Download Cardiac Malpositions

Cardiac Malpositions
An Overview Based on
Study of Sixty-five Necropsy Specimens
PAUL STANGER, M.D., ABRAHAM M. RUDOLPH, M.D.,
AND
JESSE E. EDWARDS, M.D.
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Levocardia, dextrocardia and mesocardia are general
terms indicating cardiac position only. They do not give any
indication of cardiac structure, body situs, or electrocardiographic findings. Levocardia denotes a left-sided heart; dextrocardia denotes a right-sided heart; and mesocardia
denotes a midline heart.
Cardiac displacement is the shifting of the heart within the
thorax by extracardiac factors such as a hypoplastic lung.
This has also been referred to in the literature as dextroposition, mesoposition or levoposition, depending on the
direction of the shift.
Inversion is an alteration in the lateral relationships of
asymmetric body structures so that a structure which normally lies on the right side of the body is situated on the left
and vice versa. Inversion may involve the entire body (situs
inversus) or only certain structures such as the great arteries.
Heterotaxy is abnormal arrangement of organs different
from the orderly arrangement of either situs solitus or situs
inversus, e.g., malrotation of bowel.
Transposition means that the aorta arises from the
morphologic right ventricle (RV), and the pulmonary artery
from the morphologic left ventricle (LV). With rare exceptions,2 there is aortic-mitral discontinuity. The aorta is
usually anterior to, but may be lateral to, the main
pulmonary artery.
Single L V or single R V is a situation in which one ventricle receives the entire portion of both atrioventricular valves
or a common atrioventricular valve. This also has been
termed double inlet left ventricle or double inlet right ventricle.
Double outlet right ventricle (DOR V) denotes both great
arteries arising from the morphologic right ventricle.
Usually neither semilunar valve has continuity with the
mitral valve (subaortic and subpulmonic conus).
Double outlet left ventricle (DOL V) denotes both great
arteries arising from the morphologic left ventricle. The conus anatomy in this situation is variable but is usually
bilate.rally deficient.
It should be noted that as used herein DORV differs from
the broader use proposed by Lev,' i.e., aorta and pulmonary
artery completely or almost completely arising from the
right ventricle regardless of semilunar valve mitral continuity. The latter definition focuses entirely on the position
of the great arteries. As such it includes cases of tetralogy
with severe overriding of the aorta and excludes those cases
of Taussig-Bing anomaly in which a substantial portion of
the pulmonary artery overrides the left ventricle.6
Cardiac malformations associated with cardiac malpositions are so complex that even angiographic studies may not
afford as accurate information as direct examination of
necropsy specimens. This communication will attempt to
outline a systematic approach to cardiac malpositions based
upon necropsy studies of 65 cases. Where possible, morphologic features characteristic of the entities are correlated with
clinical, roentgenographic, electrocardiographic and
catheterization findings. Embryologic considerations are
also discussed.
The problems of terminology in complex congenital cardiac anomalies, particularly those with abnormalities of
position, are well known. For an excellent discussion, the
reader is referred to the recent article by Wilkinson and
Acerete.5 Rather than creating new terms, the authors
selected existing terms which they considered the least ambiguous and least confusing. We have used the selected terms
as defined in that article with three exceptions. 1) The
asplenia and the polysplenia syndromes are sufficiently distinct to warrant separate categories, rather than grouping
them as situs ambiguus. The reasons for this are discussed in
the sections dealing with these entities. 2) Transposition
herein refers only to transposition of the great arteries as
defined by Van Praagh,2 i.e., aorta arising from the
morphologic right, and pulmonary artery from the
morphologic left, ventricle. 3) We concur with Van Praagh in
classifying Taussig-Bing anomaly as a form of double outlet
right ventricle with a subpulmonic ventricular septal defect.3
Definitions
Cardiac malposition. Normally the major portion of the
heart lies to the left of midline. For the purposes of this
study, any heart other than a left-sided heart in a situs solitus
individual represents a cardiac malposition. This definition
refers not only to the cardiac position but also the appropriateness of the cardiac position in relation to the total
body situs. A right-sided heart is clearly unusual even though
it may be appropriate in an individual with situs inversus. A
left-sided heart, however, is inappropriate in situs inversus
and is also an example of cardiac malposition.
For theoretical reasons to be discussed later, all cases of
asplenia and polysplenia are regarded as having cardiac
malpositions.
From the Cardiovascular Research Institute and Department of
Pediatrics, University of California, San Francisco, California, and the
Departments of Pathology, United Hospitals-Miller Division, St. Paul and
University of Minnesota, Minneapolis, Minnesota.
Supported by Public Health Service Research Grant HE 05694, National
Heart Institute Research Training Grant HE 05570, Program Project Grant
HL 06285 and Training Grant HL 05886 from the NHLBI; the St. Paul
Foundation and the Bremer Foundation, St. Paul, Minnesota.
Address for reprints: Paul Stanger, M.D., Cardiovascular Research
Institute, University of California, San Francisco, California 94143.
Received September 13, 1976; revision accepted March 11, 1977.
General Features of Cardiac Anatomy
In describing an anatomic cardiac complex, three
segments must be considered: 1) the total body configuration or situs, including the atria; 2) the ventricular positions
159
160
CIRCULATION
and connections to the atria; 3) the positions of the great
arteries and connections to the ventricles.
Anatomic Features of Body Configuration or Situs
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Although many paired structures of the body are normally
symmetrical (e.g., brain, kidneys, ureters), several paired
viscera are asymmetric (e.g., tracheobronchial tree, lungs,
atria). The liver, although a solitary organ, has two unequal
lobes. Solitary structures, such as the spleen and gastrointestinal tract, have a specific rightward-leftward orientation
within the abdominal cavity. The positions of these asymmetric structures express the situs or body configuration of
an individual. Classically, these have been divided into two
asymmetrical body configurations: 1) situs solitus or conventional normal, and 2) situs inversus or complete inversion
(fig. 1). In situs solitus, the right lung has three lobes and an
eparterial bronchus while the left has two lobes and a
hyparterial bronchus. The larger lobe of the liver is on the
right and the stomach and spleen are on the left. The
morphologic left atrium is posterior and leftward. In situs inversus, the left lung has three lobes and the right lung has
two. The tracheobronchial tree and atria are similarly inverted. The larger lobe of the liver is on the left while the
stomach and spleen are situated on the right.
In addition, two symmetrical body configurations have
been found to be associated with splenic anomalies. Asplenia
syndrome is characterized by bilateral right-sidedness or
duplication of right-sided structures6 10 including bilateral
right lungs with bilateral eparterial bronchi. Both atria
morphologically resemble right atria, the liver is
symmetrical and horizontal and the stomach tends to be near
C
Asplenia
it Polysplenia
..
FIGURE 1. A natomic features of thoracic and abdominal organs
in each of the body configurations. Organs outlined in dots show
variation in position.
VOL 56, No 2, AUGUST 1977
the midline. Polysplenia syndrome is characterized by a
tendency toward bilateral left-sidedness 11, 12 which may include bilateral left atria and bilateral left lungs with bilateral
hyparterial bronchi. The latter is the most constant feature
of symmetry.'2 The abdominal organs tend less toward
symmetry than in asplenia. Although the liver may have two
roughly equal halves, the major portion often lies to one side
of the abdomen. Similarly, the stomach is seldom midline
and considerable abdominal heterotaxy is often present. The
multiple spleens in this condition are situated adjacent to the
stomach and usually resemble a cluster of grapes or a bilobed or tri-lobed spleen. In a given case, the size of the individual spleens may vary but each is much smaller than a
normal spleen. This is in contrast to accessory spleens
wherein one or more spleniculi are present in addition to a
normal-sized spleen. The absence of a spleen or the presence
of multiple spleens also may be regarded as additional
manifestations of the bilateral right-sidedness or leftsidedness, respectively.'2 Although there may be some
overlap of the anatomic features of asplenia and polysplenia
syndromes, the differences are considerably more frequent
and are sufficiently consistent to warrant designations as
separate body configurations.
Cases of isolated absence of the spleen, i.e., without
associated visceral and cardiac anomalies, are herein
regarded as not having the developmental complex of
asplenia syndrome.
Anatomic Features of Cardiac Chambers
The morphologic features of right and left atria are listed
in table 1. Van Praagh has stated that the atria follow the
body situs; however; he designated the atria and situs of
asplenia as uncertain.13, 14 In our experience, the
morphologic atria conform to the situs even in cases of
asplenia or polysplenia, i.e., bilateral morphologic right atria
in asplenia and a distinct tendency toward bilateral left atria
in polysplenia. The atrial symmetry has also been reported
by Van Mierop.6' 12
The morphologic features of right and left ventricles are
listed in table 1 and illustrated in figure 2. When the
morphologic right ventricle is situated on the right and the
morphologic left ventricle is situated on the left, the ventricles are considered to be noninverted and the result of a
d-bulboventricular loop.'4 Conversely, when the morphologic
right ventricle is on the left and the morphologic left ventricle
is on the right, the ventricles are considered to be inverted
and the result of an I -bulboventricular loop.14 Regardless of
where the morphologic right ventricle lies, the infundibulum
is almost always the most anterior cardiac structure and connects with the anterior great artery. The left ventricular outflow tract lies posterior to the infundibulum and connects
with the posterior great artery. The terms noninversion and
inversion of the ventricles correspond to the d- and I-loops in
the nomenclature of Van Praagh."4
The atrioventricular valve of each ventricle is
characteristic of that ventricle. While the atrioventricular
node and the initial segment of the bundle of His lie in the
right atrial wall, the branches of the bundle follow the
respective ventricles.'5'I
A d-loop is normal for situs solitus and an 1-loop for situs
inversus. Van Praagh termed these concordant loops.
CARDIAC MALPOSITIONS/Stanger, Rudolph, Edwards
161
TABLE 1. Anatomic Features of Cardiac Chambers*
Morphologic left
Morphologic right
Atria
Ventricles
Lies on same side as trilobed lung.
Receives the inferior vena cava.
Crista terminalis.
Pectinate muscles in the atrial
appendage.
Fossa ovalis lies on the right side of the
atrial septum.
Lies on same side as bilobed lung.
Tricuspid valve.
Trabeculated septum with coarse,
parallel trabeculations.
Crista supraventricularis separates
tricuspid and semilunar valves.
Papillary muscle of the conus.
Right branch of the bundle of His.
Mitral valve.
Smooth walled septum with fine,
oblique trabeculations in apex.
Fibrous continuity between mitral and
semilunar valves.
No septal papillary muscles.
Left branch of the bundle of His.
Trabeculated appendage but without
parallel muscles of pectinate type.
Interatrial ostium II on the left side of
atrial septum.
*The above anatomic features are the usual for the atria and ventricles. Individual chambers may lack one or more of the usual
features and identification of the chamber is presumptive and based on how many of the features are present. In rare cases identification may be impossible.
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Discordant loops are an I-loop in situs solitus and a d-loop in
situs inversus. With rare exceptions,17 discordant loops are
associated with abnormally related great arteries. We have
chosen to designate all cases of splenic anomalies as having
discordant loops because symmetry of the atria, by definition, precludes connection with the appropriate morphologic
ventricles.
great arteries, the ascending aorta sweeps to the left and lies
to the left of the main pulmonary artery. These lateral
relationships apply to normally related great arteries,
transposed great arteries, and to situations in which both
great arteries arise from one ventricle. In addition, there are
transpositions in which the aorta lies directly in front of the
pulmonary artery, a situation which has been designated as
a-trans (for anterotransposition).'9
Anatomic Features of the Great Arteries
The anatomy of the great arteries may best be defined in
terms of their lateral interrelationships and ventricular attachments. Normally attached great arteries are characterized by the pulmonary artery arising from the right ventricle and the aorta from the left ventricle. In this situation,
the origin of the pulmonary artery lies anterior to the origin
of the aorta. As the infundibulum is longer than the left ventricular outflow tract, the pulmonary valve is usually more
cephalad than the aortic. In transposition of the great
arteries, the origin of the aorta usually lies anterior to that of
the pulmonary artery and arises from the infundibulum. As a
result, the aorta is the more cephalad semilunar valve and
there is no fibrous continuity between the aortic and mitral
valves. The latter was considered by some authors an essential feature of transposition;18 however, exceptions have been
found.2
The lateral interrelationships of the great arteries are best
described using "d" and "I" terms. With "d" related great
arteries, the ascending aorta sweeps toward the right and lies
to the right of the main pulmonary artery. With "I" related
Nomenclature
The original Van Praagh nomenclature", 20 has been particularly useful in describing complex cardiac anatomy and
in focusing attention on the embryological development of
complex anomalies. Certain exceptions, however, did not
conform to the loop rule and made use of the original Van
Praagh nomenclature in these cases difficult, e.g., situs
solitus with complete transposition but with the great
arteries in the I-transposition configuration. The
nomenclature was subsequently enlarged so that in situations
where the great artery interrelationship might be confused by
the designation d- or 1-transposition and in double outlet
right ventricle, the term d- or 1- malposition was used.21 22
More recently, Van Praagh has introduced a
nomenclature modified from the original. The modification
is an entirely symbolic representation of the basic cardiac
structure, designating the situs, ventricular interrelationships and great artery interrelationships in that sequence.23' 24 Although the symbolic representation may
prove quite useful for pediatric cardiologists and cardiac
FIGURE 2. Diagrammatic representation of the
features of morphologic right (RV) and left ventricles (LV). SL septal limb of the crista supraventricularis, PL parietal limb, PMC papillary
muscle of the conus, PA = pulmonary artery,
S -septal tricuspid leaflet, MS membraneous
septum, Ao Aorta, AM anterior mitral leaflet.
=
=
162
CIRCULATION
pathologists, we find it of limited value in trying to convey information to other physicians who may also be involved in
the patient's care - surgeons, house officers, referring
physicians, etc. Each physician requires a lengthy explanation of both the anatomy and the "code," a quantum of information which may not be readily absorbed in a single
sitting.
Consequently, we have sought to use Van Praagh's
segmental approach but to modify it so that a) existing,
easily understood terms are used; b) only a few terms are abbreviated and each abbreviated term is self-explanatory; c)
the terms describe the interrelationships within a given segment as well as connections with the previous segment. The
terms used are:
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Situs
solitus
inversus
asplenia
polysplenia
Ventricles
d- or 1-loop
d- or 1-single RV
d- or 1-single LV
Great Arteries
d- or 1-normal
d- or 1- or a-trans
d- or l-DORV
d- or I-DOLV
d- or 1-malposition
truncus
The segmental set is written as follows: situs/ventricles/great arteries, e.g., inversus/d-loop/d-trans.
The situs portion of the segmental set implies the atrial
anatomy since there is visceroatrial concordance even in
cases of asplenia or polysplenia.
The ventricular segment includes three terms which
describe three distinct aspects of ventricular anatomy; i.e.,
ventricular interrelationships, the connections to the atria
and the position of the ventricular portion of the heart within
the thorax. As in the Van Praagh nomenclature, a "d"symbol indicates that the morphologic right ventricle lies to
the right of the morphologic left ventricle, while an "1"-
VOL 56, No 2, AUGUST 1977
symbol indicates that the morphologic right ventricle lies to
the left of the morphologic left ventricle.
The second term in the ventricular designation has been
modified from the original Van Praagh nomenclature in
order to permit description of the atrial connections. If there
are two ventricles and atrial-ventricular connections are of
the simple type, i.e., right-sided atrium to right-sided ventricle, and left-sided atrium to left-sided ventricle, then no
modification is necessary and the terms d-loop or I-loop are
used. These designations are also used for cases in which one
of the atrioventricular valves straddles the ventricular septum. If, however, both atria connect to one ventricle this is
designated as d or 1-single LV or RV. The third portion of
the ventricular segment describes the position of the ventricular portion of the heart within the thorax. The latter may
vary considerably for a given bulboventricular loop in a
given situs, e.g., a d-loop in situs solitus may have the ventricular portion of the heart in the right hemithorax (R), left
hemithorax (L), or in midline (M) (fig. 3). The variable position within the thorax is the result of varying degrees of
pivoting of the bulboventricular loop toward the opposite
hemithorax in early fetal development. Normally, a d-bulboventricular loop pivots into the left hemithorax. Failure to
complete this pivoting is particularly common with discordant loops. Clearly, the positional term may be deleted if the
ventricular position is appropriate for the type of bulboventricular loop, e.g., left hemithorax for a d-loop and right
hemithorax for an 1-loop.
The great artery attachments to the ventricles may be
described as normal (pulmonary artery from RV, aorta from
LV), transposition (aorta from RV, pulmonary artery from
LV), DORV (double outlet right ventricle), DOLV (double
outlet left ventricle), truncus (truncus arteriosus) or
malposition21' 22 (a nonspecific term indicating an abnormal
spatial relation between the aortic and pulmonary valves).
Each of these is designated d- or 1- to indicate the lateral in-
solitus / d-loop (R)
solitus / d- loop (M)
solitus / d - Ioop (L)
-loop (R)
solitus/1-loop (M)
solitus / I-loop (L)
solitus /
FIGURE 3. Diagram of cardiac positions with concordant and discordant bulboventricular loops. A 11 six diagrams are
of situs solitus. A, B and C each have concordant loops (d-loops); however, in A the heart is in the right hemithorax
because offailure of the bulboventricular loop to pivot into the opposite hemithorax. B) Midline heart associated with
partial pivoting. C) Complete pivoting into the left hemithorax, i.e., normal cardiac position for d-loop in situs solitus.D,
E and F each contain discordant loops (I-loops) with complete, partial and no pivoting, respectively. Concordant loops
with partial pivoting and a sagitally oriented ventricular septum tend to show mesocardia. In contrast, discordant loops
with partial pivoting and a sagittally oriented septum are often more prominent on the side of the morphologic right ventricle.
163
CARDIAC MALPOSITIONS/Stanger, Rudolph, Edwards
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terrelationships of the great arteries. In cases of transposition of the great arteries in which the aorta lies directly in
front of the pulmonary artery and there is no clear d- or
1-relationship, the designation a-trans (for anterotransposition) is used. The great artery lateral interrelationships need
not correspond to the bulboventricular anatomy, e.g., a
d-loop may be associated with great arteries in the 1-position.
The following are examples of the use of this
nomenclature in complex cardiac lesions.
1) Taussig Bing: solitus/d-loop/d-DORV with subpulmonic VSD.
2) Corrected transposition in situs inversus: inversus/
d-loop/d-trans.
3) Complete transposition in situs solitus with 1-positioned great arteries (an exception to the loop rule): solitus/d-loop/l-trans.
4) Complicated double outlet right ventricle (situs solitus
with ventricular inversion and double outlet right ventricle):
In this example, the d-prefix indicates that the aorta arises to
the right of the pulmonary artery: solitus/l-loop/d-DORV.
Obviously, in each of these cases the associated malformations (VSD, ASD, stenosis, etc.) must be described. If the
conus anatomy is the usual for a given great artery attachment, no special mention is made.
The great majority of patients do not have complex cardiac anomalies or cardiac malposition. Consequently,
segmental designation is unnecessary in patients with a combination of situs solitus, a d-loop and levocardia. If, however,
any aspect of cardiac malposition is present, or there is abnormal connection of the ventricles to the atria or great
arteries, the entire designation is used.
Clearly, no nomenclature can be all encompassing. Rare
and bizarre cases such as the criss-cross hearts described by
Anderson et al.2' require special descriptions. Although these
authors favored the terms discordant and concordant ventricles as proposed by Kirklin and coworkers,2' such terms
are not applicable in the splenic syndromes since the
symmetrical atria preclude concordance.
We favor our method of describing cardiac anatomy
because it uses only a few self-explanatory abbreviations and
is quite descriptive. House officers and others not well versed
in complex cardiac anatomy can understand it after only a
brief explanation.
Pathologic Material
Sixty-five necropsy specimens exhibiting cardiac malposition were found among approximately 3,000 specimens in
the Cardiovascular Registry of the United Hospitals, Miller
Division, St. Paul, Minnesota. A summary of the body
situses and the cardiac positions may be found in table 2. The
anatomic features of the 65 cases with malposition are listed
in table 3. The tabulation includes the situs and the structure
of the cardiac chambers and great arteries as well as the
associated intracardiac and vascular anomalies. It is apparent from table 3 that each situs is associated with a
relatively small number of structural complexes but that the
associated intracardiac and vascular anomalies vary
markedly.
In most cases the lung fissure patterns were those expected for
the situs. There were, however, sufficient variations due to incomplete and/or accessory fissures to make this an unreliable method of assessing lung morphology. In contrast
the pulmonary arterial - tracheobronchial interrelationships almost always reflected the situs. This interrelationship and bronchial branching patterns were also used in
determining the number of lobes.
Situs Solitus
There were twelve cases of dextrocardia in situs solitus.
Six of these cases exhibited the normal cardiac complex of
situs solitus, i.e., noninversion of the ventricles and normally
connected great arteries (solitus/d-loop/d-normal). Dextrocardia in five of these cases was the result of displacement of
the heart (dextroposition) associated with a hypoplastic
or absent right lung. The sixth case exhibited dextrorotation
(solitus/d-loop (R)/d-normal). Associated cardiac
anomalies were found in four of these six cases.
The remaining six cases exhibited ventricular inversion
and transposition of the great arteries (solitus/l-loop (R)/
1-trans) or corrected transposition in situs solitus. In addition
to the six cases of corrected transposition in situs solitus with
dextrocardia, there were nineteen cases of corrected transposition with levocardia, i.e., without malposition, a distribution similar to that in previous reports.262' Ventricular
inversion is a feature common to all cases of corrected
transposition in situs solitus; however, the presence of dextrocardia or levocardia appears related to the degree of
pivoting of the bulboventricular loop. The latter may best be
characterized by the orientation of the ventricular septum.
When dextrocardia was present, the ventricular chambers
and septum were oriented in typical inverted fashion as illustrated in figure 4A- 1. The ventricular septum lay oriented
toward the right in a plane midway between coronal and
sagittal, and the aorta was medially situated. With levocardia, the ventricles were incompletely pivoted and oriented as
in figure 4A-2 with the septum perpendicular or nearly
perpendicular to the coronal plane. The aorta was displaced
toward the left and formed the shoulder seen in chest roentgenograms. The greater portion of the heart lay in the left
hemithorax and the apparent cardiac "apex" was formed by
the lateral convexity of the morphologic right ventricle. The
above represent the two most common orientations of the
ventricles and ventricular septum, and were the only types in
this series; however, other forms have been described2' (see
fig. 3).
Situs Inversus
There were thirteen cases of situs inversus which included
eight with concordant loops. Of these, three had normal
hearts (inversus/l-loop/l-normal), three had double outlet
TABLE 2. Cardiac Position and Situs in Approximately 3000
Specimens
Situs
Dextrocardia
Mesocardia Levocardia Malposition
Solitus
Inversus
Asplenia
Polysplenia
Total
12
11
11
9
'3000
7
2
5
8
12
13
23
17
65
CI RCU LATI ON
164
VOL 56, No 2, AUGUST 1977
TAiBLE 3. Anatomic Featurcs
Case
no.
\ge
Sex
2
7y
lrm
16(1
M solituis / d-loop (L) / d-normal
M solitus / d-loop (L) / d-normal
4
5
6
Segmental set
Cardiovascular anomalies
Cardiac _
position
SVC APVC
Other
Situs Solitus
Tricuspid atresia, bifid apex
R
R**
Total
R**
R
(RSVC)
VSD, ASD
R (i2
R**
Anomalous LPA from RPA
R**
R
R**
PDA
R
3m
3m
F solitus / d-loop (L) d-normal
M solitus / d-loop (L) d-normal
M solituis / d-loop (L) / d-normal
7fv
F
R
R
ay
F
F
R
R
R
R
R
R
R
R
R
RQ
R
R
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7
8
14y
9
10
11
3w
12
2y
13
14
15
16
17
18
19
20
21
22
35y
23
7y
7y
solitus / d-loop (R) / d-normal
solitus / 1-loop (R) / I-trans
solitus / 1-loop (R) / 1-trans
M solitus / I-loop (R) / 1-trans
F solitus / 1-loop (R) / I-trans
F solitus / 1-loop (R) / I-trans
M solitus / 1-loop (R) / 1-trans
2y
F
F
M
M
M
F
M
F
F
M
inversus / 1-loop (R) / 1-normal
inversus / 1-loop (R) / I-normal
inversus / l-loop (R) / 1-normal
inversus / 1-loop (R) 1-DORV
inversus / 1-loop (R) 1-DORV
inversus / I-loop (R) /I-DORV
inversus / 1-loop (R) / 1-trans
inversus / I-loop (R) / 1-trans
inversus / d-loop (R) / d-DORV
inversus d-loop (L) / d-DORV
R
R
R
R
R
R
R
R
R
L
14y
F
inversus
24
15m
25
ly
F
F
inversus
inversus
40y
65y
gd
7y
45y
10d
7m
26
27
5m
28
29
30
1I2d
ly
/
/
M asplenia /
M asplenia /
M asplenia /
F asplenia
F asplenia /
F asplenia /
M asplenia /
M asplenia /
L
d-loop (R)
/
d-trans
R
L
d-loop (L)
/
d-trans
L
R
L
d-loop (R) d-trans
/
L
Asplenia
L
1-loop (R) /1-DORV
1-loop (R) /1-DORV
R
R
1-loop (M) / 1-trans
I-loop (R) / 1-trans
I-loop (R) /1-trans
l-loop (R) / l-trans
M
R L
R
R
R
RL
R
R L
1-loop (R)
1-loop (R)
31
2m
6m
7wv
32
33
3w
2m
34
16m
M asplenia / I-loop (M)
35
36
4y
23m
37
38
19y
10d
M asplenia /
F asplenia /
M asplenia /
F asplenia /
39
40
17m
6h
41
42
43
lOy
44
2y
L
/
I-trans
1-trans
R
R
R L
R L
/
1-trans
M
R L
/
Partial
Total§
Total
(RSVC)
Total
1-loop (M) / 1-DORV
d-loop (L) / d-DORV
L
R L
R L
d-loop (L) / d-trans
d-loop (R) / d-trans
L
R
R L
R L
M asplenia / d-single LV (L) / d-trans
M asplenia / d-loop (R) / d-trans
R
L
RL
7d
M asplenia / d-single LV (R) / d-trans
R
ld
M asplenia / d-single LV (R) / d-trans
M asplenia / d-single LV (L) / d-normal
M asplenia / I-single LV (M) / 1-trans
R
M
Totalt
Total
(LSVC)
R L
(LSVC)
Total
(RSVC)
Total
(RSVC)
Total
(RSVC)
Total
L
L
RL
M
R L
(LSVC)
Total
(LSVC)
Total
(RA)
Hypoplastic R lung
2
3 2
3 2
Primary pulm. hypertension
2 3
AV canal
AV canal, inf. PS,
canal,
canal,
canal,
canal,
pulm.
pulm.
pulm.
pulm.
Absent R lung
R bronchusuis
Hypoplastic R lung,
L lobar emphysema
3 2
3 2
3 2
3 2
3 2
Juxtaposed atrial
appendages
2 3
2 3
2 3
2 3
2 3
2 3
2tt 3tt
2 3 Bilateral eparterial
2 3
2 3
2 3
bronchi
Accessory spleen
3 3
3 3
atresia,
atresia,
atresia
atresia,
3 3
3 3
3 3
AV canal, pulm. atresia,
AV canal, PS, cor
triatriatum
AV canal, pulm. atresia,
PDA,
AV canal, PS,
AV canal, mild PS,
3 3
AV canal, PS,
AV canal, pulm. atresia,
3 3
3 3
AV canal, PS,
AV canal, pulm. atresia,
PDA,
AV canal, PS, PDA,
3 3
3 3
AV
AV
AV
AV
Miscellaneous
Hypoplastic R lung
3 2
VSD, ASD, PDA
VSD, valvar and inf. PS
VSD, valvar and inf. PS
ASD
VSD, PDA
AV canal
VSD, ASD, PDA, valvar and
subvalvar PS
ASD, subvalvar PS,
subvalvar AS
VSD, ASD, PS
VSD, pulm. atresia, PDA
L
L
L
3 2
12
VSD, inf. PS., anomalous
ufmbilical vein
VSD, ASD, pulm. atresia
VSD, subpulm. atresia,
Valvar PS
VSD
Subvalvar PS, cleft mitral
Cor triatriatum, Multiple
VSDs
VSD, ASD, subvalvar PS,
PDA
Situs Inversus
L
L
L
L
per lung
R L
3 3
Rudimentary spleen
3 3
3 3
3 3
AV canal, no PS, subvalvar
AS, bilateral PDAs
AV canal, PS,
3 3
AV canal, PS, cor
triatriatum mild
3
Bilateral bronchosuis
3 3
3
-
right ventricle (inversus/l-loop/l-DORV), and two had
transposition of the great arteries in situs inversus
(inversus/l-loop/l-trans). There were five cases of situs inversus with discordant loops. Three of these had corrected
transposition of situs inversus (inversus/d-loop/d-trans) and
two had double outlet of the noninverted right ventricle in
situs inversus (inversus/d-loop/d-DORV). Those cases with
concordant loops all exhibited dextrocardia, i.e., cardiac
position appropriate for that situs. The cases with discordant
loops demonstrated variation in cardiac position. The combination of situs inversus and a d-loop may be regarded as a
mirror image of situs solitus with an 1-loop, and similar but
inverted anatomic features were found.
When the discordant ventricles were associated with complete pivoting, the cardiac apex was in the hemithorax opposite to that appropriate for the situs. In these cases the
ventricular septum was oriented toward the apex (fig. 4A-1
and B- 1). With incomplete pivoting, the ventricles were
separated by a septum oriented in the sagittal plane, the apparent apex was formed by the convexity of the morphologic
right ventricle, and the characteristic shoulder was formed
by the aorta and infundibulum (fig. 4A-2 and B-2). Note that
in situs inversus the shoulder is on the right side as one might
expect.
Asplenia
There were 23 cases of asplenia in the present series; 11
with dextrocardia, seven with mesocardia, and five with levocardia. All were regarded as cardiac malpositions as no appropriate cardiac position could be assigned in a
symmetrical situs.
There were 21 specimens in which lungs were attached and
each showed bilateral eparterial bronchi and bilateral right
CARDIAC MALPOSITIONS/Stanger, Rudolph, Edwards
Case
no.
Age
45
2m
46
47
4w
33d
48
3w
49
50
51
9y
7y
27d
52
53
54
55
56
57
2d
18y
16h
2m
Downloaded from http://circ.ahajournals.org/ by guest on June 15, 2017
58
59
60
61
62
63
64
65
2m
3m
4w
low
5y
18m
lm
ld
3'y
10y
Cardiovascular anomalies
Cardiac
position
SVC
APVC
LV (M) / 1-trans
LV (M) / 1-trans
LV (L) / 1-trans
LV (M) / 1-trans
M
R L
M
L
M
Total
(RSVC)
R L
R L
Total
polysplenia / d-loop (R) / d-normal
polysplenia / d-loop (L) / d-normal
polysplenia / d-loop (L) / d-normal
polysplenia / d-loop (L) / d-normal
polysplenia / d-loop (R) / d-normal
polysplenia / d-loop (R) / d-normal
polysplenia / d-loop (R) / d-normal
polysplenia / d-loop (L) / d-DORV
polysplenia / d-loop (L) / d-DORV
polysplenia / d-loop (R) / d-DORV
polysplenia / d-loop (L) / d-DORV
polysplenia / d-loop (L) / d-trans
M polysplenia / 1-loop (R) / 1-normal
F polysplenia / I-loop (L) / 1-normal
F polysplenia / l-loop (R) / I-normal
F polysplenia / 1-loop (R) / 1-normal
F polysplenia / I-loop (R) / I-DORV
R
L
L
Sex
Segmental set
asplenia / 1-single
M asplenia / 1-single
F asplenia / 1-single
M asplenia / 1-single
F
M
M
F
F
F
F
M
M
M
M
F
M
R L
Polysplenia
L
R
R
R
L
L
R
R
R
R L
R
R L
R L
R
R
R
R L
L
R L
R L
L
R
R L
R
R
L
L
L
R
L
(RSVC)
Total
(LSVC)
Partial
Partial
Partial
Partial
Partial
Partial
Total
Partial
Partial
Partial
Total
Partial
Total
Total
L
Partial
Other
165
No. lobes*
per lung
R L
AV canal, PS,
3 3
AV canal, PDA, no PS
AV canal, PS,
AV canal, Ps
3 3
3 3
3 3
ASD, PDA,
PS, primum ASD, sub AS
AV canal, ASD, PDA, subvalvar AS, inter. IVC
ASD, aortic atresia,
ASD, subvalvar AS,
Miscellaneous
2 2
R bronchusuis
3 3
Common atrium
3ft 2tf
2tt 2tt
2 2 Common atrium
ASD
2 2
VSD, ASD, interrupted IVC
2 2
VSD, ASD, interrupted IVC
2 2
VSD, ASD, interrupted IVC
2 2
VSD, ASD, PDA, coarct,
2 2
interrupted IVC
AV canal, ASD, PDA,
3 3
subvalvar AS
VSD, AS cleft mitral,
2 2
sub PS
ASD, PDA, VSD,
2 2
interrupted IVC
AV canal, ASD, PDA,
2 2
interrupted IVC
AV canal, ASD, PDA,
2 2
cor triatriatum
VSD, interrupted IVC,
5ff 3ff
coarct
AV canal, interrupted IVC,
2 2
ASD
patterns and relationships with pulmonary arteries.
*Lung morphology as determined not only by fissure pattern but by bronchial branching
**Cardiac displacement due to extracardiac forces.
tRUPV to innominate vein; remaining pulmonary veins connect to portal vein.
§Connect to mesenteric vessels.
ftFrom necropsyVSD
report. Lungs and tracheobronchial tree not available for inspection.
= ventricular septal defect; ASD = atrial septal defect; PDA = patent ductus arteriosus; PS = pulmonic stenosis; AS = aortic
Abbreviations:
=
stenosis; Pulm pulmonary; AV canal = atrioventricular canal; IVC = inferior vena cava; SVC = superior vena cava; RPA = right pulmonary artery;
LPA = left pulmonary artery; R = right; L = left;®orr'D = right or left superior vena cava connecting to coronary sinus. If no circle the superior vena
cava connects to the ipsilateral atrium.
bronchial branching patterns. Fissures were a less reliable indicator of lung symmetry since not all lungs externally
showed a bilateral right pattern.
The cardiac anomalies associated with asplenia were: a)
anomalous systemic venous connection; b) large atrial septal
defect; c) atrioventricular canal; d) common ventricle or
large ventricular septal defect as part of the A-V canal; e)
transposition of the great arteries; f) severe pulmonic
stenosis or atresia; g) anomalous pulmonary venous connection; and h) cardiac malposition.
In all cases, both atria bore resemblance to right atria
(right atrial isomerism). Two large interatrial communications were commonly found. The first was an atrial septal
defect of the foramen ovale type. The fossa ovalis (a right
atrial structure) was usually present; however, the valve of
the foramen ovale (a left atrial structure) was absent. The
second interatrial communication was the atrial portion of
the complete atrioventricular canal. Both defects were usually quite large with only a strand of septal tissue separating
them so that functionally there was a common atrium (fig. 5).
There were two ventricles in 14 cases and a single ventricle
in nine cases. All cases had a complete atrioventricular
(A-V) canal. When two ventricles were present, the intraventricular portion of the A-V canal was sufficiently large to
result in a hemodynamic common ventricle with a rudimentary septum. When two ventricles were present, there was
commonly inversion of the ventricles (nine of fourteen
cases).
Severe pulmonic stenosis or atresia was found in all but
two cases and was usually of both the subvalvar and valvar
types. Transposition of the great arteries was found in 19
cases, double outlet right ventricle in three cases, and normally related great arteries in only one case.
Anomalous systemic venous connection was also a common feature. Twenty cases exhibited bilateral superior vena
cavae and in each case right and left superior vena cavae connected directly to their respective atria. The inferior vena
cava terminated in either atrium.
Anomalies of pulmonary venous connection occurred in
16 of the 23 cases of asplenia. The majority of these were
total anomalous pulmonary venous connection. The sites of
connection of the anomalous pulmonary veins were the portal system or a superior vena cava, i.e., anastomoses with
vessels derived from the umbilicovitelline or anterior cardinal systems, respectively.
Thirteen of the cases of asplenia in the present series (cases
28-33, 35, 37, 40, 43-45 and 48) have been reported
previously.9
Polysplenia
There were 17 cases of polysplenia in the present series;
nine with dextrocardia and eight with levocardia.
Some, if not all, of the features of bilateral left-sidedness
were found in each case. These included a tendency toward
bilateral left atria and bilateral left lungs. There were 14
specimens in which the lungs were available and 12 showed
bilateral hyparterial bronchi and bilateral left bronchial
branching patterns. The remaining two specimens showed
bilateral eparterial bronchi and bilateral right bronchial
A.
VOL 56, No 2, AUGUST 1977
CIRCULATION
166
B
Situs Solitus
Situs
The cardiovascular manifestations of polysplenia included: a) anomalous systemic venous connection; b)
anomalous pulmonary venous connection; c) atrial septal
defects; d) ventricular septal defects; e) double outlet right
ventricle; f) left-sided obstructive lesions; and g) cardiac
malposition. In contrast to asplenia, transposition of the
great arteries and pulmonic stenosis were unusual.
Anomalies of the systemic venous drainage may involve
the superior and/or inferior vena cavae. In eight cases of
polysplenia, bilateral superior vena cavae connected directly
to their respective atria, while in two cases the second
superior cava connected to the coronary sinus. Nine cases
also exhibited interruption of the hepatic portion of the inferior vena cava with drainage into a superior vena cava by
the hemiazygos or azygos system. When interruption of the
inferior vena cava was present, the hepatic veins drained
directly into one or both atria. The atrium into which the inferior vena cava drained, either directly or by the azygos
system, received most of the systemic venous return and we
have designated this the systemic venous atrium.
Often both atria morphologically resembled left atria (left
atrial isomerism) and each contained a smooth-walled atrial
appendage. Both sides of the atrial septum frequently bore
resemblance to the normal left atrial aspect of the atrial septum (septum primum) and in these cases the foramen ovale
was absent (fig. 6).
Anomalous pulmonary venous connection was found in 15
cases. Eleven were partial with the right pulmonary veins
connecting directly to the right-sided atrium. There were
four cases of total anomalous pulmonary venous connection
and in each the veins connected with the systemic venous
atrium directly or through a confluens.
Defects of the atrial and/or ventricular septum were present in all 17 cases of polysplenia. There were 12 specimens
with ventricular communications; in five the ventricular septal defect was part of an atrioventricular canal and in seven it
was a discrete lesion. Fifteen specimens had one or more
defects of the atrial septum. In one the defect was of the ostium primum type, and in two the atrial septum was completely lacking. Twelve specimens exhibited atrial septal
defects which were the result of fenestrations or deficiencies
Inversus
6 cases
Downloaded from http://circ.ahajournals.org/ by guest on June 15, 2017
3 cases
(9 cases)
FIGURE 4. Cardiac position in situs solitus and situs inversus
with discordant loops. The orientation of the ventricular septum is
closely related to cardiac position. When the ventricular septum is
in the sagittal plane, the right ventricular outflow tract and ascending aorta form the characteristic shoulder deformity (A2, B2).
branching patterns. Lung fissures varied somewhat but in
of the bilateral left pattern. As in the
asplenia group, lung fissures were less reliable than
pulmonary artery-bronchial relationships in evaluating lung
symmetry. The abdominal organs displayed less symmetry
than in asplenia; malrotation of the bowel was present in at
least three cases.
most cases were
FIGURE 5. Photograph of atrial septum in asplenia. A) Right atrial view. B) Left atrial
present. ASD
=
secundum atrial
septal defect,
strand of muscle separates the two defects
ECD
=
atrial
portion of
a
view. Two
large defects are
large endocardial cushion defect.
A
thin
CARDIAC MALPOSITIONS/Stanger, Rudolph, Edwards
167
FIGURE 6. Photograph of the atrial septum in polysplenia. A) Right atrial view. B) Left atrial view. The fossa ovalis is absent.
Downloaded from http://circ.ahajournals.org/ by guest on June 15, 2017
in the valve of the foramen ovale and/or absence of both lrmbi of the fossa ovalis. Seven cases also had patency of the
ductus arteriosus. The above communications, as well as the
anomalous pulmonary venous connections, are lesions
which, in the absence of pulmonary stenosis, would result in
pulmonary overcirculation.
Pulmonic stenosis was uncommon, being found in only
two cases. In contrast, left-sided obstructive lesions were
common. There were five cases with aortic outflow obstruction and two with aortic coarctation.
Twelve of the cases of polysplenia in the present series
(cases 49-52, 56, 57 and 60-65) have been reported
previously.'1
Discussion
The anatomic findings in the present series were very
similar to those of Lev and associates30 and Van Praagh and
associates,'4 although neither study classified polysplenia as
a distinct situs. Tetralogy of Fallot with cardiac malposition
was virtually absent in both these series as well as in our
cases. This differed considerably from the earlier work of Arcilla and Gasul' which reported seven cases of tetralogy;
however, only two of their seven cases of tetralogy were examined at necropsy. It is possible that some of the cases of
tetralogy may have had ventricular inversion (i.e., "corrected
transposition" with pulmonic stenosis and ventricular septal
defect).
The large proportion of cases of malposition associated
with splenic anomalies is noteworthy and is in agreement
with the findings of others.'3 80, 1' It is quite likely that many
of the cases previously reported as "mixed situs or "incomplete situs inversus" were, in reality, examples of splenic
anomaly syndromes, particularly polysplenia.
The findings in the asplenia and polysplenia cases are
similar to those reported by Van Mierop"2 and Rose and coworkers;32 however, the latter reported an unusually high incidence of pulmonary outflow obstruction in polysplenia
(four of 12 cases). Pulmonic stenosis was present in only two
of 17 cases in the present series. In contrast, seven of 17 cases
in the present series showed aortic outflow obstruction or
coarctation.
Ivemark reported four cases of type IV truncus arteriosus
in association with asplenia;33 truncus was not present in any
of the asplenia cases in this series as well as others.'4' s 31
The high incidence of cardiac anomalies in cases of situs
inversus (11 of 13 cases) exceeded that found by Arcilla and
Gasul3' and contrasted sharply with the findings of Keith and
co-workers," Grant,33 and Torgersen."3 The latter study was
based, in part, on screening chest roentgenograms of persons
over 15 years of age and excluded cases with severe
anomalies which caused an early death. The present necropsy study is probably weighted to the opposite extreme. The
true incidence of cardiac anomalies in situs inversus
probably lies somewhere in between.
Similarly, the incidence and severity of congenital cardiac
anomalies associated with polysplenia is probably greater in
necropsy series than in catheterization series. Although there
were no cases of polysplenia without cardiac anomalies in
the present series, the authors have catheterized two patients
with probable polysplenia, dextrocardia, an interrupted inferior vena cava and no intracardiac anomalies. Individuals
with polysplenia, levocardia and no intracardiac anomalies
might not even come to a physician's attention.
Clinical Correlates of Anatomic Features
Identifying the Situs
The situs of the individual patient is best determined by
chest and abdomen roentgenograms with additional
laboratory studies (table 4).
In situs solitus, the viscera are normally situated while in
situs inversus inverted viscera are evident. In asplenia, the
abdominal viscera are very symmetrical with a horizontal
liver and a stomach bubble which tends to lie toward the
midline."0 In polysplenia, the tendency toward symmetry is
also present but is not as striking as in asplenia. As both
lungs are often bilobed in polysplenia, the presence of a
minor lobe fissure on chest roentgenograms is strong
evidence against polysplenia. In contrast, the finding of the
upper abdominal portion of the aorta on the side opposite
the stomach is strong evidence for polysplenia.37 Roentgenograms showing the symmetrical bronchial patterns in the
splenic anomaly syndromes have also been helpful."
Malrotations of the bowel are common in both asplenia and
polysplenia.Y9 Radioisotopic scanning may demonstrate absent or multiple spleens.2" 40, 41
CIRCULATION
168
VOL 56, No 2, AUGUST 1977
TABLE 4. Clinical and Laboratory Features of the Four Body Configurations
Polysplenia
Solitus
Inversus
Presenting symptoms
Varies
Varies
Cyanosis (-95%)
CHF (-5%)
Cyanosis (-20%)
CHF (,80%)
Roentgenograms Abdomen
Normal
Inverted
Horizontal liver
Midline stomach
Malrotation
i Horizontal liver
Stomach not midline
Malrotation
Absent IVC
R
Normal
Varies
L
Inverted
Varies
R,L
Bilat. right
Usually increased
Asplenia
-
Chest
Minor fissures
Pattern of bronchi
Vascularity
/
P axis in ECG
Miscellaneous
Heinz or Howell Jolly
bodies
Biliary atresia
Spleen scan
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Catheterization
SVc
Interrupted IVC
APVC
Pulmonary arterial
interrelationship to
bronchi
\,, and/or /
Usually bilat. left
Usually decreased
T (-65 o)
+
Multiple but not
L
R
Absent
R
L
Usually bilat.
Frequently bilat.
(+ 510% )
To systemic or
portal veins
To atria
Bilat. right
Usually bilat. left
Normal
always evident
Inverted
The numbers in parentheses are approximate incidences based on information in the literature as well as the authors' clinical experience. (R = right; I L = left; SVC = superior vena cava; IVC = inferior vena cava; APVC = anomalous pulmonary venous
connection; CHF = congestive heart failure.)
As the atria almost always follow the situs, the direction of
the P vector on the electrocardiogram may be of some value
in determining the situs (fig. 7). In situs solitus, atrial
depolarization proceeds from the sinoatrial node toward the
left and inferiorly resulting in an upright P in I, II, III, aVL
and aVF. In situs inversus, the P vector is from left to right
and inferiorly with an upright P in II, III, aVF and inverted P
in I and aVL. In asplenia, both atria are morphologic right
atria and each may have a sinoatrial node.6 Consequently,
either of the above P vectors may be present and both may be
present in the same patient at different times. In polysplenia, ectopic low atrial pacemakers are common42-" with
negative P waves in II, III and aVF. This may be the result of
bilateral left atria and absent sinoatrial nodes. We know of
no histologic studies of sinoatrial nodes in polysplenia.
heard in the vicinity of the displaced pulmonary valve, i.e.,
the mid or right sternal edge. When pulmonic stenosis is
present, the murmur may be maximal retrosternally or to the
right of the upper sternum. The murmur of the left atrioventricular valve insufficiency may be present in patients
with Ebstein's malformation of this valve.
Situs Solitus
Cardiac malpositions in situs solitus in this series were the
result of either cardiac displacement (dextroposition), dextrorotation, or a discordant loop (solitus/l-loop).
Dextroposition may be recognized readily by an
asymmetric thorax and decreased breath sounds on the right
as well as an absent or hypoplastic right lung in chest
roentgenograms.
The physical findings in corrected transposition in situs
solitus (solitus/l-loop/l-trans) are the result of the abnormally positioned semilunar valves and the associated cardiac
anomalies. The anterior and leftward position of the aortic
valve results in a very loud aortic closure on auscultation
which is usually maximal at the upper left sternal edge. The
second sound is usually single, but occasionally a split is
FIGURE 7. Direction of atrial depolarization in patients with cardiac malposition. A) Situs solitus. B) Situs inversus. C) Asplenia.
D) Polysplenia. In asplenia there may be two sinoauricular nodes
and the P vector may vary with time. Superiorly directed P vectors
are common in polysplenia.
CARDIAC MALPOSITIONS/Stanger, Rudolph, Edwards
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The roentgenographic features of corrected transposition
in situs solitus (solitus/l-loop/l-trans) are quite variable. The
two general forms of cardiac silhouette have been described
earlier. The pulmonary vascularity is related to the degree of
pulmonic stenosis and/or shunting at the ventricular level.
Even in the absence of pulmonic stenosis, the main
pulmonary artery may not be evident because of its medial
position.
The bundle branches also follow the respective ventricles"' 16, " and this probably explains the electrocardiographic features of corrected transposition. In d-loops
(including cardiac displacement) septal depolarization
proceeds from left to right and a Q wave is recorded in the
left precordial leads. With I-loops, septal depolarization
proceeds from right to left and a Q wave is frequently
recorded in the right but not over the left precordium. As the
degree of ventricular rotation and, therefore, septal position
may vary, the Q waves may not be evident in V1 but may be
present in the more rightward chest leads. This feature is not
constant and similar Q wave patterns may be found with
right ventricular hypertrophy without ventricular inversion.
In addition, atrioventricular conduction defects are common
in corrected transposition."
The anatomic positions of the valves of the great arteries
result in unusual catheter positions during cardiac
catheterization.27 The location of the pulmonary valve orifice
behind the venous atrioventricular valve and subpulmonic
stenosis may preclude entering the pulmonary artery. Even
when the main pulmonary artery is entered the acute angulation of the catheter frequently prevents advancement to the
pulmonary arterial wedge position unless a balloon tipped
catheter is used.
Situs Inversus
Cases of situs inversus with concordant ventricles show
dextrocardia as a constant feature and this is evident by
physical and roentgenographic examination as well as
"6mirror image" progression of precordial QRS complexes
on the electrocardiogram. There is a rightward inferior P
axis (fig. 7) and no findings suggestive of cardiac disease.
The physical findings in corrected transposition in situs inversus (inversus/d-loop/d-trans) include a very loud aortic
closure maximal at the upper right sternal edge and the
features of associated anomalies. The two general forms of
cardiac silhouette seen on roentgenograms have been
described above (fig. 4). When a "shoulder" is present in corrected transposition in situs inversus it is on the right heart
border, i.e., the same side as the apparent cardiac apex.
When the heart is left-sided, a "shoulder" is notably absent.
The electrocardiographic features are the rightward P axis of
situs inversus and septal depolarization proceeding from left
to right.
Aspienia
The clinical picture begins with cyanosis in the neonatal
period. Survival beyond infancy is unusual and serious infections such as meningitis are not rare." 8 With the exception
of a horizontal liver, the physical findings are not peculiar to
asplenia.
The roentgenographic features are those of pulmonary un-
169
dercirculation, a markedly symmetrical liver,'0 a midline
stomach bubble,10 malrotation of the bowel,3' symmetry of
the tracheobronchial tree,8' and decreased pulmonary
vascularity. There is commonly mesocardia; however, dextrocardia or levocardia sometimes occur. The abdominal
aorta and inferior vena cava have also been found to lie on
the same side."
As two sinoatrial nodes may be present, the electrocardiogram may show either an inferior rightward or inferior
leftward P axis. The same patient may show each at different
times. Although all cases of asplenia have an atrioventricular canal, the QRS axis in the cases exhibiting a single ventricle may be inferior and rightward while cases with two
ventricles usually have a superior QRS axis.9
The presence of Heinz or Howell-Jolly Bodies on a
peripheral blood smear is additional strong evidence of
asplenia." 47
Polyspienia
The clinical features of polysplenia are in marked contrast
to those of asplenia. Cyanosis is usually absent or minimal
and congestive heart failure is common as most patients with
polysplenia have cardiac anomalies resulting in pulmonary
overcirculation, either alone or in association with left-sided
obstructive lesions.
The diagnosis of polysplenia may be suggested by a
clustering of clinical and laboratory findings. The findings on
physical examination are primarily those of the associated
cardiac anomalies and are not distinctive for polysplenia.
Chest and abdomen roentgenograms show a variety of
hepatic and cardiac positions; however, mesocardia is rare.
Focusing attention on the position of the heart and lungs
may result in cases of polysplenia being missed or categorizing them as situs inversus or partial situs inversus. Additional roentgenographic findings that favor the diagnosis of
polysplenia are bilateral left bronchial pattern,38 absence of a
minor lobe fissure in both lungs and malrotation of the
bowel.8' A feature peculiar to polysplenia is the upper abdominal aorta lying on the side opposite the stomach
bubble.87, 42
Low atrial pacemakers are found frequently on electrocardiogram.42-" Peripheral blood smears show no Heinz or
Howell-Jolly Bodies (unpublished observations). Although
more than 100 cases of polysplenia have been documented
there are no reports of unusual susceptibility to infection.
Recent publications82 '" added six cases of extrahepatic
biliary atresia to the seven previously reported cases.
At cardiac catheterization interruption of the inferior vena
cava with azygos continuation is strong evidence for
polyspleniall' 12, 82 and should alert the cardiologist to this
possibility even in the absence of cardiac or hepatic malposition. Symmetry of the pulmonary arteries may be apparent
in the posterior-anterior projection but the "bilateral-left"
configuration is best verified in the lateral projection. In this
view both lower lobe pulmonary arteries lie in the same coronal plane and are posterior to the bronchi.
Although there are several clinical indicators for
polysplenia, none are pathognomonic. Unless a radioisotope splenic scan shows an irregular splenic mass
suggestive of polysplenia the diagnosis is usually presumptive and its likelihood depends on how many of the above
CIRCULATION
170
features are present. A definitive diagnosis occasionally is
made at laparotomy for bowel obstruction or biliary atresia.
Embryologic Considerations
Situs
The anatomic features of the viscera in each of the situses
be explained readily if one hypothesizes that there are
separate factors for controlling the development of
morphologic right and morphologic left structures from
paired lateral isomers. When both factors are present, the
resulting body configuration is either situs solitus or inversus,
depending on the factors' interrelationships. When the factors controlling right morphology are present bilaterally,
asplenia syndrome may be expected to occur and with
duplicate left factors, polysplenia syndrome. Although many
organs show symmetry in asplenia and polysplenia, others do
not. The lungs, tracheobronchial tree, atria and liver are
symmetric or tend toward symmetry while the ventricles and
great arteries are asymmetric. The symmetric organs
develop from midline anlage which have undergone a sagittal
division into right and left isomers. Whatever factors control
right-left morphology probably influence these isomers to be
symmetric in each of the splenic syndromes. On the other
hand, structures which result from cephalad-caudad or coronal division are not symmetric. The great arteries are the
result of a coronal division of the truncus arteriosus into
anterior and posterior portions (aorta and pulmonary artery,
respectively). Similarly, the right and left ventricles develop
from anlage that are at least partially cephalad-caudad in the
cardiac tube. In each of these instances, the paired structures
are not derived from lateral isomers and might not be expected to be influenced by factors controlling right-left
morphology.
The gastrointestinal tract is asymmetric but has a specific
orderly arrangement in both situs solitus and situs inversus.
This orderly arrangement within the body might require the
influence of both right and left factors. The presence of
bilateral right or left factors might result in a disorderly
arrangement of the bowel, i.e., malrotation.
The splenic anlage makes its appearance relatively late in
gestation (i.e., 30 days). Normally, the splenic anlage
appears as a small bud on the left side of the dorsal
mesogastrium. Van Mierop has examined the splenic tissue
of patients with polysplenia at necropsy and found spleens on
each side of the dorsal mesogastrium.12 The latter lends support to the concept of bilateral left-sidedness.
Conversely, absence of the spleen in asplenia syndrome is
probably another manifestation of bilateral right-sidedness
may
VOL 56, No 2, AUGUST 1977
with either suppression or agenesis of the splenic anlage as
part of the developmental complex. On the other hand,
isolated absence of the spleen, i.e., without visceral abnormalities, is probably the result of agenesis of the splenic
anlage as an independent event. There is one such case in the
Cardiovascular Registry of the United Hospitals, Miller
Division.
The significance of accessory spleen in these developmental complexes is unclear. Accessory spleens are a fairly common finding at routine postmortem examinations and
usually are not associated with other congenital visceral or
cardiac anomalies. Case 59, in the present series, is an exception. Lung fissures, atrial morphology and atrial septal
morphology were similar to that in polysplenia; however,
tracheobronchial and pulmonary arterial relationships were
typical of bilateral right-sidedness.
Cardiac Position
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The d- or 1- bulboventricular loop determines the positions
of the ventricles relative to each other and to the atria. The
position of the heart within the thorax is dependent not only
on the type of bulboventricular loop but also on the degree of
pivoting of the ventricular portion of the heart. Normally, at
four weeks when a d-loop forms the ventricles, the ventricular portion of the heart is still directed toward the right with
the ventricles situated side by side. At nine weeks, the ventricular portion of the heart pivots toward the left, placing
the heart in the left hemithorax and the right ventricle
anterior to the left ventricle. Conversely, with an 1-loop the
ventricular portion pivots toward the right hemithorax. In
our experience, when the loop was concordant with the situs,
the pivoting was complete in almost all cases. The only exception was the case of solitus/d-loop (R)/d-normal. With
discordant loops, the pivoting is frequently incomplete
resulting in the varying cardiac positions found in corrected
transposition of situs solitus (solitus/l-loop/l-trans), as well
as corrected transposition of situs inversus (inversus/
d-loop/d-trans). This same principle can be applied to cases
of asplenia and polysplenia. The symmetry of these situses
precludes designating concordant loops. Therefore, it is not
surprising that each type of bulboventricular loop in each of
these situses showed variation in degrees of pivoting and cardiac position (table 5).
Pulmonary Veins
The differing patterns of pulmonary venous connection
found in asplenia and polysplenia syndromes have been
related to the type of atrial isomerism found in each. In
TABLE 5. Cardiac Position Related to Situs and Bulboventricular Loop
Situs
Solitus
Inversus
Asplenia
Polysplenia
Loop
Total no. cases
Dextrocardia
d-loop
r3000
6t
6
3
8
4
7
5
4
l-loop*
d-loop*
I-loop
d-loop*
l-loop*
d-loop*
I-loop*
15
5
8
8
15
12
5
Mesocardia
Levocardia
('3000)t
(19)t
2
7
*Discordant bulboventricular loops.
t5( cases of cardiac displacement and I of incomplete pivoting of the ventricles, i.e. solitus/ d-loop (R).
) indicates specimens without cardiac malposition and not included in this study.
4
1
7
1
CARDIAC MALPOSITIONS/Stanger, Rudolph, Edwards
asplenia there are bilateral right atria and consequently
bilateral absence of the common pulmonary vein.6 As a
result, the sites of connection of the anomalous pulmonary
veins in asplenia are the superior vena cavae or the portal
system (fig. 8). As there are two left atria in polysplenia, a
common pulmonary vein may develop from either or both12
and the pulmonary veins may connect directly to either or
both atria. Partial anomalous pulmonary venous connection
may be the result of a common pulmonary vein arising from
each of the morphologic "left" atria, whereas total
anomalous pulmonary venous connection to the venous
atrium may be the result of a common pulmonary vein
developing from that atrium (fig. 9).
In cases of polysplenia where the pulmonary veins connect
directly to both atria, they do so in a distinctive manner. The
right veins connect to the right-sided atrium and the left
veins to the left-sided atrium. Van Mierop has pointed out
that the sites of connection are not at the intercaval portions
derived from the sinus horns but rather more medially and
adjacent to each side of the atrial septum.'2 The latter connections suggested that the partial anomalous pulmonary
venous connection in polysplenia was the result of bilateral
common pulmonary veins in bilateral left atria.
r
RA
171
I
'1
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Acknowledgment
The authors wish to thank Dr. Julien I. E. Hoffman for his interest, constructive criticism and advice.
FIGURE 8. Anomalous pulmonary venous connection in asplenia.
As both atria are morphologic right atria and there may be no
common pulmonary
vein, persistence ofpulmonary venous connec-
tions to anterior cardinal or umbilicovitelline veins are common.
RA = morphologic right atrium, R V = morphologic right ventricle, L V = morphologic left ventricle.
Lung
d
LA
LA
La
Normal
LA
LA
LA
Partial
FIGURE 9. Anomalous pulmonary venous connection in polysplenia. As both atria are morphologic left atria, each may have a
common pulmonary vein. The pulmonary veins may connect to
either atrium or both atria. LA = left atrium, C = common
pulmonary vein.
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Circulation. 1977;56:159-172
doi: 10.1161/01.CIR.56.2.159
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