Hypoplastic Left Heart Syndrome (HLHS) is a heart condition where the mitral and aortic valves don’t develop properly. The left ventricle and aorta are also underdeveloped and very small (hypoplastic). This prevents oxygenated blood from reaching the body. Instead, blood is forced through a hole (an atrial septal defect) from the left atrium to the right atrium with blood reaching the aorta though the pulmonary artery and ductus arteriosus (a connection between the aorta and pulmonary artery) to reach the body. There can be other differences in the heart that can occur with HLHS. Your medical team will let you know if there are any other differences that your baby’s heart may have. Model ID: MS AA