A blood clot in the arm is also called a deep venous thrombosis (DVT) of the upper extremity. There are two main types of blood clots in the arm:
- Provoked by central IV lines.
Having a central IV line placed while hospitalized puts you at a higher risk of getting a blood clot in your arm. These blood clots are provoked by the central lines. A blood clot in the arm that happens to anyone else is unprovoked, or a spontaneous blood clot. Blood clots related to the central line are more common than unprovoked blood clots in the arms, happening in about 1 in 10,000 people who are hospitalized.
Unprovoked blood clots in the arm are relatively uncommon compared to blood clots in the legs. However, an unprovoked blood clot in the arm can unexpectedly happen in young and otherwise healthy people. 1 in 100,000 adults have a new blood clot in the arm every year.
Where exactly does a blood clot form in your arm, and why?
As you can see in the picture, your arm has outer veins and deeper veins. A set of outer veins run along the thumb side of your arm, and another set runs along the pinkie side. Eventually, they unite to form one main outer vein.
Another set of deep veins drain blood from the deeper areas of your forearm and go up towards the armpit. The deeper veins join together to form one large vein that drains all the blood from from arm into your chest. Just before going inside the chest, this large vein also gets blood from the main outer vein.
Blood clots in the arm mostly happen at the main vein draining blood into the chest. They may also happen inside the chest after draining blood from the whole arm. The main vein has to cross a few structures before going inside the chest. This is a vulnerable spot for the vein. If the path is too narrow, blood flow may be restricted. This vein might be pinched by bones or squeezed by muscles.
Some people are born with an extra pair of ribs. This extra pair grows out of the neck spine and narrows the already tight space. People with this extra pair of neck ribs are at a higher risk of getting a blood clot in the arm.
Some people are born with extra muscles in the narrow area that may compress the vein.
In other people, the narrowing of the area happens after birth. People who have had fractures or surgeries of the collar bone or first rib may have abnormal growth spurs of bones when healing. People who perform repeated and strenuous tasks while holding their arms above their heads may have an overgrowth of muscles, as shown in the picture. The overgrown muscle may press on the vein and restrict blood flow. Repetitive and persistent overhead arm movement may impede the flow of blood even without any permanent changes, helping form a clot in the vein that drains blood from the arm to the chest.
Athletes whose jobs involve strenuous and repetitive overhead arm movement, such as baseball pitching, frequently have blood clots in their arms.
Why don’t all baseball pitchers get blood clots in their arms?
Despite all the possible ways your arm vein can get compressed while going from arm to chest, the number of people who actually get blood clots in the arm is very low. That is because there is one important factor that decides whether or not you get blood clots: the coagulability of your blood. The coagulability of the blood measures how easily your blood forms blood clots.
Making blood clots are one of the defensive mechanisms of our body. People get cuts and scratches all the time. Our body stops the bleeding by making clots. Without the ability to make blood clots, we could bleed to death from a minor cut. Some people have an overactive blood clotting tendency. Those people form clots very easily. An area of turbulent or decreased blood flow may trigger the clotting mechanism, and blood clots may form inside blood vessels, causing a blockage.
People who get blood clots in the arm usually have a greater tendency to form blood clots. If you happen to be a baseball pitcher with a higher tendency to make blood clots, you may get blood clots in your arms. Not all baseball pitchers have clotting tendencies.
What are potentially life-threatening complications of blood clots in the arm?
In most cases, blood clots in an arm is a source of major inconvenience and disability, but it may become life-threatening in a small number of cases. As you can see in this picture, the arm vein that goes inside the chest combines with the vein that drains blood from the head and neck, going into the right side of the heart. The right side then pumps the blood out to the lungs from two large arteries called the pulmonary arteries. They divide into smaller branches after going inside the lungs.
Sometimes, blood clots break off and travel forward. They go to the right side of the heart and to the pulmonary arteries. The blood clots may get trapped, because the pulmonary artery gets narrower and narrower as it divides. When a blood clot breaks off of the deep vein in the arm and gets trapped in your lungs, you have a blood clot in your lungs, or a pulmonary embolism. A large pulmonary embolism at the main brach of your pulmonary artery may stop all blood flow, killing you instantly. Fortunately, this is very rare with blood clots in the arm.
Please read “blood clot in the lungs” to understand more about pulmonary embolisms.
What are common symptoms of blood clots in the arm?
Here are common symptoms of an unprovoked blood clot in the arm:
- Sudden onset pain and swelling of the whole arm in a young and athletic person
- Up to 80% of people with blood clots in the arm had performed strenuous overhead arm movements within 24 hours of the onset of symptoms
- Most patients have had some discomfort in their neck, shoulder, or armpit in the weeks preceding the clot
- The arm swelling is associated with an increased visibility of the outer veins
Here are common symptoms of blood clots in the arm provoked by a central IV line:
- Recently having central IV lines placed. Central IV lines are inserted through a major, deep vein, and are pushed to the opening of the right side of the heart. They are used to infuse large amounts of fluids, blood products, or chemo drugs in hospitalized patients.
- New pain and swelling of the whole arm on the side where the central line was placed
- Increased visibility of swollen outer veins
What are the risk factors for blood clots in the arm?
There are two categories of risk factors for blood clots in the arm.
Category 1: Risk factors for the arm vein being pinched:
- Presence of an extra pair of neck ribs
- Deformity of the first rib
- Abnormal muscle in the narrow area where the main arm vein enters the chest
- Overgrowth of muscles in the narrow area where the main arm vein enters the chest due to an exercise involving the arms above the head
- Repeated strenuous movements of the arms above the head in activities such as baseball pitching
Category 2: Risk factors for increased coagulability of the blood:
- A previous history of blood clots
- Taking medications known to increase risks of blood clots such as oral contraceptives or hormone replacements
- A strong family history of blood clots
- A history of cancer
- Being a smoker
- Certain disorders of the coagulation system
What are treatment options for blood clots in the arm?
Due to advances in medical technology, there are more treatment options available now than ever before. However, the treatment needs to be individualized based on the patient. Here are some of the options:
- Radiology-guided clot-busting medication use: A tube is passed through your arm veins and guided to the blood clot with the help of an ultrasound. A clot-busting medication is then infused to try and dissolve the clots. This option may be beneficial to someone with a large clot and severe symptoms. This treatment is more successful when done early after the clot formation.
- Clot retrieval by a catheter: They may guide a catheter to the clots and use an instrument to cut, dissolve, and retrieve them.
- Surgery: In some cases, surgery may be necessary to prevent another clot in the future. For example, people with the extra pair of ribs will need those removed, and people with extra muscles need those repaired. When performing these surgeries, the surgeons may also be able to repair the clotted veins and make blood flow through them using advanced vascular surgery techniques.
- Blood thinners: Almost everyone with blood clots in the arm needs at least 3 months of blood thinners regardless of what other treatments they got. It helps prevent the formation of another clot, and may also help prevent blood clots in the lungs. Some people may need lifelong blood thinners if they are identified to be more susceptible to blood clots in general.
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