clinical significance of this observation is unclear," as none of the runners reported symptoms suggestive of DVT. However, the researchers could not exclude asymptomatic venous disease or the possibility that these individuals developed thrombi that lysed, as venous studies were not performed.
Soluble p-selectin increased significantly with exercise in both groups but was not associated with the mode of travel. Age, however, was significantly and positively correlated with p-selectin level before and after the marathon.
"This observation could explain in part the increased risk of cardiac events in older subjects running marathons," the researchers suggest.
Plasma microparticle activity also increased significantly following the marathon in both groups, with even greater increases observed the day after the race, independent of mode of travel and age.
Parker and team conclude: "The combination of exercise and travel increases biomarkers of thrombotic and vascular risk and might contribute to the small but increased risk of cardiac events associated with endurance running in susceptible subjects."
By Laura Cowen