In dogs, patent ductus arteriosus (PDA) stands as a congenital heart defect, indicating it forms in the womb and persists from birth. To comprehend the impact of PDA on a dog’s physiology, grasping puppy development and fundamental anatomy is crucial.
Dog Heart Anatomy and Development
In the canine cardiovascular system, deoxygenated blood returns from the body to the right side of the heart. Subsequently, it travels to the lungs via the pulmonary artery for oxygenation before returning to the left side of the heart. The aorta serves as the primary artery distributing oxygenated blood from the left side of the heart to the body.
During fetal development in the womb, the fetal aorta links to the pulmonary artery through a specialized blood vessel known as the ductus arteriosus. This vessel allows blood to bypass the lungs and flow directly from the right side of the heart to the aorta. This setup is functional in the womb because the fetus receives oxygen from the mother’s bloodstream via the placenta, bypassing the need for lung oxygenation.
Normally, at birth, the connection through the ductus arteriosus closes as the newborn begins to breathe independently. The closure of the ductus arteriosus allows blood to flow from the right side of the heart into the lungs for oxygenation through the pulmonary artery. However, in cases of patent ductus arteriosis (PDA), the connection remains open, leading to abnormal blood flow patterns through the heart and lungs. A PDA permits blood to flow directly from the aorta into the pulmonary artery, creating a shunt.
If the shunt is moderate to large, it can result in left-sided congestive heart failure due to the overload of blood volume on the left side of the heart. Less commonly, a large PDA can cause damage to the lung blood vessels due to excessive blood flow. Elevated blood pressure in the lungs may cause the shunt to reverse, directing blood from the right to the left (from the pulmonary artery to the aorta).
This abnormal right-to-left shunting of a PDA can lead to the aorta carrying oxygen-deficient blood to the body, resulting in issues such as increased red blood cell production (as they carry oxygen), leading to thickened blood.
Symptoms and Types
The symptoms linked to patent ductus arteriosus in dogs vary based on the seriousness of the anomaly and its duration. Typically, affected dogs display a combination of the following signs early in life:
- Heart murmur
- Exercise intolerance
- Poor growth
- Weakness
Collapse
- For left-to-right shunting PDA:
- Coughing
- Rapid breathing
Difficulty breathing
- For right-to-left shunting PDA:
- Weakness in hind legs
- Bluish gums and skin
Causes
The main cause of patent ductus arteriosus (PDA) in dogs is genetics. Female purebred dogs are particularly at risk. Among the popular breeds predisposed to PDA are:
- American cocker spaniel
- Bichon frise
- Chihuahua
- Collie
- English springer spaniel
- German shepherd dog
- Irish setter
- Keeshond
- Kerry blue terrier
- Labrador retriever
- Maltese
- Newfoundland
- Pomeranian
- Poodle
- Shetland sheepdog
- Yorkshire terrier
Diagnosis
The veterinarian will conduct a comprehensive physical examination of your dog, typically followed by a chemical blood profile, a complete blood count, and a urinalysis to gather general health information. You’ll be required to provide a detailed history of your pet’s health leading up to the onset of symptoms.
To ensure an accurate diagnosis of PDA and to determine the suitable treatment plan, visualization of the heart using radiographs (x-rays) and ultrasound is essential.
Treatment
In cases of left to right Patent Ductus Arteriosus (PDA) in dogs, surgical intervention becomes necessary to gradually close the abnormal connection between the aorta and pulmonary artery. Before proceeding with surgery, it may be essential to stabilize the dog’s condition through oxygen therapy and appropriate medications. The surgical procedure can be safely performed on puppies as young as seven to eight weeks old. While surgery carries inherent risks, many dogs exhibit significant improvement post-operation.
For pets with a right to left shunting PDA, surgical correction is not feasible. While medical management may provide temporary relief, most dogs with this condition eventually succumb to the effects of their PDA.
Recovery and Management
Dogs diagnosed with a mild to moderate, left to right Patent Ductus Arteriosus (PDA) can resume normal activities after a few weeks of recovery following surgical correction. The surgeon overseeing your dog’s treatment will offer personalized guidelines for postoperative care and ongoing monitoring.
Prevention
Due to the genetic transmission of this trait, dogs diagnosed with Patent Ductus Arteriosus (PDA) should not be used for breeding purposes.