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.

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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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