Superior vena cava syndrome is the obstruction of blood flow through the superior vena cava. It is a medical emergency and is most commonly seen in patients with malignant disease in the thoracic cavity. Patients with superior vena cava syndrome need to be diagnostically evaluated and treated as soon as possible.
The first case of superior vena cava syndrome was reported in 1757 and its etiology was syphilitic aortic aneurysm. At one time, the etiology of superior vena cava syndrome was primarily syphilitic aneurysm or tuberculous mediastinitis. Currently, approximately 70% of the causes of superior vena cava syndrome are lung cancer, specifically adenocarcinoma.
Why does superior vena cava syndrome occur?
The superior vena cava drains venous blood from the head, neck, upper extremities and upper chest. It is located within the body’s thoracic cavity and is surrounded by a number of relatively fixed structures: the sternum, trachea, right main bronchus, aorta, pulmonary artery, hilar and parabronchial lymph nodes. It begins at the junction of the left and right unnamed arteries and ends at the right atrium, which is 6-8 cm long. it is a thin-walled, low-pressure vascular structure. It is susceptible to compression as it passes to the right side of the mediastinum.
Obstruction of the superior vena cava can be caused by tumor invasion of the vein wall with intravascular thrombosis or by direct external pressure of the tumor on the thin-walled superior vena cava. Complete obstruction of the superior vena cava is often the result of intravascular thrombosis combined with external compression; partial obstruction is often the result of external compression without thrombosis. Other causes are endovascular devices, and their incidence is increasing with the increasing use of endovascular devices.
When the superior vena cava is obstructed, venous blood flow from the upper part of the body returns to the heart through the collateral circulation, which includes four main pathways. The most important of these pathways is the odd vein system, which includes the odd and semi-oval veins, which communicate with the intercostal veins. The second pathway is the internal mammary vein system and its branch vessels, which communicate with the superior and inferior abdominal wall veins. The third and fourth collateral circulation are the long thoracic venous system with the femoral and vertebral veins, respectively.
In superior vena cava obstruction, despite these collateral pathways, the upper venous pressure is generally elevated. In severe cases of superior vena cava syndrome, venous pressure can be as high as 200 to 500 cm of water column.
What is the morbidity and mortality of superior vena cava syndrome?
Morbidity Superior vena cava syndrome occurs in 5-10% of patients with right-sided intrathoracic malignant disease. Superior vena cava syndrome occurs in 4.2% of patients with lung cancer, of which 80% have tumor involvement of the right lung; 9-19% of patients with small cell lung cancer and 1.9% of patients with lymphoma.
The prognosis of patients with superior vena cava syndrome in terms of mortality depends mainly on the underlying disease. Mild venous congestion by itself does not lead to death.
The life expectancy of patients with benign superior vena cava syndrome remains unchanged. In superior vena cava syndrome due to malignant disease, mortality is mainly related to tumor histology. The most dangerous manifestation of superior vena cava syndrome is the risk of sudden death if the patient presents with signs and symptoms of laryngeal edema and cerebral edema. Clinical observations suggest that 10% of patients with bronchopulmonary cancer and 45% of patients with lymphoma can survive at least 30 months with radiation therapy; whereas if malignant superior vena cava syndrome is left untreated it survives only about 30 days.
What are the clinical manifestations of superior vena cava syndrome?
Superior vena cava syndrome is early in the course of the disease and may be asymptomatic with partial obstruction, but more commonly the signs and symptoms are mild and easily missed.
When superior vena cava syndrome progresses to complete obstruction, typical signs and symptoms appear.
The most common symptom is dyspnea, which is present in 63% of patients with superior vena cava syndrome.
Other symptoms are.
Facial swelling.
Head swelling.
Cough.
Swelling of the arms.
Chest pain.
Difficulty in swallowing.
End-stage breathing.
Visual changes.
Hoarseness.
Headache.
Nasal congestion.
Nausea.
Pleural effusion.
Feeling of heaviness in the head and feet.
Dilated veins in the neck and chest wall.
Facial edema.
Edema of the upper extremities.
Changes in mental awareness.
Congestion of blood.
Cyanosis.
Optic papilla edema.
Xerosis.
Coma.
Signs and symptoms may be worsened by forward bending or lying flat on the body.
What causes superior vena cava syndrome?
More than 80% of cases of superior vena cava syndrome are due to malignant mediastinal tumors, including 75-80% of bronchial lung cancers, mostly small cell lung cancer. Non-Hodgkin’s lymphoma (especially the large cell type) accounts for 10-15%. Less common malignant diseases include Hodgkin’s disease, metastatic carcinoma, primary smooth muscle sarcoma of the mediastinal vessels, and plasmacytoma.
Non-malignant diseases causing superior vena cava syndrome, which account for approximately 22% of cases, are.
1) mediastinal fibrosis.
2) vascular diseases, such as aortic aneurysms, vasculitis and arteriovenous fistulas.
3) infections, such as histoplasmosis, tuberculosis, syphilis, etc.
4) benign mediastinal tumors, such as teratomas, thymomas, dermatomal cysts, etc.
5) heart disease, such as pericarditis and atrial mucinous tumors
6) central venous placement leading to thrombosis.
What tests are needed to suspect or diagnose superior vena cava syndrome?
A chest radiograph may reveal a widened mediastinum or a right thoracic mass. Only 16% of chest films are unremarkable.
CT CT examination may provide more accurate information about the location of the obstruction and may guide mediastinoscopy, bronchoscopy, or percutaneous needle aspiration biopsy. It can also provide information about other important structures such as the bronchi and vocal cords.
A CT of the chest should be examined first to clarify whether the cause of the obstruction is external pressure or thrombosis.
The diagnostic value of MRIMRI for this disease has not been adequately studied, although it may be valuable. Its advantages over CT include the ability to image in multiple planes, the ability to directly visualize blood flow, and the fact that iodine contrast is not required.
MRI may be an alternative option for patients with renal failure and for patients with contrast allergy. Disadvantages include increased scan time, decreased patient compliance and increased cost.
VenographyInvasive contrast venography is the most definitive diagnostic tool. It allows precise determination of the cause of obstruction. It is particularly important when surgical treatment is being considered.
SPECT may be valuable in some cases.
How is superior vena cava syndrome treated?
Superior vena cava syndrome may require medical or surgical treatment. The goal of treatment for superior vena cava syndrome is to relieve symptoms and to cure the primary malignant disease as much as possible. Only a few rapid onset episodes of superior vena cava obstruction may lead to life-threatening complications.
Patients with clinical vena cava syndrome often experience significant symptomatic relief with conservative management, including elevation of the head of the bed and oxygenation. Indications for emergency management include cerebral edema, decreased cardiac output, or upper airway edema. Glucocorticoids and diuretics are often applied to relieve laryngeal edema or cerebral edema, although the results are not definitive.
Radiotherapy is the standard of care for most patients with superior vena cava syndrome. It may be the initial treatment if a histologic diagnosis cannot be established and the patient’s clinical condition worsens; however, a review of the literature suggests that simple superior vena cava obstruction rarely requires urgent treatment before diagnosis is confirmed.
The radiotherapy regimen usually starts with two to four high doses of 3-4 Gy, after which conventional doses of 1.5-2 Gy per day are applied until a total dose of 30-50 Gy. The radiation dose depends on the tumor size and radiation response. The radiation coverage should include 2-cm around the tumor margin.
After irradiation, patients show clinical improvement before chest imaging suggests significant tumor shrinkage. Improvement of superior vena cava obstruction with radiation therapy is seen in 70% of patients with lung cancer and in more than 95% of patients with lymphoma.
Radiotherapy is preferred for patients with superior vena cava syndrome secondary to non-small cell lung cancer and is highly effective, but has a poor overall prognosis.
Chemotherapy may be preferable to radiotherapy for patients with chemosensitive tumors. One study showed that in small cell lung cancer combined with superior vena cava syndrome, radiotherapy alone was 56% effective, chemotherapy was 100% effective, and combination therapy was 83% effective.
In non-Hodgkin’s lymphoma causing superior vena cava syndrome, all patients had complete resolution of superior vena cava syndrome symptoms within 2 weeks, regardless of whether chemotherapy alone, combined chemoradiotherapy, or radiotherapy alone was administered.
For superior vena cava syndrome due to thrombosis around a central venous placement, thrombolysis (e.g., streptokinase, urokinase, or rt-PA) or anticoagulation (e.g., heparin or oral anticoagulants) is indicated. If possible, the catheter is withdrawn and must also be anticoagulated to prevent embolization. These treatments are most effective when applied within 5 days of symptom onset.
One investigator reported that in malignant superior vena cava syndrome with thromboprophylaxis to prevent embolic events, thromboembolic events occurred in 5 of 10 patients without anticoagulation and were fatal in 2 cases. In contrast, fatal intracranial hemorrhage occurred in 2 of 20 anticoagulated patients. Therefore, anticoagulation therapy has yet to be proven in prospective randomized clinical trials.
Surgical bypass of the superior vena cava may provide symptomatic relief, but the indications are not fully established.
The current mainstay of endovascular therapy is stenting or percutaneous transluminal angioplasty, thrombolysis, or some combination.