A congenital heart defect is a problem with the structure of the heart. It is present at birth. The defects can involve the walls of the heart, the valves of the heart, arteries, and veins near the heart. They can disrupt the normal flow of blood, slow down blood, go in the wrong direction or be blocked completely. Doctors use a physical exam and special heart tests to diagnose congenital heart defects. Symptoms include rapid breathing, bluish tint to the skin, lips, and fingernails, fatigue, poor blood circulation. Treatment is done by pediatricians.