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.