Superior Vena Cava Syndrome
Overview
Etiology/Physiology
Assessment/Diagnosis
Treatment Options
Medical Management
Radiation Therapy
Chemotherapy
Thrombolysis
Stent Placement
Surgery
Psychosocial Considerations
Pediatric Considerations
Overview
Superior vena cava syndrome (SVCS) is an array of symptoms caused by the
impairment of blood flow through the superior vena cava (SVC) to the right
atrium. Symptoms that prompt suspicion of this syndrome include dyspnea,
coughing, and swelling of the face, neck, upper trunk, and extremities. In rare
instances, patients may complain of hoarseness, chest pain, dysphagia, and
hemoptysis. Physical signs that may be noted on presentation are neck vein
distention, thoracic vein distention, edema of the face or upper extremities,
plethora, and tachypnea. Rarely, cyanosis, Horner syndrome, and a paralyzed
vocal cord may also be present.[1]
SVCS is usually a sign of locally advanced bronchogenic carcinoma. Survival
depends on the status of the patient’s disease. When small cell bronchogenic
carcinoma is treated with chemotherapy, the median survival times with or
without SVCS are almost identical (42 weeks or 40 weeks, respectively). The 24-month
survival rate is 9% in patients without SVCS and 3% in those with the syndrome.
When the malignancy is treated with radiation therapy, 46% of patients who have
non-small cell lung cancer experience relief of symptoms compared with 62% of
patients who have small cell bronchogenic carcinoma. The 2-year survival rate of 5%
is almost the same for both groups.[2]
Most non-Hodgkin lymphoma patients with SVCS respond to appropriate
chemotherapy or to combined modality regimens.
Etiology/Physiology
Since SVCS was first described by William Hunter
in 1757, the spectrum of underlying conditions associated with it has shifted
from tuberculosis and syphilitic aneurysms of the ascending aorta to malignant
disorders. Almost 95% of SVCS cases described in published modern series are
due to cancer; the most common cause is small cell bronchogenic carcinoma,
followed by squamous cell carcinoma of the lung, adenocarcinoma of the lung,
non-Hodgkin lymphoma, and large cell carcinoma of the lung.[3] A
nonmalignant cause of SVCS in cancer patients is thrombosis that is associated
with intracaval catheters or pacemaker wires.[4] A rare cause of SVCS is
fibrosing mediastinitis, either idiopathic or associated with
histoplasmosis.[5] Additional rare causes of SVCS include metastatic germ cell
neoplasms, metastatic breast cancer, colon cancer, Kaposi sarcoma, esophageal
carcinoma, fibrous mesothelioma, Behçet syndrome, thymoma, substernal thyroid
goiter, Hodgkin lymphoma, and sarcoidosis.[6]
Knowledge of the anatomy of the SVC and its relationship
to the surrounding lymph nodes is essential to understanding the development of
the syndrome. The SVC is formed by the junction of the left and right
brachiocephalic veins in the mid third of the mediastinum. The SVC 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 SVC 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 SVC, creating a confined space, and the SVC is adjacent to the
right paratracheal, azygous, right hilar, and subcarinal lymph node groups.
The vessel itself is thin-walled, and the blood flowing therein is under low
pressure. Thus, when the nodes or ascending aorta enlarge, the SVC is
compressed, blood flow slows, and complete occlusion may occur.
The severity of the syndrome depends on the rapidity of onset of the
obstruction and its location. The more rapid the onset, the more severe the
symptoms because the collateral veins do not have time to distend to
accommodate an increased blood flow. If the obstruction is above the entry of
the azygos vein, the syndrome is less pronounced because the azygous venous
system can readily distend to accommodate the shunted blood with less venous
pressure developing in the head, arms, and upper thorax. If the obstruction is
below the entry of the azygos vein, more florid symptoms and signs are seen
because the blood must be returned to the heart via the upper abdominal veins
and the inferior vena cava, which requires higher venous pressure.[7]
One study suggested that the general recruitment of venous collaterals over
time may lead to remission of the syndrome, although the SVC remains
obstructed.[8]
Assessment/Diagnosis
Once SVCS is recognized, prompt clinical
attention is important. A diagnosis should be established prior to initiating
therapy for the following reasons:[3]
- 75% of patients have symptoms and signs for longer than 1 week before
seeking medical attention.
- Cancer patients diagnosed with SVCS do not die of the syndrome
itself but rather from the extent of their underlying disease.
- 3% to 5% of the patients diagnosed with SVCS do not have cancer.
In the absence of tracheal obstruction, SVCS is unlikely to be a life-threatening oncologic emergency, and treatment prior to definitive diagnosis is
not justified.
The initial evaluation of the patient should include a chest radiograph to look
for mediastinal masses and associated findings, such as pleural effusion, lobar
collapse, or cardiomegaly. Computed tomography (CT) scanning of the thorax
yields the most useful diagnostic information and can define the anatomy of the
involved mediastinal nodes. Venous patency and the presence of thrombi are
assessed by using contrast and rapid scanning techniques.[9] Depending on
local expertise, contrast or nuclear venography, magnetic resonance imaging,
and ultrasound may be valuable in assessing the site and nature of the
obstruction.
If bronchogenic carcinoma is suspected, a sputum specimen should be obtained.
If the sputum specimen is negative, a biopsy specimen should be taken from the
most accessible site that is clinically involved with disease. The biopsy
approach depends on the working diagnosis, the location of the tumor, the
physiologic status of the patient, and the expertise available at the facility.
It may include bronchoscopy, biopsy of palpable cervical or supraclavicular
lymph nodes, needle biopsy of a lung mass or mediastinal nodes using either CT
or ultrasound guidance, mediastinoscopy, mediastinotomy, median sternotomy,
video-assisted thoracoscopy, and conventional thoracotomy.[10] The biopsy
findings will help the clinician plan appropriate treatment.
Treatment Options
The treatment of SVCS depends on the etiology of
the obstruction, the severity of the symptoms, the prognosis of the patient,
and patient preferences and goals for therapy. Radiation therapy or
chemotherapy should be withheld until the etiology of the obstruction is clear.
The treatments discussed here focus on SVC
obstruction caused by a malignant tumor. Since the treatment of malignant
obstruction may depend on tumor histology, a histologic diagnosis, if not made
earlier, should be made prior to initiation of treatment. Unless there is
airway obstruction or cerebral edema, there appears to be no detriment in
outcome when treatment is delayed for the assessment.[11,1,12-15] The following
treatment approaches can be used for SVCS.
Medical Management
A patient with sufficient collateral blood flow and minimal symptoms may not
need treatment. If the lesion is above the azygous vein or if the onset of SVC
occlusion is slow enough to allow sufficient collateral circulation, the
symptoms and signs may stabilize and the patient may be comfortable enough to
forego further therapy. Short-term palliation of a symptomatic patient who
does not want aggressive treatment may be achieved by elevating the head and
using corticosteroids and diuresis. There are no definitive studies that prove the
effectiveness of steroids, although they are potentially useful to treat
respiratory compromise. Diuretics may give symptomatic relief of edema but
can ultimately cause systemic complications, such as dehydration.[9,16]
Radiation Therapy
If the obstruction of the SVC is caused by a tumor that is not
sensitive to chemotherapy, radiation therapy should be given. Treatment with
larger fractions of radiation is thought to be beneficial in developing a rapid
response. One study shows, however, that there is no obvious need for large
radiation fraction sizes for the first few radiation treatments as was
previously believed.[17] Many fractionation schemes have been used, with doses
ranging from 30 Gy in 10 fractions to 50 Gy in 25 fractions. Relief of
symptoms in small cell lung cancer is reported to be 62% to 80%, whereas in non-small cell lung cancer, approximately 46% of the patients experienced
symptomatic relief.[2,18] In one study, more than 90% of the patients
achieved a partial or complete response with a 3-week regimen of 8 Gy given
once a week for a total dose of 24 Gy.[19]
Chemotherapy
Chemotherapy is the treatment of choice for sensitive tumors such as lymphoma
or small cell lung cancer. SVCS does not appear to be an independent
prognostic factor, and its presence should not change the treatment
approach. Rapid initiation of chemotherapy can result in complete and partial
response rates of the SVCS of more than 80% in small cell lung cancer
patients.[2,18]
Thrombolysis
It has been suggested that SVCS arises when a thrombus forms in a partially
occluded vein. In patients with a documented thrombus in the SVC, treatment
may include thrombectomy, with or without tissue plasminogen activator or
other thrombolytic agents such as streptokinase or urokinase.[1]
Stent Placement
There have been numerous small studies using an intravascular expandable stent
to reopen the occluded SVC; however, no prospectively designed comparative
studies have been published.[20] The reported response rates have been about
90% or greater.[21] There is no agreement on the need for anticoagulant
therapy after stent placement. In one series that used anticoagulant therapy
for patients as part of the treatment protocol, there were reports of
reocclusion after this therapy was stopped.[22] However, in another study, 17
cancer patients who were treated with stents and who did not have anticoagulant
therapy had no occlusions.[23]
Surgery
Surgical bypass of an obstructed SVC is more appropriate for patients with a
benign obstruction than with a malignant obstruction,[24] although surgical
bypass has also been used for patients with malignant obstructions.
Psychosocial Considerations
Patients and family members are often frightened and anxious because of the
symptoms produced by SVCS, particularly swelling,
dysphagia, coughing, and hoarseness. It is important to provide information to
patients and family members on the cause of the symptoms and on short-term
measures for palliation, especially during the diagnostic period. When
aggressive treatment is declined because of the terminal nature of the
underlying disease, it may be necessary to teach symptom management approaches
to patients and family members.
Because most adult patients who develop SVCS have lung cancer, the treatment
and psychologic support approaches that are developed for SVCS should take into
account the patient’s prognosis and psychologic condition and other symptoms
caused by the malignancy.[25]
Pediatric Considerations
As described in other sections of this summary, SVCS refers to the symptoms associated with the compression or obstruction of
the SVC; the compression of the trachea is termed superior
mediastinal syndrome (SMS). Because SMS and the resulting respiratory
compromise frequently occur in children with SVCS, the two syndromes have
become almost synonymous in pediatric practice.[26,27] In adults, the trachea
and the right mainstem bronchus are relatively rigid structures compared with
the vena cava, but in children these structures are more susceptible to
compression. In addition, the relatively smaller intraluminal diameters of a
child’s trachea and bronchus can tolerate little edema before respiratory
symptoms occur. Because of this accompanying respiratory component, SVCS in
children differs from the adult syndrome and constitutes a serious medical
emergency.
The most common symptoms of SVCS in children are similar to those in adults and
include coughing, hoarseness, dyspnea, orthopnea, and chest pain. Symptoms
that are less common but more serious are anxiety, confusion, lethargy,
headache, distorted vision, a sense of fullness in the ears, and, especially,
syncope.[26]
SVCS is rare in children and appears at presentation in 12% of pediatric
patients with malignant mediastinal tumors.[28,29] The etiology, diagnosis, and
treatment of SVCS in children differs from that in adults. Whereas the most
frequent cause of SVCS in adults is bronchogenic carcinoma,[3] in children the
most frequent malignant cause of the syndrome is non-Hodgkin lymphoma. As in
adults, a frequent nonmalignant cause is thrombosis from catheterization for
venous access.[26]
A physical examination, chest radiograph, and the medical history of the
patient are usually sufficient to establish a diagnosis of SVCS. If lymphoma
or other malignant disease is suspected, it is desirable to obtain a tissue
sample for diagnosis. However, the procedure to obtain the specimen may
involve significant risk and may not be clinically feasible. Children with
SVCS have a poor tolerance for the necessary general anesthesia because the
accompanying cardiovascular and pulmonary changes aggravate the SVCS, often
making intubation impossible. Also, extubation may be difficult or impossible,
thus requiring prolonged airway provision (intubation). A CT
scan of the chest to determine tracheal size, upright and supine
echocardiography, and a flow volume loop may help evaluate anesthetic risk.
Because anesthesia use is a serious risk, the diagnosis should be made with the
least invasive means possible.[30] Published reports suggest a stepwise
approach to diagnosis.[26]
When a malignant mass is the cause of the SVCS, the situation may be a medical
emergency with no opportunity to establish a tissue diagnosis. In these cases,
the most appropriate course may be to initiate empiric therapy prior to biopsy.
The traditional empiric therapy is irradiation, with the daily dose governed by
the presumed radiosensitivity of the tumor. After irradiation, respiratory
deterioration from the apparent tracheal swelling may occur because of the
inability of narrow lumens in children to accommodate edema and because of the
greater degree of edema at onset, which is due to the rapid speed at which
tumors grow in children. In these situations, a course of prednisone at 10 mg/m2 of body surface area 4 times per day may be necessary.[26]
In addition to radiation, empiric therapy of SVCS has included chemotherapeutic
agents incorporating steroids, cyclophosphamide, or both in combination with an
anthracycline and vincristine.[26] If the tumor fails to respond, it may be a
benign lesion.
If surgery becomes necessary, it should be performed with the patient in the
semi-Fowler’s position, allowing the surgeon the ability to rapidly change the patient's position to lateral
or prone. Cardiopulmonary bypass facilities and a rigid bronchoscope should be
available in a standby capacity.[30]
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