Venous Thoracic Outlet Syndrome

Venous Thoracic Outlet Syndrome is Uncommon

Venous thoracic outlet syndrome is quite uncommon. Of all patients who receive the diagnosis of thoracic outlet syndrome, between 2 and 5% have venous TOS.

Pre-eminent physician Sir James Paget in London was the first to describe venous thoracic outlet syndrome, in 1875. Interestingly, another pre-eminent physician, Leopold von Schroetter, recognized venous thoracic outlet syndrome simultaneously and independently in Vienna, although he did not publish the case until 1884.

Both Paget and von Schroetter described venous thoracic outlet syndrome associated with blood clot in the subclavian vein. In 1939, Charles McLaughlin described a similar clinical syndrome caused by intermittent obstruction of the subclavian vein, but without blood clot. In 1951, McCleery et al described this syndrome in further detail. Today, this syndrome is referred to as McCleery syndrome. McCleery syndrome is not as widely diagnosed as those forms of venous TOS with a venous blood clot in the arm, even though McCleery syndrome should be recognized as a form of venous TOS.

Venous Thoracic Outlet Syndrome

Causes of Venous Thoracic Outlet Syndrome

The subclavian vein provides the primary pathway for venous blood to flow from the arm to the heart. When the subclavian vein is partially or completely blocked, and the patient has symptoms of venous blood clot in the arm, venous thoracic outlet syndrome is present.

Blood flow in the body follows a well-described pattern. Blood passes through the lungs and absorbs oxygen. This oxygenated blood is pumped to the body by the heart under high pressure. This high-pressure oxygenated blood flows through arteries, which have a thick muscular wall, to every part of the body.

Each artery branches unto smaller and smaller arteries until they reach a capillary bed. Capillaries are tiny branching blood vessels with walls that are one cell layer thick. Tissues extract oxygen from the blood in the capillary bed and release metabolic end-products such as carbon dioxide and lactic acid. The capillaries then take this deoxygenated blood and send it to small veins, which join other small veins to form larger veins, which eventually empty into the two largest veins of the body, the inferior vena cava (from the abdomen and lower body), and the superior vena cava (from the head, neck, and upper extremities). The inferior vena cava and superior vena cava return blood to the heart under low pressure. Because venous blood is under low pressure, vein walls are thin and have no muscles.

Once the venous blood returns to the heart, the heart pumps it through the lungs. In the lungs, the blood releases carbon dioxide and absorbs fresh oxygen. This oxygenated blood returns to the heart, which pumps the oxygenated blood under high pressure to the body through arteries, and the cycle repeats.

In order to understand venous TOS, let us look more specifically at blood flow through the arms. Oxygenated blood is pumped by the heart into each arm through a single, large, muscular subclavian artery. When this blood reaches a capillary bed, the tissues in that area extract oxygen from the blood and deposit metabolic end-products into the blood. This deoxygenated venous blood returns to the heart through a single, large subclavian vein (although a few smaller veins may participate). This process is known as ‘venous drainage.’

Under normal circumstances, low-pressure venous blood passes easily out of the arm on its trip back to the heart. But when a person develops a venous blood clot in the arm, or if the subclavian vein is extrinsically compressed, symptoms of venous thoracic outlet syndrome may occur. This patient can now receive the diagnosis of venous TOS.

Both Paget and von Schroetter described cases of venous TOS associated caused by a venous blood clot in the arm. McLaughlin and McCleery described mechanical extrinsic compression of the subclavian vein in the arm. Both sets of patients demonstrated similar symptoms of venous TOS, albeit due to different mechanisms.

Venous Thoracic Outlet Syndrome
Sir James Paget

First description of venous thoracic outlet syndrome

Venous Thoracic Outlet Syndrome Creates Dramatic Symptoms

Patients with venous TOS frequently present with dramatic symptoms. A typical example might be the patient who appears in the emergency room with a swollen, heavy, bluish arm. The ER doctor notices strange superficial veins over the shoulder and chest on the same side as the swollen arm. The ER doctor orders a stat ultrasound examination, and the sonographer discovers a large blood clot in the subclavian vein on the side with swelling. The ER team calls in a vascular surgeon, and the surgeon tells the patient they will be jumping on the case.

In most cases, the formation of blood clot in the subclavian vein (the dominant vein bringing blood from the arm back to the heart) causes venous TOS. The blood clot prevents low-pressure venous blood from leaving the arm on its way to the heart.

Patients often note a relatively sudden onset of swelling, heaviness and pain in the affected arm. The arm may develop a dark blue color, and new superficial veins may appear over the chest and shoulder on the side of the blood clot. These superficial veins allow at least a little of the blood to drain from the arm to the heart.

Complications of venous TOS are rare, but can be serious, including blood clots traveling to the lungs. Once the venous blood clot in the arm is confirmed by ultrasound or other imaging tests, doctors treat the venous blood clot in the arm urgently. Following treatment of the venous blood clot, doctors undertake diagnosis and treatment of the underlying anatomy that compressed the vein and led to the venous blood clot in the arm.

Venous TOS

Venous Thoracic Outlet Syndrome is Relatively Easy to Diagnose

Venous thoracic outlet syndrome is quite uncommon. Among all patients with thoracic outlet syndrome, venous TOS cases comprise 2% to 5% of all cases. As noted above, the dramatic clinical presentation of patients with venous TOS is hard to miss. However, the clinical diagnosis must be confirmed with diagnostic tests.

Typically, imaging tests assist doctors in the critical decisions for the diagnosis of venous thoracic outlet syndrome. These imaging tests most commonly include ultrasound, direct venogram, CT venogram, and MR venogram.

In a typical emergency room workup, ultrasound is the first-line diagnostic test for venous thoracic outlet syndrome. Ultrasound is widely-available, free of radiation, usable in all arm positions, and relatively inexpensive. However, quality of ultrasound depends greatly on the experience of the sonographer, and some sonographers have limited experience diagnosing venous thoracic outlet syndrome. The illustration below demonstrates a venous blood clot in the arm of a patient with venous TOS.

Venous TOS

Advanced imaging tests, including CT venogram and MR venogram, are occasionally used to diagnose the venous blood clot in the arm. However, these test are more widely used to follow up complicated recurrent cases, or to show the anatomical causes of vein compression.

Treatment of Venous Thoracic Outlet Syndrome is Effective but Unsettled

Treatment of venous thoracic outlet syndrome almost always involves the care of a surgeon. Typically, vascular surgeons are the most common choice of TOS specialist for the treatment of venous thoracic outlet syndrome.

Vascular surgeons address 4 primary stages of treatment of venous TOS:

  • Immediate treatment of venous blood clot in arm

  • Correction of extrinsic vein compression
  • Repair of intrinsic vein damage
  • Follow-up to ensure patency of vein and absence of blood clot

While these goals may seem logical, the surgical literature has not definitely resolved several questions about treatment of venous thoracic outlet syndrome. Such issues include timing of treatment steps, methods of clot removal, approaches to resolving compression of the arm vein, and the use of stents. Stents are expandable metal cages that are placed within blood vessels with the intent of keeping the vessel of interest open and patent.

Venous TOS

Venous Thoracic Outlet Syndrome Recurrence

Initial treatment outcomes for patients with venous TOS are quite good. However, a small percentage of patients experience recurrence over months to years. In general, younger patients, such as college athletes, tend to do quite well, with good results of primary treatment and with few recurrences. Older patients with longer duration of symptoms prior to diagnosis tend to have less satisfactory results from primary treatment. Unfortunately, this patient population also bears a higher risk of recurrent venous blood clot in the arm.

At Vanguard Specialty Imaging, we understand how confusing the diagnosis of venous TOS can be. We provide support services for all patients with thoracic outlet syndrome, and we are widely regarded as TOS specialists. Let our team help you today!