The ductus arteriosus is the communication between the aorta and the pulmonary artery, which are the two main blood vessels leading from the heart.
During fetal development the ductus sends blood back to the body because the lungs are not yet functional, and after birth they should close naturally.
Patent Ductus Arteriosus (PDA), is a heart defect that occurs when the ductus arteriosus fails to close naturally at birth so, the blood then flows from the aorta through the Patent Ductus Arteriosus into the pulmonary artery.
The pulmonary artery then needlessly recirculates this oxygenated blood back to the lungs and since less blood is now being pumped into main circulation through the aorta with each heartbeat, the left side of the heart is forced to work harder to meet the demands of the body.
As blood continues to shunt through the PDA, it will cause irreversible changes in the heart muscle and eventually may lead to congestive heart failure.
How PDA is Diagnosed
A Patent Ductus Arteriosis (PDA) will usually be diagnosed when your veterinarian hears a loud ‘continuous’ murmur during a routine physical examination of your puppy. The sound is so loud that it is often described as a ‘washing machine murmur’ because it sounds like water being agitated through the wash cycle.
Your veterinarian may recommend chest x-rays to assess the heart and lungs, and an electrocardiogram (ECG) to assess the heart rhythm. Blood tests may show whether other organs are being affected by the abnormal blood flow, or if there is evidence of abnormal red blood cell values.
Echocardiography, or cardiac ultrasound, will be needed to definitively diagnose a PDA. The Ultrasonographer will examine a 2-dimensional image of the heart to assess the degree of enlargement of its walls and efficiency of its pumping ability. Doppler echocardiography evaluates the direction and speed of blood flow. It can also be used to help pinpoint the location and size of the shunt, and help determine the amount of turbulence associated with it.
How it is Corrected
The goal of treatment for a forward flowing PDA is to stop the blood flowing through the shunt. In some cases, the ductus will be tied off during heart surgery. Surgical repair in most cases should be performed as soon as possible. The longer the surgery is delayed, the more likely that irreversible heart damage will occur. If the dog is showing signs of heart failure, pre-surgical stabilization will be necessary.
With a clinical PDA, congestive heart failure often develops. Signs include arrhythmia (abnormal heart beats), increased lung sounds when examined with a stethoscope, and accumulation of fluid in the lungs and/or abdomen.
Some Dogs Are More Susceptible Than Others
Although any breed of dog can be affected by this heart defect, PDA does appear to have a heritable component in smaller breeds of dogs. Breeds that are reported to have more problems with this defect include Maltese, Pomeranians, Yorkshire Terriers, Shetland Sheepdogs, Toy Poodles, and Miniature Poodles. When this defect is inherited, it appears to run in families. Affected dogs should not be bred, even if the condition is successfully treated.