A patent ductus arteriosus, or PDA, is one of the most common congenital heart defects in the dog. It is more common in female dogs and in certain breeds. While the lifespan of patients with PDA is significantly shortened if left untreated, most of the patients can be treated successfully if this condition is identified prior to the onset of heart failure.
The Normal Animal
While in the womb, the fetus does not breathe air, i.e. the lungs are not yet working; instead, it receives oxygen from the mother. The ductus arteriosus is a normal blood vessel in the fetus. It connects the pulmonary artery to the aorta close to where they each leave the heart (see diagram). In this way, it allows the blood to bypass the non-functioning lungs. The ductus naturally seals off shortly after birth once an animal begins to breathe air. Sealing the ductus closes the connection between the pulmonary artery and the aorta and allows each of these vessels to have their own blood flow. The pulmonary artery only delivers blood to the now functional lungs to pick up oxygen, while the aorta delivers blood to the rest of the body.
Patent Ductus Arteriosus
In dogs with PDA, the ductus fails to seal shut after birth. This persistent connection causes an increased amount of blood to flow through the lungs and drain back into the heart, forcing it to work harder than normal (figure). This extra workload will eventually lead to heart failure if the condition is not addressed in a timely fashion.
Treatment and Prognosis
Treatment of PDA is directed at closing the ductus. This can be achieved with traditional surgery or a “keyhole” surgery (aka a minimally invasive procedure). The latter technique involves placing a small occluding device directly into the ductus to block the abnormal blood flow. This is accomplished by threading the device through a long catheter inserted in a peripheral artery. In other cases, thoracic surgery is necessary to tie off the ductus. At the Kansas State University Veterinary Health Center, we are highly experienced in both minimally-invasive and surgical techniques, and can counsel you on the best option for your pet.
Patients with corrected PDAs have an excellent prognosis, especially when the defect is corrected prior to the onset of heart failure. Therefore, as with other congenital heart defects, it is essential that correction be pursued as early as possible, before permanent changes to the heart muscle and lungs occur.
Continuous flow of blood from the aorta to the pulmonary artery through an open PDA in a dog.