Patent ductus arteriosus, or PDA, is the most common congenital heart defect in dogs. About 1 in 1000 dogs is affected. PDA is most common in miniature and toy breeds, but has been diagnosed in over 60 breeds. It is caused by a structural defect in the wall of the ductus arteriosus. This can be inherited, so affected animals should not be bred. The condition can be corrected successfully and reliably with surgery. After surgery dogs usually have a normal life span. Occlusion of the ductus also can be achieved with placement of an intravascular coil or plug.

The ductus arteriosus, shown below, extends from the pulmonary artery ventrally to the aorta dorsally, bypassing the lungs in fetal circulation (panel A, below). The ductus arteriosus is highlighted in pink in panel B, below. The aortic arch and descending aorta are highlighted in red in panel C, below. The pulmonary trunk and one of the caudal pulmonary arteries are highlighted in purple in panel D, below. After birth the blood oxygen tension increases, causing the ductus to constrict and eventually become the ligamentum arteriosum that normally persists in adult dogs.

pda3-n Panel A. The anatomy of a ductus arteriosus in a dog	pda3a-n Panel B. The ampulla of the ductus arteriosus, highlighted in pink
pda3b-n Panel C. The descending aorta, highlighted in red.	pda3c-n Panel D. The main pulmonary artery and the left caudal lobar artery, highlighted in purple.

In patent ductus arteriosus the ductus remains open after birth. In the post-mortem specimen from a dog with a PDA, above, you can see the ductus arteriosus connecting the aorta to the pulmonary artery.

This angiocardiogram shows contrast material going from the left side of the heart to the aorta and then passing through the ductus into the pulmonary artery. The ductus is pointed out on the video. It is apparent as a small funnel connecting the aorta and the pulmonary artery. Note that the left heart, aorta, and pulmonary artery are enlarged due to this abnormal circulation.

This is a closeup of a patent ductus arteriosus. The surgery to correct this condition involves isolating the ductus and carefully ligating it. If the PDA is >10 mm in diameter, it is divided and oversewn between special ductus clamps.

pda5