You Make the Call
Each month in “ You Make the Call ,” we ’ ll pick a challenging clinical question submitted through ASH ’ s Consult a Colleague program and post the expert ’ s response , but we also want to know what you would do . Send in your responses to next month ’ s clinical dilemma and see how your answer matches up to the experts ’ in the next print issue .
This month , Beth Battinelli , MD , PhD , discusses thrombosis development after extended travel .
Clinical Dilemma :
A healthy 42-year-old woman not on estrogen flew 2.5 hours to North Carolina – plus time spent sitting in the terminal . She flew home two days later . The next morning she drove 2.5 hours to her sister ’ s home and returned home the following morning . Three days later she was diagnosed with a lower extremity deep vein thrombosis ( DVT ). Would you consider her DVT provoked or unprovoked ? Would three months of anticoagulation be okay , or does she need D-dimers to help decide ? If you consider her DVT to be unprovoked , how long should she be anticoagulated ?
Expert Opinion
Elisabeth M . Battinelli , MD , PhD Associate Physician , Brigham and Women ’ s Hospital Assistant Professor of Medicine , Harvard Medical School Boston , Massachusetts
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Although we usually think of air travel as associated with thrombosis , this complication can occur with extended travel by other modes of transportation , including car , bus , or train . Each year , more than 300 million people travel long distances by air ( defined as greater than 4 hours in the air ). One serious adverse event that occurs for some longdistance travelers is the development of a venous thromboembolic event ( VTE ). Based on observational studies , an estimated one in 500 individuals ( ≥50 years old ) who fly long distances will develop a VTE . A recent study suggested that the risk is cumulative for each two hours of prolonged air travel culminating in a risk of 18 percent . Other risk factors can clearly affect overall risk , including previous VTE , thrombophilia , obesity , hormone-based therapies , recent surgery , or active malignancy . Although evidence suggests that the risk of venous thrombosis increases after air travel , questions remain about the underlying mechanism , as well as whether the mode of transportation is significant .
It is also clear that the risk does not end with the cessation of travel . Studies report that increased risk of VTE persists for the first two weeks after initiation of travel . MacCallum and colleagues carried out a casecontrol study , which included 550 VTE cases identified from practice records . Compared with patients who had no recent history of travel , the risk to those who had a cumulative flying time of greater than 12 hours in the previous four weeks was associated with a three-fold increased risk of VTE . In addition , those who had a single leg of travel greater than four hours had a two-fold increased risk . 1 This would suggest that cumulative travel over a period of days to weeks can increase an individual ’ s overall thrombotic risk .
In the RIETE registry ( Registro Infomatizado de Enfermedad ThromboEmbolica ), the authors assessed the thromboembolism prevalence in different groups of travelers , and revealed that when it comes to car travel , the drivers had a higher rate of VTE than passengers . 2 In the MEGA ( Multiple Environmental and Genetic Assessment ) study , which is a large , ongoing case-control study on risk factors for venous thrombosis in an unselected population , all modes of travel were associated with a two-fold increased risk of venous thrombosis . 3 The risk of flying was the same as the risk of traveling by car , bus , or train .
The overall risk was highest in the first week after traveling . Risk of thrombosis in individuals traveling by car , bus , or train was influenced by other risk factors such as thrombophilia , obesity , or the use of hormone therapies .
In the case in question , the patient had cumulative travel of 10 hours over the course of a few days . Based on the studies previously mentioned , this would suggest that the car travel was a provoking factor increasing her risk of VTE . I would follow current guidelines for three months of anticoagulation . The patient may have other risk factors such as obesity , recent surgical intervention , or malignancy that could increase her risk of VTE going forward and dictate a longer course of antithrombotic therapy .
REFERENCES
1 . MacCallum PK , Ashby D , Hennessy EM , et al . Cumulative flying time and risk of venous thromboembolism . Br J Haematol . 2011 ; 155:613-9 .
2 . Tsoran I , Saharov G , Brenner B , et al . Prolonged travel and venous thromboembolism findings from the RIETE registry . Thromb Res . 2010 ; 126:287-91 .
3 . Cannegieter SC , Doggen CJ , van Houwelingen HC , et al . Travel-related venous thrombosis : results from a large population-based case control study ( MEGA study ). PLoS Med . 2006 ; 3 : e307 .
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52 ASH Clinical News September 2017