What is a Patent Ductus Arteriosus?
A patent ductus arteriosus is a vessel that connects the two major vessels associated with the heart, the pulmonary artery and the aorta that should have closed at, or within a few days, following birth. Prior to birth, the ductus arteriosus connects the aorta and pulmonary artery and remains an open channel allowing blood to skip the step of circulating through the lungs and flow directly from one vessel to the other. This helps the prenatal heart work most efficiently. Once born, however, the newborn’s blood must receive oxygen from the lungs and the vessel should close. When it does not, the open hole is called a patent ductus arteriosus. If left untreated, a PDA results in heart enlargement and heart failure. Unfortunately without treatment, most dogs and cats with a PDA will die within their first year of life.
What causes Patent Ductus Arteriosus?
The cause of PDA is not known, however there is a possibility that there may be a genetic predisposition. The condition is more common in dogs than in cats and most common in females.
What clinical signs will my pet have?
In most cases, owners will not notice anything abnormal with their pet, however they may have some mild exercise intolerance or stunted growth. When clinical signs are present, they include severe exercise intolerance, coughing, increased respiratory rate, and difficulty breathing.
A different form of PDA, termed ‘reverse PDA’, can present with exercise intolerance and hind limb collapse during exercise. These animals also commonly exhibit cyanosis, and a heart murmur is often not heard.
How is a Patent Ductus Arteriosus diagnosed?
The first step is for your pet to have a thorough physical examination which includes taking a history of clinical signs and an evaluation of respiratory and cardiac function. A characteristic heart murmur is heard when listening to the heart.
Echocardiography (heart ultrasound) is recommended to confirm the diagnosis of a patent ductus arteriosus, and helps to rule out any other concurrent cardiac abnormalities. Chest radiographs will show enlargement of parts of the heart and vessels.
How is Patent Ductus Arteriosus treated?
Here at NCVS we perform surgical ligation of the PDA. Surgery is performed as soon as possible after diagnosis to minimise the damage to the heart. A thoracotomy is performed (opening of the chest between two ribs) and the PDA is visualised. Heavy silk sutures are placed around the PDA and the PDA is slowly closed by tightening and tying each suture. A chest drain will be placed prior to closing the chest to help remove air from the chest following surgery. This will only normally need to remain in place for a day or two.
This condition can also be treated in a minimally invasive approach using a device placed up through the femoral artery. This needs to be performed under the supervision of a specialist interventional cardiologist which unfortunately we cannot do here. We will discuss this procedure with you and if you would prefer to a cardiologist in Brisbane to have a discussion and possible surgery.
What happens to my pet after surgery?
Immediately after surgery your pet will be recovered from anaesthetic under the care of our fully trained nurses in our ICU that is staffed 24hrs a day. Postoperative analgesia and intensive care will be provided in our designated recovery ward where your pet will be monitored and nursed by a dedicated team of nurses and veterinarians. Your pet’s breathing and cardiac function will also be monitored closely to ensure that there are no problems.
The length of hospital stay following this surgery varies from patient to patient and is determined by their comfort levels and their recovery following surgery. Most patients can go home between 2 and 5 days after surgery.
You will be advised of the need for strict rest for your pet and to administer prescribed antibiotics. A repeat echocardiogram at 3-6 months is advised to confirm that the PDA has remained closed.
What complications can occur?
The most serious complication during surgery is rupture of the ductus arteriosus, pulmonary artery or aorta during the procedure, resulting in severe haemorrhage that can be fatal. The risk of this is greatly reduced when the procedure is performed by an experienced surgeon which we have here at North Coast Veterinary Specialist.
What is the prognosis?
The prognosis is excellent following surgery, with a normal life expectancy when there is no heart enlargement or evidence of heart failure prior to surgery. If there was evidence of heart enlargement or heart failure prior to surgery, a return to normal heart function may not occur. In these cases, the progression of heart failure is often slowed, but in badly affected dogs heart failure will still progress, resulting in a shorter life expectancy.