Clinical Case Challenge: Puppy with Quiet Heart Murmur

A seven-month-old, 2.2 kg Pomeranian named Hope presented at Henry and Lois Foster Hospital for Small Animals (FHSA) at Cummings School of Veterinary Medicine at Tufts University with a history of a soft heart murmur.

History
Hope’s primary veterinarian detected the heart murmur after evaluating the dog for a cough that resolved after a course of antibiotics. Though it appeared to be an incidental puppy murmur with no other symptoms present, the veterinarian recommended that Hope see a cardiologist to rule out a more serious condition.

Can you solve the case of the month?

Determine which additional diagnostics are required
Dr. Hannah Melhorn, cardiology resident at FHSA, conducted a physical exam of Hope and heard a continuous heart murmur, loudest at the heart base. Hope also had bounding femoral pulses.

These findings raised suspicion for a patent ductus arteriosus (PDA), a heart defect caused by incomplete closure of the ductus arteriosus after birth. An echocardiogram of Hope’s heart confirmed the diagnosis.

“It was a clear diagnosis once we had advanced imaging to aid us,” says Melhorn. “A PDA is one of the more common congenital heart diseases in puppies, and without closure, dogs can succumb to congestive heart failure often within the first year of life, so sending them early for referral is a good idea.”

Treatment
Surgical intervention is the recommended treatment to close a PDA, according to Melhorn. One option is surgical closure via a thoracotomy. This surgery requires an incision between the ribs and direct visualization and ligation of the ductus arteriosus. This is a technically challenging procedure due to the location near important vascular structures, and there is the risk of life-threatening hemorrhage. Another option is a minimally invasive catheter-based procedure. During this approach, a catheter is placed, often through the femoral artery, into the descending aorta, and across the ductus arteriosus to allow for the deployment of an occlusion device. This can be difficult to successfully complete in small dogs as vessel size may not accommodate the device equipment.

In this case, the team opted for the minimally invasive approach and implanted an Amplatz Canine Ductal Occluder (ACDO) into the ductus to close the PDA and stop continuous blood flow.

“We worried because she was a really small dog, that we might be unable to place the ACDO,” says Melhorn. “The surgery was successful, however, and she recovered smoothly and quickly with no incisional concerns."

FHSA cardiologists occluded the abnormal blood flow, giving the heart time to reverse remodel (return to normal), with the ACDO in place. Hope was put on a short course of gabapentin and trazodone to minimize pain and provide sedation. Exercise restriction is important to decrease the chance for  device dislodgement and allow the body time to heal the surgical incision. The device will eventually be covered by endothelial cells, which line the inner surface of the blood vessels, anchoring the device in place and markedly reducing the chance of device dislodgement over time.

Occasionally, dogs have enough heart enlargement from the PDA that they are placed on pimobendan, at least in the perioperative period or possibly for life. Hope’s heart showed improvement on the echocardiogram the following day, so she did not need to remain on pimobendan. The incision itself takes about two weeks to heal, although exercise restriction is often recommended for at least a month. Hope will return to FHSA for a recheck echocardiogram to assess her heart size and positioning of the ACDO and confirm complete closure of the ductus. She is expected to recover fully.

Comments from Cummings School’s Cardiology Team
Heart murmurs are often difficult to detect in puppies. Melhorn offers some recommendations, “It’s important to take the time with puppies to listen to the heart in all locations—making sure to get way up under the armpit to listen at the heart base before moving down to the apex. Also important is to listen closely on both sides, ideally in a quiet environment. Very wiggly and vocal dogs are often the most difficult to auscultate adequately.”

If a PDA is not corrected, the dog can die from congestive heart failure, or in rarer cases, develop pulmonary hypertension causing shunt reversal, which can no longer be surgically corrected.

“A loud heart murmur in a puppy is abnormal and should be referred to a cardiologist,” adds Melhorn. “Even if a quiet heart murmur is detected, consider a consultation, as the dog could be brewing something more. A PDA, if corrected early, allows a puppy a chance at a normal life.”