The signs of congenital heart disease (CHD) vary according to the defect(s) that may be present. A number of defects lead to a bluish tint to the skin, fingernails and lips called cyanosis (or blue baby in infants). Also, there are a number of different types of congenital heart disease that can lead to heart failure.

Defects that cause either decreased blood flow to the lungs, or a mixing of oxygen–rich and oxygen–poor blood flowing to the body, can result in cyanosis. This condition results when the body is not getting its full supply of oxygen. The classic signs of cyanosis are a bluish tinge to the skin, most often around the lips, fingernail beds and tongue. Infants may have fast breathing and poor feeding. Older patients may have a low tolerance for exercise. Defects that can cause cyanosis include:

• Low blood flow to the lungs.
  
  
• Critical pulmonary stenosis. A narrowing of the pulmonic valve (between the right ventricle and the pulmonary artery to the lungs), which reduces blood flow to the lungs.
  
  
• Pulmonary atresia. Complete closure of the pulmonic valve, which prevents blood flow from the right ventricle to the lungs.
  
  
• Tetralogy of Fallot. A condition that involves the “tetralogy” of the following four elements: ventricular septal defect, enlargement of the right ventricle, narrowing of the pulmonic valve and a displaced/deviated aorta.
  
  
• Tricuspid atresia. Complete closure of the tricuspid valve, which prevents blood flow from the right atrium to the right ventricle.
  
  
• Ebstein’s anomaly. The tricuspid valve is both displaced and malformed. The leaky valve allows oxygen–poor blood to flow back into the right atrium instead of out to the lungs for fresh oxygen.
  
  
• Mixing of oxygen–rich and oxygen–poor blood.
  
  
• Transposition of the great arteries. A congenital heart defect in which oxygen–rich blood from the left side of the heart is mixed with oxygen–poor blood from the right side of the heart because of the reversed locations of the two major arteries, the pulmonary artery and the aorta.
  
  
• Hypoplastic left heart syndrome (HLHS). A heart defect that can be fatal unless repaired early in life. The chambers, valves and related vessels on the left side of the heart are so underdeveloped that they cannot efficiently pump blood to the rest of the body.
  
  
• Total anomalous pulmonary venous return (TAPVR). A condition in which the four pulmonary veins that bring oxygen–rich blood from the lungs back to the heart are not connected to the left atrium.

Some types of congenital heart defects can also lead to heart failure. Some of these defects allow the blood to flow from the left side of the heart to the right side (a left–to–right shunt), progressively overloading the heart until heart failure results. Other defects may involve leakage of the valves resulting in enlargement and decreased efficiency of one or more of the heart's chambers. Signs of heart failure include:

• Rapid breathing
• Difficulty eating and sucking
• Poor weight gain
• Recurrent respiratory infections
• Low tolerance for exercise

Defects that can result in heart failure include:

• ventricular septal defect (VSD). A heart defect characterized by a hole in the wall septum that divides the two lower chambers of the heart (ventricles). This is the most common congenital heart defect requiring intervention. Also, many babies born with a small VSD will spontaneously heal without the need for medical intervention.

  

• Atrial septal defect (ASD). A heart defect characterized by a hole in the wall (septum) that divides the two upper chambers of the heart (atria). 

  

• Patent ductus arteriosus (PDA). A condition in which the prenatal channel between the aorta and the pulmonary artery (ductus arteriosus) remains open (patent) at birth. Normally, the ductus arteriosus should close as the baby starts breathing.
  
  
• Hypoplastic left heart syndrome (HLHS). A heart defect that can be fatal unless repaired early in life. The chambers, valves and related vessels on the left side of the heart are so underdeveloped that they cannot efficiently pump blood to the rest of the body.
  
  
• AV septal defect (also called atrioventricular canal defect or endocardial cushion defect). A condition in which the center portion of the heart fails to develop, creating a hole between the atria and ventricles, and abnormal mitral and tricuspid valves.
  
  
• Truncus arteriosus. A rare birth defect of the heart in which the major heart arteries fail to separate and the baby is born with one single arterial trunk that supplies blood to both the lungs and the body. This defect may also cause cyanosis.
  
  
• Interrupted aortic arch. A heart defect in which there is literally an interruption along the aorta. A ventricular septal defect (a hole in the wall between the left and right ventricles) may also be present.

Still other defects are characterized by the abnormal narrowing of a structure within the heart. These are known as stenotic defects and, depending on their severity, may cause either the right or left ventricle to fail. Stenotic defects include:

• Aortic stenosis. A narrowing of the aortic valve, restricting the amount of blood that can be pumped from the left ventricle out the aorta.
  
  
• pulmonary stenosis. A narrowing of the pulmonic valve, restricting the amount of blood that can be pumped from the right ventricle out the pulmonary artery.
  
  
• Coarctation of the aorta. A condition in which the aorta (the main artery carrying oxygen–rich blood from the heart to the rest of the body), is pinched, constricted or narrowed at some point along its length.
  
  
• Peripheral pulmonary artery stenosis. A narrowing of part of the pulmonary artery, restricting the amount of blood that can travel through the pulmonary artery and to the lungs.