Are YOU at risk for VTE?

True to the nature of this blog, I am reporting beyond the headlines. Only yesterday a study on Venous Thromboembolism was reported in the peer reviewed journal, The Annals of Internal Medicine. After seeing the Reuters story I sought the actual research article and a few other sources in order to address the issue of travel related blood clots. A venous thromboembolism is a clot in the vein. The fear with VTE is that it can lead to a clot moving through the vein to the lung. This is often referred to as PE, which is pulmonary embolism and it can cause death. It is a very serious condition. (clots can interrupt blood flow or cause an artery or vessel or vein to burst)

You may have heard at least one story about flying and the risk of getting blood clots in the last few years. What the scientists from Harvard sought to find was evidence for or against the increased risk and explanation for why some studies show an increased risk and others do not.

Much is explained in the actual research article that leads me to believe that their conclusion that traveling, by plane or car, (in other words, being immobilized) does increase the risk of VTE as compared to not being stationary for those two plus hours. They found a 3 fold increase.

There was a lot for me to sort through and a few good points to make to you. First of all, what is a 3fold risk. To the best of my understanding it is 3 times the risk. That being said, 3 times WHAT? If the risk for getting a clot or VTE is 1 percent in general and now it is 3 percent, well there is a 97% chance I won't get one, so not so bad. The best I could come up with was in reading another article about deep vein thrombosis where people were put into categories of low/no risk and moderate and high etc. It said that the low/no group had a rate of 4 per 10(4) which I interpreted to mean 4 per 100,000 people. So that many people might randomly be expected to get a blood clot. This new study would then be saying that 12 people out of 100,000 would get one from traveling. Not to0 high, but I don't like that number so much.

I learned a lot in my research today. Firstly, there is a triad of things that could lead to a blood clot, this triad is named after the clinician who described them. It is the Virchow triad. The scientists found that travel can lead to 2 of the 3 conditions of Virchow's Triad. The conditions pertain to:

the vessel wall, blood flow and blood composition

The vessel wall is lined with special flat blood cells called endothelial cells and they exists to keep blood from clotting inside the blood vessel. (coagulation is a good thing when you have a cut, but it is called thrombosis when it occurs inside the blood vessel, and a thrombosis is bad)

Endothelial cells can be damaged from smoking.
The vessel wall changes do not occur because one is traveling or immobilized. The other two conditions can. They are stasis, or sluggish blood flow and a change in blood composition. The change in blood composition means that the blood platelets are more likely to come together and form a mass or clot. Some reasons this may occur are dehydration, being on birth control pills and having a history of blood clots, as they can scar the vessel walls. Further, being obese and having high blood fats will increase thrombosis risk. Another risk factor is varicose veins. They interrupt blood flow because they are often kinked, crooked and bulging. Normal blood vessels are straight and narrow.
So what can you change and not change and what is specific to traveling. You know that you can work on weight and hyperlipidemia and stop smoking. That is a given for any disease risk.
For flying, at this time there is concern about hydration and ambulation. After two hours the risk of VTE is up 18% and so rises every two hours. Right now you can choose to stop often and walk if you are traveling by car and do drink adequate amounts of water. When I travel by plane, I sit in the aisle seat and always go to the bathroom (to stretch my legs).
The studies that were reviewed by these scientists were not experiments, so the results are not the strongest. They do call for more research and I think they make a good argument. They call the issue a public health one, as world travel has increased. They pondered measures such as having people wear TED hose to having people take medication before travel, blood thinners. They did NOT disclose any pharmaceutical ties or funding!
They noted that older persons, pregnant women and women on birth control or HRT might be in the high risk category.



My ending though is this. If this issue gains weight through additional replicable research and dehydration is a big risk factor.. will airlines, for fear of lawsuit, limit or ban caffeinated and or alcoholic beverages in flight?



Here is the published study:
http://www.annals.org/cgi/content/full/0000605-200908040-00129v1