Superior vena caval obstruction produces a distinctive clinical syndrome. Malignant tumors are the cause in 80–90% of cases; lung cancer accounts for about 90%.
The incidence of superior vena caval syndrome in lung cancer patients is 3–5%. The male:female ratio is about 5:1. Other primary mediastinal tumors that may cause superior vena caval obstruction include thymoma, Hodgkin’s disease, and lymphosarcoma. Metastatic tumors from the breast or thyroid or from melanoma also occasionally cause superior vena caval obstruction. Benign tumors are an unusual cause, but substernal goiter, any large benign mediastinal masses, and atrial myxoma have been implicated. Thrombotic conditions, either idiopathic or associated with polycythemia, mediastinal infection, or indwelling catheters, are unusual causes. The association of superior vena caval obstruction with chronic mediastinitis is discussed in the preceding section. Trauma may produce acute venous obstruction (eg, traumatic asphyxia, mediastinal hematoma).
The clinical manifestations depend on the abruptness of onset, the location of the obstruction, the completeness of occlusion, and the availability of collateral pathways. Venous pressure measured in the arms or head varies from 200 to 500 mm H2O, and severity of symptoms is correlated with the pressure. Fatal cerebral edema can occur within minutes of an acute complete obstruction, whereas a slowly evolving one permits development of collaterals and may be only mildly symptomatic. Symptoms are milder when the azygos vein is patent. Azygous blood flow—normally about 11% of the total venous return—can increase to 35% of the venous return from the head, neck, and upper extremities. Thus, the most severe cases occur when occlusion is complete and the azygos vein is involved. The thrombus may propagate proximally to occlude the innominate and axillary veins.
Symptoms include puffiness of the face, arms, and shoulders and a blue discoloration of the skin. Central nervous system symptoms include headache, nausea, dizziness, vomiting, distortion of vision, drowsiness, stupor, and convulsions. Respiratory symptoms include cough, hoarseness, and dyspnea, often due to edema of the vocal cords or trachea. Nasal congestion is often an early presenting symptom. These symptoms are made worse when the patient lies flat or bends over. In long-standing cases, esophageal varices may develop and produce gastrointestinal bleeding. The veins of the neck and upper extremities are visibly distended, and in long-standing cases there are marked collateral venous channels over the anterior chest and abdomen. Chronic pleural effusions may develop as a result of impaired lymphatic drainage. Onset of symptoms in fibrosing mediastinitis may be insidious, consisting initially of early morning edema of the face, hands. Occasionally, symptoms and findings are localized to one side when the level of obstruction is above the vena cava and only the innominate vein is blocked. In this situation, symptoms are mild because communicating veins in the neck usually decompress the affected side.
The diagnosis is confirmed by measuring upper extremity venous pressure; in patients with severe symptoms, a pressure of 350 mm H2O or more is usual. The location and extent of obstruction are best determined by venography. When patients with malignant vena caval obstruction are studied by venography, 35% have thrombosis involving the innominate or axillary veins, 15% have complete caval obstruction without thrombosis, and 50% have partial superior vena caval obstruction. If patency of the azygos vein is in question, interosseous azygography may be useful. Chest x-ray may show a right upper lobe lung lesion or right paratracheal mass. Aortography is occasionally required to exclude aortic aneurysm, though CT scan with contrast enhancement for such lesions is increasingly diagnostic. The differential diagnosis include angioneurotic edema, congestive heart failure, constrictive pericarditis, and fibrosing mediastinitis. Effort thrombosis of the axillary vein, innominate vein obstruction from elongation and buckling of the innominate artery can be considered in unilateral cases.
Complications of superior vena caval syndrome
In patients with partial superior vena caval obstruction, thrombosis may suddenly change mild symptoms to marked venous distention, cyanotic swelling, vocal cord edema, and impaired cerebration. Bleeding from esophageal varices is rare except in severe long-standing cases.
Treatment of superior vena caval syndrome
Superior vena caval obstruction caused by cancer should be treated with diuretics, restriction, avoidance of upper extremity intravenous lines, head elevation, and prompt radiation therapy. Cases of superior vena cava obstruction due to tumor begin to subside by 7 days of treatment. Because of the possibility of thrombosis in malignant cases, the use of fibrinolytic agents has been suggested. Caution must be advised in using anticoagulants, however, because many patients have advanced disease and may harbor occult cerebral metastases. Therefore, before starting therapy, patients should undergo CT or MRI brain scanning to prevent the occurrence of intracerebral hemorrhage. Recently, the use of intravascular expansile stents has been pioneered. Limited early experience suggests that the lumen can be reopened and that good venous drainage and decompression can be achieved by minimally invasive interventional radiologic techniques. Long-term results have not been reported, disadvantages include the need for anticoagulation to prevent recurrent thrombosis. Chemotherapy is sometimes used alone or with radiotherapy. Most cases of malignant superior vena caval obstruction are not remediable by operation. Tissue diagnosis is important for diagnosis and for guiding therapy. Invasive procedures, however, must be tailored to the individual patient and the severity of the caval obstruction. Patients with new, severe, or rapidly progressive symptoms should receive immediate palliative radiation therapy. Patients with subacute presentations can better tolerate the time required to make the diagnosis.
Fine-needle aspiration, bronchoscopy, cervical mediastinoscopy, and anterior mediastinotomy — and even, occasionally, thoracotomy — offer possible approaches for obtaining tissue. Caution must be advised, however, in the setting of acute fulminant superior vena caval obstruction as any invasive procedure will carry a significantly higher morbidity due to bleeding from venous obstruction. In this case, attempts at invasive techniques for tissue diagnosis should be avoided. Most frequently, the disease process has been previously histologically confirmed because superior vena caval obstruction presents typically as a complication of locally advanced disease. In benign incomplete superior vena caval obstruction, surgical excision of the compressing mass can provide an excellent result. In total obstruction, such as occurs in fibrosing mediastinitis, most patients will gradually improve without treatment. There are numerous surgical procedures designed to bypass caval obstruction, replace the superior vena cava, or recanalize the vena caval lumen. These procedures have been dramatically effective in some cases, but only recently have they been sufficiently successful to warrant consideration.
Radiotherapy is most effective when superior vena caval obstruction is incomplete. Mean survival of patients with malignant caval obstruction from lung cancer is 6–8 months. The death rate from causes related to vena caval obstruction itself is only 1–2%.