matters of heart: patent ductus arteriosis
We’re continuing our series on congenital heart conditions in pets with the most common congenital heart defect in dogs – a condition called Patent Ductus Arteriosis (or PDA, for short). Again, to understand how PDA affects our pets, it is helpful to get a short primer (this time on fetal mammals).
One of the heart’s functions is to pump blood to the lungs so that it can become oxygenated, but before a mammal is born, its lungs aren’t yet functional. Instead, the fetus gets oxygenated blood though the umbilical cord. Blood still pumps out of the heart, but it bypasses the lungs by way of a channel called the ductus arteriosis. The ductus arteriosis connects the pulmonary artery (which will one day carry blood to the lungs) with the aorta, which carries oxygenated blood to the tissues of the body.
After birth, the lungs begin to function, as evidenced by a baby’s first scream and a puppy or kitten’s first cry. Blood begins to flow to the lungs at this time, and the ductus arteriosis should start to close. Typically, it closes within three to seven days, but if it fails to close, the affected animal will have a patent (or open) ductus arteriosis.
A patent ductus arteriosis causes blood to shunt from the left heart to the right heart. Blood from the left heart, which is meant to go on to the tissues of the body, ends up heading to the lungs instead. The heart has to work harder to do its job, and eventually this can lead to failure.
Weakness, coughing and respiratory trouble are all signs of heart failure, and about a quarter of puppies with PDAs will have some degree of heart failure at the time of diagnosis.
Breeds that have an increased incidence of PDA are:
A PDA is first detected when your veterinarian hears a heart murmur when he or she listens to your pet’s chest. A heart murmur simply means that somewhere in the heart, there is turbulent blood flow. Heart murmurs occur for many reasons, some of which are completely benign. Heart murmurs due to PDAs have a distinctive sound, so your veterinarian may suspect a PDA simply by listening your pet’s heart.
From there, X-rays and a cardiac ultrasound (echocardiogram) will be performed to assess heart size and confirm the PDA. Your veterinarian may want to refer you to a veterinary cardiologist for these tests.
Once confirmed, a patent ductus arteriosis should be corrected. Without treatment, two-thirds of pets will die before their first birthday. Correction of a PDA can either be done by surgically ligating (or tying off) the ductus arteriosis, or by a procedure called a coil embolization, in which a tiny coil is placed in the ductus arteriosis to block it.
Though these surgeries sound frightening, when done by capable veterinary specialists, the prognosis is excellent. And if you have dog insurance from Petplan pet insurance, which can cover chronic heart conditions such as PDA, the costs of your pet's treatment can be reimbursed, allowing you to focus on your pet's recovery and aftercare instead of the costs.