Patent Ductus Arteriosus in Dogs: An Overview

Dog Breeds

Patent ductus arteriosus (PDA) in dogs is a type of abnormal intracardiac shunt within the heart that is located between the aorta and the pulmonary trunk. When this abnormal shunting of blood develops, extreme pressure builds up in the dog's heart, arteries, and veins due to increased blood pressure. Without treatment, PDA will eventually result in congestive heart failure in dogs.

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Definition of Patent Ductus Arteriosus

Abnormal connections between different chambers of the heart, or between heart vessels, are called cardiac or arterial shunts. The most common of these in dogs is known as patent ductus arteriosus, or “PDA”. A PDA is an abnormal persistent arterial connection between the aorta and the pulmonary artery after birth. During prenatal life, the ductus arteriosus is a normal anatomical feature that allows most fetal blood to bypass the nonfunctioning fetal lungs. However, this fetal channel should close shortly before or within a day or two after birth - once the puppy takes its first few breaths and its lungs become inflated. When the ductus arteriosus remains open -or “patent” - it puts increased burdens on the heart’s left chambers, which causes them to enlarge or dilate. This, in turn, reduces the flow of blood out through the aorta and thereby decreases oxygen delivery to all body tissues. PDAs occur in all breeds and ages of dogs, but they most commonly are identified in young animals. Left untreated, a PDA will contribute to congestive heart failure in dogs and will almost always be fatal.

Causes of Patent Ductus Arteriosus in Dogs

Arterial shunts are normal in fetal animals (including people), but they should close within a short time of birth. A patent ductus arteriosus is one of the most common congenital heart defects in dogs (congenital defects are those which are present at birth). Unfortunately, little is known about why PDA develops so frequently in domestic dogs. It may be influenced by a number of factors or combinations of factors, including environmental, infectious, nutritional, pharmaceutical and/or toxicological factors, among others. Usually, the exact causes of PDA are never determined. However, there are strong genetic factors which predispose certain dogs to retain a patent ductus arteriosus, especially in some smaller dog breeds. This is considered to be an inherited disorder by most veterinary cardiologists.

Prevention

Affected dogs should not be bred and should be spayed or neutered once they are stable enough for elective surgery. There is no other known way to prevent patent ductus arteriosus in companion dogs.

Symptoms and Types