Constellation of signs and symptoms
caused by obstruction of blood flow in
the superior vena cava secondary to
external compression, invasion,
constriction or thrombosis of the SVC
Can be partial or complete obstruction
First recorded description of SVC
obstruction (SVCO) - 1757 when William
Hunter described the entity in a patient
with a syphilitic aortic aneurysm.
For nearly two centuries- nonmalignant
processes such as aortic aneurysms,
syphilitic aortitis, or chronic mediastinitis
due to tuberculosis were the
predominant etiologic factors.
In the preantibiotic era-
◦ syphilitic thoracic aortic aneurysms,
untreated infection were frequent causes of the SVC
Subsequently, malignancy became the most
common cause, accounting for 90 percent of
cases by the 1980s.
More recently, the incidence of SVC
syndrome due to thrombosis has risen,
largely because of increased use of
intravascular devices such as catheters and
Benign causes now account for 10 to 20
percent of cases of SVC syndrome.
SVC originates in the chest, behind the first right
sternocostal articulation, from the confluence of two
main collector vessels: Right and Left
brachiocephalic veins which receive the ipsilateral
internal jugular and subclavian veins.
Internal jugular vein drains-----head and deep
sections of the neck
Subclavian vein--- upper limbs, superior chest and
superficial head and neck.
After the brachiocephalic convergence, the SVC
follows the right lateral margin of the sternum in an
Finally, it enters the pericardium superiorly and
opens into the right atrium
The SVC’s length ranges from 6 to 8 cm.
Its diameter is usually 20-22 mm.
The blood pressure ranges from -5 to 5
mmHg and the flow is discontinuous
depending on the heart pulse cycle.
The SVC receives a single affluent vein:
the azygos vein.
The azygos vein joins the SVC from the
right side, at its mid length, above the
No valve divides the superior vena
cava from the right atrium. As a result,
the right atrial and right ventricular
contractions are conducted up into
the internal jugular vein and, through
the sternocleidomastoid muscle,
can be seen as the jugular venous
Azygos vein transports deoxygenated blood from the posterior
walls of the thorax and abdomen into the superior
It is formed by the union of
Ascending lumbar veins with
Right subcostal veins
At the level of the 12th thoracic vertebra
Ascending in the posterior mediastinum, and arching over the
right main bronchus posteriorly at the root of the right lung to
join the superior vena cava.
A major tributary is the hemiazygos vein, a similar
structure on the opposite side of the vertebral
Other tributaries include
Pericardial veins, and
Posterior right intercostal veins.
It communicates with the vertebral venous plexuses.
It runs superiorly in the lower thoracic region, just
to the left side of the vertebral column.
Hemiazygos vein and the accessory hemiazygos
vein, when taken together, essentially serve as the
left-sided equivalent of the azygos vein.
It usually begins in the left ascending lumbar vein
or renal vein, and passes upward through the left
crus of the diaphragm to enter the thorax.
It continues ascending on the left side of the
vertebral column, and at the level of the 9th
thoracic vertebra, it passes rightward across the
vertebral column, behind the aorta, esophagus, and
thoracic duct, to end in the azygos vein.
The hemiazygos may or may not be continuous
superiorly with the accessory hemiazygos vein.
It receives the 9th, 10th, and 11th posterior
intercostal veins and the subcostal vein of the left
side, and some esophageal and mediastinal veins.
Receives the posterior intercostal veins from the
4th, 5th, 6th, and 7th ICS.
It either crosses the body of 8th thoracic vertebra
to join the azygous vein or ends in the
When this vein is small, or altogether absent, the
left superior intercostal vein may extend as low as
the 5th or 6th ICS.
Posterior intercostal veins
There are eleven posterior intercostal veins on each side.
The 1st posterior intercostal vein, drains into the
brachiocephalic vein or the vertebral vein.
The 2nd and 3rd (and often 4th) posterior intercostal
veins drain into the superior intercostal vein.
The remaining posterior intercostal veins drain into the
azygos vein on the right, or the hemiazygos vein and
accessory hemiazygous on the left.
In SVC obstruction, the azygos vein is
responsible for the most important
According to the expected collateral pathways,
the SVC can be divided into two segments:
Supra-azygos or preazygos and
Infra-azygos or postazygos SVC.
There are four possible collateral systems
which were first described in 1949 by McIntire
They are represented by
1. Azygos venous system,
2. Internal thoracic venous system,
3. Vertebral venous system and
4. External thoracic venous system.
1. Azygos venous system is the only direct path
into the SVC.
2. Internal thoracic vein is the collector between
SVC and inferior vena cava (IVC) via
epigastric and iliac veins.
3. Vertebral veins with intercostals, lumbar and
sacral veins, represent the posterior network
between SVC and IVC.
4. External thoracic vein system is the most
superficial and it is represented by axillary,
lateral thoracic and superficial epigastric
Pathogenetic basis of SVCS is obstruction to the
It can be intrinsic or extrinsic obstruction.
Intrinsic—uncommon, caused by thrombosis or
Extrinsic factors develop from compression or
stricture of the vein.
In physiologic conditions, blood return to the right
atrium is facilitated by the pressure gradient
between the right atrium and venae cavae.
When obstruction of the SVC occurs, the vascular
resistances rise and the venous return decreases.
When SVC shows a significant stenosis (3/5 of the
lumen or more), blood flow is redirected through the
collateral circulation in order to bypass the
obstruction and restore the venous return.
In acute impairments, the blood flow is not
rapidly distributed through the collateral network
so symptoms arise markedly.
In the case of slow-growing diseases, the
collateral venous network has enough time to
expand in order to receive the circulating volume.
For this reason, long-lasting, severe SVC
obstruction can sometimes be found without
The clinical seriousness is related to several factors:
1. Level of obstruction and rapidity of
development, determining the effectiveness of
2. Impairment of lymphatic drainage (pulmonary
interstitial edema or pleural effusion)
3. Involvement of other mediastinal structures
(compression or invasion of heart, pulmonary
artery and central airways, phrenic nerve
Superficial dilated vascular routes are the main sign of
collateral circulation and appear swollen and non-
In case of marked obesity, superficial veins can be
missing at inspection.
Variety of collateral circulation and the differences in the
venous rearrangement are expression of the SVC
Anatomic classification includes three levels of
1. Obstruction of the upper SVC, proximal to (above the
level of) azygos entry point.
2. Obstruction with azygos involvement.
3. Obstruction of the lower SVC, distal to (below the level
of) azygos entry point.
Obstruction of the upper SVC
proximal to the azygos entry point.
In this situation, there is no impediment to normal
blood flow through the azygos vein which opens
into the patent tract of the SVC.
Venous drainage coming from the head neck,
shoulders and arms cannot directly reach the
From the superior tract of the SVC, blood flow
is reversed and directed to the azygos, mainly
through the right superior intercostal vein.
Obstruction with azygos
In this case, the azygos vein cannot be used as
collateral pathway and the only viable blood return is
carried by minor vessels to IVC (cava-cava or
From the internal thoracic veins, blood is forced to the
intercostal veins, then to azygos and hemiazygos veins.
The flow is thus reversed into the ascending lumbar
veins to the iliac veins.
Direct anastomosis between the azygos’ origin and
the IVC and between hemiazygos and left renal vein
are also active.
In addition, the internal thoracic veins can flow into
the superior epigastric veins.
From the superior epigastric veins, blood is carried
to the inferior epigastric veins across the superficial
system of the cutaneous abdominal veins and finally
to the iliac veins.
Another course is between the thoraco-epigastric
vein (collateral of the axillary vein) and the external
In these conditions, the collateral circulation is partly
deep and partly superficial.
Physical examination often reveals SVC obstruction.
The reversed circulation through the described
pathways, remains less efficient than the azygos
system and venous hypertension is usually more
For this reason, this kind of SVC obstruction is often
related to important symptoms, dyspnea and pleural
The ensuing slow blood flow may be responsible for
Obstruction of the lower SVC
distal to the azygos entry point
In this condition, the obstruction is just below
the azygos arch.
The blood flow is distributed from the
superior body into the azygos and
hemiazygos veins, in which the flow is
inverted, to the IVC tributaries.
In this type of obstruction, the superficial collateral
system is not always evident but the azygos and
hemiazygos congestion and dilatation are usually
The hemodynamic changes lead to edema and
cyanosis of the upper chest and pleural effusion.
Pleural effusion is often slowly-growing and
rightsided, probably due to anatomical reasons:
There is a wider anastomosis between hemiazygos
and IVC than between azygos and IVC.
Classification of SVCS
There are three main classification proposals which
follow different methods of categorization.
Doty and Standford’s classification (anatomical)
1. Type I: stenosis of up to 90% of the supra-
2. Type II: stenosis of more than 90% of the supra-
3. Type III: complete occlusion of SVC with azygos
reverse blood flow
4. Type IV: complete occlusion of SVC with the
involvement of the major tributaries and azygos
Yu’s classification (clinical)
1. Grade 0: asymptomatic (imaging evidence of SVC
2. Grade 1: mild (plethora, cyanosis, head and neck
3. Grade 2: moderate (grade 1 evidence + functional
4. Grade 3: severe (mild/moderate cerebral or
laryngeal edema, limited cardiac reserve)
5. Grade 4: life-threatening (significant cerebral or
laryngeal edema, cardiac failure)
6. Grade 5: fatal
Bigsby’s classification (operative risk)
The low risk patients present with
No dyspnea at rest,
No facial cyanosis in the upright position,
No change of dyspnea, No worsening of facial
edema and Cyanosis during the supine
The high risk patients present with facial
cyanosis or dyspnea at rest in the sitting
• Diagnosis is made by history, physical
examination, and lab studies
• findings will depend on
1. The degree of occlusion
2. The rapidity of development
3. Presence or absence of collateral
PRESENTING SYMPTOMS OF SVCO
These symptoms may be worsened by positional changes such as bending
forward, stooping, or lying down.
Common symptoms Less common
•Persistent cough (24%-55%)
• Erythema , Swelling of the neck
•Visible dilatation of the veins in
the upper extremity.
•Nasal stuffiness, Pleural effusions
Venous distension of neck-66%
Venous distension of Chest-54%
Edema upper half of the body-50%
Paleness of lower half of the body-18%
Engorged abdomen veins-12%
Papilledema, stupor, and even coma.
Cyanosis and edema are aggravated by
horizontal position and relived by upright
Superior vena cava syndrome in a person with
brochogenic carcinoma. Note the swelling of his face first
thing in the morning (left) and its resolution after being
upright all day (right).
Diagnosis of SVCS can be made simply on physical
When the extent of disease is minimal, the physical
findings may not be prominent then it is difficult to
Establishing the underlying etiology is more
important because certain disorders that cause
SVCS may be more amenable to specific treatment
SCLC and lymphoma -Chemotherapy/irradiation,
thrombosis does not respond to this treatment.
Lower chest torniquet test
Chest x ray
Pressure readings are taken from the ante-cubital
vein with a 3-way stopcock spinal mannometer
using 2.5 % citrate solution
Exercise test (Hussay et al)
Patient opens and closes his fist forcefully for one minute
while venous pressure readings are being noted.
In normal individuals, it remains constant
In SVCO pressure will rise 10 cm. or more and then
gradually recedes to normal.
Lower chest tourniquet test
in which a tourniquet constricts the
superficial thoracic collaterals and
raises the venous pressure if
obstruction is below the azygos.
Circulatory time is prolonged in SVCO
Infra –red photography demonstrates
a) CHEST RADIOGRAPHY
The initial diagnostic test for suspected SVCS.
Is not specific for SVCS.
helpful in identifying the cause of the disorder.
Parish and colleagues in 1981 –(16%) of the
patients With SVCS had normal Chest
Right sided findings are common.
X-Ray findings suggestive of underlying malignancy,
Right hilar mass
Calcified paratracheal lymph nodes-
Anterior mediastinal mass
In the absence of previous catheterization or surgery, a
normal result on chest radiography in a patient with
SVCS is almost pathognomonic of chronic fibrous
Seen as a small soft-tissue density adjacent
to the lateral border of the aortic knob on a
an aortic nipple is a radiological sign that
represents the left superior intercostal vein
as it runs around the aortic arch before
joining the left brachiocephalic vein.
In certain conditions the aortic nipple can
become enlarged and mimic
lymphadenopathy or aortic aneurysm.
No treatment is needed other than treatment
of the underlying condition.
Conditions that can cause an aortic nipple
a) Normal variant
is usually found in normal healthy patients in anywhere
from 1.4-9.5% of people.
b) Increase in venous flow such as
Recumbant position, or during expiration
Portal venous hypertension secondary to hepatofugal
shunting from the liver,
congenital anomalies of the caval, azygos or
hemiazygos circulation results in enlargement of the left
superior intercostal vein.
partial or total anomalous pulmonary venous drainage
c) Caused by increased venous resistance as in
Congestive heart failure,
Budd Chiari sydrome
absence or obstruction of the inferior vena
The left superior intercostal vein may act as
a collateral pathway, and therefore become
distended, in patients with impending or
actual superior vena caval obstruction
Impending Superior Vena Cava
Detection of ‘aortic nipple’ on chest
roentgenogram predates the clinical
syndrome by 7 to10 weeks
Development of SVCS requires severe
venous compromise, whereas the left SICV
(superior intercostal vein) may be more
sensitive indicator because of
Its small caliber,
Clearly defined and highly visible location
Capacity to greatly enlarge with increased
SVC cannot be imaged because of
poor acoustic window
Patency can be indirectly determined
with normal wave forms in
brachiocephalic and subclavian veins.
Exclusion of thrombus in upper
extremity, subclavian, brachiocephalic
and axillary veins.
Computed tomography scanning
CT-Provides an effective, noninvasive evaluation of
the superior vena cava and its collateral circulation.
CT scanning provides
1) Anatomic details of the mediastinal and thoracic
2) Allows identification of the cause and extent of
3) Documents collateral circulation,
4) Provides guidance for Percutaneous biopsies
5) Guides the formulation for radiotherapy.
Recently,, MDCT(multidetector CT) is
gaining importance, with its
multiplanar and 3D images combining
cross-sectional imaging for diagnosis
of the cause of the superior vena cava
obstruction with multiplanar
reformation that best delineates the
level and extent of venous obstruction
Magnetic resonance imaging (MRI)
MRI is often important in determining the cause of
MRI, by virtue of its multidimensional capabilities,
shows the relationships of vessels, lymph nodes,
and other mediastinal structures.
It is an acceptable alternative for patients with renal
failure or those with contrast allergies.
An x-ray test that provides an image of the veins after a
contrast dye is injected into a vein.
The extent and site of obstruction.
The nature and degree of obstruction.
Patency of the superior vena cava.
Differentiation between intrinsic and extrinsic obstruction.
Assessment of collateral vessels
the degree of venous distension of the neck and arms
Measurement of actual venous pressure
The presence of the internal jugular vein reflux.
Is essential prior to planning any surgical bypass
Surgical bypass operations are easier to accomplish
when the brachiocephalic veins are not involved.
However, if all the intrathoracic veins are obstructed,
extrathoracic bypass operations can be undertaken,
Very helpful in documenting obstructions caused by
thrombus formation. When thrombosis is present,
treatment with fibrinolytic agents (eg, urokinase,
streptokinase) is pursued and
Repeat venography can be used to evaluate
1. Type I: stenosis of up to 90% of the
2. Type II: stenosis of more than 90%
of the supra-azygos SVC
3. Type III: complete occlusion of SVC
with azygos reverse blood flow
4. Type IV: complete occlusion of SVC
with the involvement of the major
tributaries and azygos vein
This test is less invasive than contrast
is less specific in defining Patency and
Radionuclide venography may be of
value in long-term follow-up studies.
When all other diagnostic procedures fail to provide
information about the cause of SVCS, Exploratory
thoracotomy be the last alternative.
Advantages—surgery allows direct visualization of
the underlying disease process, assessment of the
extent of disease involvement, and accessibility for
However, this procedure is the most invasive and is
associated with increased risks.
Current guidelines stress the
importance of accurate histologic
diagnosis prior to starting therapy,
and the upfront use of endovascular
stents in severely symptomatic
patients to provide more rapid relief
than can be achieved using RT.
Kvale PA, Selecky PA, Prakash UB, American College of Chest
Physicians. Palliative care in lung cancer: ACCP evidence-
based clinical practice guidelines (2nd edition). Chest 2007;
Treatment Of SVCO
Depending on the underlying condition,
multiple treatment options are available
for superior vena cava obstruction. The
primary treatment options include
Stents and balloon angioplasty and
The goals of SVCS management are to relieve
symptoms and to attempt cure of the primary
Conservative treatment -symptomatic improvement
including elevation of the head end of the bed
and supplemental oxygen.
Emergency treatment (Corticosteroids and
For Brain edema,
decreased cardiac output,
or upper airway edema
Their efficacy is questionable.
For symptomatic management in tumor-
8-40 mg IV once initially, followed by
4-6 mg IV/PO q6-8h
Loop Diuretic agents
The majority of cases of SVCS are caused by
malignancy; thus, most patients receive radiation
treatment at some point in their illness.
Emergency radiation treatment
To life-threatening cerebral or laryngeal edema
prior to a tissue diagnosis of malignancy.
To relieve obstructive symptoms
Inappropriate for the treatment of an underlying
thrombosis or granulomatosis causing the
Initiated at high dose daily for the first few
days. followed by conventional low daily
doses. total dose is dependent on tumor
Lymphomas (3000 to 4000 cGy,)
Carcinomas require (4000 to 5000 cGy or more)
Lower doses of radiation treatment
When systemic disease is present and short-
term palliation is the goal.
Radiation to Heart and Spinal cord.
who are receiving chemotherapeutic agents
such as doxorubicin, which can enhance
Response to RT
3 to 4 days- Resolution of facial edema and
venous distension of the upper extremities .
1 to 3 weeks- Radiographic improvement .
Not effective -Thrombosis is cause for SVCO
When RT successfully completed in pts of
SVCS with malignancies, 10% to 20% survive
more than 2 years.
Side effects of RT.
Bleeding or SVC perforation at the site of
Pulmonary or mediastinal fibrosis;
Chemotherapy may be used as a
primary therapy or as an adjunct to
treatment of choice for SVCS caused
by Mediastinal lymphoma is a
combination of chemotherapy and
Pericatheter thrombosis is seen in
approximately 50% of Non-
anticoagulated patients with long term
Central vein Catheters
Acute Cases- excellent results with
Benefits of Thrombolytic therapy
Fast dissolution of emboli,
Prevention of recurrent thrombus
Rapid restoration of hemodynamic
Converts plasminogen to plasmin,
which degrades fibrin clots, fibrinogen,
and other plasma proteins.
Loading dose: 4400 U/kg IV over 10
min and increase to 6000 U/kg/h
Maintenance dose: 4400-6000 U/kg/h
Patients with SVCS are at increased risk
for deep vein thrombosis and pulmonary
In patients for whom thrombosis is the
cause of SVCS, anticoagulation therapy
should be administered after successful
Once the symptoms subside after
thrombolytic therapy, anticoagulation
should be maintained as long as the
central venous catheter is present.
Anticoagulants - Heparin
Inhibits thrombosis by inactivating activated
factor X and inhibiting conversion of prothrombin
5000 U IV bolus, then infusion to maintain aPTT
2-3 times the reference range
Initial dose: 50 U/kg IV
Maintenance infusion: 15-25 U/kg/h IV
Increase dose by 2-4 U/kg/h IV q6-8h using aPTT
Inhibits synthesis of vitamin K–dependent
coagulation factors (factors II, VII, IX, X).
Initial: 5-10 mg PO
Maintenance: 2-10 mg PO qd to maintain
INR of 2-3
0.05-0.34 mg/kg/d PO; adjust dose according
to desired INR
Recent advances in interventional radiology have
contributed expandable wire stents and balloon
can be placed across the stenotic portion.
stents have little thrombogenic potential
After thrombolytic therapy, stent placement has
been noted to be a more successful approach.
After stent, patients experience instantaneous relief
The placement of stents is performed under local
palliation of the symptoms
For localized lesions, balloon angioplasty
with or without stenting has also been
shown to significantly reduce the
symptoms of SVCS
Stent mounted on a balloon Status post SVC stent
Surgical bypass is an additional alternative to relieve SVCS.
is usually recommended to benign disease and to only a few
patients with malignancy.
Patients selected for surgery should have the Category-IV
venographic signs, i.e, total vena caval obstruction.
Surgery in cases of fibrosing mediastinitis can be extremely
complicated, because of the extensive collateral circulation
under high venous pressure.
Advantage is definitive removal of the obstruction and direct
Long-term results after surgical bypass are lacking, because
their life expectancy is short.
Benign disease-life expectancy
Malignant obstruction of SVC
Untreated - 30 days average life
Treated - < 7 month average life
- 20% 1-year survival for lung cancer
-NSCLC-poor prognosis, palliative care+RT
- 50% 2-year survival for lymphoma