Download Congenital absence of pericardium revisited

The International Journal of Cardiovascular Imaging 18: 67–73, 2002.
Ó 2002 Kluwer Academic Publishers. Printed in the Netherlands.
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Congenital absence of pericardium revisited
Yang Faridah & Paul R. Julsrud
Department of Radiology, Mayo Clinic, 200 First Street Southwest, Rochester, 55905 MN, USA
Received 29 May 2001; accepted in revised form 16 July 2001
Key words: congenital, magnetic resonance imaging, pericardium
Abstract
Although much have been published regarding congenital absence of pericardium, it is essential that this
anomaly, like an old friend, be revisited from time to time. Review of this anomaly with emphasis on its
embryological process is discussed. Furthermore, with the advances in magnetic resonance imaging, absence of pericardium can now be diagnosed with ease and the radiological findings of this condition are
reviewed as well.
Introduction
Congenital defects of the pericardium are a relatively rare anomaly that was first described in 1559
by Columbus [1]. Following this, there were still
reservations about the true existence of this condition and it was not until 1778 when Baillie [2] gave a
detailed description of a case that all doubts were
laid to rest. Since then numerous cases and studies
have been published. A review of this anomaly with
regards to its classification and epidemiology, embryology, clinical features and radiological features
is presented here with the aid of a case report, to
illustrate the radiological findings and technical
aspects of magnetic resonance imaging (MRI).
Classification and epidemiology
Pericardial defects have generally been classified as
being complete or partial. In the majority of cases
these pericardial defects, both complete and partial
types, affect the left side of pericardium rather than
the right. Complete absence of the left pericardium
is the most common defect accounting for 76% of
all pericardial defects in one large series [3]. Right
sided and bilateral partial absences of the pericar-
dium are extremely rare [4]. Seventy seven percent
of all types of pericardial defect occur in males [3].
Embryology
During the first week of development, irregular
cavities are formed in the mesodermal substance of
the embryo. These cavities enlarge and coalesce to
form the primitive pericardial, peritoneal and
pleural cavities (Figure 1).
By the fourth week, a wedge of mesoderm, has
begun to grow and interposed itself between the
primitive pericardial and peritoneal cavities. This is
the septum transversum and it contains the developing liver and termination of the umbilical and
vitelline veins (Figure 2). This separation however
is not complete, as there exist pericardio–peritoneal
canals bilaterally, just medial to the common cardinal veins (ducts of Cuvier) (Figure 1). The lung
buds grow and protrudes into these canals, which
fold about them forming the pleural sacs (Figures 2
and 3). At the end of the fourth week, twofolds
begin to grow out from the ducts of Cuvier, on each
side, the ventral fold forming the pleuropericardial
membrane while the dorsal fold forms the pleuroperitoneal membrane (Figures 2 and 3).
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Figure 1. Diagrammatic representation of a fetus in early development in the sagittal plane showing formation of the pericardial, pleural and peritoneal cavities. Curved arrow represents
the position of the pericardio–peritoneal canal which lies medial
to the bilateral ducts of Cuvier. PC1 – pericardial cavity; PC2 –
peritoneal cavity; PC3 – pleural cavity; PPM1 – pleuropericardial membrane; PPM2 – pleuroperitoneal membrane; ST –
septum transversum; * – common cardinal vein (duct of Cuvier); ACV – anterior cardinal vein; PCV – posterior cardinal
vein; PN – phrenic nerve.
By the fifth week, these membranes reach and
fuse with the medial wall of the pleuroperitoneal
canal on each side of the lung bud, separating the
pericardial and pleural cavities from the peritoneal
cavity (Figure 3). The pleuropericardial membrane
obliterates the pleuropericardial opening while the
pleuroperitoneal membrane obliterates the pleuroperitoneal opening. Each lung extends anteriorly to
the front of the heart. The complete separation of
the pericardial cavity from the pleural cavity takes
place when the pleuropericardial membrane unites
with the root of lung (Figure 3).
Figure 2. Diagrammatic representation of a fetus at fourth
week of development in the sagittal plane showing the formation of the septum transversum and the eventual division of the
pleuropericardial and pleuroperitoneal membranes. PC1 –
pericardial cavity; PC2 – peritoneal cavity; PC3 – pleural cavity;
PPM1 – pleuropericardial membrane; PPM2 – pleuroperitoneal
membrane; ST – septum transversum; * – common cardinal
vein (duct of Cuvier); ACV – anterior cardinal vein; PCV –
posterior cardinal vein; PN – phrenic nerve.
Failure of the pleuropericardial membranes to
close completely on one or both sides will result in
pericardial deficiencies. It is generally accepted
that defects in the pericardium are due to the
persistence of the pleuropericardial foramen, but
there are differing opinions on the causative factor
that prevents this closure:
(a) Perna (1909) [5] proposed the current generally
accepted theory that the arrested closure of the
pleuropericardial membrane is due to the premature atrophy of the left duct of Cuvier. In
normal development, the right duct of Cuvier
develops into the superior vena cava. As the left
brachiocephalic vein forms, the left duct of
Cuvier atrophies with its distal portion persist-
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Figure 3. Diagrammatic representation of a developing fetus from fourth to sixth week of gestation in the axial plane. A. Normal
development of the pericardium. B. Proposed abnormal development resulting in absence of the left pericardium as hypothesized by
Perna. a – aorta; aldc – atretic left duct of Cuvier; es – esophagus; da – dorsal aorta; dc – duct of Cuvier; h – heart; ivc – inferior vena
cava; l – lung; lb – lung bud; nt – notochord; pp – parietal pericardium; ppl – parietal pleura; ppm1 – pleuropericardial membrane; vp –
visceral pericardium; vpl – visceral pleura.
ing as the coronary sinus. The early obliteration
of the duct diminishes the blood supply to the
growing pleuropericardial membrane resulting
in a defect in the left pericardium. This theory
explains why the majority of these defects involve the left pericardium (Figure 3).
(b) An alternative hypothesis postulates that the
heart enlarges and stretches the enveloping
pericardium during development [6]. It is
thought that the pleuropericardial foramen has
to close before the heart enlarges. Failure of the
membrane to grow and fuse in time would result in a persistent defect. This can affect the
whole membrane in total or either the pericardial or pleural membrane in isolation. The
size of the defect would depend on the rate of
growth of the heart and the enveloping mem-
brane. This theory would explain the preponderance of the defect to the left, as the heart is a
left-sided structure. It would also explain the
rare circumstance of right-sided defect and total absence of pericardium depending on which
membrane is affected. The types of defect, either total or partial absence, is also explained
by this. Cases in which there is absence of
pericardium but with an intact pleural membrane can be attributed to this as well [7].
Clinical features
Most patients are asymptomatic and the discovery
of this defect is incidental. The most common
symptom of complete absence of pericardium is
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vague chest pain occurring in up to 33% of patients [8, 9]. Dyspnea, dizziness and syncope have
also been reported [10].
Marked displacement of the apical impulse into
the mid-axillary line is seen in patients with complete absence of pericardium. The heart appears
enlarged in approximately 50% of cases, which
may be partially due to the slight rotation of the
heart into the left chest [3, 11]. This coupled with
the presence of a strong and displaced apical impulse, tends to give the impression of an enlarged
heart on physical examination and on chest radiograph when no actual enlargement is present
[12]. Cardiac murmurs are not specific to the
condition. When present, an ejection systolic
murmur is heard most often in the second left intercostal space or along the sternal border. Sinus
bradycardia is not an uncommon finding [4, 10].
Electrocardiograpy (ECG) changes are commonly
seen in cases of complete left pericardial defect and
consist of right axis deviation, incomplete right
bundle branch block pattern and leftward displacement of the transitional zone in precordial
leads.
Patients with partial defect of the pericardium
are more at risk of morbidity than those with
complete defects, as herniation of the heart
through a partial defect may occur resulting in
Figure 4. Posteroanterior chest radiograph reveals slight rotation of the heart into the left chest and a prominent aortopulmonary
notch.
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strangulation of the heart and death. Conversely,
the physical examination and ECG in patients
with partial defect are usually normal [13].
Associated cardiac anomalies are seen in 30% of
all pericardial defect cases, both complete and
partial. These anomalies include atrial septal defect, patent ductus arteriosus, bicuspid aortic
valve, bronchogenic cyst, pulmonary sequestration
and diaphragmatic hernia [4].
Radiological features
Complete absence of pericardium gives a distinctive radiographic picture on a chest radiograph.
There is rotation of the heart into the left chest with
the right cardiac border projected over the midline.
The contour of the left cardiac border is prominent
with accentuation of the convexities of the aortic
knob, the main pulmonary artery and the left
ventricle. The space between the aorta and the
main pulmonary artery may appear widened due to
the presence of aerated lung between these two
vessels. This also results in sharp demarcation of
the pulmonary artery. The inferior cardiac border
is elongated and flatten and there is commonly
interposition of lung between the dome of the left
hemidiaphragm and the inferior cardiac border.
The trachea and esophagus remain as midline
structures [4]. Leftward rotation of the heart is also
Figure 5. Coronal T1-weighted spin-echo image demonstrates complete absence of the left pericardium with a prominent aortopulmonary notch. Note the presence of lung between the base of the heart and left diaphragm.
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seen in atrial septal defect, mitral valve disease and
pulmonary valvular stenosis, which may mimic
absence of pericardium radiographically [11].
Baim et al. (1980) first described the computed
tomography (CT) findings of complete absence of
pericardium. Prominence of the main pulmonary
artery and interposition of the left lung between
the great vessels was described [9]. Vesely and
Julsrud (1989) further described tethering of the
right pericardium to the anterior chest wall by
sternopericardial ligaments as a radiographic sign
seen on axial computed tomography [14].
MRI findings of complete pericardial defect
were presented by Gutierrez et al. in 1985 [15].
MRI coronal sections through the heart demonstrated actual absence of the pericardium. There
was leftward displacement of the heart, a bulging
pulmonary artery and herniation of lung between
the base of the heart and the left diaphragm
[15].
Partial cardiac defect usually presents with a
normal chest radiograph. Occasionally, a prominent bulge along the left side of the cardiac
silhouette in the vicinity of the left atrial appendage maybe seen [8, 16]. Herniation of the heart
through the partial defect can be appreciated,
forming an indentation on the heart or a myocardial crease on CT or MRI [17, 18].
Figure 6. Axial T1-weighted spin-echo image illustrates prominence of the main pulmonary artery with extension of the lung between
the pulmonary artery and aorta. Presence of the sternopericardial ligament is clearly depicted (arrow).
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Case report
A 59-year-old male presented with shortness of
breath for 5 months and investigations to assess his
cardiac status were performed. Chest radiograph
was reported as normal. On echocardiogram, his
left ventricle was found to be displaced to the left
axilla. Although actual pericardium cannot be visualized, the abnormal position of the heart raised
the suspicion of absent pericardium. Subsequent
MRI confirmed the diagnosis.
Retrospective analysis of the chest radiograph
reveals slight rotation of the heart to the left and a
prominent aortopulmonary notch (Figure 4). The
MRI demonstrated complete absence of the left
side of pericardial sac (Figures 5 and 6). There was
difficulty in cardiac gating using chest leads, as the
signal from this was bizarre and unreadable.
Switching to peripheral leads for cardiac gating
solved this problem. On MRI, there is rotation of
the heart into the left chest with prominence of the
right ventricular outflow tract (Figure 5). There
is presence of sternopericardial ligament tethering
the heart and great vessels to the sternum
(Figure 6). The lung extends in between the pulmonary artery and ascending aorta. There is a
tongue of lung extending between the heart and
left hemidiaphragm (Figure 5).
Discussion
Gutierrez et al. [15] predicted that MRI would
become the preferred technique for the definitive
diagnosis of absence pericardium due to its capability to image in any plane. We believe this prediction was correct. The presence of other
congenital anomalies can also be observed as both
morphological and functional imaging may be
performed with MRI.
Thus, we consider MRI with its unique ability to
display anatomy of the heart, including pericar-
dium, to be the diagnostic tool of choice for
evaluating pericardial defects.
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