Atrial Septal Defect (ASD) An atrial septal defect is an opening in the dividing wall between the two upper chambers of the heart known as the right and left atria. Ventricular Septal Defect (VSD) A ventricular septal defect is an opening in the dividing wall between the two lower chambers of the heart known as the right and left ventricles. Atrioventricular Canal (AV Canal or AVC) AV canal is a complex heart problem that involves several abnormalities of structures inside the heart. Tricuspid Atresia (TA) In tricuspid atresia, the tricuspid valve, normally located between the right atrium and the right ventricle, does not develop properly. Pulmonary Atresia (PA) PA is a serious heart defect in which the pulmonary valve does not allow blood to flow from the heart to the lungs to pick up oxygen. Transposition of the Great Arteries (TGA) Because of abnormal development of the fetal heart, the large vessels that take blood away from the heart to the lungs, or to the body, are improperly connected. Tetralogy of Fallot Tetralogy of Fallot is a complex condition of several congenital heart defects. Coarctation of the Aorta Coarctation of the aorta refers to a narrowing of the aorta that restricts the amount of oxygen-rich blood that can travel to the lower part of the body. Aortic Stenosis Aortic stenosis affects the amount of blood that can flow from the left ventricle to the aorta. Symptoms vary with the degree of blockage. Pulmonary Stenosis Pulmonary stenosis affects the leaflets of the pulmonary valve, making it difficult for blood to flow from the right ventricle to the lungs. Patent Ductus Arteriosus (PDA) PDA is a heart problem in which the connection between the aorta and pulmonary artery remains open after birth, instead of closing as it should.