Patent ductus arteriosus with pulmonary hypertension in the dog.

The clinical, physiologic, and pathologic manifestations of patent ductus arteriosus (PDA) with pulmonary hypertension (right to left type PDA) were studied in 5 dogs. Cyanosis, hindlimb collapse, low-intensity heart murmurs, and splitting of the 2nd heart sound were prominent clinical findings. Secondary polycythemia was a feature in 3 dogs. Electrocardiography revealed marked frontal plane right axis deviation in all dogs. Radiographic findings in all dogs consisted of an enlarged right ventricle and main pulmonary artery segment, with a hypovascular pulmonary pattern. A wide descending aorta was evident in 4 dogs. Pulmonary arteriography revealed blunt, tortuous secondary and tertiary vessels. Blood flow through the PDA was from right to left in 4 dogs and bidirectional in 1. Necropsy of 1 dog revealed extensive pulmonary arterial disease characterized by fibromuscular intimal proliferation. Surgical correction was contraindicated, and medical therapy was not required in the 4 dogs retained by the owners as pets. Due to the persisting congenital heart defect and the real and potential sequelae, the prognosis is guarded.