Superior vena cava syndrome (SVCS) is a disorder defined by internal or external obstruction of the superior vena cava (SVC), leading to reduced venous blood return into the right heart. The presence of this complication is an ominous prognostic sign, carrying a life expectancy of 4 to 6 months in recurrent malignant disease (Anderson & Coia, 2000; Tanigawa et al., 1998; Wilson, Lyn, Lynn & Khan, 2002).

A. When less blood returns to the heart, cardiac output is compromised.

B. The primary clinical outcomes are venous congestion and low cardiac output.

When more than one potential mechanism of vena caval obstruction is involved, the risk of this complication is proportionately increased. The degree of obstruction and the speed of onset will be reflected in the severity of signs and symptoms.

A. Direct Tumor Involvement: Malignancies associated with tumor involvement of the SVC are more likely to involve the mediastinum, and particularly the vasculature.

1. The most prevalent malignant cause of SVCS is bronchogenic lung carcinoma (may be small-cell or adenocarcinoma, occasionally large-cell lung cancer). This accounts for about 80% of all cases.

2. Breast cancer and lymphoma are the two other tumors that comprise the majority of the remaining 20% of cases.

3. Other tumors identified as metastasizing to the chest vessels and causing SVCS include head and neck cancers, renal cell carcinoma, and malignant melanoma.

4. Five-year survival rate after diagnosis of SVCS due to mediastinal tumor is 0% to 5% (Roberts, Bueno & Sugarbaker, 1999).

B. Extrinsic Compression: The SVC is a low-pressure vessel anatomically positioned between two immovable bone structures, the clavicle and scapula. When mediastinal structures become edematous or when mass-occupying lesions are introduced, there is insufficient room for all structures, and the soft-walled vena cava becomes occluded.

1. Many lymph nodes in the region (˜20) can become enlarged with infection or malignancy.

2. A tumor in this region can compress the vena cava, causing obstruction of venous return. In addition to the most common malignancies associated with SVCS, lung metastases from tumors such as thymoma, thyroid cancer, myxoma, prostate, and Wilms’ have caused extrinsic compression of the vena cava.

3. Adhesions from previous radiation therapy, centrally placed venous access devices (eg, implanted ports), mediastinal devices (eg, pacing
or internal defibrillator wires), or cavitating infections (eg, aspergillosis, tuberculosis) may increase the risk of SVCS.

4. There are a number of reported cases of cardiovascular or thoracic surgical interventions that have caused vena caval obstruction. This is a particularly common etiology among children. Occlusion of vena caval filters (eg, Greenfield filter) placed for recurrent thromboemboli has also caused SVCS syndrome when multiple clots are trapped in the device.

5. Nonmalignant conditions causing benign masses (eg, lipoma), or mass-occupying lesions (eg, cystic fibrosis, sarcoidosis, amyloidosis) can cause compression of the vena cava.

C. Intraluminal Thrombosis: This is the most common benign etiology of SVCS (Morales, Comas, Trujillo & Dorta, 2000). When an indwelling venous catheter is positioned in the vena cava, it occupies space normally used by the flow of blood, slowing the blood flow and enhancing the risk of blood stagnation and thrombosis around the catheter. This thrombosis reduces venous inflow and cardiac filling, causing SVCS.

1. Catheter variables increasing the risk of thrombosis include large lumen size and multiple lumens.

2. Host variables increasing the risk of SVCS in patients include hypercoagulability, multiple previous central venous catheter placements, and tumor involvement of the vena cava.

3. About one third of cases of SVCS involve thrombosis in addition to other etiologic factors.

4. A hypercoagulable tendency will also increase the risk of venous thrombosis. Hypercoagulability is enhanced by mucin-producing tumors (ie, any adenocarcinomas), procoagulants produced by myelocytic leukemias, hyperviscosity as seen in abnormal immunoglobulins with multiple myeloma, and other tumors associated with hypercoagulable states (eg, lymphoma or glioblastoma). Hypercoagulability leading to possible superior vena cava thrombosis is enhanced with infection, disseminated intravascular coagulation (DIC), and Trousseau’s syndrome.

A. Assessment: Most assessment findings in SVCS occur in the head, neck, and upper extremities and are related to the backflow of venous blood, normally drained by the SVC, into other body organs. Many of these physiologic symptoms persist even after the SVCS has resolved, particularly if symptoms have been prolonged and permanent vascular changes have occurred.

1. Dyspnea is the most common symptom of SVCS. It occurs because of venous congestion and cardiac failure due to inadequate blood volume.

2. If blood flow through the coronary arteries is compromised, reduced cardiac output will produce weak peripheral pulses, cool extremities, central cyanosis, and bradydysrhythmias.

3. A feeling of fullness in the head, headaches, neck swelling, distended neck veins, facial edema with flushing, conjunctivitis, and conjunctival hemorrhage occur due to venous congestion in the head and neck region.

4. Difficulty swallowing and hoarseness reflect congestion with edema of the neck and indicate a greater risk of airway obstruction.

5. Sensory disturbances, such as blurred vision and tinnitus, occur due to the excess venous blood in the head region.

6. Lethargy or somnolence, confusion, and enlarged or sluggish papillary response occur when venous congestion is severe enough to cause increased intracranial pressure. Papilledema on fundoscopic eye examination is also detectable in patients with increased intracranial pressure.

7. Headache or visual disturbances may be present due to head and neck congestion.

8. Veins in the chest will be distended, tortuous, and prominent due to venous congestion. Although more common on the right side, they may be present diffusely across the thorax.

9. Veins in the upper extremities, especially on the right side, will be distended and prominent, and edema of that extremity will range from mild to severe. This will be most noticeable in the brachial area.

10. Blood pressure will be elevated in the arm most affected, usually the right side.

B. Diagnostic Parameters: There are no serum or urine tests used to diagnose SVCS; however, other tests assist in diagnosis of the condition.

1. Chest x-ray is not diagnostic but is used to complement key clinical presentation cues.

a. Show mediastinal masses in the hilar region that may contribute to SVCS.

b. Show the right middle lobe congestion that is typical in SVCS.

c. Lateral x-rays can show masses and enlarged nodes between the clavicle and scapula.

2. Computed tomography (CT) scans

a. More precisely show the location and size of tumors or enlarged lymph nodes.

b. Better demonstrate whether the vessel is externally compressed or has tumor growth into the vessel.

c. A spiral CT scan is thought to best show the multiple dimensions needed to precisely define the perimeters and involvement of tumor near and within the vena cava.

3. When the spiral CT scan is inconclusive, venogram is performed to clarify whether there is a venous thrombosis causing or contributing to the SVCS.

a. Most patients with SVCS demonstrate some degree of thrombosis, even if the main etiologic factor is external compression of the vena cava.

b. The confirmation of thrombosis through venogram validates the decision to add thrombolytic therapy to the treatment plan.

c. Doppler flow studies may replace the use of venogram in patients with significant blood flow disturbances (Panzironi, Rainaldi, Ricci, Casale & Macciucca, 2003).

d. Transesophageal echocardiography has been used to diagnose vena caval thrombi, with reported success exceeding other noninvasive diagnostic methods (Shapiro, Johnson & Feinstein, 2002).

C. Treatment: SVCS is best treated by definitive antineoplastic therapy. The nature of this therapy will depend on the tumor type and its responsiveness to radiation therapy and chemotherapy.

1. Radiation therapy is used on radiosensitive tumors such as Hodgkin’s disease and thyroid cancer.

a. Patients receive 3,000 to 5,000 Cy of radiotherapy, given as 300 to 400 Cy for the first 2 to 4 days, then 150 to 200 Cy daily until the total dose is given.

b. Hyperfractionation schedules have not been proven superior to traditional 3- to 4-week therapy plans (Anderson & Coia, 2000).

2. Chemotherapy is administered when radiation therapy is not likely to succeed, when patients have received the maximum tolerated dose of radiation, or when patients have chemosensitive tumors (eg, small-cell lung cancer).

3. Endovascular stenting of the vena cava (Lanciego et al., 2001)

a. Stents may be made of flexible wire (self-expandable) or Silastic.

b. Placement percutaneously by interventional cardiovascular specialists.

c. Potential adverse effects include pulmonary emboli, hemorrhage, pericardial tamponade, stent malposition, and recurrence of SVCS.

d. Rapid return of venous blood into the heart after stenting procedure may cause transient congestive heart failure due to sudden increased workload on the heart. This is more likely if SVCS has been long-standing and severe (Yamagami, Nakamura, Kato, Iida & Nishimura, 2002).