Dr Ira Shah
Consultant Pediatrician - B.J.Wadia Hospital for Children
Editor - Pediatric Oncall

What is pulmonary atresia?
The heart consists of 4 chambers - the right and left atrium. atrium (These are the chambers that receive the blood - the right atrium receives impure blood from the rest of the body and left atrium receives pure blood from the lungs) and the right and left ventricles (These are the chambers that pump the blood from the heart - right ventricle receives impure blood from right atrium and sends it to the lungs and left ventricle receives pure blood from left atrium and sends it to the body). Right atrium is separated from the right ventricle by a valve called as tricuspid valve. Left atrium is separated from the left ventricle by a valve called as mitral valve. The blood flow from the right ventricle to the lungs via the pulmonary artery is regulated by the pulmonary valve while the blood flow from the left ventricle to the rest of the body via the aorta is regulated by the aortic valve. In pulmonary atresia, no pulmonary valve exists, so blood can’t flow from the right ventricle into the pulmonary artery and on to the lungs. The tricuspid valve is often poorly developed too. Thus for the blood to go to the lungs, either blood flows from the right ventricle to the left ventricle by a hole in the ventricular wall (ventricular septal defect) or from the right atrium to the left atrium by a hole in the atrial wall (atrial septal defect). So there is mixing of both impure blood and oxygen rich blood on the left side of the heart. The left ventricle pumps this mixture of blood into the aorta and the rest of the body. Part of the blood from the aorta is sent to the lungs through a connection between the aorta and the pulmonary artery called as patient ductus arteriosus (PDA). This blood then gets oxygen in the lungs and comes back to the left atrium.