Atrioventricular canal defect, also known as atrioventricular septal defect, is a congenital heart condition characterized by a combination of heart defects that affect the atria, ventricles, and valves of the heart. These defects result in abnormal blood flow to the lungs, causing the heart to work harder. Symptoms are similar to those of heart failure, including difficulty or rapid breathing, excessive sweating, fatigue, irregular heartbeat, swelling of legs, ankles, and feet, and wheezing.