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Original Article
1 2 3Sabita Singh , Parineeta Suman , A.David Ebenezer
INTRODUCTION:
he precise anatomical knowledge of
vascular system anomalies is essential Tdue to its significance in different
developmental problems in adventant and injury in
various invasive procedures. Normal anatomy
describes the formation of a single superior
venacava by the union of right and left
brachiocephalic veins which drains the blood from
upper part of the body.
Superior vena cava anomalies are caused by variations in the development of the embryonic thoracic venous system. The anomalies that involve the superior vena cava include the persistent left superior vena cava with or without the right supe-rior vena cava, absence of superior vena cava, hypoplasia of the superior vena cava, and abnormal opening of the superior vena cava into the left atrium, coronary sinus, azygous venous system,
1and the pulmonary vein.
Persistent left superior vena cava (PLSVC) occurs
as a result of failure of regression of left anterior
Address for correspondence:
Dr. Parineeta Suman,2C, Kaveri Block, Velammal Medical College, Anuppanadi, Madurai- 625009E-mail : [email protected] Mobile : 9159969772
1Asst. Professor, Dept. of Anatomy, Veer Surendra Sai Institute of Medical Science & Research, Sambalpur, Odisha- 7680172Associate Professor, Department of Anatomy, Velammal Medical College, Madurai, Tamilnadu - 625009, India3Assistant Professor, Department of Anatomy, Velammal Medical College, Madurai, Tamilnadu - 625009, India
A Cadaveric Study of Double Superior Vena Cava with Paired Azygos Vein & its Clinical Implications
http://dx.doi.org/10.31975/NJBMS.2019.9301
ABSTRACT
Introduction: Double superior vena cava with a Persistent Left Superior Vena Cava (PLSVC) is an
uncommon abnormality but is the most common thoracic venous anomaly in the setting of SVC. It is
estimated to occur in 0.3- 0.5% of the general population and 3-10% of patients with other forms of
congenital heart disease. The present study aimed to find the frequency of double superior vena
cava, its embryological basis and to correlate its clinical significance.
Materials and methods: The present study, a descriptive study includes sixty cadavers allotted for
first year MBBS students in Department of Anatomy at Velammal Medical College, Madurai during
year 2013-2018. Superior vena cava along with other veins had been traced and studied in detail.
Results : Double superior vena cava was found in 2 cadavers out of 60 cadavers (3.33%). Persistent
left superior vena cava opened into an enlarged coronary sinus that further drained into the right
atrium in both the cases. Left brachiocephalic vein was present in one of them and left azygos vein
ran upward along the left side of vertebral column and drained into PLSVC in the cadaver. There
was no anastomosis between azygos and hemiazygos vein.
Conclusion : Persistent left superior vena cava (PLSVC) occurs as a result of failure of regression of
left anterior cardinal and left common cardinal veins. The precise knowledge of double superior
vena cava by surgeons, sonographers and interventional radiologists can prevent possible
complications in routine clinical practice and during cardiopulmonary bypass.
Key words : Double superior vena cava, Persistent left superior vena cava, Left azygos vein,
Anterior cardinal vein, Coronary sinus
National Journal of Basic Medical Sciences | Volume 9 | Issue 3 | 2019
108
College, Madurai during year 2013-2018. The
mode of formation and drainage of persistent left
superior vena cava along with other thoracic veins
have been properly traced and studied in detail.
RESULTS
We found the presence of persistent left superior
vena cava among 2 cadavers out of 60 cadavers
(3.33%). Persistent left superior vena cava was
observed in adult male cadaver aged 50 years and
adult female cadaver aged 55 years.
Case 1- Adult male cadaver aged 50 years:
Persistent left superior vena cava was formed by
the union of left internal jugular vein and left
subclavian vein. Left brachiocephalic vein was
absent. Persistent left superior vena cava coursed
vertically down anterior to arch of aorta and left
pulmonary trunk (Fig.1). When traced, it opened
into an enlarged coronary sinus that further drained
into the right atrium (Fig.2). There was no
communication between the two vena cavae. The
persistent left superior vena cava had the same
length and caliber as compared to the right superior
vena cava (Fig.1, Fig.2). A left azygos vein
replaced the accessory azygos and the hemiazygos
veins. It ran upward along the left side of vertebral
column and arched over the root of the left lung to
drain into PLSVC (Fig.3).
The azygos and the left azygos veins did not
communicate with each other. Azygos system was
made up of bilaterally symmetrical veins. Right
superior vena cava was present as a continuation of
right brachiocephalic vein which in turn formed by
the union of right internal jugular vein and right sub
clavian vein. Right superior vena cava opened into
right atrium and received the drainage of azygos
vein (Fig.2). No other associated anomaly of heart
was observed.
cardinal and leftcommon cardinal veins. PLSVC
may open into left atrium of the heart, coronary 2sinus, right superior vena cava is innominate vein.
Persistent left superior vena cava is a rare venous
malformation. There is limited number of
cadaveric study on this anomaly.
The reason is that the double superior vena cava
often associated with cardiovascular anomalies,
allowing only the limited number of adult patients
to survive. However, the developments of
procedures for cardiovascular catheterization and
clinical imaging examinations have increased the
number of anomaly is being reported. It is
estimated to occur in 0.3- 0.5% of the general
population and 3-10% of patients with other forms 3,4
of congenital heart disease.
Double superior vena cava is usually asymptomatic
unless other cardiac anomalies exist. It is frequently
associated with cardiac abnormalities like
ventricular septal defect, atrial septal defect or
endocardial cushion defect that have significant 5mortality and morbidity. PLSVC may also
interfere and cause problems during various
invasive procedures such as pacemaker
implantation, central venous catheterisation,
retrograde delivery of cardioplegia and retrograde 6,7,8left ventricular pacing.
The aim of the present study is to find the frequency
of double superior vena cava, its embryological
basis and to correlate its clinical significance. The
present study also compared the frequency of
double superior vena cava reported in other similar
studies.
MATERIALS AND METHODS:
This is a descriptive study which includes the
cadavers allotted for first year MBBS students in
Department of Anatomy at VelammalMedical
Sabita Singh, et.al : Double Superior vena cava with paired Azygos vein
National Journal of Basic Medical Sciences | Volume 9 | Issue 3 | 2019
109
Fig.1 : Heart in situ showing double superior vena cavae without any communication between them.
RSVC- right superior vena cava, PLSVC- persistent left superior vena cava, PT- pulmonary trunk.
Fig.2. : Posterior view of resected heart showing double azygos vein with double superior vena cavae.
Rightazygos draining into right superior vena cava and left azygos vein draining into persistent left
superior vena cava. Persistent left superior vena opening into enlarged coronary sinus. RSVC- right
superior vena cava, PLSVC- persistent left superior vena cava, RAV- right azygos vein, LAV-left azygos
vein, CS-coronary sinus.
Fig.3 : Dissected thoracic cavity showing left azygos vein draining into persistent left superior vena cava.
LAV- left azygos vein, PLSVC- persistent left superior vena cava
Fig.4 : Posterior view of resected heart showing double superior vena cava with double azygos vein. Left
brachiocephalic vein present which unite with right brahiocephalic vein to form right superior vena cava.
Persistent left superior vena cava and left azygos vein are of reduced dimension as compared to right side.
Coronary sinus are dilated into which persistent left superior vena cava drained. RSVC- right superior
vena cava, PLSVC- persistent left superior vena cava, RBCV- right brachiocehalic vein, LBCV- left
brachiocephalic vein, CS-coronary sinus
Sabita Singh, et.al : Double Superior vena cava with paired Azygos vein
National Journal of Basic Medical Sciences | Volume 9 | Issue 3 | 2019
110
present study. They classified the cases according
to the presence / absence of pairing of
azygousveins, as well as the presence / absence of
anastomotic branch, into the following 4 types:
I) The pattern with an anastomotic branch
between the right and left superior vena cava, II) the pattern without any anastomotic branch, III) the pattern showing the presence of the left
superior vena cava alone and degeneration and
disappearance of the right superior vena cava,
andIV) the pattern of the double superior vena cava
12with paired azygos veins . In the present study
cases were of type IV.
During the fifth week of intrauterine life, in the
human fetus, three pairs of major veins can be
distinguished: the vitelline veins, carrying blood
from the yolk sac to the sinus venosus; the
umbilical veins, originating in the chorionic villi
and carrying oxygenated blood to the embryo; and
the cardinal veins, draining the body of the embryo
proper. The cardinal veins form a pair of
symmetrical venous system. They consist of the
anterior cardinal veins, which drain the cephalic
part of the embryo, and the posterior cardinal veins,
draining the remaining part of the body of the
embryo.
The anterior and posterior cardinal veins join to
form common cardinal veins and enter the right and
left horns of the sinus venosus. Formation of the
vena cava system is characterized by the
appearance of anastomosis between the left and
right sides in such a manner that the blood from the
left side is directed to the right side. The left anterior
cardinal vein above and the anastomosis between
the anterior cardinal veins develops into the left
brachiocephalic vein. Most of the blood from the
left side of the head and the left upper extremity is
thus directed to the right. The superior vena cava is
Case 2- Adult female cadaver aged 55 years :
PLSVC was formed by the union of left internal
jugular vein and left subclavian vein which in turn
opened into coronary sinus. PLSVC was smaller in
size than right superior vena cava. Right superior
vena cava was formed by the joining of right and
left brachiocephalic vein. Azygos system was made
up of bilaterally symmetrical veins like that of
previous case. But left side azygos vein was very
small (Fig.4). Patent foramen ovale was present in
the heart.
DISCUSSION :
There are many anatomical variations of superior
vena cava found due to its complex development. A
double superior vena cava with a persistent left
superior vena cava is an uncommon abnormality
but is the most common thoracic venous anomaly 9
in the setting of SVC . Anomalies of superior vena
cava have been classified by many authors.
McCotters classified double superior vena cava
into following five types based upon anastomosis
between right and left superior vena cava:
1) Double superior vena cava without anastomosis, 2) Double superior vena cava with small
anastomosis,3) Double superior vena cava with normal
anastomosis, 4) Left superior vena cava without right, and
105) Persistent left superior vena cava unclassified.
In the present study, case1 belonged to type 1 and
case 2 was of type 5. Thomas et al classified the
PLSVC into two types one connecting to right
atrium via the coronary sinus (90%) and the other 11
connecting to left atrium (10%) . Rare cases of
double superior vena cava with pairedazygos vein
had been reported. Nandy and Blair had reported
double superior vena cavae with bilaterally
symmetrical azygos veins, which was similar to the
Sabita Singh, et.al : Double Superior vena cava with paired Azygos vein
National Journal of Basic Medical Sciences | Volume 9 | Issue 3 | 2019
111
M.Uemura. 2,17 But AP. Gesase et al have shown
highfrequency10 - 11% of the double superior vena
cava but that was observed in congenital heart 18
disease patients. The present study showed 2.22%
of frequency of double superior vena cava.
PLSVC is asymptomatic and compatible with life
unless the PLSVC opens into the left atrium or is
accompanied by other congenital heart defects like
atrial septal defect, ventricular septal defect and 19tetralogy of Fallot. Other congenital anomalies in
the heart and an associated shunt between the right
and the left cardiac system occurring should be
considered from the presence of the persistent left 14superior vena cava. PLSVC may drain into left
atrium in 7.5% cases which results in small right to
left shunt. This hasa minor haemo dynamic effect,
mainly a variable degree of systemic cyanosis and 20,21
may lead to clinical symptoms. PLSVC may
also give rise to rhythm disturbances such assinus
node dysfunction and atrioventricular block. The
serhythm problems may be related to the stretching
of the conduction tissue caused by the enlargement 7,8
of the coronary sinus. LSVC has been associated
with an increased risk of arrhythmias, most 22
commonly atrial fibrillation.
The knowledge of existence of PLSVC during CT
scan evaluation of the mediastinum is important
because LSVC can be mistaken for alymph node 23and result in false staging of lung cancer. Invasive
procedures like cardiac pacemaker implantation,
resynchronization therapy, radio frequency
catheter ablation, internal jugular or subclavian
vein catheter insertion require detailed echo cardio
graphic studies of this rare congenital anomaly to 6,7,20
avoid further complication. Awareness of
PLSVC is necessary for intensive care clinicians
not to place catheters outside the venous circulation
& to avoid complications like perforation, shock, 20
cardiac arrest, cardiac tamponade and thrombosis.
thus formed by the right common cardinal vein and
the proximal portion of the right anterior cardinal
vein. On the other hand, the left common cardinal
vein and the distal part of the left horn become
atretic and forms the ligament of Marshall or
ligament of the left superior vena cava. The caudal
part of anterior cardinal vein distal to the
anastomosis obliterates. The failure of this normal
regression i.e, persistence of left anterior cardinal
vein and left common cardinal vein results in
PLSVC.
During fifth to seventh week, a number of
additional veins are formed: a) subcardinal vein,
which mainly drain the kidneys b) sacrocardinal
vein, which drain the lower extremity and
c)supracardinal vein, which drain the body wall by
way of the intercostal veins, taking over the
functions of the posterior cardinal vein after its
major obliteration. Azygos venous system
develops from a pair of the right and left
supracardinal veins. Both supracardinal veins
communicate with the posterior cardinal veins to
form the primordium of a pair of right and left
azygos veins. Subsequently, right supracardinal
together with a portion of posterior cardinal forms
the azygos vein. On the other hand, left
supracardinal vein forms hemiazygos vein which
drains into azygos vein.13 The left azygos vein
appears to be developed from the persistent
proximal portion of the left posterior cardinal vein 12
and the left supracardinal vein.
There are differences in frequency of double
superior vena cava showed by various studies. A
persistent left superior vena cava is the most
common anomaly of abnormal veins flowing into
the heart, with a frequency of 0.3 - 0.5% in healthy
individuals, and 2 - 4% in patients with congenital 14,15,16heart diseases. The frequency of double
superior vena cava reported by various authors are
as follows- 0.16% by Bergman RA, and 0.3% by
Sabita Singh, et.al : Double Superior vena cava with paired Azygos vein
National Journal of Basic Medical Sciences | Volume 9 | Issue 3 | 2019
112
these diagnostic techniques, other associated
congenital anomalies should be investigated so as
to comprehend the risks related to catheterization
and selection of a safe route should be considered.
CONCLUSION :
Although the double superior vena cava is a rare
congenital anomaly, prior knowledge of it and the
associated anomalies should be considered
seriously by surgeons, sonographers and
interventional radiologists. This can prevent
possible complications in routine clinical practice
and during cardiopulmonary bypass and minimize
the diagnostic errors. As the literature available on
this congenital anomaly is sparse, the present study
can add to the existing knowledge of this congenital
anomaly and stresses on its significant clinical
implications, especially during central venous
catheter placement or during surgical procedures in
the chest.
CONFLICTS OF INTEREST :
The authors have none to declare.
ACKNOWLEDGEMENT :
The authors would like to acknowledge the help
and support rendered by the faculties of
Department of Anatomy and dissection hall staff of
Velammal Medical College, Madurai.
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National Journal of Basic Medical Sciences | Volume 9 | Issue 3 | 2019
Received on 23/01/2019 Revised on 25/02/2019 Accepted on 07/03/2019