AJR 2004; 182:1139-1150
© American Roentgen Ray Society
Venous Anomalies of the Thorax
Terrence C. Demos1,
Harold V. Posniak,
Kenneth L. Pierce,
Mary C. Olson and
Mark Muscato
1 All authors: Department of Radiology, Loyola University Medical Center, 2160 S
First Ave., Maywood, IL 60153.
Received July 28, 2003;
accepted after revision November 6, 2003.
Address correspondence to T. C. Demos.
Presented at the 2003 annual meeting of the American Roentgen Ray Society,
San Diego, CA.
Introduction
Venous anomalies of the thorax can involve systemic or pulmonary veins and
range from isolated incidental findings to components of more complex
anomalies, most often congenital heart disease. Radiologists often encounter
these anomalies unexpectedly. Correct diagnosis can affect patient treatment
and also help avoid unnecessary additional studies when the anomalies simulate
thoracic disease
[1–3].
Many anomalies of these veins are revealed by radiography
[4], but more are seen on
cross-sectional imaging. In this article, CT
[5,
6] and MRI
[7] are emphasized and the
salient features of the anomalies are discussed. The review is divided into
three sections. The first two sections, the Superior Vena Cava and the Azygos
System, address systemic venous anomalies, and the third addresses the
pulmonary veins.
Superior Vena Cava
Anatomy
The proximal superior vena cava (SVC) is formed by the confluence of the
right and left brachiocephalic veins on the right side of the superior
mediastinum at the level of the first costal cartilage. The SVC then extends
caudally, and slightly anteromedially, for 5–7 cm before entering the
right atrium in the middle mediastinum at the level of the right third costal
cartilage [8].
Embryology
Venous anomalies of the thorax are the result of complex variations in the
persistence and regression of segments of three sets of veins during the first
2 months of fetal development: the umbilical, vitelline, and cardinal venous
systems [8,
9]. Normally, the right
anterior cardinal and common cardinal veins form the SVC and the left anterior
cardinal vein regresses. A double SVC is the result of persistence of the left
anterior cardinal vein. If, in addition, the normally persistent right
cardinal vein regresses, then there is only a left SVC
[8,
10].
Anomalies
Left SVC.—A persistent left SVC is an incidental finding in
less than 0.5% of the general population but occurs in approximately 4% of
patients with congenital heart disease. In most cases, the left SVC is a
component of a duplicated SVC. The left brachiocephalic vein is absent, and
the right SVC is smaller than the left in 65% of SVC duplications
[8,
10,
11].
As an isolated anomaly in the absence of congenital heart disease, a left
SVC or left component of a duplicated SVC almost always drains into the
coronary sinus (Figs. 1 and
2). Drainage to the left atrium
(Fig. 3A,
3B) is associated with many
types of congenital heart disease but is rare if the heart is normal
[8].
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Fig. 1. —54-year-old man with normal heart and duplicated superior
vena cava (SVC). Chest radiograph shows pulmonary artery catheter
(arrows) in left SVC extending through coronary sinus to right
atrium.
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Fig. 2. —50-year-old woman with duplicated superior vena cava (SVC).
Series of CT scans shows course of left SVC (short arrows) along left
side of mediastinum. SVC drains into characteristically enlarged coronary
sinus. Right SVC (arrowheads) is faintly opacified. Note left
superior pulmonary vein (long arrow) and mediastinal lymphadenopathy
caused by lymphoma.
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Fig. 3A. —35-year-old woman with coronary sinus type of atrial septal
defect with left superior vena cava (SVC) draining into left atrium.
Gradient-echo MR image obtained at level of pulmonary trunk shows right
(arrowheads) and left (white arrow) SVC. Left superior
pulmonary vein (black arrow) is also shown.
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Fig. 3B. —35-year-old woman with coronary sinus type of atrial septal
defect with left superior vena cava (SVC) draining into left atrium.
Gradient-echo MR image obtained caudad to A shows that left SVC has now
joined left atrium (LA). Note left atrial appendage (arrow). Drainage
to left atrium is almost always associated with congenital heart disease.
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The left SVC descends lateral to the aortic arch and anterior to the hilum,
enters the pericardium in the posterior atrioventricular groove, and drains
into the coronary sinus [8,
10,
11]. The coronary sinus is
usually enlarged and may be densely opacified on CT when IV contrast material
is injected into the left arm (Fig.
2). A large coronary sinus identified on CT or MRI of the abdomen
can lead to the diagnosis of a left SVC
[8,
11].
A left SVC is also occasionally detectable, usually in retrospect, as a
focal widening of the mediastinum superior to the left side of the aortic knob
on a chest radiograph. Most often, however, a left SVC or left component of a
duplicated SVC is revealed by radiography when traversed by an IV catheter
(Fig. 1). With a solitary left
SVC, the ascending aorta can appear unusually prominent on radiographs because
no right SVC obscures it. This circumstance can simulate an abnormal aorta
[12]
(Fig. 4A).
A left SVC is most often an incidental finding that is not clinically
significant, but patients with a left SVC draining into a coronary sinus that
has a narrowed ostium have presented difficulties in introducing IV lines and
pacemaker or defibrillator leads
[11]. Rarely, atresia of the
ostium of the coronary sinus occurs
[13–15].
Although occluded, the coronary sinus, by way of collateral vessels, still
receives the total venous output of the coronary veins. The coronary venous
drainage to the heart, however, is then retrograde through the left SVC to the
left brachiocephalic vein. When this circumstance is unrecognized, ligation of
the left SVC as part of a cardiac surgical procedure has led to acute coronary
venous hypertension and myocardial ischemia
[14,
15].
Right SVC.—Isolated anomalies of the right SVC are rare. A
right SVC can insert low into the right atrium, drain to the left atrium, or
be congenitally dilated [8]. On
radiography, a congenitally dilated SVC has the appearance of a mediastinal
mass (Fig. 5A). This anomaly is
usually an incidental finding but has been associated with thrombosis leading
to embolization and SVC obstruction
[16]. Congenital aneurysmal
dilatation has been associated with cystic hygromas and may alter the surgical
procedure for an associated cystic hygroma
[17,
18]
(Fig. 5B).
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Fig. 5B. —9-year-old boy with superior vena cava (SVC) aneurysm.
(Courtesy of Donaldson J, Chicago, IL) CT scan shows markedly dilated SVC
(arrowhead). Patient also had cystic hygroma of right axilla
(arrow) and neck.
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An anomalous left brachiocephalic vein is usually associated with
congenital heart disease. This vein, rather than joining the right
brachiocephalic vein ventral to the aorta, crosses the midline dorsal to the
ascending aorta to join the SVC caudal to the azygos vein. Located lateral and
cephalad to the aortic arch, this vein resembles a left SVC or partial
anomalous pulmonary venous return (PAPVR), but, more caudally, it can be
traced to the right SVC [19,
20].
For a list of the anomalies of the SVC, see Appendix 1.
Azygos System
Anatomy
The azygos system is a paired paravertebral venous pathway in the posterior
thorax. The azygos vein originates at the junction of the right ascending
lumbar and subcostal veins, enters the chest through the aortic hiatus, and
ascends along the anterolateral surface of the thoracic vertebrae
(Fig. 6). At T5–T6, it
arches ventrally just cephalad to the right main bronchus and drains into the
SVC or, rarely, into the right brachiocephalic vein, right subclavian vein,
intrapericardial SVC, or right atrium
[21,
22].
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Fig. 6. —Azygos anatomy on venogram of 60-year-old woman with inferior
vena cava (IVC) stricture. Ascending lumbar veins drain to azygos (short
black arrows) and hemiazygos vein (long black arrows) in chest.
Hemiazygos vein joins azygos vein (white arrowhead) at T9. Azygos
vein continues cephalad and forms azygos arch (black arrowheads)
draining into superior vena cava. Note small accessory hemiazygos vein
(white arrow) and stenosis of IVC (c).
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Fig. 4B. —29-year-old man with left but no right superior vena cava
(SVC). CT scan shows single left SVC (arrow). Aorta is normal.
Ascending aorta is prominent on radiograph because right SVC is absent. Thus,
right upper lobe outlines ascending aorta.
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Similar to the azygos vein, the hemiazygos vein originates at the junction
of the left ascending lumbar and left subcostal veins and often receives
tributaries from the left renal vein and inferior vena cava (IVC). The
hemiazygos vein ascends along the left anterolateral aspect of the thoracic
vertebrae and at T8–T9 crosses dorsal to the descending thoracic aorta
to join the azygos vein (Fig.
6). From this point, the accessory hemiazygos vein extends further
cephalad in a left paravertebral position and may communicate with the azygos
vein at different levels. Intercostal veins and mediastinal tributaries drain
into the azygos, hemiazygos, and accessory hemiazygos veins. The right
superior intercostal vein drains the right second through the fourth
intercostal spaces and joins the azygos vein just proximal to the azygos
arching over the right main bronchus. The left superior intercostal vein
drains the left second through the fourth intercostal spaces and communicates
with the accessory hemiazygos vein in 75% of patients. It then arches
ventrally adjacent to the aortic arch and drains into the left brachiocephalic
vein. This vein seen en face adjacent to the aortic knob on frontal
chest radiographs is termed the "aortic nipple." The right and
left supreme intercostal veins drain the first intercostal spaces and usually
empty into the brachiocephalic veins. They may communicate with the
corresponding superior intercostal veins
[21,
22].
Embryology
The embryology of the azygos–hemiazygos system is controversial, but
the azygos vein is considered to derive from the upper right supracardinal
vein, the azygos arch from an upper segment of the right posterior cardinal
vein, and the hemiazygos vein from the upper left supracardinal vein.
Development of an azygos lobe, also a controversial topic, has been attributed
to the posterior cardinal vein failing to migrate over the apex of the right
lung, resulting in the vein indenting the lung
[21,
22].
During development, the intermediate segment of the right supracardinal
vein joins the IVC and azygos or hemiazygos veins, but this segment normally
regresses. If the suprarenal segment of the IVC fails to develop, however, the
intermediate segment of the supracardinal vein persists, resulting in azygos
or hemiazygos continuation [6,
9,
21]. Thus, although the large
azygos or hemiazygos vein is the predominant finding in these patients, the
primary anomaly involves the inferior vena cava.
Anomalies
Absent azygos vein.—Congenital absence of the azygos vein is
rare [23]. Enlargement of the
hemiazygos, accessory hemiazygos, and left superior intercostal veins is
associated with it (Fig. 7A,
7B).
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Fig. 7A. —42-year-old man with absent azygos vein. Chest radiograph
shows prominent left superior intercostal vein (arrow) simulating
mediastinal abnormality. Note absent en face azygos arch at right
tracheobronchial junction.
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Azygos lobe.—An anomalous course of the azygos vein in the
right lung apex gives rise to an azygos lobe in approximately 0.4–1.0%
of the population [21]. This
anomaly is easily identified on imaging studies (Fig.
8A,
8B). The abnormally located
vessel indents the lung and its overlying parietal and visceral layers of
pleura. This situation results in four pleural layers that form a
mesenterylike structure, the mesoazygos, containing the azygos vein
[21,
22]. The much less frequent
left azygos or hemiazygos lobe is caused by a malpositioned left superior
intercostal vein draining into the left brachiocephalic vein
[24]
(Fig. 9).
Azygos and hemiazygos continuation of the IVC.—These
anomalies may be isolated [25,
26] or associated with other
anomalies
[27–35].
The incidence in patients with congenital heart disease undergoing cardiac
catheterization ranges from 0.2% to 1.3%
[21,
22]. Azygos continuation is
common in patients with polysplenia (left isomerism)
[34] but rare in patients with
asplenia (right isomerism)
[29,
34]. Other associated
anomalies have included abnormal abdominal situs and a left or duplicated IVC
[21,
22,
25].
The imaging features of azygos continuation of the IVC include dilatation
of the azygos vein, azygos arch, and SVC caused by increased flow (Figs.
10,
11,
12A,
12B,
12C). The hepatic veins drain
into the right atrium via the suprahepatic IVC. The hepatic segment of the IVC
is absent or hypoplastic, and this condition must be documented to exclude
other causes of an enlarged azygos vein
[21,
22]. Azygos continuation has
also been reported in association with an azygos lobe
[27]
(Fig. 11).
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Fig. 10. —32-year-old man with azygos continuation of inferior vena
cava. Chest radiograph shows large azygos vein (arrowheads) extending
to dilated azygos arch (arrow) at right tracheobronchial junction.
Patient had osteosarcoma of femur, and chest radiograph shows findings
suspicious for enlarged azygos lymph node.
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Hemiazygos continuation of a left-sided IVC has several variations
[21,
22,
30,
31] (Figs.
13A,
13B and
14A,
14B), including three possible
routes for blood in the hemiazygos vein to reach the right atrium. In the
first route, the hemiazygos vein drains into the azygos vein at T8–T9.
In this case, the findings at more cephalad levels are similar to azygos
continuation with enlargement of the distal azygos vein. The hemiazygos vein
is also enlarged. The second route involves a persistent left SVC, and blood
flows from the hemiazygos vein into the accessory hemiazygos vein and left SVC
and then into the coronary sinus, all of which are dilated. In the third
route, the hemiazygos vein drains to the accessory hemiazygos vein, left
superior intercostal vein, and left brachiocephalic vein into a normal right
SVC [21,
22].
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Fig. 13A. —32-year-old man with polysplenia and situs inversus and
hemiazygos continuation of inferior vena cava. CT scan shows right and left
pulmonary arteries ventral to main bronchi, indicating bilateral left lung
anatomy (left isomerism). Note duplicated superior vena cava
(arrows), right descending aorta (A), and dilated hemiazygos vein
(arrowhead).
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Fig. 13B. —32-year-old man with polysplenia and situs inversus and
hemiazygos continuation of inferior vena cava. CT scan shows liver in left
upper quadrant. Note two of several right upper quadrant spleens (s).
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Fig. 14A. —36-year-old woman with complex congenital heart disease and
hemiazygos continuation of inferior vena cava draining into left superior vena
cava (SVC). CT scan shows dilated left superior intercostal vein
(arrowheads) arching anteriorly to join left SVC.
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Fig. 14B. —36-year-old woman with complex congenital heart disease and
hemiazygos continuation of inferior vena cava draining into left superior vena
cava (SVC). CT scan obtained at level of right pulmonary artery shows dilated
left SVC (long arrow) and accessory hemiazygos vein
(arrowhead). Note small right SVC (short arrow) and right
descending aorta (A).
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For a list of the anomalies of the azygos system, see Appendix 2.
Pulmonary Veins
Anatomy
Four veins drain into the left atrium. The right superior vein drains the
upper and middle lobes, the left superior vein drains the left upper lobe and
lingula, and the right and left inferior veins drain the lower lobes
(Fig. 15). At the hila, the
superior veins are anterior and caudal to the pulmonary arteries. The ostia of
the inferior veins are more dorsal and more medial than the superior veins
[36].
Embryology
During the first 2 months in utero, the lung buds develop from the foregut
and drain the systemic veins of the embryo. At the same time, an outpouching
from the primitive left atrium forms a common pulmonary vein. Later, when the
lung buds fuse with the common pulmonary vein, the connections between the
pulmonary veins and the systemic veins are obliterated. Subsequently, the
common pulmonary vein becomes incorporated into the left atrium so that two
pulmonary veins remain, draining each lung
[36,
37]. In addition to stenosis
[38–40]
and atresia [41], altered
absorption of these developing structures can result in abnormal venous
caliber, increase or decrease in the number of veins, and abnormal drainage of
pulmonary veins to systemic veins or the right atrium.
Anomalies
Variation in number of veins.—These anatomic variations have
become important and increasingly recognized because of the use of CT to
depict pulmonary vein anatomy in patients with atrial fibrillation who are
treated by radiofrequency ablation of arrhythmogenic foci located near
pulmonary vein ostia [42,
43]. The most common
variation, three right veins, was found in nine (16%) of 58 patients in one
study [42]
(Fig. 16A). The third vein
drained the right middle lobe. A single left vein was found in two (3%) of 58
patients [42]
(Fig. 16B). Familiarity with
the anatomic variations is important for both conducting the ablation
procedure [42,
43] and detecting and
quantifying pulmonary vein complications after the procedure
[44,
45], which is most often
venous stenosis [44].
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Fig. 16B. —Pulmonary vein variants. Posterior view of CT volume-rendered
image shows single left pulmonary vein (arrow) draining left lung of
46-year-old man. Note stenosis (arrowhead) of superior right
pulmonary vein.
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Pulmonary vein varix.—A dilated pulmonary vein, either
congenital or acquired, can simulate a lung nodule on a chest radiograph
[46,
47].
PAPVR.—The overall incidence of PAPVR is approximately 0.5%
[48–56].
PAPVR involves the right lung
[48] more frequently than the
left [49,
51] and is more often
hemodynamically significant when associated with congenital heart disease or
scimitar syndrome. Anomalous right lung veins can drain into the SVC
[48], azygos vein
[50], right atrium
[48], coronary sinus
[52], or IVC (Figs.
17,
18A,
18B,
19A,
19B). Most frequent is an
isolated inconsequential PAPVR of the right upper lobe draining to the SVC.
This type of drainage, however, is frequent in patients who have a sinus
venosus type of atrial septal defect located high in the septum near the SVC
orifice
[54–56]
(Fig. 18A,
18B). This type of atrial
septal defect often goes undiagnosed because it does not produce
cardiovascular symptoms. In these patients, however, identification of the
associated PAPVR can lead to the diagnosis
[55].
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Fig. 17. —64-year-old man with partial anomalous pulmonary venous
return to azygos vein. Series of CT scans shows anomalous right upper lobe
vein (arrows) draining into dilated azygos arch (AZ).
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Fig. 18A. —48-year-old woman with partial anomalous pulmonary venous
return (PAPVR) to superior vena cava (SVC) associated with sinus venosus
atrial septal defect. Gradient-echo MR image shows anomalous right upper lobe
pulmonary veins (arrows) draining into SVC (S).
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Fig. 18B. —48-year-old woman with partial anomalous pulmonary venous
return (PAPVR) to superior vena cava (SVC) associated with sinus venosus
atrial septal defect. T1-weighted MR image shows sinus venosus atrial septal
defect (arrow). This uncommon type of atrial septal defect is often
associated with PAPVR.
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Fig. 19A. —21-year-old woman with scimitar syndrome. Chest radiograph
shows large curved vein (arrows) extending to diaphragm. Note
relatively small right lung with decreased pulmonary vascularity.
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Anomalous veins of the left lung most often drain the left upper lobe.
After entering the mediastinum, these pulmonary veins continue cephalad and
lateral to the aortic arch in a vertical vein that then joins the left
brachiocephalic vein (Figs. 20
and 21A,
21B). All PAPVRs are
left-to-right shunts, but the shunt is usually hemodynamically insignificant
[51]. This anomaly can be seen
as an abnormal finding on radiography
(Fig. 21A), suspected when the
anomalous vein is entered by an IV catheter
(Fig. 20), and revealed by CT
(Fig. 21B). Most often this
type of PAPVR is an incidental finding in adults with normal hearts. A
right-to-left shunt caused by reversal of flow in a left upper lobe PAPVR that
occurred after thrombosis of a brachiocephalic vein traversed by a central
venous catheter, a rare complication, has been reported
[53]. On cross-sectional
images at and cephalad to the level of the aortic arch, a left SVC
(Fig. 2) and a vertical vein
receiving a left-sided PAPVR (Fig.
21B) appear similar, but more caudal at the level of the left main
bronchus the appearance is different. Normally there is a single vessel, the
left superior pulmonary vein, ventral to the left main bronchus. With PAPVR,
the normal left superior pulmonary vein is absent so there is no vessel
ventral to the bronchus and the pulmonary veins of the left upper lobe that
can be followed to the anomalous vein in the aortopulmonary window
(Fig. 21B). With a left SVC,
there are two vessels ventral to the left main bronchus: the normal superior
pulmonary vein and the left SVC
[51] (Figs.
2 and
3A). Furthermore, with a left
SVC, the left upper veins drain into the normally positioned superior
pulmonary vein, and the left SVC can be followed to the coronary sinus
(Fig. 2).
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Fig. 20. —55-year-old woman with partial anomalous pulmonary venous
return from left upper lobe. Unusual position of left jugular IV catheter
(arrows) on radiograph led to venogram with opacification of
anomalous left pulmonary vein draining into right superior vena cava (S) via
vertical vein (white arrowheads) and left brachiocephalic vein
(black arrowheads).
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Fig. 21A. —66-year-old woman with partial anomalous pulmonary venous
return (PAPVR) from left upper lobe. Chest radiograph shows sharply defined
paraaortic opacity (arrows) that represents vertical vein connecting
anomalous left upper lobe pulmonary vein to brachiocephalic vein.
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Fig. 21B. —66-year-old woman with partial anomalous pulmonary venous
return (PAPVR) from left upper lobe. Series of CT scans show left upper lobe
PAPVR (long arrows) draining via vertical vein (short
arrows) into left brachiocephalic vein (arrowhead).
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A PAPVR draining into the IVC, portal, hepatic, or other veins below the
diaphragm in association with hypoplasia of the right lung has been called the
scimitar, venolobar, or hypogenetic lung syndrome
[57–62]
(Fig. 19A,
19B). The spectrum of
anomalies and of prognosis in patients with this syndrome is variable. Some
patients have severe cardiorespiratory symptoms and large left-to-right shunts
requiring surgery, but many others lead a healthy life without surgical
correction [58]. Associated
anomalies include many types of congenital heart disease but most frequent are
an atrial septal defect, systemic blood supply to the lung, extralobar
sequestration, horseshoe lung, and pulmonary arteriovenous malformation
[59]. The findings on chest
radiography often strongly suggest the diagnosis. The anomalous vein draining
into the IVC can be seen as a curved opacity that has been likened to a curved
Turkish sword or scimitar in addition to a small right lung and dextroversion.
However, other anomalous right pulmonary veins closely resembling scimitar
veins on chest radiographs have been reported, but these anomalous veins drain
to the left atrium rather than the IVC. This misleading appearance on chest
radiography has been termed the "pseudoscimitar syndrome." While
simulating a scimitar vein extending to the IVC on radiography, the actual
drainage to the left atrium is shown by cross-sectional imaging or angiography
[38,
63,
64]. Other anomalies have been
associated with the pseudoscimitar vein including a small right lung
[62,
63] and a sequestration
[62].
Total anomalous pulmonary venous return (TAPVR).—TAPVR has
been classified by the venous drainage routes into four types: supracardiac
(Figs. 22 and
23A,
23B) to the left
brachiocephalic vein, right SVC, or azygos vein; cardiac to the coronary sinus
or right atrium; infracardiac to the portal vein, ductus venosus, or right
atrium; and mixed [36]. TAPVR
is an admixture lesion with an obligatory interatrial communication through an
atrial septal duct or patent foramen ovale. Pulmonary vascularity is increased
and there is cyanosis. Supracardiac drainage to a vertical vein that extends
to the left brachiocephalic vein is most common. This results in the
"snowman" sign; the dilated vertical vein on the left and the
large superior vena cava on the right form the head of the snowman, and the
body of the snowman is formed by the heart
[65]
(Fig. 22). TAPVR is common
with asplenia (right isomerism). Infracardiac drainage, the least common type,
often results in early and severe congestive heart failure and can result in
lymphangiectasia caused by obstruction of venous return through the vein that
extends below the diaphragm. The diagnosis of TAPVR is usually made by
echocardiography, but CT angiography and MRI have been shown to provide
accurate anatomic information for preoperative planning
[7,
66–69].
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Fig. 22. —3-month-old cyanotic boy with total anomalous pulmonary
venous return and "snowman" sign. Chest radiograph shows rounded
superior mediastinum. Head of snowman is formed by large left vertical vein
and large right superior vena cava. Body of snowman is heart.
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Fig. 23A. —5-month-old boy with pulmonary atresia, atrioventricular
canal, and azygos continuation of inferior vena cava and total anomalous
pulmonary venous return draining into superior vena cava (SVC). T1-weighted MR
image shows left pulmonary vein (arrow) draining into anomalous
retrocardiac vein (v). Note large azygos vein (arrowhead) caused by
azygos continuation. EN = large endocardial cushion defect, A = aorta.
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Fig. 23B. —5-month-old boy with pulmonary atresia, atrioventricular
canal, and azygos continuation of inferior vena cava and total anomalous
pulmonary venous return draining into superior vena cava (SVC). Sagittal
T1-weighted MR image shows distal anomalous retrocardiac vein (v) that
receives all pulmonary veins and arches to join SVC (long arrows).
Note enlarged azygos arch (short arrows).
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For a list of the anomalies of the pulmonary veins, see Appendix 3.
Conclusion
Venous anomalies of the thorax are frequently shown on imaging studies. In
some cases, the diagnosis is based on a chest radiograph when a radiopaque IV
catheter takes an unusual but distinctive course, such as a catheter in a left
SVC. More often, venous anomalies are subtle and difficult to identify on
radiography, and, more important, some of these anomalies simulate
abnormalities in the thorax. These pseudolesions can be accurately diagnosed
noninvasively by cross-sectional imaging studies.
Complications in patient treatment related to some anomalies have been
reported. Patients with a left SVC and narrowing of the coronary sinus ostium
have presented difficulties in introducing pacemaker or defibrillator leads,
and surgical ligation of a single left SVC with an atretic coronary sinus
ostium has led to myocardial ischemia.
Discovery of PAPVR from the right upper lobe can lead to the diagnosis of
an atrial septal defect. This diagnosis can be significant because an
undiagnosed atrial septal defect predisposes the patient to paradoxical emboli
that can cause strokes and other ischemic events.
Congenital heart disease is routinely studied with echocardiography and
angiography, but both MRI and CT are increasingly capable of providing both
anatomic and functional information. The capability to provide detailed 3D and
volume-rendered studies is recognized as a unique contribution to both
diagnosis and treatment. Complex congenital heart disease is frequently
associated with venous anomalies so that knowledge of these anomalies is
essential for treating patients.
Radiofrequency ablation of arrhythmogenic pulmonary vein foci is being
performed with increasing frequency. CT and MRI are used before procedures to
identify venous anomalies and precisely display venous anatomy and, after
procedures, to quantify pulmonary vein stenosis.
Recognition of anatomic variations and anomalies has always been necessary
to make accurate diagnoses. Knowledge of thoracic vein anomalies has gained
increased significance because of continued advances in the capability of CT
and MRI to provide information for patient treatment.
,
,
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Top
Introduction
Superior Vena Cava
