Patent Ductus Arteriosus

Patent Ductus Arteriosus is the most common congenital heart defect occurring in the dog. It is also common in cats. It is an abnormal communication between the pulmonary artery and the aorta. It allows blood to shunt from the aorta to the pulmonary artery throughout the cardiac cycle. There is no disruption in the direction of blood flow during diastole so the mumur heard is continuous and uninterrupted. It will wax and wane in intensity however. The direction of blood flow is from the high pressure aorta to the lower pressure pulmonary artery and results in an over-perfused lung field. Increased blood flow to the lungs results in increase return to the left atrium. It enlarges in size as does the left ventricle. Changes in the lung to this increased flow (pulmonary hypertension) and lead to a reverse shunting PDA. At this point this condition becomes nonsurgical.