Critical Care Medicine

Superior Vena Cava (SVC) syndrome

Superior vena cava syndrome

Also known as: SVC syndrome

Related conditions

Thrombosis

Venous obstruction

Shortness of breath

Facial swelling

Mediastinal disease

Oncologic emergencies

1. Description of the problem

SVC syndrome is caused by obstruction of blood flow through the SVC. This can be due to extrinsic compression of the vessel (tumor), intrinsic obstruction (thrombus), or a combination of the two. At one extreme, this disease process can be indolent, slowly progressing over a long period of time. On the other end of the spectrum, this can present as a fulminant event requiring immediate diagnosis and intervention.

Clinical features

This clinical diagnosis is based on the signs and symptoms of central venous obstruction. Dyspnea is the most common symptom. Other symptoms are cough, facial swelling, arm swelling, chest pain, dysphagia and hoarseness, cyanosis, cerebral edema, and mental status changes. Frequently, symptoms get worse over time and then improve as collateral vessels form and shunt blood back to the heart.

Key management points

The first and most important task in managing the patient with SVC syndrome is to correctly identify the cause. The urgency with which the diagnosis must be made and therapy administered is based on the severity of symptoms. For SVC syndrome associated with malignancy, the goal is to alleviate symptoms and treat the underlying disease.

2. Emergency Management

SVC syndrome is often clinically striking but rarely requires emergent intervention. Clinically significant obstruction is typically a subacute process that develops over weeks or longer. Such a time course thus allows for the development of a collateral venous system that is able to return blood to the heart. On the other hand, fast-growing malignancies such as small cell lung cancer (SCLC) and non-Hodgkin's lymphoma (NHL) may require urgent therapy.

Emergency treatment should always be considered in patients who present with stridor or severe laryngeal edema. Endovascular stent placement and radiation therapy are the treatments of choice in these instances. Patients presenting with cerebral edema also require emergent intervention.

Management points not to be missed

A tissue diagnosis should be obtained prior to any therapeutic intervention, except in life-threatening situations.

Most cases usually do not require emergent intervention because of the formation of collateral vessels that shunt blood back to the heart.

For patients with a history of malignancy, every effort should be made to obtain previous treatment records. The history of previous therapies administered will dictate the best treatment options for management of SVC syndrome.

3. Diagnosis

SVC syndrome is a clinical diagnosis based on the signs and symptoms of central obstruction. Clinical history, radiographic findings, and pathologic evaluation all support diagnosis.

Typical physical findings: Facial edema, arm swelling, venous distention in neck and chest wall, and cyanosis

Imaging studies

Chest X-ray is abnormal in >75% of patients.

An enlarged mediastinal shadow is common.

Pleural effusions may be present.

CT scan with contrast is the study of choice. The level and extent of venous blockage can be identified. Identification of collateral vessels supports the diagnosis. Both extrinsic and extrinsic sources of blockage can be noted.

Bilateral upper extremity venography is the gold standard for identifying SVC obstruction due to venous thrombus formation.

MR venography should be considered for patients with contrast dye allergies.

Tissue Diagnosis

Histologic confirmation is necessary prior to institution of therapy. Diagnostic techniques and procedures include: sputum cytology, pleural cytology, bronchoscopy with biopsy, mediastinoscopy with biopsy, CT-guided biopsy, bone marrow biopsy, and video-assisted thoracotomy.

Differential diagnosis

Differential diagnosis includes: ARDS, pneumonia, cardiac tamponade, COPD, syphilis, tuberculosis, aortic aneurysm, postradiation fibrosis (in patients who previously received thoracic radiation).

4. Specific Treatment

Chemotherapy

Chemotherapy is frequently used as initial therapy for germ cell tumors, NHL, and SCLC (non-small cell lung cancer [NSCLC] is almost always treated with radiation therapy +/- chemotherapy). Clinical responses can be rapid (within 72 hours), with significant symptomatic relief occurring within 1-2 weeks. The addition of concurrent radiation therapy may be considered for particular cases.

Radiation Therapy

Most malignancies that cause SVC syndrome are radio-sensitive. Unlike SCLC, NSCLC is generally less responsive to chemotherapy alone. In these cases, radiation therapy should be considered. Except in rare circumstances, radiation should not be administered until a tissue diagnosis has been made. If radiation is administered first, there is a risk that the tissue will be sterilized and no longer amenable to diagnosis. Additionally, caution should be taken when considering radiation therapy in a patient who has previously received thoracic radiation. Symptomatic relief from radiation may be seen in several days or take as long as several weeks. A typical palliative course is given over two weeks.

Surgery

Surgery may be considered for fibrosing mediastinitis.

Intravascular Stent Placement

Percutaneous placement of self-expanding endovascular stents may also be considered. Stents can be particularly useful for patients who have rapidly worsening respiratory distress and require urgent intervention. Stents should also be considered when SVC syndrome is caused by thrombus formation from an indwelling catheter. Mesothelioma, a pleural-based malignancy of the lung, is not considered to be very responsive to chemotherapy or radiation therapy and so stent placement should be considered. Finally, stents are considered for those patients who have failed to respond to previous therapies (chemotherapy and radiation).

Drugs and dosages

Chemotherapy choice and dose will be directed by tumor type.

Glucocorticoids (dexamethasone, 4 mg every 6 hours) can be used to reduce tumor burden in patients with steroid-responsive malignancies such as lymphoma or thymoma. Steroids are also helpful in reducing laryngeal edema, which may result from administration of radiation therapy.

Diuretics may offer some clinical benefit.

Anticoagulants are often recommended after stent placement. Anticoagulation is also recommended after thrombolysis of existing thrombus.

5. Disease monitoring, follow-up and disposition

Expected response to treatment

For those patients treated with chemotherapy alone (SCLC, NHL, germ cell tumors), symptomatic improvement typically occurs within 1-2 weeks.

Patients treated with radiation therapy typically see some symptomatic improvement within 72 hours, with maximal relief achieved by 2-4 weeks.

Approximately 20% of patients treated with either radiation therapy or chemotherapy do not obtain any measurable symptom relief.

Radiographic evidence of tumor regression and SVC decompression does not always parallel subjective symptom relief.

Incorrect diagnosis

The initial diagnosis should be questioned if there is a poor response to therapy. However, particular malignancies such as NSCLC may not show a significant response to either radiation or chemotherapy.

Follow-up

With malignant causes of SVC syndrome it is frequently possible to reduce tumor bulk enough to allow for significant decompression of the vena cava and improvement in symptoms. But essentially all of these patients will need more cytoreductive therapy for treatment of their underlying malignancy. Accordingly, it is imperative that a future care plan be established with consulting radiation oncologists and medical oncologists before discharge. This plan then must be clearly communicated to the patient and/or care providers.

Pathophysiology

As noted above, obstruction of blood flow through the SVC can be caused by extrinsic compression of the vessel, or by thrombus within the SVC. If this blockage is subacute or chronic, then venous collaterals will develop, allowing for alternative pathways back to the right atrium. Collateral veins may form off the azygous, internal mammary, lateral thoracic, and esophageal venous systems. But even with development of these collaterals central venous pressures are typically elevated, producing the signs and symptoms of SVC syndrome. But if complete obstruction happens acutely (rapidly growing tumor) there may not be enough time for collaterals to develop and signs and symptoms will rapidly progress.

Epidemiology

Etiology

60%-85% of cases of SVC syndrome are due to intrathoracic malignancies, with the remainder due to benign causes. NSCLC accounts for 50% of all malignant causes, followed by by SCLC (25% of malignant cases) and NHL (10%). Rare malignant causes include Hodgkin's lymphoma, metastatic disease, leiomyosarcomas of the mediastinal vessels, plasmacytomas, germ cell neoplasms, and thymoma.

Nonmalignant processes make up the remainder of causes for SVC syndrome. Until about 50 years ago, infectious causes (syphilitic aortic aneurysm and tuberculosis) accounted for the majority of cases of SVC syndrome. Now, thrombosis has become a more common nonmalignant cause. This almost certainly reflects the increased use of intravascular devices such as central venous catheters and pacemaker leads.

Fibrosing mediastinitis is another frequent nonmalignant cause of SVC syndrome. This proliferative process is most commonly the result of prior infection by Histoplasma capsulatum (although other infectious causes may be responsible). Heavy ectopic calcifications are frequently seen with the Histoplasma subtype.

Lung cancer

For SCLC, SVC syndrome occurs in approximately 10% of cases at presentation, while fewer than 2% of patients presenting with NSCLC have SVC syndrome. But because there is a higher incidence of NSCLC, SCLC is a less frequent cause of SVC syndrome.

Lymphoma

SVC syndrome occurs in up to 4% of patients with NHL. The syndrome is rarely seen with Hodgkin's lymphoma. Diffuse large cell and lymphoblastic lymphomas are the most common subtypes associated with SVC syndrome. Patients with primary mediastinal B-cell lymphoma typically present with a rapidly enlarging anterior mediastinal mass and up to 80% of patients may show evidence of SVC compression.

Prognosis

The average life expectancy for patients who present with malignancy-related SVC syndrome is 6 months, although the prognosis is quite variable depending on the type of malignancy. SVC obstruction in patients with NSCLC portends a particularly poor prognosis.

What's the evidence?

Schraufnagel, DE, Hill, R, Leech, JA, Pare, JAP. "Superior vena caval obstruction: is it a medical emergency?". Am J Med. vol. 70. 1981. pp. 1169-1174.

Uberoi, R. "Cirse guidelines: quality assurance guidelines for superior vena cava stenting in malignant disease". Cardiovasc Intervent Radiol. vol. 29. 2006. pp. 319-322.

Wilson, LD, Detterbeck, FC, Yahalom, J. "Clinical practice. Superior vena cava syndrome with malignant causes". N Engl J Med. vol. 356. 2007. pp. 1862-1869.

(This is the most comprehensive article to date, from clinicians at Yale and Memorial Sloan Kettering.)

Yu, JB, Wilson, LD, Detterbeck, FC. "Superior vena cava syndrome--a proposed classification system and algorithm for management". J Thorac Oncol. vol. 3. 2008. pp. 811.

(Another useful article from the Yale group.)
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