2. Anatomy of venous drainage
Etiology
Pathophysiology
Clinical features
Investigations
Treatment
3. Anatomy
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 collects-----head and deep
sections of the neck
Subclavian vein---superior limbs, superior chest and
superficial head and neck.
4.
After the brachiocephalic convergence, the SVC
follows the right lateral margin of the sternum in an
inferoposterior direction.
Finally, it enters the pericardium superiorly and
flows into the right atrium;
No valve divides the SVC from right atrium.
The SVC’s length ranges from 6 to 8 cm.
Its diameter is usually 20-22 mm.
5.
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
right bronchus.
6. Azygos vein
Azygos vein transports deoxygenated blood from the posterior
walls of the thorax and abdomen into the superior venacava.
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.
This "arch of the azygos vein― is an important anatomic
landmark.
7.
A major tributary is the hemiazygos vein, a similar
structure on the opposite side of the vertebral
column.
Other tributaries include
Bronchial veins,
Pericardial veins, and
Posterior right intercostal veins.
It communicates with the vertebral venous plexuses.
8. Hemiazygos vein
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.
9.
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
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.
10. Accessory hemiazygos vein
Receives the posterior intercoastal 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
hemiazygos.
When this vein is small, or altogether absent, the
left superior intercostal vein may extend as low as
the 5th or 6th ICS.
11. 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.
12.
13.
14. SVC obstruction
In SVC obstruction, the azygos vein is
responsible for the most important collateral
circulation.
According to the expected collateral pathways,
the SVC can be divided into two segments:
Supra-azygos or preazygos and
Infra-azygos or postazygos SVC.
15.
There are four possible collateral systems which
were first described in 1949 by McIntire and
Sykes.
They are represented by
1. Azygos venous system,
2. Internal thoracic venous system,
3. Vertebral venous system and
4. External thoracic venous system.
McIntire FT, Sykes EM jr. Obstruction of the superior vena cava:
Ann Intern Med 1949; 30:925.
1.
16. 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 veins.
17. Etiology
May be related to various etiological factors.
Malignancies are predominant (95%) while, in
the past, infectious diseases used to be
common.
During the last century, progression in antibacterial therapies and improvement in social
conditions have led to a consistent decrease in
the benign origin.
Incidence of iatrogenic SVCS is currently
increasing.
21. Pathophysiology
Pathogenetic basis of SVCS is obstruction to
the blood flow.
It can result from intrinsic or extrinsic
obstacles.
Intrinsic—uncommon, caused by thrombosis
or invading tissue.
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
22.
When obstruction of the SVC occurs, the vascular
resistances rise and the venous return decreases.
SVC pressure may increase consistently.
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.
images.
Sy WM, Lao RS. Collateral pathways in superior vena cava obstruction as seen on gamma
Br J Radiol 1982; 55:294-300
The timing of the obstruction development is
important for its clinical implications.
23.
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
significant symptoms
24. Clinical presentation
The SVC wall does not offer resistance to compression.
When SVC lumen reduction is greater than 60%,
hemodynamic changes occur:
Proximal dilatation,
Congestion and
Flow slowdown.
1.
2.
3.
The clinical signs of this condition are mainly represented by
Cyanosis (due to venous stasis with normal arterial
oxygenation) and
Edema of the upper chest, arms, neck and face (periorbital
initially).
25.
Swelling is usually more important on the right side,
because of the better possibility of collateral circulation in
the left brachiocephalic vein compared to the
contralateral.
Vein varicosities of the proximal tongue and dark
purple ears are also typical.
Other signs or symptoms are:
1. Coughing,
2. Epistaxis,
3. Hemoptysis,
4. Dysphagia,
5. Dysphonia and
6. Hoarseness (caused by vocal cord congestion),
7. Esophageal, Retinal and Conjuntival bleeding.
26.
27.
28.
29.
In the case of significant cephalic venous
stasis--1. Headache,
2. Dizziness,
3. Buzzing,
4. Drowsiness,
5. Stupor, Lethargy and even coma may be
encountered.
Headache is a common symptom and it is
usually continuous and
pressing, exacerbated by coughing.
30.
Epilepsy has been occasionally reported as well
as psychosis, probably due to carbon dioxide
accumulation.
Dyspnea can be directly related to1. Mediastinal mass or
2. Pleural effusion or
3. Cardiocirculatory impairment.
Supine position may worsen the clinical
scenarios.
31. The clinical seriousness is related to several factors:
1. Level of obstruction and rapidity of development,
determining the effectiveness of collateral
circulation
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
paralysis…)
32.
Superficial dilated vascular routes are the main sign of
collateral circulation and appear swollen and nonpulsating.
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
obstruction site.
Anatomic classification includes three levels of obstruction:
1. Obstruction of the upper SVC, proximal to the azygos
entry point.
2. Obstruction with azygos involvement.
3. Obstruction of the lower SVC, distal to the azygos
entry point.
33. 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 right
atrium.
A longer but effective way is provided by several
veins, the most important being the right superior
intercostal vein.
34.
From the superior tract of the SVC, blood flow is
reversed and directed to the azygos, mainly through the
right superior intercostal vein.
Azygos collateral system is eminently deep;
therefore the presence of superficial vessels is
usually lacking, even if possible in the area of the
internal thoracic vein’s superficial tributaries.
Volumetric increase of the vessels can be consistent
and capacity may increase up to 8 times.
The efficiency of this collateral route is reliable, thus the
clinical compensation is unbalanced only in the case of
a rapid development of the obstruction or if the stenosis
is more than 90%.
35.
36. Obstruction with azygos
involvement.
In this case, the azygos vein cannot be available as
collateral pathway and the only viable blood return is
carried by minor vessels to IVC (cava-cava or
anazygotic circulation).
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.
37.
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
iliac vein.
38.
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
severe.
For this reason, this kind of SVC obstruction is often
related to important symptoms, dyspnea and pleural
effusion.
The ensuing slow blood flow may be responsible for
39.
40. 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.
41.
In this type of case, the superficial collateral system
is not always evident but the azygos and
hemiazygos congestion and dilatation are usually
important.
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.
42.
43. 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-azygos
SVC
2.
Type II: stenosis of more than 90% of the supraazygos 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
44.
45. Yu’s classification (clinical)
1.
Grade 0: asymptomatic (imaging evidence of SVC
obstruction)
2.
Grade 1: mild (plethora, cyanosis, head and neck
edema)
3.
Grade 2: moderate (grade 1 evidence + functional
impairment)
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
46. Bigsby’s classification (operative risk)
Low risk
High risk
The low risk patients present:
No dyspnea at rest,
No facial cyanosis in the upright position,
No change of dyspnea and
No worsening of facial edema and
Cyanosis, during the supine position.
The high risk patients present facial cyanosis
or dyspnea at rest in the sitting position.
47. Diagnosis
Physical examination is often crucial:
Presence of edema and superficial venous network
of the upper chest may support the clinical
diagnosis.
Imaging studies are however required.
Most cases are suspected at the standard chest Xray and the most common radiological findings are
right mediastinal widening and pleural effusion.
48.
CT with multislice detector is the most useful tool in
the evaluation of the mediastinal syndromes.
Intravenous contrast should be administered, in
order to provide high-quality vascular imaging.
Contrast enhanced multidetector CT may show
Site of the obstruction,
Some aspects of the primary disease and
Eventual intraluminal thrombi.
The contrast flow can also help to distinguish the
extent of the collateral network
49.
50.
51.
MRI plays a side role; it is indicated when CT cannot
be performed (e.g. pregnancy, endovenous contrast
intollerance).
Invasive venography –
Now arely used due to the huge improvement in
vascular CT imaging.
It is currently performed only as a preliminary to
operative procedures such as stent placement.
Once the thoracic imaging is obtained, the work-up
should include brain, abdominal and bone studies in
view of the probable malignant nature of the primary
lesion.
Recently Fluorodeoxyglucose-Positron Emission
Tomography has gained an important role.
52.
The histological diagnosis remains the key factor
for the causative treatment, in the case of
neoplastic etiology.
Superficial adenopathies have to be carefully
investigated in order to find a possible source of
tissue and the easiest target for biopsy.
The invasive diagnostic procedure varies largely
depending on the suspected malignancy and its
site.
53. The biopsy can be obtained through
Traditional bronchoscopy or
Echo-guided endoscopy,
Superficial node biopsy,
Mediastinoscopy,
Mediastinotomy,
Transthoracic needle biopsy,
Thoracoscopy,
Cervical or supraclavicular biopsies;
Thoracotomy and sternotomy are rarely indicated.
54. Treatment
Therapy should be causative.
Syndrome management recognizes different levels of
priority depending on the
1. Severity of symptoms,
2. Etiology and
3. Prognosis.
The therapeutic plan is usually targeted to clinical
palliation.
In fact, most cases are diagnosed as advanced-stage
malignancies.
55. Supportive Care
Elevate the patient’s head to decrease the
hydrostatic pressure and thereby the edema.
Oxygen,
Glucocorticoid therapy (dexamethasone, 4 mg every
6 hours) is commonly prescribed, although its effects
have not been formally well studied,
Glucocorticoids reduce the tumor burden in
lymphoma and thymoma and are therefore more
likely to reduce the obstruction in pts with lymphoma
or thymoma than in those with other types of tumor.
56.
Loop diuretics are also commonly used, but it is
unclear whether venous pressure distal to the
obstruction is affected by small changes in right
atrial pressure.
In
malignancy, the treatment can have palliative or,
rarely, curative intent.
Chemotherapy
is usually employed in lymphomas,
small-cell lung cancer and germ cell tumors.
Besides
chemotherapy, radiotherapy is widely used
in the treatment of non-small cell lung cancer.
57.
Some cases must be approached as an emergency.
In this type of situation, the treatment of choice is
usually endovascular with the aim of restoring
blood flow as soon as possible.
Acute lifethreatening presentation is the only
situation in which radiotherapy before
histological diagnosis can be considered.
However, this approach should be avoided,
whenever possible.
RT prior to biopsy may obscure the histologic
diagnosis.
58.
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 evidencebased clinical practice guidelines (2nd edition). Chest 2007;
132:368S.
59.
Important exceptions to this general approach
are pts who present with stridor due to central
airway obstruction or severe laryngeal edema,
and those with coma from cerebral edema.
These situations represent a true medical
emergency, and these patients require
immediate treatment (stent placement and RT)
to decrease the risk of sudden respiratory
failure and death.
60.
For pts who have obstruction of the SVC resulting from
intravascular thrombus associated with an indwelling
catheter, removal of the catheter is indicated, in
conjunction with systemic anticoagulation to limit
extension of thrombus.
Radiation therapy —
RT provides considerable relief by reducing tumor burden
Symptomatic improvement is usually apparent within 72
hours.
Relief of symptoms may not be achieved for up to four
weeks, and approximately 20 percent of pts do not obtain
symptomatic relief from RT
61.
The benefits of RT are often temporary, with many
patients developing recurrent symptoms before
dying of the underlying disease
Particularly if symptoms are severe, more rapid
palliation can be achieved through the use of an
intraluminal stent, followed by RT for disease
control.
Stent placement is also effective in relieving
symptoms in patients who fail to respond to RT.
62. Endovascular stents
The placement of an endovascular stent restores
venous return and provides rapid and sustained
symptom palliation in pts with SVC syndrome.
The technical success rate is in the range of 95 to
100%, and over 90% of pts report relief of
symptoms
Endovascular stenting provides fast functional
relief.
63. Indications
It is a useful procedure for pts with severe symptoms
(eg, stridor) who require urgent intervention.
Can be placed before a tissue diagnosis is available,
For rapid symptom palliation in pts with NSCLC and
mesothelioma and for those with recurrent disease
who have previously received systemic therapy or
RT.
64. Complications
Reported in 3 to 7% of patients.
Early complications include
Infection,
Pulmonary embolus,
Stent migration,
Hematoma at the insertion site,
Bleeding, and
Rarely, perforation or rupture of the SVC.
65. Late complications include
Bleeding (1 to 14 percent) and
Death (1 to 2 percent) from anticoagulation
and
Stent failure with reocclusion.
Stent failure is most often caused by
thrombus or tumor ingrowth.
However, since most pts with malignancy
related SVC syndrome have a short life
expectancy, the stent usually remains patent
until death.
66.
If reocclusion does occur, it can be treated with a
second stent or thrombolytic therapy, with good
secondary patency rates.
Need for long-term anticoagulation — Short-term
anticoagulation/antiplatelet therapy is often
recommended
But whether long-term treatment is necessary is
an area of uncertainty
67. Surgical intervention
Although effective and a/w relatively few
complications, surgical bypass is rarely performed
in pts with malignant cause of SVC syndrome
because of the success of endovascular stenting.
Surgical management is more often undertaken in
patients with benign causes of SVC syndrome.
Surgical resection of mediastinal tumor and
reconstruction of the SVC is rarely considered in
view of its morbidity and mortality and the limited
life expectancy of most pts who present with this
complication.
68.
One possible exception is malignant thymoma and
thymic carcinoma, which are relatively resistant to
chemotherapy and radiation
The
main proposal for SVC resection is direct
infiltration in thymomas or in N0-N1 non-small cell
lung cancer.
In case of infiltration of < 30% of the SVC
circumference, direct suture is favored
69.
Larger involvements require a prosthetic repair.
Armoured PTFE grafts and biologic material are the
preferred choices.
Morbidity after SVC surgical procedures is high and
the post-operative care must be intensive.
Long-term patency of a SVC by-pass graft is
uncertain but, usually, the slow onset of the graft
thrombosis favors the development of effective
collateral circulation.
