Patent ductus arteriosus Patent Ductus Arteriosus in Animals Patent ductus arteriosus (PDA) is a common congenital defect of dogs, and it occurs less commonly in cats. Persistent flow through the ductus leads to excess blood flow (volume overload) to... read more , ventricular septal defect Ventricular Septal Defects in Animals Ventricular septal defect is a common congenital defect of cats and also occurs in dogs and can vary in location and size. Most defects are small enough to restrict significant shunting between... read more , and atrial septal defect Atrial Septal Defects in Animals Atrial septal defect is an uncommon congenital defect of dogs and cats. The mid-septal location (secundum-type) is most common. Small defects may be hemodynamically insignificant and require... read more with Eisenmenger syndrome are described elsewhere. Other cyanotic heart diseases, including truncus arteriosus, ventricular septal defect with pulmonary atresia, double-outlet right ventricle, and D-transposition of the great arteries, are rare in dogs and cats.