What is patent ductus arteriosus (PDA)?

The ductus arteriosus is a small communicating blood vessel that runts between the pulmonary artery and the aorta. The pulmonary artery is responsible for brining blood to the lungs, while the aorta brings blood to the rest of the dog’s body. When the puppy foetus is still quite undeveloped, a majority of the blood from the heart will bypass the lungs through the ductus arteriosus. The lungs are not fully developed until quite late in the course of foetal development. When the blood supply from the mother dog is cut off at birth, the puppy will take its first breath and the blood flow through the ductus arteriosus will decrease dramatically. After a few days, the ductus arteriosus closes will become completely closed and no more blood will be able to pass. In some dogs, the ductus arteriosus will not seal properly and the dog retains an opening through which blood can flow. This is called patent ductus arteriosus (PDA). Some dogs develop no symptoms at all, while others experience severe problems. Patent ductus arteriosus can lead to heart failure and death. 

Patent ductus arteriosus symptoms in dogs

The severity of the symptoms will depend on how significant the defect is. In some dogs, there is only a small blind pocket off the aorta and such dogs rarely display any symptoms of patent ductus arteriosus at all.

The most commonly occurring type of patent ductus arteriosus has a left-to-right shunt. This causes blood from the aorta – where the pressure is higher – to be continuously shunted to the main pulmonary artery. This means that the lungs are forced to receive more blood than normally, which in turn can lead to fluid accumulation. Symptoms of this type of patent ductus arteriosus in dogs include exercise intolerance, coughing, and weight loss. If not treated, congestive heart failure is common and dogs suffering from this type of patent ductus arteriosus will often die a premature death unless they receive surgical treatment.

Right-to-left shunt is rare in dogs, but it does occur. Some dogs have this problem from birth, while others develop it since the patent ductus arteriosus is to significant. In dog with a right-to-left shunt some of the blood that leaves the right side of the heart will never reach the lungs. This means the poorly oxygenated blood will circulate in the body of the dog. Symptoms of this type of patent ductus arteriosus in dogs include weakness, shortness of breath, and collapse of the hind limbs.

Patent ductus arteriosus treatment for dogs

If a dog with patent ductus arteriosus receives early surgery, the prognosis is very good. Heart surgery is however always risky and many dogs need medical stabilization before (and sometimes after) the procedure. If your dog is younger than 2 years and have a left-to-right shunting PDA, surgery is definitely recommended. The surgeon will tie off the patent ductus. This should ideally be performed as soon as possible, before the patent ductus arteriosus starts to cause permanent changes in the heart. (The heart will try to compensate for the abnormality.) Puppies as young as 8 weeks can have this type of surgery, and it is recommended to carry out the procedure when the dog is between 8 and 16 weeks of age.

Right-to-left shunt is much less common than left-to-right shunt, and this type of patent ductus arteriosus is normally medically treated than surgically corrected. In addition to medication, the dog must be given plenty of rest, not be exposed to stressful situations, and its exercise must be limited.

Cardiovascular and circulatory problems in dogs: (click for more info)
Aortic stenosis in dogs
Congestive heart failure in dogs
Degenerative mitral valve disease in dogs
Dilated cardiomyopathy in dogs
Heart valve dysplasia in dogs
Hemolytic anemia in dogs
Patent ductus arteriosus in dogs
Pericardial effusion in dogs
Pulmonary hypertension in dogs
Pulmonic stenosis in dogs
Thrombocytopenia in dogs
Ventricular septal defect in dogs
Atrial septal defect in dogs
Tetralogy of Fallot in dogs
Von Willebrand disease in dogs