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T. NAKAMURA
̶ ̶
41
Case report
A Dog with Right Auricular Aneurysm Diagnosed
with Computed Tomography Angiography
Takashi NAKAMURA1), Haruna TATEISHI2), Chieko ISHIKAWA2),
Kenji KUTARA2), Junseok LEE1) and Masami UECHI*, 1, 2)
(Received 8 April 2014; Accepted 25 October 2014)
Abstract. A 7-year-old Golden Retriever with mild exercise intolerance and presence of an ar-
rhythmia was referred to Nihon University. Electrocardiographic findings included wide QRS com-
plexes, irregular R‒R intervals, small irregular baseline undulations and no P waves. Thoracic radi-
ography revealed a large mass of soft tissue opacity obliterating the cranial cardiac silhouette and
the dilation of the pulmonary artery silhouette. Transthoracic echocardiography showed a type III
pulmonary artery flow pattern, but it did not reveal the presence of a mass in the cranial mediasti-
num. Computed tomography angiography identified an enlarged right auricle that was consistent
with a right auricular aneurysm in the region of the suspected mass. This case was therefore diag-
nosed with a right auricular aneurysm. These findings suggest that computed tomography angiog-
raphy may be a useful diagnostic tool in the diagnosis of the right auricular aneurysm.
Key words: dog, right auricular aneurysm, computed tomography, atrial fibrillation, exercise in-
tolerance
Introduction
Aneurysmal dilation of the right auricle, oth-
erwise referred to as right auricular aneurysm,
is a rare cardiac disease in dogs.1) In humans,
these aneurysms are usually diagnosed by
transthoracic or transesophageal echocardiog-
raphy.2‒4) However, previous reports in dogs
have reported difficulties in identifying abnor-
mal right auricles by echocardiography alone.5, 6)
Therefore, the diagnosis of a right auricular
aneurysm in dogs requires additional diagnos-
tic procedures, including nonselective angiog-
動物の循環器 第 47 巻 2 号41‒46 (2014)
* Correspondence to: Masami UECHI
JASMINE Veterinary Cardiovascular Medical
Center
2‒7‒3 Nakagawa, Tsuzuki, Yokohama, Kanagawa
224‒0001 Japan
Tel: ＋81‒45‒532‒8451
Fax:＋81‒45‒532‒8456
E-mail: uechi.masami@cardiovets.jp
Dog with Right Auricular Aneurysm
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42
raphy or computed tomography (CT).
In this report, we describe a dog with diag-
nosed with a right auricular aneurysm that
necessitated CT angiography after failed at-
tempts with transthoracic echocardiography.
Case
A 7-year-old, male castrated, Golden Re-
triever weighing 29.1 kg was referred to the
Nihon University Animal Medical Center Vet-
erinary Cardiovascular Medicine and Surgery
Unit following the detection of an arrhythmia
and the presence of mild exercise intolerance.
There was no history of trauma. On clinical
examination, the dog was alert and in good
body condition. The heart rate was 136 beats/
min with an irregular rhythm. No cardiac
murmur was auscultated. The remainder of
the physical examination was unremarkable.
The hematology and chemistry panels were
normal, but the levels of plasma atrial natri-
uretic peptide (131 pg/mL; normal ＜25 pg/
mL7)) and N-terminal pro-B-type natriuretic
peptide (2,407 pmol/L; normal ＜900 pmol/L8))
were above the reference range. Electrocardi-
ography (α6000 AX-D, Fukuda M-E Kogyo
Co., Ltd., Tokyo) showed wide QRS complexes
(0.09 s), irregular R‒R intervals, small irregular
baseline undulations, and no P waves (Fig. 1).
Systolic blood pressure, which was measured
by the oscillometric method (BP-100D, Fukuda
M-E Kogyo Co., Ltd.), was 147 mmHg. Thorac-
ic radiography revealed a large soft tissue
opacity that obliterated the cranial aspect of
the cardiac silhouette. The diameter of the
pulmonary artery silhouette that crossed the
9th rib was 1.3 times the diameter of the 9th
rib in the ventrodorsal view. Thus, the pulmo-
nary artery silhouette was mildly enlarged
(Fig. 2). Transthoracic echocardiographic find-
ings (Aplio SSA-700A, Toshiba Medical Sys-
Fig. 1. Electrocardiography: wide QRS complexes, irregular R‒R intervals, small irregular baseline
undulations, and no P waves were found
The heart rate was 101 beats/min during the examination. Paper-speed was 50 mm/s.
T. NAKAMURA
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43
tems Co., Ltd., Tochigi) revealed mild tricus-
pid regurgitation and a type III pulmonary
artery flow pattern9, 10) (Fig. 3). However, the
velocity of the tricuspid regurgitation could
not be measured exactly. Other echocardio-
graphic findings were within normal limits,
and enlargement of the right atrium and ven-
tricle was not found. In addition, echocardiog-
raphy did not reveal the presence of a mass
in the cranial mediastinum.
To confirm the presence of a soft tissue
mass in the cranial mediastinum, CT angiog-
Fig. 2. Right lateral (A) and ventrodorsal (B) thoracic radiographs
A large soft tissue mass opacity (red arrows) in the cranial mediastinal and the dilation of the
pulmonary artery (red lines) in the ventrodorsal view at the 9th rib was shown.
Fig. 3. Pulsed-wave Doppler examination of the pulmonary flow
The pulmonary flow was recorded from the right parasternal short-axis view at the level of the
pulmonary artery, with the gate placed distally to the pulmonary valve (A). The pulmonary blood flow
was a type III, which is characterized by a rapid rise that is followed by a delayed deceleration and
notching (red arrows) during mid-systole (B). Ao＝Aorta, PA＝Pulmonary artery, RA＝Right atrium,
RV＝Right ventricle.
Dog with Right Auricular Aneurysm
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44
raphy (Aquilion 16, Toshiba Medical Systems
Co., Ltd., Tochigi) was performed while the
dog was under general anesthesia. CT angiog-
raphy revealed an enlarged right auricle that
was connected to the right atrium (Fig. 4). On
the basis of CT findings, a diagnosis of a right
auricular aneurysm was made.
The cases heart rate was not fast despite
the arrhythmia, and the clinical symptoms
were mild in this dog. Thus, no treatment was
prescribed for the condition.
Discussion
In this case, an aneurysmal right auricle
was not identified with echocardiography be-
cause of the region of examination, which re-
sulted in significant artifact due to the pres-
ence of the lung lobes. The right parasternal
long-axis and short-axis views were the stan-
dardized views that were used to assess the
right atrium.11) However, visualization of the
dilated right auricle that protruded far into
the cranial mediastinum was difficult because
of the well-aerated lung lobes.5) Therefore, a
suspected right auricular aneurysm should
not be ruled out in dogs on the basis of echo-
cardiographic findings alone. As illustrated by
the dog in our report, the contrast CT clearly
delineated the dilated right auricle. Therefore,
CT angiography may be a useful diagnostic
tool in the diagnosis of this disease. We rec-
ommend the use of CT angiography to differ-
entiate the cause of the soft tissue mass that
is detected with thoracic radiography in the
cranial mediastinum.
There are various causes of atrial auricular
aneurysms in dogs. These include herniation
of the right auricle through a defect of the
pericardial sac,5) myocarditis that is accompa-
Fig. 4. Contrast computed tomography (CT) image at a sagittal section (A) and a three-dimensional
reconstruction of a contrast CT image (B) of the thorax
A large right auricular aneurysm (RAA) is visible. CaVC＝Caudal vena cava, CrVC＝Cranial vena
cava, LA＝Left atrium, LV＝Left ventricle, RA＝Right atrium, RV＝Right ventricle.
T. NAKAMURA
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45
nied by polymyositis,12) and congenital abnor-
malities.6) Partial defects of the parietal peri-
cardium occur in dogs in association with
trauma.5) In humans, atrial septal defects or
tricuspid regurgitation resulting in elevated
right atrial pressure have also been shown to
cause an atrial auricular aneurysm.2) In our
case, the velocity of the tricuspid regurgita-
tion was not known. However, the pulmonary
blood flow was shown by the Pulsed-wave
Doppler examination to have a type III pro-
file, which is characterized by a rapid rise fol-
lowed by a delayed deceleration and notching
during mid-systole. This finding indicated the
elevation of systolic pulmonary artery pres-
sure.9, 10) In addition, our case showed mild di-
lation of the pulmonary artery silhouette by
thoracic radiography in the ventrodorsal view.
These findings indicated that this dog might
have increased pulmonary artery pressure. In
addition, our case showed increased levels of
the plasma atrial natriuretic peptide and N-
terminal pro-B-type natriuretic peptide. Plas-
ma atrial natriuretic peptide and N-terminal
pro-B-type natriuretic peptide levels are in-
creased in dogs with pulmonary hyperten-
sion.13) Thus, the increased levels of these
plasma natriuretic peptides indicated the in-
creasing pulmonary artery pressure due to
the absence of findings of left heart dysfunc-
tion. However, our case did not show findings
that indicated right ventricular dysfunction
and increased right atrial pressure. Thus, the
relationship between the right auricular aneu-
rysm and increased pulmonary artery pres-
sure in our case was unknown.
Previous reports have indicated the devel-
opment of supraventricular tachyarrythmias
in dogs with right auricular aneurysms.5, 6, 12)
The relationships between right atrial aneu-
rysms and supraventricular tachyarrythmia
have not been fully discussed. However, Zee-
bregts have suggested that the atrial
tissue itself might be responsible for the ar-
rhythmias in human with this disease.2) In our
case, the electrocardiographic findings includ-
ed the wide QRS complexes, irregular R‒R in-
tervals, small irregular baseline undulations,
and no P waves. These electrocardiographic
findings and previous reports suggested that
the present case might be affected with atrial
fibrillation with a complete left bundle branch
block. However, further diagnostics to identify
the cause of the arrhythmia were not per-
formed.
The prognoses of dogs with right auricular
aneurysms were variable,5, 6, 12) but they may
have an increased risk for thromboembolism
due to the congestion of blood flow in the
right atrium.5) Therefore, close follow up was
performed to identify any signs of the devel-
opment of thromboembolism.
In conclusion, our case was diagnosed with
the right auricular aneurysm with CT angiog-
raphy. A suspected right auricular aneurysm
should not be ruled out in dogs on the basis of
echocardiographic findings alone because of
the difficulty of the visualization of the dilated
right auricle, and CT angiography is a useful
diagnostic tool to differentiate the cause of the
soft tissue masses that are detected with tho-
racic radiography in the cranial mediastinum.
Dog with Right Auricular Aneurysm
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46
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