Pulmonary atresia means that there is no connection between the right ventricle and the pulmonary artery, which prevents blood from flowing out of the right ventricle and to the lungs. There is also a hole present in the ventricular septum (ventricular septal defect or VSD). Blood flows from the right ventricle to the left ventricle and the deoxygenated blood can leave the heart through the aorta. The deoxygenated blood travels through the aorta to the lungs through the ductus arteriosus (a connection between the aorta and pulmonary artery).