Veazie Veterinary Clinic
1522 State Street, Veazie, ME
(207) 941-8840

PDA & Congenital Heart Disease

Congenital heart disease describes a defect in the structure of your pet’s heart that has been present from birth. These are often genetic, but does not mean the whole litter suffers the same defect. Patent Ductus Arteriosus is one of the more common defects we see apart from benign murmurs.

Congenital Heart Defects

Congenital heart defects are structural abnormalities in the heart that develop in the fetus and are therefore present at the time of birth. Most of these defects will be found by a veterinarian on the pet’s first few visits. There are four main categories of defects:

  • Obstruction of blood flow
  • Abnormal communication between the left and right sides of the heart
  • Abnormal communications sending blood opposite to normal flow
  • Vessel abnormalities that obstruct and interfere with normal function

Patent Ductus Arteriosus (PDA)

Every normal fetus has a ductus arteriosus,. This enables the umbilical circulation to supply oxygen, allowing the blood bypass the fetus’ non-functional lungs. The ductus arteriosus is a small channel that connects the pulmonary artery (which in a mature animal carries blood to the lungs) and the aorta (which carries blood to the rest of the body).

At birth this system is no longer needed. We can breath, our lungs work and we are meant to exchange gases to circulate oxygen in the blood. It becomes easier for blood to flow to the lungs than through the ductus. The ductus closes within the first 3 to 10 days of life, allowing the blood to begin its normal blood flow through the heart.


Normal Embryo


Patent Ductus Arteriosus










If the ductus does not close it remains open or “patent.” When this happens blood from the aorta will want to flow to the pulmonary artery not the body as its supposed to. This is called a left to right shunt and creates problems in the young animal.

Why is this a problem?

Depending on the size of the shunt, it causes a certain amount of blood to circulate around inside the heart instead of through the body. Since the body has specific requirements for how much oxygen and blood it needs, the heart needs to pump harder in order to meet those requirements. This puts extra strain on the heart and can lead to heart failure. Signs include coughing, weakness and difficulty breathing.

Diagnosis of PDA

A PDA has a very characteristic murmur that can be heard by a veterinarian during your pet’s first check-ups. A full work-up to confirm the presence of the ductus includes radiographs to check for heart failure and enlargement of the aorta, and an ultrasound to visualize the chamber sizes and the patent ductus itself.

Maddie Norris PDA Sx

Maddie was 12 weeks old when Dr. Cloutier conducted her PDA surgery. 6 hours after surgery she was already sitting up and eating.

Is It Treatable?

Yes, PDA is treatable. If there are signs of heart failure, the young pet will need to first be put on medications to stabilize the condition.

To treat the PDA, however, your new pet will need surgery. The surgery is surgical ligation which means that the chest is opened and a piece of suture is used to tie the patent ductus closed.

Without treatment 2/3 of pups will die before they reach one year of age.

Learn About PDA Surgery