Blood clots in the arm and venous thoracic outlet syndrome (vTOS)

Most venous disease does not occur in the arms due to gravity; there is less pooling of blood than in the legs and valve dysfunction is infrequent. That being said, the arm veins have to pass from the arm back to the hear through the subclavian vein.  At the base of the neck, this vein goes through a tight passageway called the thoracic outlet.  Nearby muscle and the 1^st rib and collarbone can repeatedly squeeze the vein as the arm is raised and lowered, such as with athletic activities or jobs requiring overhead arm movements.  As such, clots developing in this area tend to disproportionately affect younger people.  When a narrowed subclavian vein results in arm symptoms, it is called venous thoracic outlet syndrome, or venous TOS.

Cumulative injury over time causes a buildup of scar tissue and progressive narrowing of the subclavian vein until blood flow decreases enough to potentially result in a blood clot in the deep veins of the arm and chest, called a deep venous thrombosis (DVT).

Risk factors include any situations in which the arms are elevated at or above 90 degrees from the body for a significant amount of time. Examples include car mechanic work, house painting, weightlifting, and sports such as baseball, softball, tennis, swimming, volleyball, and badminton.  Athleticism itself is a major risk factor as it results in hypertrophy of muscles in the upper chest, shoulder, and neck, resulting in greater venous compression. 

Another major risk factor for upper extremity vein blood clots are having a pacemaker or catheter inside the veins of the arm or chest.  These are foreign to the body and cause irritation inside the vein and can result in scar tissue and blood clots.

Thus, unlike the legs, the usual cause of blood clots in the arms is a mechanical problem.

Symptoms

Before a clot has developed or before a vein draining the arm is completely blocked, a person may feel heaviness or achiness in the arms when raised.  This may return quickly to normal when they are lowered.  Temporary swelling and arm discoloration may also develop, and it is common for people no to seek treatment at this stage when symptoms are not constant or severe.

Once a clot develops and most blood flow from the arm is blocked, it my become swollen, heavy, painful and discolored.  It is important to seek emergent medical treatment.

Diagnosis

The diagnosis of a blood clot in the arm may be easily made by physical exam and can be confirmed with an ultrasound. CT or MR imaging is not necessary to make this diagnosis, but these imaging modalities may be useful in some patients to identify any important findings within the chest related to clot formation.

Many physicians and non-physician providers are not familiar with TOS, and if this is a suspected cause of an arm DVT, the best option is to see a vascular surgeon capable of treating this condition surgically.

Treatment

Blood thinners alone are not adequate treatment for subclavian vein thrombosis if it is due to TOS or extrinsic compression. Although blood clots traveling to the lung (pulmonary embolism or PE) are uncommon, blood thinners prevent further clot formation and make subsequent treatment more effective.

The thrombus may persist or recur if the extrinsic compression of a narrow thoracic outlet is not addressed surgically.  Early clot removal and surgical thoracic outlet decompression results in a cure in more than 95% of patients, while a third or more of people treated only with blood thinners will have lifelong symptoms.

Generally, hospital admission is recommended for initial administration of intravenous blood thinners and to streamline the treatment process. After confirming the diagnosis and initiating blood thinners, removing the clot is the next step. Dissolving the clot through catheter-directed thrombolysis (CDT) or mechanical or suction-based removal of the clot is essentially always required.

The final stage of treatment is surgery, which can be performed at a later date or during the same admission. Surgery involves relieving the bony compression of the thoracic outlet by removing the anterior portion of the first rib, dividing one of the muscles of the neck that attaches to this rib, and releasing any connective tissue attachments causing narrowing of the affected vein.  In rare cases, the vein requires repair or replacement to address any scar tissue that continues to prevent adequate blood flow through the vein.  Most surgeons then recommend physical therapy and continuing blood thinners for 3 months, minimum. A successful outcome would be the patient returning to their baseline without activity restrictions. Re-clotting is unusual.

Other arm vein problems

Other problems can occur with the veins of the arms, most of which are caused by instrumentation or placement of a foreign body within the vein. Common examples include pacemakers, defibrillators, a dialysis catheter, port, or any other central intravenous line. This can cause irritation or injury to the inside of the vein resulting in clot formation. Treatments in these cases is removal of the foreign body (tube or wire) and initiation of blood thinners for at least 3 months. 

Similarly, smaller veins in the arms can develop inflammation and clot formation, referred to as thrombophlebitis, from placement of a peripheral IV. Because there is no significant risk of these blood clots traveling to the lungs, treatment with anti-inflammatory medications (aspirin, ibuprofen, etc.) rather than blood thinners is appropriate. Along with the use of warm compresses these treatments result in resolution in virtually all cases. However, this can take weeks to months.  In rare cases, such a vein can become infected and require surgical removal.