1. Definition/Overview Etiology/Pathophysiology · 2015-03-10 · important with PDA’s. 2. Etiology/Pathophysiology PDA’s occur due to histologic abnormalities within the ductal
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Cardiology Service
VCA West Los Angeles Animal Hospital
1900 S. Sepulveda Boulevard
Los Angeles, CA 90025
P 310-473-2951 | F 310-979-5400
VCAwestlaspecialty.com
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VCA West Los Angeles recently performed closure of a patent ductus arteriosus via
percutaneous transarterial embolization with an Amplatz canine ductal occluder on a
female, four-month-old Newfoundland. We would like to share her case and provide a
review on PDA’s in dogs.
1. Definition/Overview
Patent ductus arteriosus (PDA) is a persistent communication between the pulmonary
artery and the descending aorta that diverts blood away from the non-functional fetal
lungs. The ductus should close shortly after birth but in some patients remains open. It is
the second most common congenital malformation after subaortic stenosis and the most
common congenital abnormality requiring intervention. The poor prognosis if left untreated
and potential fast progression of disease makes recognition and prompt intervention very
important with PDA’s.
2. Etiology/Pathophysiology
PDA’s occur due to histologic abnormalities within the ductal wall. In dogs with PDA’s, the
contractile smooth muscle fibers are replaced to varying degrees with elastic fibers, which
inhibits proper closure. Immediately after birth, the lungs fill with oxygen and release
bradykinin. Bradykinin along with local inhibition of prostaglandin, causes constriction of
the smooth muscle that forms the ductus resulting in functional closure. When closure fails,
blood is shunted from left (descending aorta) to the right (pulmonary artery) because
systemic blood pressure in the aorta is much higher than the blood pressure in the
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Cardiology Service
VCA West Los Angeles Animal Hospital
1900 S. Sepulveda Boulevard
Los Angeles, CA 90025
P 310-473-2951 | F 310-979-5400
pulmonary artery. The continuous flow of blood across the PDA is what creates the
continuous murmur heard on auscultation. In time, the volume overload to the left atrium
and ventricle can lead to congestive heart failure because a portion of the cardiac output is
recirculating through the pulmonary vasculature and returning to the left side of the heart.
3. Signalment/History
Our recent case was a patient named Pink, an intact female, four-month-old Newfoundland
that presented to our cardiologist Dr. Kirstie Barrett at VCA West Los Angeles Animal
Hospital.
PDA’s are more common in female dogs than males with an odds ratio of 3:1. Although
any dog can develop a PDA, the most common breeds are Chihuahua, Collie, Maltese,
German Shepherd, Newfoundland, Poodle, Pomeranian, English Springer Spaniel,
Keeshond, Bichon Frise, and Shetland Sheepdog.
4. Clinical Evaluation
On presentation “Pink” had a grade 5/6 continuous heart murmur with a point of maximum
intensity towards the heart base. A grade 2/6 left apical systolic murmur over the mitral
valve was also present. She had a normal sinus rhythm, was eupneic, and had pink mucus
membranes. She had synchronous and bounding, water-hammer like femoral pulses.
By 7-10 days of age the ductus should be closed, and a continuous murmur after this age
is abnormal. The murmur will be continuous with a point of maximum intensity near the
base of the heart (axillary region). A mitral valve murmur may also be auscultated due to
left atrial enlargement secondary to volume overload. Another common finding with PDA’s
is a bounding femoral pulse due to increased aortic systolic and decreased aortic diastolic
pressures. Depending on severity, the patient may be otherwise normal or may have signs
consistent with congestive heart failure. If pulmonary hypertension is developing the
murmur may be absent to faint during diastole.
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Cardiology Service
VCA West Los Angeles Animal Hospital
1900 S. Sepulveda Boulevard
Los Angeles, CA 90025
P 310-473-2951 | F 310-979-5400
5. Diagnostics
At initial presentation, we performed thoracic radiographs, an echocardiogram, and
laboratory testing. A PCV/TS was 32%/5.2 g/dl and a CBC/chemistry profile was within
normal limits. Thoracic radiographs revealed a characteristic bulge of the descending
aorta with dilation of the main pulmonary artery due to over-circulation on the VD
projection. The left atrium was not enlarged on lateral projections but there was distension
of the cranial pulmonary artery and vein. A PDA was confirmed on echocardiography along
with mitral regurgitation and mild elevation in pulmonary systolic pressure.
Any time a continuous heart murmur is found on physical exam, a PDA should be
suspected. Additional diagnostics to confirm the diagnosis should be completed so that
treatment can be instituted promptly. Thoracic radiographs and echocardiography are
often used to confirm the presence of a PDA.
6. Treatment
We elected to close “Pink’s” PDA with percutaneous, fluoroscopically guided, trans-arterial
embolization with an Amplatz canine ductal occluder (ACDO) via the femoral artery. Prior
to device deployment, angiographic evaluation of the PDA was performed to visualize the
size and shape of the PDA. The procedure and anesthesia were uneventful. Radiographs
obtained the following day confirmed the ACDO had not migrated. Her continuous murmur
was absent but a mitral valve murmur was still present.
Treatment options for PDA closure include surgical ligation or embolization with a
thrombogenic coil or an expandable plug-like device (ACDO). Transarterial closure is
advantageous to surgical closure due to lower morbidity, shorter hospitalization, and faster
recovery. The size and shape of the ductus is important in embolization device selection.
Both coil embolization and ACDO placement is done with fluoroscopy through a small
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Cardiology Service
VCA West Los Angeles Animal Hospital
1900 S. Sepulveda Boulevard
Los Angeles, CA 90025
P 310-473-2951 | F 310-979-5400
incision into the femoral artery so the patient must be large enough to accommodate
catheters and deployment devices. ACDO’s are currently limited to patients ≥ 2.5kg while
coils can be placed in smaller patients. A coil is most successful in smaller, funnel shaped
PDA’s. Advantages to ACDO’s include use in patients with larger PDA’s that are conical or
cylindrical in shape, closer can be obtained with a single device, and they have a lower
rate of dislodgement.
In patients that do not undergo PDA closure, the success of medical management varies
based on degree and direction of shunting. Right-to-left shunting results from pulmonary
hypertension, causing hypoxemia and polycythemia and is managed with phlebotomy,
hydroxyurea and treatment for pulmonary hypertension. Left-to right shunting can lead to
left sided congestive heart failure and is managed with diuretics, ace-inhibitors, and
pimobendan.
7. Prognosis
The prognosis for “Pink” is excellent and she should go on to live a happy, normal life. The
prognosis was due to early and prompt diagnosis and surgical correction.
Figure A: Contrast angiogram prior to ACDO deployment. Contrast is seen leaving the catheter and crossing the PDA
into the pulmonary artery. Figure B: ACDO device is being deployed into the ductus. Figure C: Contrast angiogram
after ACDO deployment demonstrating resolution of blood flow across the PDA.
A B C
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Cardiology Service
VCA West Los Angeles Animal Hospital
1900 S. Sepulveda Boulevard
Los Angeles, CA 90025
P 310-473-2951 | F 310-979-5400
Patients diagnosed with a left-to-right shunting PDA carry a poor prognosis with 60% dying
within 1 year after diagnosis if there is no intervention. Dogs with small, modest shunts can
go on to live beyond 10 years of age.
If the PDA is surgically corrected prior to heart failure or shunt reversal the prognosis is
quite good. It is important to quickly investigate any murmur suspected to be a PDA so that
the window of opportunity to intervene is not missed. Closure of a PDA should never be
delayed because development of irreversible cardiac damage and progressive clinical
signs inhibit our ability to arrive at a successful outcome.
A B C
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Cardiology Service
VCA West Los Angeles Animal Hospital
1900 S. Sepulveda Boulevard
Los Angeles, CA 90025
P 310-473-2951 | F 310-979-5400
Suggested Reading:
Achen, S.E., Miller, M.W., Gordon, S.G., Saunders, A.B., Roland, R.M. and Drourr, L.T.
(2008), Transarterial Ductal Occlusion with the Amplatzer Vascular Plug in 31 Dogs.
Journal of Veterinary Internal Medicine, 22: 1348–1352. doi: 10.1111/j.1939-
1676.2008.0185.x
Bonagura, J.D., Twedt, D.C. Patent Ductus Arteriosus. In: Kirk’s Current Veterinary
Therapy XIV. St. Louis, Missouri: Saunders Elsevier, 2009; 744-747.
Buchanan, J. W. and Patterson, D. F. (2003), Etiology of Patent Ductus Arteriosus in
Dogs. Journal of Veterinary Internal Medicine, 17: 167–171. doi: 10.1111/j.1939-
1676.2003.tb02429.x
Côté, E. and Ettinger, S. J. (2001), Long-Term Clinical Management of Right-to-Left
(“Reversed”) Patent Ductus Arteriosus in 3 Dogs. Journal of Veterinary Internal Medicine,
15: 39–42. doi: 10.1111/j.1939-1676.2001.tb02295.x
Oyama, M.A., Sisson, D.D., Thomas, W.P., Bongura, J.D. Congenital Heart Disease. In:
Textbook of Veterinary Internal Medicine. 7th ed. St. Louis, Missouri: Saunders Elsevier,
2010; 1256-1264.
Moore, K. W. and Stepien, R. L. (2001), Hydroxyurea for Treatment of Polycythemia
Secondary to Right-to-Left Shunting Patent Ductus Arteriosus in 4 Dogs. Journal of
Veterinary Internal Medicine, 15: 418–421. doi: 10.1111/j.1939-1676.2001.tb02340.x
Saunders, A.B., Gordon, S.G., Boggess, M.M. and Miller, M.W. (2014), Long-Term
Outcome in Dogs with Patent Ductus Arteriosus: 520 Cases (1994–2009). Journal of
Veterinary Internal Medicine, 28: 401–410. doi: 10.1111/jvim.12267
Singh, M. K., Kittleson, M. D., Kass, P. H. and Griffiths, L. G. (2012), Occlusion Devices
and Approaches in Canine Patent Ductus Arteriosus: Comparison of Outcomes. Journal of
Veterinary Internal Medicine, 26: 85–92. doi: 10.1111/j.1939-1676.2011.00859.x
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