Patent Ductus Arteriosus in Cats

The ductus arteriosus is a blood vessel that connects the two main arteries of the body - the aorta and the pulmonary artery. This blood vessel is normal in the fetus, but shortly after birth, it should close. When the ductus arteriosus remains open or patent after birth, this abnormal communication between the aorta and pulmonary artery passes extra volumes of blood into the lungs.

Patent ductus arteriosis (PDA) is a birth defect representing the second most common congenital heart defect of cats. Approximately seven out of 1000 live birth kittens are affected.

Generally, there are no serious symptoms of PDA unless congestive heart failure has caused fluid buildup in the lungs. The condition is typically identified in kittens during a routine veterinary visit for vaccinations. Continual blood flow through the PDA into the lungs produces a continuous (machinery) heart murmur.

Even when the veterinarian identifies a PDA, most people believe their cat is normal. In some cases, the cat can be smaller than littermates or play less vigorously. However, the situation can be very misleading as symptoms usually occur within a year of diagnosis. If untreated, about 60 percent of affected cats die within a year of diagnosis.

When caught early, and following treatment with successful closure of the PDA, most cats live a normal life. Unless there are complications from other heart defects or heart failure has already developed, there is rarely any future need for medication. While special circumstances can influence the prognosis, most cases are straightforward.

Patent ductus arteriosus is genetically determined in almost every case, and this fact impacts the value of purebred cats used for breeding.

What to Watch For

Respiratory distress

Coughing

Exercise intolerance

Stunted growth

These are common symptoms, but not specific for PDA.

Diagnosis

Veterinary care should include diagnostic tests and subsequent treatment recommendations. Diagnostic tests are needed to recognize PDA, and exclude other diseases. Tests may include:

Complete medical history and physical examination including auscultation (stethoscope examination) of the heart and lungs. The heart murmur of PDA is characteristic and most experienced veterinarians learn to make the diagnosis simply by listening. Since other birth defects can also cause heart murmurs, a veterinary cardiologist may be consulted if the diagnosis is in doubt.

A chest X-ray (radiograph) can help determine the severity of the problem.

An electrocardiogram (EKG) can assist with the diagnosis.

An echocardiogram with Doppler (cardiac ultrasound) is the definitive diagnostic test. This may require referral.

Routine blood tests may be performed prior to any anesthesia.

Treatment

The conventional treatment is an operation done shortly after diagnosis. The PDA is closed with surgical suture.

Aspirin, indomethacin and other prostaglandin inhibitors do NOT work in cats and should not be given to close the ductus - these are dangerous drugs in young pets.

Surgery should not be delayed by waiting for symptoms to develop.

Medical treatment may be necessary before surgery if symptoms (coughing, difficult breathing) are present.

In some referral centers, the PDA may be closed using special catheterization techniques.

Home Care and Prevention

Before any surgery, provide only the exercise your pet can tolerate. Do not allow your pet to become short of breath with activity.

Follow-up with your veterinarian after surgery or surgical closure. In most cases, only a suture removal is needed and further follow-up is unnecessary.

Kittens should be vaccinated against infectious diseases and dewormed.

Never breed cats with PDA, even if the defect has been corrected.