What is Deep Venous Thrombosis (DVT)?
Learn what DVTs are, what causes them, and why they are so dangerous.
Rob Lamberts, MD
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What is Deep Venous Thrombosis (DVT)?
What do you know about Deep Venous Thrombosis? I got a request from a reader named Linda to cover this topic in honor DVT awareness month in April. It’s a really important subject; nearly 350,000 to 600,000 Americans get a DVT each year, and 100,000 of those die from it. These numbers may actually be an underestimate, as most researchers believe it is significantly underdiagnosed.
What is Deep Venous Thrombosis?
So what the heck is a deep venous thrombosis? Thrombosis is a fancy word doctors have for a blood clot, which is a mix of clotting proteins and clotting cells known as platelets. Normally, clotting happens when a blood vessel breaks open, threatening to leak blood. The platelets and clotting proteins form a plug in the hole of the blood vessel and get the process of permanently healing the hole started.
But with a DVT, a blood clot doesn’t form to repair a broken blood vessel, but for some other reason. DVTs form in blood vessels– specifically in veins. The deep part of deep venous thrombosis refers to the fact that the clot forms in a vein that is deep inside a part of the body, usually in the leg; I’ll explain later why this is significant. The bottom line is that a clot forms at a place in time when it shouldn’t happen, and the consequences can be deadly.
What Causes Deep Venous Thrombosis?
A DVT forms in veins when the blood doesn’t flow and move around like it should. That’s because blood coagulates, or clots, when it sits around. Prolonged inactivity, such as when sitting on a long airplane flight, often causes blood to not move around so well and coagulate. Blood coagulation happens most in the legs because blood in the legs has to fight gravity to flow back to the heart. If a clot forms and is big enough, it blocks the flow of the blood in the vein, making the blood stand still even more. That makes the clot grow larger.
DVTs and Pulmonary Embolism
As the clot grows, it causes swelling in the leg; it often causes pain as well. The real danger of a DVT, however, is not from what goes on in the leg. If a clot grows big enough, a piece of the clot can break free and travel up to the heart and eventually the lungs. When a clot does that it is called a pulmonary embolism, or a PE. PE is the enemy, as it can be fatal if the clot going to the lungs is big enough.
The deep veins in the legs are the veins associated with most PE’s. Superficial clots (such as those with varicose veins) or clots in the arms thankfully don’t cause PE’s.
Risk factors for DVT
People who are healthy and active are generally not at risk of getting a DVT, but a number of things increase DVT risk, including:
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Cigarette smoking
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Use of estrogen-containing medications (including birth control pills) by women
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Prolonged inactivity, such as long car or airplane trips, or prolonged periods of confinement to a bed.
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Cancer, which increases the blood’s tendency to clot
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Surgery, especially orthopedic surgery on the legs, such as hip and knee replacement surgery.
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Other serious conditions, such as pneumonia or heart failure, that result in prolonged hospitalization
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Leg trauma
Anyone with swelling and pain in one leg should be assessed immediately for DVT, especially those with significant risk factors. Everyone who is in the hospital for more than a few days should be watched very closely for the formation of a DVT. Diagnosis is generally made by getting an ultrasound of the leg blood vessels, and certain blood tests can help in making the diagnosis.
What is the Treatment for Deep Venous Thrombosis?
The mainstay of treatment in this area is a class of medications known as “blood thinners.” That is really a confusing name, as the blood is not actually made thinner, but made so it doesn’t clot as easily. I prefer the term anticoagulant. The two main anticoagulants used are:
Heparin: Heparin is given by injection and starts preventing clots faster, so is usually the first medication given in the hospital for DVT.
Warfarin: Warfarin (better known as Coumadin) is a pill, and so is usually used to treat DVT outside of the hospital.
The Risks of Heparin and Warfarin
Decreasing the clotting of the blood is very risky because it can lead to hemorrhage, which is a catastrophic loss of blood. Heparin and Warfarin are generally monitored closely using blood tests. These tests are done every day on people getting Heparin in the hospital, and tests are done once a month for people stable on Warfarin. Once the blood clotting is adequately decreased with these medications, the likelihood of PE goes down significantly.
I want to underscore how cautious we need to be with anticoagulants. I got a moving email recently from a woman who lost her 29-year-old son who was on anticoagulants. After having surgery, it wasn’t recognized that he was having a hemorrhage.
Quick and Dirty Tips on DVT
So in closing, here are my quick and dirty tips about DVT:
Don’t smoke: women who smoke should be very cautious about taking birth control pills or other estrogen-containing medications.
Get up and walk: people taking long car or air trips should get up and walk every few hours to prevent clots from forming. That goes for truck drivers too.
Get attention: if you have leg swelling in one leg, especially if it’s painful, get attention immediately. You could say, to prevent PE from DVT go see the MD in the ER PDQ. As always, if you are not certain, get seen. It’s far better to go to the doctor for something that is not serious than it is to stay at home with a DVT.
Pay attention: People in the hospital should ask their doctor if they should be on thinners to prevent blood clots. And people who are on blood thinners to treat DVT should be very cautious.
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Let me once again remind you that this podcast is for informational purposes only. My goal is to add to your medical knowledge and translate some of the weird medical stuff you hear, so when you do go to your doctor, your visits will be more fruitful. I don’t intend to replace your doctor; he or she is the one you should always consult about your own medical condition.
Catch you next time! Stay Healthy!
Deep Vein Thrombosis image courtesy of Shutterstock