Patent Ductus Arteriosus Prognosis

Definition

• Before birth, a puppy has no need for its lungs because the mother oxygenates its blood through the placenta. Therefore, a puppy in the womb will have a short blood vessel in its heart called the ductus arteriosus. It shunts blood from the pulmonary artery directly into the aorta, bypassing the puppy's nonfunctioning lungs. Shortly after birth, the ductus arteriosus should close, allowing the blood to flow normally through the lungs, where it receives oxygen. Sometimes, though, the ductus arteriosus remains open, or "patent," resulting in a patent ductus arteriosus.

Shunting From Left to Right

• Most commonly the PDA will shunt the blood from left to right. This leads to volume overload of the left atrium, left ventricle, and pulmonary arteries and veins. A dog with this type of PDA will have a heart murmur, cardiac arrhythmias and signs of left-sided congestive heart failure. If the dog does not undergo surgery to correct the shunt, the prognosis is not good, with around 64 percent of dogs dying within a year of diagnosis. There are, however, cases of dogs with extremely small PDAs living to adulthood, some living 10 years or more.

Shunting From Right to Left

• Sometimes a PDA will shunt the blood from right to left. In these cases, there will be no heart murmur, but the right ventricle will become enlarged and the kidneys, responding to low oxygen levels in the blood, will signal an overproduction of red blood cells, leading to polycythemia (an overly high red blood cell count) and thick blood. Dogs with this type of PDA cannot undergo surgery to correct the problem. Closing the duct would result in an increase in pulmonary hypertension and usually death. Instead, the dog will need periodic phlebotomies. The veterinarian performs a phlebotomy by draining some blood from the dog to lower the viscosity of the blood and to manage the red blood cell count. Long-term prognosis in these dogs is not good. Most dogs will live between three and five years, though some have lived beyond seven.

Interventional Catheterization

• Interventional catheterization is one type of surgery for the correction of PDA. Dogs must weigh at least 4 to 5 lbs. for this surgery, in which a catheter is inserted into a vein in the dog's right inner thigh and then guided into the aorta. The surgeon will inject dye into the catheter to determine the size and shape of the PDA, then place a device--such as a coil, plug or canine duct occluder--into the PDA, stopping the abnormal flow of blood. The survival rate for this surgery is high (about 98 percent) and the prognosis for the dog that successfully undergoes this procedure is excellent.

Surgical Ligation

• In surgical ligation, the surgeon makes an incision between the ribs on the left side of the dog's chest, exposing the heart, then ties off the PDA to stop the errant blood flow. While dogs that undergo this type of surgery will require pain medication and a longer recovery period, if the procedure is successful, prognosis is excellent. Like catheterization, the survival rate for this surgery is about 98 percent.

After Surgery

• If the dog was showing symptoms of the condition, the owner will likely notice a dramatic improvement once the PDA is closed. Most dogs' hearts will return to a normal size in time, but some enlarged hearts may not. The vet will probably perform an echocardiogram one to three months after surgery to check the dog's heart size and function. Occasionally a heart murmur will remain even after the PDA has been corrected. While this should disappear once the heart returns to a normal size, sometimes the murmur will persist.