Subclavian Vein Thrombosis

What is Subclavian Vein Thrombosis?

Subclavian vein thrombosis, or SCVT, is a condition where a clot forms in the subclavian vein, a major blood vessel in the body. This can happen for many reasons, and if not treated quickly, it can be life-threatening. There are two main reasons why this happens: a primary cause or a secondary cause. The primary cause can either happen due to physical exertion (known as Paget-Schroetter syndrome) or for no known reason (often linked to an undiagnosed severe illness like cancer). The secondary cause is usually associated with medical devices or tubes inserted into the vein. While the primary cause is not that common, secondary vein clots are increasing, especially in patients who have complex heart devices or long-term central venous catheters — a tube placed in a patient’s vein to give them medicines or nutrients — due to cancer. Without the right and timely treatment, SCVT can lead to death or long-term disability. Therefore, early diagnosis and treatment are crucial to prevent fatal complications, including lung clots and long-term health issues associated with restricting blood flow.

A common cause of clot formation in the subclavian artery, not the vein, is a condition called atherosclerosis, in which the blood vessels become narrow due to fat deposition. Other rare causes include birth defects, abnormal growth of muscle and fibrous tissues in arteries (fibro-muscular dysplasia), a genetic disorder that causes tumors to form (neurofibromatosis), an autoimmune disease like Takayasu’s arteritis that causes inflammation of arteries, harmful radiation exposure, injury, or swelling due to mechanical pressures.

There are two primary categories of upper extremity deep vein thrombosis (UEDVT, a blood clot in any of the veins in your arms): primary and secondary, with secondary UEDVT being more prevalent. Among primary UEDVT, the most common is Paget-Schroetter syndrome, usually seen in healthy males who engage in strenuous upper body exercises like weightlifting or baseball pitching. Even repetitive physical activities, like painting, have been linked with UEDVT, usually when it results in the compression of the subclavian vein in the confluence of the collarbone, first rib, and specific muscles and ligaments.

Contrary to this, idiopathic UEDVT, as its name suggests, does not have a clear cause. Moreover, idiopathic UEDVT patients are less likely to have abnormal blood clot results in tests compared to those with a lower extremity deep vein thrombosis (LEDVT, a blood clot in the leg veins). However, if a patient with UEDVT does test positive for unusual blood clot results, it is more likely to be someone with an unknown cause rather than those with effort-induced or catheter-associated UEDVT.

Catheter-associated DVT makes up most secondary UEDVT cases, often related to central venous catheters, chemo ports, pacemakers, or defibrillators. Certain types of cancer, particularly ovarian and lung adenocarcinoma, and advanced cancer stages, especially metastatic stages (cancer has spread to other organs), increase the chances of blood clots in patients with devices inserted into their veins. In fact, up to 25% of those initially diagnosed with idiopathic UEDVT end up being diagnosed with cancer, typically lung adenocarcinoma and lymphoma. This emphasizes the importance of detailed investigations and monitoring in patients with UEDVT, even when an apparent cause is not immediately identified.

What Causes Subclavian Vein Thrombosis?

Primary Subclavian Vein Thrombosis (SCVT), which is a blockage in the main vein in the upper chest or lower neck, has two main causes. One is effort-induced thrombosis, also known as Paget von Schroetter syndrome. This happens when frequent, strenuous use of the arms leads to a blood clot forming in the vein. The other cause is often linked to an undiagnosed cancer, but the exact cause isn’t known.

There are also several causes of Secondary SCVT. These include:

• Mechanical injuries such as from a long-standing central venous catheter (a tube placed into a patient’s large vein), pacemaker leads, a broken collarbone, or hemodialysis catheters (tubes used to remove waste products from the blood when the kidneys can’t).
• Long term use of feeding tubes
• Lying face down during surgery
• Some blood disorders like Antithrombin III deficiency, Factor V Leiden mutation, Protein C deficiency, and Protein S deficiency, which can increase the risk of blood clotting.
• After a surgery
• Superior vena cava syndrome (a group of symptoms caused by obstruction of the superior vena cava – a large vein that carries blood from the body back to the heart).
• Underlying cancers that can cause blood clotting, put pressure on the veins, or infiltrate the veins.
• Ovarian hyperstimulation syndrome (a severe reaction to fertility drugs).

Although rare, lung cancer, particularly Pancoast tumor, can also cause SCVT.

Various risk factors associated with catheters could also contribute to SCVT, including:

1. Insertion of the catheter into the subclavian vein
2. Difficult placement of the catheter, especially on the left side
3. A catheter tip placed far from the right atrium (one of the four chambers in the heart) and the junction of the superior and inferior vena cava (the large veins that return deoxygenated blood from the body back to the heart).
4. Previous placement of a central venous catheter
5. Use of catheters with larger diameters
6. Use of peripherally-inserted central catheters compared to chemotherapy ports.

Some existing conditions, such as chest radiation therapy, certain forms of chemotherapy, and parenteral nutrition (nutrition delivered directly into a vein) could also play a role.

Risk Factors and Frequency for Subclavian Vein Thrombosis

Deep vein thrombosis in the upper extremity appears in about 10 percent of all deep vein thrombosis cases and makes up 28% of thrombosis related to catheter use. However, thrombosis caused by exertion is rare and happens primarily in young, healthy athletes at a rate of 2 in 100,000 people per year. This kind of thrombosis occurs about twice as often in men as women.

We don’t have a specific number for the incidence of idiopathic thrombosis, thrombosis due to an inherited condition, because we lack enough data. What’s interesting though, is that when we can’t explain why upper extremity thrombosis occurs, there is a 25% to 30% chance the patient has an underlying cancer. Furthermore, thrombosis in the upper extremities is found in up to two-thirds of cancer patients who have central venous catheters. Research hasn’t been able to provide a clear picture yet on whether oral contraceptives can increase the risk for subclavian vein thrombosis (SCVT).

The numbers for secondary subclavian thrombosis, another type of thrombosis in the upper extremities, increase with the use of complex heart devices and chronic central venous catheters. Catheter-related thrombosis is responsible for 93% of upper extremity thromboses. This happens more often with catheters inserted in peripheral veins than those in central veins. Poor positioning of the catheter tip also increases the risk of thrombosis.

Signs and Symptoms of Subclavian Vein Thrombosis

Subclavian vein thrombosis (SCVT) is a condition where patients often experience discomfort or pain in the upper extremity or neck. This discomfort might feel like a “sense of unclear fullness”, with possible swelling in the affected upper arm. SCVT often affects healthy individuals, typically between their teenage years and 40, with it being more common in males. An individual’s history might contain information about recent intense or repetitive movements. However, if the SCVT is idiopathic, meaning its cause is unknown, there won’t be a history of strenuous activity. For secondary SCVT, which is often caused by a medical device or trauma, the symptoms remain similar, but there will also be a history of a catheter, device lead, or trauma. Frequently, the catheter is also found to be not working properly.

Upon physical examination, medical professionals might observe fullness above the collarbone, a lump that can be felt, changes in the color of the extremity, and Urschel’s sign — which is the swelling of the veins in the front part of the chest wall. How severe these symptoms are can change based on how much the vein is blocked. At the early stages of the disease, patients will usually report mild discomfort. As the condition gets worse, the signs and symptoms will become more obvious.

Testing for Subclavian Vein Thrombosis

If a healthy and active person suddenly experiences swelling in their upper extremity (any part of the arm), then they should be examined for a condition called subclavian vein thrombosis (SCVT). This is a blood clot that forms in a vein located under the collarbone.

The go-to method for diagnosing this condition is an ultrasound, which is very reliable with a specificity of 96% (ability to properly identify those without the condition) and a sensitivity of 97% (ability to correctly identify patients with the condition).

If the ultrasound results are unclear, other tests like a computed tomography, magnetic resonance imaging (MRI), and direct venography can help with diagnosis. However, these tests do come with certain disadvantages, including being costly, exposing the patient to radiation, requiring the use of intravenous contrast (a type of dye that helps see vessels and organs more clearly), and they could potentially delay the diagnosis.

Additional tests for blood clotting disorders should be carried out only for patients with idiopathic primary SCVT, which means those who developed SCVT without an apparent cause or trigger.

Treatment Options for Subclavian Vein Thrombosis

The main way to treat subclavian vein thrombosis (SCVT), a blood clot in the vein under the collarbone, is with blood-thinning medications, also known as anticoagulants. In the first two weeks, drugs or procedures to dissolve the clot can be very successful. Doctors usually recommend taking blood thinners like low molecular weight heparin (LMWH), warfarin, or direct oral anticoagulants (DOAC) for three to six months.

The American College of Chest Physicians suggests using LMWH or a similar drug called fondaparinux to treat SCVT, and recommends continuing this for at least five days. After this, they suggest taking vitamin K antagonists, another type of blood thinner, for at least three months.

In cases where the SCVT is caused by repeated strain and the symptoms keep coming back, surgery could be beneficial. This could involve making more space in the area near the collarbone or removing the first rib and some of the muscles and ligaments, depending on the patient’s specific body structure. Sometimes, doctors might need to use a procedure to widen the vein (angioplasty) or put a small tube inside it to keep it open (stenting). These are more involved procedures and usually kept as options if the problem keeps recurring.

If the SCVT is related to cancer, doctors usually prefer to use LMWH alone rather than vitamin K antagonists. When the vein clot is in the arm (UEDVT), doctors don’t recommend using compression therapy (like sleeves or bandages) during the acute phase of the disease. However, it might be considered for the management of long-term symptoms (PTS).

If the SCVT occurs by itself and there’s no sign of cancer, it’s treated with blood thinners for three to six months. If the SCVT is related to cancer, doctors usually treat it with LMWH until the cancer is cured or under control.

If the SCVT is related to a catheter (a thin tube used to give medications or fluids), the management varies. If it’s safe to remove the cathenter and there’s a low risk for blood clots breaking off and causing problems elsewhere (embolization), doctors usually remove the catheter and then there’s no need for blood thinners. However, if there’s a high risk of embolization, doctors usually start blood thinner therapy. Once long-term catheter use is done, the catheter is removed, and blood thinner treatment continues for at least six weeks afterwards. If the clot happens and the catheter is still needed for treatment and works fine, doctors start blood thinners right away and continue for at least three months after removing the catheter. There’s no agreed-upon advice about using compression sleeves in these cases.

Using a catheter to help treat UEDVT is the preferred choice for patients who have just developed the condition, are experiencing severe symptoms, are at low risk for bleeding issues, and have a good overall level of health and ability to function.

What else can Subclavian Vein Thrombosis be?

When a doctor is trying to diagnose a condition called subclavian vein thrombosis, several other conditions may have similar symptoms. These could include:

• Superior vena cava syndrome, a condition that affects the flow of blood to the heart,
• Lymphatic obstruction, a blockage in the lymphatic system,
• Cellulitis, a common and sometimes painful skin infection,
• Thoracic outlet obstruction, a blockage in the major veins and arteries in the lower neck and upper chest, and can include a type of lung cancer known as a Pancoast tumor,
• Necrotizing fasciitis, a serious bacterial infection that destroys skin and muscle, and
• Superficial thrombophlebitis, inflammation of a vein just under the skin, usually in the leg.

Different tests may need to be carried out to determine the exact condition.

What to expect with Subclavian Vein Thrombosis

The outlook varies depending on individual risk factors for blood clots and the extent of vein blockage. If left untreated, 78% of patients with Paget-Schroetter, a condition that causes blood clots in the upper part of your body, experience lasting symptoms. Blood clots can lead to disability in 41% to 91% of cases.

However, if treated correctly with conservative measures, like lifestyle changes and blood-thinning medication, or undergoing surgery, the outlook is generally very good for patients suffering from exertion-induced Subclavian Vein Thrombosis(SCVT), a kind of blood clot.

Whether or not a patient with SCVT has cancer or a blood clotting disorder, called thrombophilia, could impact their overall outlook. Patients with these complications can have rates of further complications as high as 50%. Some of these severe complications include a pulmonary embolism (a blockage in one of your lungs) at about 9.2%, superior vena cava syndrome (a group of symptoms caused by obstruction of the superior vena cava, a large vein that carries blood from the head and arms back to the heart) at 14.9%, and post-thrombotic syndrome (long-term symptoms after a blood clot) at about 26.4%.

When a patient has upper extremity deep vein thrombosis (UEDVT, a type of blood clot in the arms) without a known cause, their risk for complications from moving blood clots is lower than if it’s a secondary condition to something else. However, cancer patients with SCVT have a reportedly high 12-month death rate of up to 40%. But remember, these outcomes are mainly due to underlying diseases like cancer or multi-system disease, not directly due to SCVT.

Possible Complications When Diagnosed with Subclavian Vein Thrombosis

Common Complications of Certain Conditions:

• Blood clot in the lungs (Pulmonary embolism)
• Post-thrombotic syndrome: this is when blood flow obstruction and unhealthy valves cause everything from slight swelling to severe stasis, which can result in skin ulcers or gangrene
• Infection of the vein (Septic thrombophlebitis)
• Blockage of a blood vessel by a foreign substance (Embolism)
• Issues with the major vein that carries blood from the upper half of the body back to the heart (Superior vena cava)
• Inability to use a certain vein for medical procedures due to blockage (Loss of access due to occlusion)

Preventing Subclavian Vein Thrombosis

The medical community hasn’t yet reached a general agreement about whether preventive blood-thinning treatment, also known as prophylactic anticoagulation, is necessary. Recent research has suggested that this preventive treatment may not always be beneficial. However, certain groups of patients might still benefit from using a specific type of blood-thinning medication known as low molecular weight heparin.

It’s important to ensure that the placement of the catheter, which is a flexible tube inserted into the body to deliver or drain fluids, is correct in the superior vena cava, a large vein that carries blood back to the heart. Any incorrect placement should be identified and fixed. If possible, doctors should avoid placing the catheter on the left side of the body.

Patients should also be aware of certain risk factors that could increase their chances of forming dangerous blood clots, or thromboses. These risk factors include smoking, pregnancy, and obesity. Having this knowledge can guide patients into making healthier choices that could potentially lower their risk for developing blood clots.