Patent ductus arteriosus (PDA) or Botall's duct is a common congenital heart defect in dogs and is less common in cats. This condition occurs when the blood vessel connecting the pulmonary artery to the aorta in the fetus (ductus arteriosus) fails to close properly after birth.
Normal blood circulation in the fetus and newborn
▫️During fetal development, the ductus arteriosus allows blood to bypass the lungs, since they are not yet functioning. After birth, once breathing begins, the ductus arteriosus usually closes within a few days, and blood begins to circulate through the lungs to be oxygenated.
What happens with VAP?
In patent ductus arteriosus, the ductus arteriosus remains open. This leads to abnormal blood shunting between the aorta and the pulmonary artery. Oxygen-rich blood from the aorta flows back into the pulmonary artery, mixing with blood heading to the lungs. This forces the heart to work harder to pump a greater volume of blood and can lead to:
- Left-sided heart overload: The increased blood volume causes the left ventricle and left atrium to enlarge.
- Congestive heart failure: Over time, excessive strain can lead to heart failure.
- Pulmonary hypertension: In some cases, high blood pressure in the pulmonary arteries may develop.
Breeds prone to VAP
Although VAP can occur in any dog breed, certain breeds are more prone to it, including:
▫️VAP is less common in cats, but can occur in any breed.
▫️Toy Poodle
▫️Yorkshire Terrier
▫️Chihuahua
▫️Pomeranian
▫️Cocker Spaniel
Normal blood flow and an open ductus arteriosus
Clinical signs
The clinical signs of VAP may vary depending on the size of the ductus and the severity of cardiac involvement. Some animals with a small VAP may show no symptoms, while others may exhibit:
▫️Characteristic heart murmur: The most common sign is a loud, continuous "machinery-like" murmur that can be heard during auscultation.
▫️Shortness of breath or rapid breathing: Especially during physical activity.
▫️Cough: May be a sign of congestive heart failure.
▫️Weakness or rapid fatigue: The animal may tire quickly during play or exercise.
▫️Growth retardation: In severe cases, young animals may grow more slowly than their peers.
▫️"Jumping" pulse: Due to increased stroke volume of the left ventricle.
Diagnostics
The diagnosis of VAP typically includes:
▫️Auscultation: Listening for characteristic heart sounds using a stethoscope.
▫️Echocardiography: An ultrasound examination of the heart that allows visualization of the heart’s structure, blood flow, and the presence of a VSD. This is the most important diagnostic tool.
▫️Chest X-ray: Can show an enlarged heart and the presence of fluid in the lungs (pulmonary edema) in heart failure.
▫️Electrocardiogram (ECG): Measures the heart’s electrical activity and can detect arrhythmias or other signs of heart damage.
Treatment
Treatment of VAP is recommended in most cases to prevent the development of heart failure and other complications. There are two main treatment methods:
▫️Surgical treatment (ligation): A traditional method involving the surgical closure of the duct using sutures.
▫️Interventional treatment (occlusion): A less invasive procedure in which a special device (such as a coil or occluder) is inserted through a catheter to close the duct.
Forecast
▫️The prognosis following treatment for VAP is generally excellent, especially if the procedure is performed at an early stage, before significant complications develop. After successful closure of the duct, most animals can lead normal, healthy lives. Failure to treat VAP in animals will lead to heart failure and premature death.
Conclusion
▫️VAP is a serious but often treatable congenital heart defect in dogs and cats. Early diagnosis and timely treatment are crucial for ensuring a positive outcome and a long, healthy life for the animal.