Many dog owners are not aware of PDA (patent ductus arteriosis), a congenital heart defect in dogs. PDA is the most common congenital heart defect in dogs and can often go undetected. In this post, we'll take a closer look at PDA in dogs, including the symptoms to watch for and how it's treated. So whether you're just starting out as a dog parent or you've been one for years, read on to learn more about this important subject.
What is a PDA in dogs and how does it develop?
A PDA in dogs is called patent ductus arteriosis and is the most common congenital heart defect in dogs, affecting approximately 1 in 1000 dogs. It is thought to be an inherited genetic disorder.
In order to understand what a PDA (patent ductus arteriosis) is and how it affects dogs, we must first take a look at what is considered normal.
During fetal development, a structure called the fetal ductus arteriosis connects the pulmonary artery to the aorta, therefore diverting blood away from the lungs. Fetuses do not breathe inside of the womb, so this structure is necessary for fetal life. After birth, the ductus arteriosis normally closes within a few days after birth.
In PDA in dogs, however, the fetal ductus arteriosis fails to close completely and remains open into puppyhood. The resultant patent ductus arteriosis results in the shunting of blood from the high-pressure aorta to the lesser-pressure pulmonary artery. The effect is more blood than normal being delivered to the lungs via the pulmonary artery which will result in a volume overload and distension of the left side of the heart as the blood backs up in the left atrium and left ventricle.
PDA in dogs can affect males or females but it occurs most often in purebred females. If a large PDA is present, congestive heart failure (CHF) usually develops within the first year of life.
PDA in dogs can affect males or females but it occurs most often in purebred females. If a large PDA is present, congestive heart failure (CHF) usually develops within the first year of life.
What are the symptoms dogs show if they have a PDA?
Dogs with a PDA may not have any symptoms, but the classic continuous murmur may be detected during a routine puppy physical examination by your veterinarian.
Clinical symptoms may include:
- Weakness
- Exercise intolerance
- Failure to thrive
- Exercise-induced collapse
If the PDA has caused congestive heart failure (CHF), clinical symptoms of cough, difficulty, and rapid breathing may be noticed.
How is a PDA in dogs diagnosed?
An astute veterinarian should be able to tentatively diagnose PDA in a dog given their physical examination findings. Dogs with a PDA have a classical continuous heart murmur at the region of the heart base, palpable thrill on precordial palpation (i.e. the murmur can be felt when hands are placed on either side of the heart), and strong, bounding femoral pulses. If these clinical examination features are noticed on a routine puppy examination, PDA should be considered until proven otherwise.
Tests used to definitively diagnose a PDA in dogs include chest X-rays and an echocardiogram (heart ultrasound). Chest X-rays can reveal PDA by showing an enlarged, rounded heart shape. An echocardiogram is the most sensitive and specific test for PDA diagnosis. It will show PDA in over 99% of affected dogs and can also quantify the size of PDA by measuring the diameter of the PDA opening.
There is a particular blood test called NT-proBNP which is elevated in PDA and other cardiac diseases. This test is not very specific for PDA but may be helpful in ruling out other causes of heart disease.
What are the treatment options for PDA in dogs?
The most common treatment for PDA in dogs is surgical correction. This involves closing the PDA with an occlusion device. Surgery is best performed at 2-4 months of age to ensure the best outcomes. Various occlusion devices have been used with success and are placed within the PDA via the femoral artery and using fluoroscopy for guidance. The success rate for PDA surgery is very high, with most dogs going on to lead normal, happy lives after surgery.
The advantage of employing an occlusion device is that, while it is a surgical procedure, it is less invasive than thoracic surgery in manually ligating the PDA.
What is the prognosis for dogs with a PDA?
For dogs that have undergone treatment for a PDA, the prognosis is excellent as the treatment is usually curative. Dogs with a PDA that has not been treated, however, generally succumb to the disease by the age of one year.
Can PDA in dogs be prevented?
The gene that causes PDA in dogs is inherited, therefore breeding affected dogs is not advised. It's also best to avoid repeating the sire's breedings to the dam.
What is a reverse PDA in dogs?
The typical, most common type of PDA in dogs is a left-to-right shunt. As blood is under higher pressure in the aorta, blood is forced to the pulmonary artery resulting in fluid overload and cardiac distension and enlargement.
With a reverse PDA, pulmonary hypertension that is present as a result of pulmonary over-circulation can lead to a right-to-left shunting of blood. A reverse PDA in dogs typically occurs secondary to very large PDAs.
Is a PDA in dogs fatal?
In most cases, PDA in dogs is not a fatal condition. PDA that has been successfully repaired via surgery can typically live long and healthy lives after treatment. However, a PDA in dogs that is left untreated can often be fatal within the first year of life. If left untreated, PDA will eventually lead to heart failure due to the constant pressure on the heart, resulting in irregular heart rhythms and eventually cardiac arrest. PDA that is left untreated can often be fatal within the first year of life.
PDA in dogs is a congenital heart defect that affects the flow of blood to the puppy's lungs. PDA can cause congestive heart failure (CHF) and symptoms may include coughing, difficulty breathing, and exercise intolerance. PDA is diagnosed with a physical examination, chest X-rays, and echocardiography (heart ultrasound) and treatment are generally surgical. The prognosis for dogs with PDA is excellent if the PDA is treated.
If you think your dog may have PDA, please contact your veterinarian right away for further testing and treatment options.