Congenital
By Mary
Anomalies
G. Cormier,
Joseph
of the Superior
W. Yedlicka,
T
HE PRECISE and elegant rendering of the
human anatomy achieved by CT has, for
over a decade, provided a novel perspective to the
medical diagnostic armamentarium.
CT has had
a significant impact on almost every avenue in
the daily practice of medicine and has gained
broad acceptance by our clinical colleagues.
A wide variety of congenital vascular anomalies of the upper mediastinum exist. Since most
of these are clinically silent, they are often unsuspected and discovered incidentally on radiographic studies done for other reasons. Familiarity with the CT appearance of such anomalies
may aid in the interpretation of otherwise potentially confusing CT images.
Innovative techniques for solving clinical problems have been designed. Some have improved
our diagnostic capabilities, while others have
introduced interventional techniques that offer
therapeutic and palliative alternatives to surgery.
CT has had a significant impact on just about
every avenue in the daily practice of medicine. Its
broad acceptance by our clinical colleagues and
the documented direct benefit to the patient
crown a historical decade of medical imaging
progress.
ANATOMIC
CONSIDERATIONS
The normal SVC is devoid of venous valves; it
drains the returning blood flow of the head and
upper half of the trunk. The vessel measures
approximately 7 cm in length. Its cross-sectional
shape varies in proportion to its intraluminal flow
or pressure, and generally exhibits an oblong,
flat, or rounded contour; the latter more often
seen when the patient is examined during a
Valsalva maneuver. The caliber of the SVC
varies, but generally is 1.5 cm and rarely as much
as 2.0 cm at its greatest diameter.
The short and vertically oriented right brachiocephalic vein and its longer oblique counterpart on the left form the origin of the SVC at the
level of the first right costal cartilage. From this
point, the SVC descends vertically along the
right side of the mediastinum to end in the upper
part of the right atrium at the level of the right
third costal cartilage. In its descent it describes a
minimal convexity to the right. Its lower half is
covered by the parietal pericardium and its wall
Seminars
in Roentgenolow.
Vol XXIV, No 2 (April),
1989:
pp 77-83
Richard
Vena Cava: A CT Study
J. Gray,
and
Rogelio
Moncada
is partially composed of visceral pericardium.
The major tributary of the SVC, the azygos vein,
enters the dorsal aspect of the mid-SVC.
Ventrally, the SVC is related to the mediastinal fat, pleura, thymus, and adjacent right lung.
Caudally, it is overlapped at the left margin of its
intrapericardial
portion by the ascending aorta.
The SVC is related posteriorly to the innominate
artery, trachea, right main bronchus, right main
pulmonary artery, right superior pulmonary
vein, and vagus nerve. In addition, the SVC is
flanked by a large number of adjacent lymph
nodes; most of these occur along the dorsal
aspect.
EMBRYOLOGY
The embryo has a closed blood circuit by the
end of the second week of fetal development. By
the third or fourth week, two paired venous
trunks are formed: the anterior cardinal veins,
arising from the cranial part of the body, and the
posterior cardinal veins, arising from the caudal
part of the body. On each side of the heart the
ipsilateral anterior and posterior cardinal veins
unite into a short main trunk called the common
cardinal vein or duct of Cuvier. Each duct of
Cuvier in turn empties into the sinus venosus.’
ABBREVlATlONS
ASD,
IVC,
PDA,
RA,
SVC,
VSD,
atrial septal defect
inferior vena cava
patent ductus arteriosus
right atrium
superior vena cava
ventricular
septal defect
From the Department
of Radiology.
Loyola
University
Medical Center, Maywood,
IL and the Department
of Radiology. University
of Minnesota,
Minneapolis.
Mary G. Cormier:
Assistant
Professor,
Department
of
Radiology,
Dartmouth-Hitchcock
Medical
Center, Hanover. NH; Joseph W. Yedlicka: Fellow, Department
of Radiology, University
of Minnesota;
Richard
J. Gray;
Rogelio
Moncada:
Professor and Chairman,
Department
of Radiology, Loyola University
Medical Center.
Address
reprint
requests
to Mary
G. Cormier,
MD,
Department
of Radiology,
Dartmouth-Hitchcock
Medical
Center. Hanover,
NH 03756.
o I989 by W.B. Saunders Company.
0037-
I98X/89/2402-0003$5.00/O
77
CORMIER
Normally, as the heart descends caudally, a
wide transverse anastomosis forms between the
two anterior cardinal veins; this channel becomes
the left innominate vein, presumably derived
from the union of smaller thyroid or thymic
branches of the primitive jugular veins.2 The
segment of the right anterior cardinal vein that
lies caudal to this anastomosis, together with the
right common cardinal vein (right duct of
Cuvier), forms the primitive SVC.’
At this stage a left SVC also exists, similarly
formed by the corresponding segment of the left
anterior cardinal vein that lies caudal to the
primitive left innominate vein, and the left common cardinal vein (left duct of Cuvier). A major
portion of this left SVC undergoes atrophy during the following few weeks. Its cranial remnant
forms the trunk of the first left intercostal vein,
and its caudal remnant becomes the oblique vein
of the left atrium.’ In some cases the involuted
vessel remains as a few fibrous strands or as a
fibrous cord that attaches to the posterolateral
aspect of the pericardium and coronary sinus,
referred to as the oblique ligament of Marshall.2
The sinus venosus is oriented transversely, lies
dorsal to the undivided atria1 part of the heart,
and communicates with the single common atria1
chamber through an oval opening. Its lateral
portions, known as horns, become directed
upward and posteriorly as the heart descends into
the thorax. By approximately 4 to 5 weeks the
symmetric arrangement is lost. The sinoatrial
opening migrates to the right, and an atria1
septum is formed in such a manner that the sinus
venosus communicates only with the right atria1
chamber. Eventually the left horn of the sinus
venosus becomes the coronary sinus. The right
horn expands, receiving blood from the SVC and
future IVC, and ultimately is totally absorbed
into the wall of the right atrium.‘*3v4
Many anomalies of the SVC are known, each
representing some form of developmental arrest.
The basic abnormality is failure of the left anterior cardinal vein to involute normally, resulting
in persistence of a left SVC.
LEFT SUPERIOR VENA
CAVA
The sign of a left SVC, either alone or in
conjunction with a right SVC, depends upon
resultant hemodynamic effects. Approximately
75% of both double SVC and single left SVC are
asymptomatic and have no circulatory distur-
ET AL
bance. However, in the remainder significant
dysfunction may exist, possibly severe enough to
be incompatible with life.4
Incidence
The true overall incidence of this condition is
difficult to establish. Estimates ranging from 1
per 330 to 1 per 750 normal individuals, and 1
per 25 patients with congenital heart disease are
reported.4 Among these, a coexisting right SVC
is present in about 85%.5
Anatomic Relations
When a double SVC exists, the left SVC
descends vertically, anterior and to the left of the
aortic arch and main pulmonary artery, slightly
lateral to the left vagus nerve. It has been said by
some to course between the left pulmonary artery
and pulmonary veins, and by others to lie anterior to all of the left pulmonary vessels. The latter
position corresponds to that of the right SVC
relative to the right pulmonary vessels.
The left SVC then swings medially, pierces the
pericardium to run in the posterior atrioventricular groove, and enters the coronary sinus. In this
case, the coronary sinus is often abnormally
large, perhaps due in part to an increased volume
flowing through it, and partially to regurgitant
enlargement
during atria1 contraction.
In
approximately 25% of 174 cases of left SVC,
Winter2 found the left hemiazygos vein looping
over the left main bronchus to enter the left SVC
posteriorly, at the same level that the azygos vein
enters the right SVC.
When a double SVC exists, the caliber of the
right vessel is often normal; however, it may be
smaller than usual because of reduced blood
volume. The diameter of the left cava rarely
exceeds that of the right; it is frequently equal to
it or smaller.
Specific Entities
Figure 1 schematically depicts the major patterns and types of developmental anomalies of
the SVC. The most frequent is a double vena
cava, with normal right SVC anatomy and a left
SVC entering the coronary sinus, and subsequently draining into the right ,atrium. There
may or may not be a transverse anastomosis
between the paired cavas. When there is none,
the right and left halves of the head and upper
truck drain back to the heart independently, and
CONGENITAL
ANOMALIES
OF THE SVC:
CT STUDY
Fig 1.
Schematic
depiction
of SVC
anomalies.
SVC,
superior
vena cava;
WC, inferior
vena cava:
CS. coronary
sinus;
LA,
left
atrium;
RA.
right
atrium.
WC
Normal
anatomy
Double
SVC;
Left SVC to C-S.
No venous
intercommunication
Double
Len svc
SVC;
to cs.
Double
SVC;
Len svc to u.
:-1
>rl ‘;‘ b-b
A
Venous
intercommunication
0
0
c
:
0
:
:
c
0
:
:
)
C
B
Absent
Right
SVC:
Left svCt0 cs..
I
Absent
Vertical
Right
Vein
SVC;
Left SVC to LA.
the coronary sinus is large, approaching the
caliber of the cava entering it (Fig 2).6
When an anastomosis does exist between the
two cavas, it may be oriented inferiorly toward
the right, inferiorly toward the left, or directed
transversely. The relative size of the two cavas
and of the coronary sinus depends on the amount
of blood each carries as routed above. In some
cases, additional cross-communication exists in
the form of several small, slender, irregularly
branching veins, a plexiform arrangement that
Papez7 suggests probably represents the persistence of vessels that normally contribute to the
formation of the left innominate vein.7
The most frequent cardiac anomaly associated
with a left SVC that drains into the RA is an
ASD. Gensini et al* noted that a left-to-right
shunt at the atria1 level is often present in
conjunction with anomalous pulmonary venous
drainage into either a left or right SVC. The
anomalous drainage in the majority of cases is
total. Septal defects always coexist.
Infrequently the left SVC enters the left
atrium or the left side of a common atrium. In
this case other cardiac anomalies are almost
always associated.’
The true incidence of a persistent left SVC
with absence of a right SVC is not known, but it
Anomalous
venous
pulmonary
drainage
to svc.
D
1
Fusiform
I
aneurysm
of svc.
Saccular
aneurysm
Of svc.
is rare. Functionally, this arrangement results in
no circulatory disturbance if the left SVC drains
directly or indirectly into the right atrium (Fig
3).
lo-12
A left SVC may be associated with a wide
variety of cardiac defects, including single
atrium, VSD, PDA, tetralogy of Fallot, truncus
arteriosus, pulmonary stenosis or atresia, Ebstein
malformation,
atrioventricular
canal defects,
Taussig-Bing complex, mitral atresia, tricuspid
atresia, transposition,
anomalous pulmonary
venous return, and coarctation of the aorta.“2*‘3
There is a higher incidence of left SVC in
cases of transposition of the viscera. Campbell
and Deuchar’ found a left SVC in 40% of 46
cases of congenital heart disease in which there
was also some degree of visceral transposition. A
double SVC is more common when visceral
transposition is partial than when it is complete.
Finally, left SVC is frequently described with
asplenia.3,4,‘3
VERTICAL
VEIN
Careful distinction should be made between a
persistent left SVC and an anomalous left vertical vein. The left vertical pulmonary vein that
receives partial or total left pulmonary venous
drainage, ascends superiorly, usually anterior to
Fig 2.
Double
SVC with normal
right SVC
anatomy
and the left SVC draining
into
en
enlarged
coronary
sinus.
This patient
also
had an unrelated
incidental
finding:
hemiazygos continuation
of a left inferior
vena cave.
SVC.
superior
vena
ceva;
Ao. aorta:
MPA.
main pulmonary
ertery:
LPA, left Pulmonary
artery;
CS, coronary
sinus:
R. right:
L. left: h.
hemiazygos
vein.
80
Fig 3.
Left WC
in the absence
of a
right SVC.
The right suparior
pulmonary
vein should
not be mistaken
for a right
SVC. R In V, right innominate
vein:
I. In V.
left innominate
vain:
SVC,
superior
vena
cava: Ao, aorta:
LPA, left pulmonary
artery: RPA, right pulmonary
artery:
PA. main
pulmonary
artery:
Ft. right: L. left.
82
CORMIER
ET AL
Fig 4.
Fusiform
aneurysm
of the
superior
vena
cava.
Ao. aorta:
SVC an.
superior
vena cava aneurysm;
PA. pul Imonary artery.
the aorta, and drains into the left innominate
vein. It is now generally accepted that a true left
SVC drains into the heart.13*14
ANOMALIES
OF THE RIGHT SUi’ERIOR
VENA CAVA
Relatively few intrinsic right SVC anomalies
occur. The right SVC rarely drains into the left
atrium without any coexisting defects. This creates a right-to-left shunt with cyanosis. Only a
handful of cases have been reported.11*‘5*‘6
Freedom et al” reported a case in which the
right SVC drained into the RA via a low insertion associated with complex congenital heart
defects.”
Congenital aneurysm of the SVC is rare. It is
nonetheless important in the differential diagnosis of a superior mediastinal mass. Two distinct types are recognized: saccular and fusiform.
Direct opacification of the vascular lesion, either
angiographically
or on contrast-enhanced CT,
provides the diagnosis (Fig 4). It is generally
accepted that because this is a low-pressure
system, the aneurysm does not thrombose,
enlarge, or rupture, making conservative management appropriate.‘8*19
REFERENCES
1. Kjellberg SR, Mannheimer E, Rudhe U, et al: Diagnosis of congenital heart disease. Chicago: Year Book Medical, 1959
CONGENITAL
ANOMALIES
OF THE
SVC:
CT STUDY
2. Winter FS: Persistent left superior vena cava. Survey of
world literature and report of thirty additional cases. Angiology 1954;5:90-132
3. Campbell M, Deuchar DC: The left-sided superior vena
cava. Br Heart J 1954;16:423-39
4. Gray SW, Skandalakis JE: Embryology for Surgeons.
Philadephia: Saunders, 1972
5. Webb WR, Gamsu G, Speckman JM, et al: Computed
tomographic demonstration of mediastinal venous anomalies.
AJR 1982;139:157-61
6. McManus JFA: A case in which both pulmonary veins
emptied into a persistent left superior vena cava. Can Med
Assoc J 1941;45:261-4
7. Papez JW: Two cases of persistent left superior vena
cava in man. Anat Ret 1938;70:191-8
8. Gensini GG, Caldini P, Casaccio F, et al: Persistent left
superior vena cava. Am J Cardiol1959;4:677-85
9. Shumacker HB, King H, Waldhausen JA: The persistent left superior vena cava. Surgical implications, with
special reference to caval drainage into the left atrium. Ann
Surg 1967;165:797-805
10. Pugliese P, Murzi B, Aliboni M, et al: Absent right
superior vena cava and persistent left superior vena cava:
Clinical and surgical considerations. J Cardiovasc
Surg
I984;25: 134-7
11. Vasquez-Perez J, Frontera-Izquierdo P: Anomalous
drainage of the right superior vena cava into the left atrium
a3
as an isolated anomaly. Rare case report. Am Heart J
1979;97:89-91
12. Lenox CC, Zuberbuhler JR, Park SC, et al: Absent
right superior vena cava with persistent left superior vena
cava: Implications and management. Am J Cardiol
1980;45: 1 S7-22
13. Cha EM, Khoury GH: Persistent Left superior vena
cava. Radiologic and clinical significance. Radiology
1972;103:375-81
14. Caffey J: Pediatric x-ray diagnosis (ed 7). Chicago:
Year Book Medical, 1978
15. Braudo M, Beanlands DS, Trusler G: Anomalous
drainage of the right superior vena cava into the left atrium.
Can Med Associ J 1968;99:7
15-9
16. Park HY, Summerer MH, Preuss K, et al: Anomalous
drainage of the right superior vena cava into the left atrium. /
Am Co11 Cardiol
1983;2:358-62
17. Freedom RM, Schaffer MS, Rowe RD: Anomalous
low insertion of right superior vena cava. Br Heart J
1982;48:601-3
18. Modry DL, Hidvegi RS, LaFIeche LR: Congenital
saccular aneurysm of the superior vena cava. Ann Thorac
Surg 1980; 29125862
19. Train JS, Mandel G, Efremidis SC: Fusiform aneurysm of the superior vena cava. MZ Sinai J Med 198 1;48: 12830