Venous Thoracic Outlet Syndrome

Venous thoracic outlet syndrome is a condition that results in compression of the axillary/subclavian vein as it exits the arm and enters the thoracic cavity resulting in arm swelling and discomfort. The condition is most commonly diagnosed when the a patient presents with a significantly swollen arm and is found to have a clot in the subclavian vein (DVT or deep venous thrombosis).

Venous thoracic outlet syndrome usually occurs due to problems with the subclavian vein being compressed in the costo-clavicular space, the small area where the first rib, clavicle (collarbone) and the sternum (breastbone) all connect. The costo-clavicular space is also home to the costo-clavicular ligament and the subclavius muscles. Repeated compression and pinching of the subclavian vein due to these structures in the costo-clavicular space results in narrowing and scarring of the vein, eventually leading to an occlusion or thrombosis (clotting of the vein). This condition is often referred to as “effort thrombosis”.

Common repetitive activities of the arm (e.g swimming, weightlifting, throwing etc) can all contribute to the vein being compressed. vTOS occurs equally in men and women and usually manifests in the early stages with some mild swelling, discomfort and possibly some numbness of the arm with repeated use of the arm. As the condition worsens and the vein becomes more scarred, the patient may develop cyanosis (bluish discolouration) of the arm and develop small collateral veins around the neck, chest and shoulder region whereby smaller veins are recruited to help drain the blood from the arm as the main vein (axillary or subclavian vein) is compressed.

Ultrasound, MRI or CT-scans are usually the scans of choice when trying to prove/disprove the diagnosis of venous thoracic outlet syndrome, however these scans cannot always accurately predict when the vein is being compressed given that most of the compression occurs when the arm is moving while the scans are done with the patient still. Occasionally a venogram is required, whereby contrast is injected into the veins of the arm, with the arm in different position to check whether there is compression of the vein when the arm is moving.

When the diagnosis of venous thoracic outlet syndrome is confirmed, treatment consists of surgery to decompress of the costo-clavicular space and removal of the front part of the 1st rib. If the vein is still seen to be narrow due to chronic scarring, additional techniques, such as a vein patch or venous angioplasty may be needed to help open up the vein. In cases where the vein is blocked due to fresh clot, techniques to unblock the vein (thrombolysis) are used to first try to re-open the vein. If successful, the patient is prescribed blood thinning medications for a short period of time before undergoing first rib resection and decompression of the costo-clavicular space.

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