Subclavian Vein Thrombosis

Excerpt

Subclavian vein thrombosis (SCVT) is a condition where a blood clot forms in the subclavian vein. SCVT can occur from multiple etiologies and is a potentially life-threatening pathology if not treated promptly. SCVT occurs due to either a primary etiology or a secondary etiology. Primary thrombosis is further delineated as effort-induced (Paget-Schroetter syndrome) or idiopathic (frequently associated with undiagnosed malignancy). Secondary subclavian vein thrombosis is associated with catheters or lines in the vein. While primary thrombosis is rare, the incidence of secondary thrombosis continues to rise due to complex cardiac devices and long-term central venous catheter (CVC) placement in cancer patients. SCVT has high rates of acute mortality and long-term disability without proper and timely treatment. Early diagnosis and treatment are essential in preventing fatal acute complications, such as pulmonary embolism and long-term morbidity related to venous inflow restriction.

The most widely recognized etiology for subclavian artery thrombosis is atherosclerosis; other uncommon etiologies are congenital deformities, fibro-muscular dysplasia, neurofibromatosis, autoimmune vasculitis-like Takayasu, radiation exposure, neurofibromatosis, and mechanical causes including injury or compression disorders.

The UEDVT is classified into two major primary and secondary categories. The secondary UEDVT is more common. Among the primary UEDVT subtypes, effort-related thrombosis or Paget-Schroetter syndrome is the most common. Typically, it is reported in otherwise healthy male patients with a history of vigorous upper extremity exercises, including but not limited to weight lifting and pitching a baseball. Moreover, repetitive physical activities, including painting, were associated with UEDVTs. The latter association was more common in venous thoracic outlet syndrome (VTOS). VTOS or effort thrombosis results in the subclavian vein compression in the following anatomic borders; 1. the intersection of the clavicle and first rib with the subclavian muscle and the costoclavicular ligament anteromedially and 2. the anterior scalene muscle posterolateral.

The idiopathic UEDVT, as implied by its nomenclature, lacks an apparent underlying risk factor. Moreover, the abnormal results in thrombophilia measures in patients with idiopathic UEDVT are less often predicted compared to the lower extremity deep vein thrombosis (LEDVTs). It should be noted that positive thrombophilia test results in patients with UEDVTs are more predicted in idiopathic patients than in patients with effort-related or catheter-associated UEDVT.

Catheter-associated-DVT accounts for the majority of secondary UEDVTs. Secondary UEDVTs are mostly related to indwelling catheters, either central venous catheters, chemo ports, pacemakers, or defibrillators.

Specific cancer types, including ovarian and lung adenocarcinoma, and higher cancer stages, specifically metastatic ones, increase the risk of cancer-associated thrombosis in indwelling catheters. The significance of cancer-related thromboembolism in patients primarily diagnosed as idiopathic UEDVT is the potential for subsequent cancer diagnosis. Accordingly, in up to 25% of those initially diagnosed as idiopathic UEDVT, further cancer diagnosis with mainly lung adenocarcinoma and lymphoma is predicted.