DOI:10.2214/AJR.05.1655
AJR 2007; 189:W312-W314
© American Roentgen Ray Society
Functional MRI of Congenital Absence of the Pericardium
Panagiotis Psychidis-Papakyritsis1,
Albert de Roos and
Lucia J. M. Kroft
1 All authors: Department of Radiology, Leiden University Medical Center, C2-S,
Albinusdreef 2, 2333 ZA Leiden, The Netherlands.
Received September 16, 2005;
accepted after revision April 11, 2006.
Address correspondence to L. J. M. Kroft
(l.j.m.kroft{at}lumc.nl).
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Keywords: anatomy • congenital anomaly • cardiac imaging • dynamic MRI • MRI
Introduction
Congenital absence of the pericardium is a rare anomaly. The
prevalence, including cases with other cardiopulmonary anomalies, is
approximately 0.002-0.004% of surgical and pathologic series
[1]. The defects are on the
left side of the heart in most cases but can be located anywhere in the
pericardium. Absence of the pericardium is classified as complete or partial.
Complete defects are of little clinical importance. A subgroup of partial
defects, however, the so-called foramen-type defects, can be fatal when they
allow herniation of a part of the myocardium while some of the pericardium
stays intact. The diagnosis of congenital absence of the pericardium usually
can be established with visualization of the morphologic characteristics on CT
or MRI
[1-5].
We describe the case of a patient with congenital absence of the pericardium,
and we suggest two functional MRI findings that may be helpful criteria to
support the diagnosis.
Case Report
A 69-year-old woman was admitted for CT evaluation of fever that occurred
with treated systemic lupus erythematosus. She was known to have an abnormally
positioned heart without further specifications. Because of the development of
ankle edema and orthopnea, MRI of the heart (1.5-T unit, MR Intera, Philips
Medical Systems) was performed for further analysis. No contrast material was
used. For postprocessing, dedicated cardiac software (MASS and Flow, Medis)
was used on a PC workstation running Linux software (SUSE Linux, Novell).
Transverse, coronal, and sagittal black-blood turbo spin-echo MR images
(field of view, 280 mm; TR/TE, 1,846/8.6; slice thickness, 4.0 mm; gap, 0.4
mm; echo-train length, 24; number of signals averaged, 2; matrix size, 512
x 512; rectangular field of view, 80%) showed a normal, symmetric chest
wall and a normal midline position of the trachea. There was extreme
levoposition and posterior rotation of the heart, but the venous-to-atrial,
atrioventricular, and ventriculoarterial connections were normal. In
association with the excessive left posterior rotation, the pulmonary artery
was to the left and in front of the aorta, a normal finding that excluded
transposition (Fig. 1A). In
addition, the anatomic right ventricle, recognized on the basis of the
moderator band and muscular outflow tract, was in front of the left ventricle
(Fig. 1B). The mitral and
tricuspid valves were located at the same level. The right leaf of the
pericardium was clearly visualized (Fig.
1B), although the left leaf of the pericardium and the anterior
portion of the superior pericardial recess were not identified. Interposition
of lung between the aorta and the pulmonary artery
(Fig. 1A) established the
diagnosis of congenital absence of the pericardium
[2].
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Fig. 1A —69-year-old woman with congenital absence of pericardium. See
also Figure S1E, cine loop, in supplemental data. MR images obtained with
turbo spin-echo sequence in transverse plane (TR/TE, 1,846/8.6) show
interposition (arrow, A) of lung between aorta (A) and main
pulmonary artery (P), which is pathognomonic of pericardial absence. Extreme
levoposition and levorotation of heart are evident. Right leaf of pericardium
(arrow, B) is next to right atrium (RA). LA = left atrium, RV
= right ventricle, LV = left ventricle.
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Fig. 1B —69-year-old woman with congenital absence of pericardium. See
also Figure S1E, cine loop, in supplemental data. MR images obtained with
turbo spin-echo sequence in transverse plane (TR/TE, 1,846/8.6) show
interposition (arrow, A) of lung between aorta (A) and main
pulmonary artery (P), which is pathognomonic of pericardial absence. Extreme
levoposition and levorotation of heart are evident. Right leaf of pericardium
(arrow, B) is next to right atrium (RA). LA = left atrium, RV
= right ventricle, LV = left ventricle.
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Findings on velocity-encoded (phase-contrast) cine MRI (9.1/5.8; fast-field
echo sequence with angulation perpendicular to the valve orifice; field of
view, 300 mm2; flip angle, 20°; slice thickness, 8.0 mm; number
of signals averaged, 2; number of phases, 36; phase-contrast velocity, 100-150
cm/s; matrix size, 256 x 256; rectangular field of view, 84%) excluded
valvular dysfunction. Normal outflow curves were present across the aortic and
pulmonary valves without regurgitation. Flow curves across the mitral valve
and tricuspid valve had normal biphasic inflow patterns. Early-to-late
diastolic ventricular filling ratios were normal, representing normal
diastolic biventricular function without regurgitation.
Functional analysis dynamic gradient-echo (bright-blood) cine MRI was
performed with the following parameters: transverse balanced turbo field echo;
3.2/1.6; field of view, 350 mm2; flip angle, 70°; slice
thickness, 8.0 mm; gap, 0.0 mm; number of slices, 16; number of phases, 30;
number of signals averaged, 1; matrix size, 256 x 256; rectangular field
of view, 80% (Fig. S1E in supplemental data). Calculated left and right
ventricular end-diastolic volumes, stroke volume, and ejection fraction were
normal, representing normal systolic biventricular function. Further analysis
of the cine-loop images showed the myocardial borders were smooth. No signs of
indentation of the outer margin of the heart or myocardial crease suggested
the presence of a foramen with herniation. A remarkable range of ventricular
motion was observed. The motion was most evident with a range of 15 mm (Figs.
1C and
1D) at the anterior apical and
lateral apical parts of the left ventricle. The total heart volume was
measured by tracing of the myocardial borders at end diastole and end systole.
The calculated difference in total heart volume between these phases was
21%.
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Fig. 1C —69-year-old woman with congenital absence of pericardium. See
also Figure S1E, cine loop, in supplemental data. MR images obtained with
transverse gradient-echo sequence (TR/TE, 3.2/1.6; flip angle, 70°) show
that compared with normal heart (Fig.
2A,
2B), excessive range of motion
is present at apex of heart during cardiac cycle (white blocks,
D and Fig. 2B). Images
at all slice levels were used to measure total heart volume by contour tracing
around heart. Levorotation in heart with pericardial absence that measures
approximately 90° (compare C with
Fig. 2A) is evident. RV = right
ventricle, LV = left ventricle. Dashed lines assist in indicating amount of
apical motion by providing equal anatomic locations.
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Fig. 1D —69-year-old woman with congenital absence of pericardium. See
also Figure S1E, cine loop, in supplemental data. MR images obtained with
transverse gradient-echo sequence (TR/TE, 3.2/1.6; flip angle, 70°) show
that compared with normal heart (Fig.
2A,
2B), excessive range of motion
is present at apex of heart during cardiac cycle (white blocks,
D and Fig. 2B). Images
at all slice levels were used to measure total heart volume by contour tracing
around heart. Levorotation in heart with pericardial absence that measures
approximately 90° (compare C with
Fig. 2A) is evident. RV = right
ventricle, LV = left ventricle. Dashed lines assist in indicating amount of
apical motion by providing equal anatomic locations.
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Fig. 2A —45-year-old man with normal heart. See also Figure S2C, cine
loop, in supplemental data. MR images obtained with transverse gradient-echo
sequence (TR/TE, 3.2/1.6; flip angle, 70°) show end-diastolic (A)
and end-systolic (B) phases. White block (B) indicates apical
part of heart during cardiac cycle (compare with
Fig. 1D). RV = right ventricle,
LV = left ventricle. Dashed lines assist in indicating amount of apical motion
by providing equal anatomic locations.
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Fig. 2B —45-year-old man with normal heart. See also Figure S2C, cine
loop, in supplemental data. MR images obtained with transverse gradient-echo
sequence (TR/TE, 3.2/1.6; flip angle, 70°) show end-diastolic (A)
and end-systolic (B) phases. White block (B) indicates apical
part of heart during cardiac cycle (compare with
Fig. 1D). RV = right ventricle,
LV = left ventricle. Dashed lines assist in indicating amount of apical motion
by providing equal anatomic locations.
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For comparison, we performed the same measurements on three patients
referred for cardiac analysis but with no abnormalities on MRI (Fig.
2A,
2B). (See Fig. S2C in
supplemental data.) The maximum motion ranges found in these patients were 1,
6, and 7 mm. The reductions in total heart volume during the cardiac cycle in
these patients were 8%, 10%, and 11%, respectively, which were normal
[6]. Therefore, the abnormally
large range of myocardial motion and abnormally large variation in total heart
volume in our patient strongly suggested nonexistent pericardial constraint
with a nonfatal, nonforamen type of pericardial defect.
Discussion
CT and MRI are well-recognized tools for establishing the diagnosis of
congenital absence of the pericardium. Although the pericardium is usually
sufficiently thick to be identified on CT and MRI, visualization at the most
common site of pericardial defects, the lateral left ventricular wall, can be
poor because of a paucity of fat
[3,
4].
Several indirect morphologic signs have been accepted as diagnostic of
pericardial defects. Interposition of lung tissue between the aorta and
pulmonary artery or between the diaphragm and the base of the heart is the
most specific sign, occurring in all patients with complete left pericardial
defects or partial defects overlying these anatomic structures
[2]. Leftward cardiac
displacement usually accompanies complete left pericardial absence, and
excessive levorotation has been proposed as pathognomonic of this type of
defect [5]. Nevertheless,
cardiac displacement also can occur in left partial pericardial defects
[1,
2] or can be absent in young
children with complete pericardial defects
[5]. Even if morphologic signs
are strongly suggestive of complete left pericardial defect, contradictory
findings in several cases decrease confidence in the diagnosis. In addition,
levorotation can be present in other conditions, such as atrial septal defect,
pulmonic valvular stenosis, mitral valve disease, and cor pulmonale with right
ventricular dilatation [7].
Functional characteristics can be helpful in establishing the diagnosis of
congenital pericardial defect. Physiologically, the normal heart apex is
essentially stationary in the chest during the cardiac cycle
[6]. The apical part of the
left ventricle in our patient moved substantially during the cardiac cycle.
Excessive myocardial displacement in congenital absence of the pericardium has
been noticed on ECG studies
[8]. We found that excessive
cardiac myocardial mobility (15 mm instead of 1-7 mm) as a sign of congenital
absence of the pericardium can be derived from cine gradient-echo imaging.
This functional MRI characteristic may be helpful in establishing the
diagnosis of congenital pericardial defect.
The total heart volume in healthy persons varies during the cardiac cycle.
The volume is smaller at systole, and the difference between systole and
diastole is 5-11% [6]. We
confirmed these findings in three patients who had normal findings at cardiac
MRI examination. In our patient with congenital absence of the pericardium, we
found a large difference (21%). This functional MRI finding strongly suggested
the presence of a large pericardial defect, indicated by absence of the normal
pericardial constraining action. Even if the pericardium itself cannot be
adequately visualized morphologically, this functional MRI finding may be
helpful in establishing the diagnosis of congenital pericardial defect. The
two functional MRI findings that can be used to support the diagnosis of
congenital pericardial defect are excessive myocardial displacement and a
large difference in total heart volume in the end-systolic and end-diastolic
phases.
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Introduction
Case Report
