Superior vena cava syndrome

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Maria Fernanda Villarreal, M.D. [2]

Superior vena cava syndrome (also known as SVCS), is a group of symptoms caused by obstruction of the superior vena cava. More than 60% of cases of superior vena cava obstruction are caused by malignant causes, typically a tumor outside the vessel compressing the vessel wall. However, in 20% of the cases, the cause is benign. Characteristic features are edema (swelling due to excess fluid) of the face and arms and development of swollen collateral veins on the front of the chest wall. Shortness of breath and coughing are quite common symptoms; difficulty swallowing is reported in 11% of cases, headache in 6%, and stridor in 4%. The prognosis is generally poor and the survival rate of patients with superior vena cava syndrome is approximately 10-20% at 6 months. In less than 5% of cases of superior vena cava syndrome, severe neurological symptoms or airway compromise are reported. Treatment mainly consists of careful medical therapy (glucocorticoids) and surgery.

Superior vena cava syndrome was first discovered by William Hunter (1718-1783), a Scottish obstetrician, in 1757.

Superior vena cava syndrome arises from the obstruction of venous blood drainage of the superior vena cava, which is normally involved in the major blood flow return from head, neck, upper extremities, and upper thorax to the heart. Superior vena cava syndrome is a complication of a partial or complete obstruction due to malignant causes (60%) or benign causes (20%). This syndrome consists on the invasion of the venous wall associated with intravascular thrombosis, enlarged nodes, enlarged ascending aorta, or by extrinsic pressure of a tumor mass against the thin-walled superior vena cava which leads to the development of superior vena cava syndrome. Superior vena cava syndrome is associated with a number of conditions that include malignant tumors, tuberculosis, histoplasmosis, and syphilis.

Superior vena cava syndrome may be caused by obstruction of the superior vena cava by neoplastic invasion of the venous wall, intravascular thrombosis, enlarged lymph nodes, enlarged ascending aorta, or by extrinsic pressure of a tumor against the thin-walled superior vena cava.

Superior vena cava syndrome should be differentiated from other causes of dyspnea and jugular venous distention, such as, cardiac tamponade, chronic obstructive pulmonary disease, mediastinitis, pneumonia, acute respiratory distress syndrome, and syphilis.

Superior vena cava syndrome is a common oncologic emergency. The incidence rate in the United States is approximately 15,000 individuals each year. The incidence of superior vena cava syndrome increases with age; the median age of diagnosis is between 40-60 years. Males are more commonly affected with superior vena cava syndrome than females.

The most potent risk factor in the development of superior vena cava syndrome is intrathoracic malignancies. Other common risk factors include thrombosis (due to intravascular devices), postradiation fibrosis, and mediastinitis.

According to the the National Cancer Institute, there is insufficient evidence to recommend routine screening for superior vena cava syndrome.

If left untreated, patients with superior vena cava syndrome may progress to develop a complete blood flow obstruction and a decreased cardiac output with hypotension, leading to heart failure and death. Common complications of superior vena cava syndrome include airway obstruction, increased ICP, laryngeal edema, and cerebral edema. The prognosis will vary depending on the cause of the syndrome, and the amount of blockage that has already occurred. Prognosis is generally poor and the survival rate of patients with superior vena cava syndrome is approximately 10-20% at 6 months.

According to the Journal of Thoracic Oncology, there are 5 stages of superior vena cava syndrome based on the severity and incidence. Each stage is assigned a grade and a description that designate disease severity.

The hallmark of superior vena cava syndrome is elevated jugular venous pressure. A positive history of cancer and intra-vascular devices are suggestive of superior vena cava syndrome. The most common symptoms of superior vena cava syndrome include upper body swelling, dyspnea, and cough.

Common physical examination findings of superior vena cava syndrome include the pemberton’s sign, facial swelling, and jugular venous distension.

There are no diagnostic laboratory findings associated with superior vena cava syndrome.

On chest x-ray, indirect signs such as superior mediastinal widening and right hilar prominence may indicate the presence of a mediastinal mass.

On enhanced CT scan, findings include location and severity of the superior vena cava obstruction, superimposed thrombosis, a mediastinal mass or lymphadenopathy, collateral vessels, and associated lung masses. CT scan is the imaging modality of choice.

MRI may be helful to provide images without the use of contrast (useful in patients with renal failure).

Doppler ultrasound may be valuable in assessing the site and nature of the obstruction in superior vena cava syndrome. Venous patency and the presence of thrombi can also be assessed by using contrast and rapid scanning techniques.

Other imaging finding is the radionuclide technetium-99m venography.

Other diagnostic studies in the evaluation of superior vena cava syndrome include sputum tests, bronchoscopy, and biopsy. In addition, invasive contrast venography is also a diagnostic tool in the diagnosis of superior vena cava syndrome. It may be useful on the etiology of obstruction and exact location of the obstruction, also helpful in the surgical management of the obstructed vena cava.

Superior vena cava syndrome is a medical emergency and requires prompt treatment. The treatment of superior vena cava syndrome depends on the etiology of the obstruction, the severity of the symptoms, the prognosis of the patient, patient preferences, and goals for therapy.

Elective stent placement and surgical bypass is recommended for all patients who develop superior vena cava syndrome.

Rapid radiotherapy is recommended for all patients who develop superior vena cava syndrome secondary to malignant tumor. The feasibility of radiation therapy depends on the stage of cancer at diagnosis. Radiation dosage will depend on clinical features.

There are no primary preventive measures available for superior vena cava syndrome.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Maria Fernanda Villarreal, M.D. [2]

Superior vena cava syndrome arises from the obstruction of venous blood drainage of the superior vena cava, which is normally involved in the major blood flow return from head, neck, upper extremities, and upper thorax to the heart. Superior vena cava syndrome is a complication of a partial or complete obstruction due to malignant causes (60%) or benign causes (20%). This syndrome consists on the invasion of the venous wall associated with intravascular thrombosis, enlarged nodes, enlarged ascending aorta, or by extrinsic pressure of a tumor mass against the thin-walled superior vena cava which leads to the development of superior vena cava syndrome. Superior vena cava syndrome is associated with a number of conditions that include malignant tumors, tuberculosis, histoplasmosis, and syphilis.

Knowledge of the anatomy of the superior vena cava and its relationship to the surrounding lymph nodes is essential to understanding the development of the syndrome.^[1]

• The superior vena cava is the major blood vessel for the drainage of the upper body (head, neck, upper extremities, and upper thorax).
• Extrinsic compression of the superior vena cava by a mediastinal tumor is possible because it has a low intravascular pressure. In addition, the superior vena cava is also surrounded by rigid structures, so it is relatively easy to compress.
• Moreover, the superior vena cava is thin-walled, and the blood flowing therein is under low pressure. Therefore, when the nodes or ascending aorta enlarge, the superior vena cava is compressed, blood flow slows, and complete occlusion may occur.^[2]
• The superior vena cava is formed by the junction of the left and right brachiocephalic veins in the mid third of the mediastinum. It extends caudally for 6 to 8 cm, coursing anterior to the right mainstem bronchus and terminating in the superior right atrium, and extends anteriorly to the right mainstem bronchus.
• The superior vena cava is joined posteriorly by the azygos vein as it loops over the right mainstem bronchus and lies posterior to and to the right of the ascending aorta. The mediastinal parietal pleura is lateral to the superior vena cava, creating a confined space, and the superior vena cava is adjacent to the right paratracheal, azygous, right hilar, and subcarinal lymph node groups.^[3]
• In long standing cases with 60% or more stenosis, collateral channels are formed to restore venous return. Various collaterals are formed depending up on the site of the obstruction:

• Pre-azygos: in this conditions mainly the right superior intercostal veins serves as the collateral pathway to drain into the azygos vein.
• Azygos: when the azygos vein is also obstructed the collateral circulation establishes between superior vena cava and inferior vena cava via minor communicating channels i.e. internal mammary veins, superior and inferior epigastric veins to iliac veins and finally into the inferior vena cava.
• Post-azygos: in this case the blood from the superior vena cava is distributed into the azygos and hemiazygos and then into the inferior vena cava tubutaries i.e. ascending lumbar and lumbar veins.

• Superior vena cava syndrome is associated with a number of conditions that include:

• Malignancy^[4]
  • Lymph node metastasis
  • Non–small cell lung cancer
  • Small cell lung cancer
  • Lymphoma
  • Metastatic lesions (most commonly from breast and testicular cancers)
• Infections
• Iatrogenic intravascular devices
• Thyroid goiter
• Thrombosis
• Pericardial constriction
• Idiopathic sclerosing mediastinitis
• Aortic aneurysm

On gross pathology, there are no characteristic findings of superior vena syndrome.

On microscopic pathology, there are no characteristic findings of superior vena syndrome.

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