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Congenital heart defects can involve the anterior walls of the heart, valves inside the heart, or the vessels that carry blood to or away from the heart.
There are many different types of congenital heart defects, but most alter the normal flow of blood through the heart. For example, right-to-left shunts, (RTLS), cause blood to flow from the right heart to the left heart, whereas in left-to-right shunts, the inverse occurs. RTLS are also called cyanotic congenital heart disease, because from birth or soon after, blood that is poorly oxygenated enters the systemic circulation and causes cyanosis.
People with RTLS often experience breathlessness, fainting, or chest pain during physical activity. Affected infants may fail to gain weight due to fatigue during feeding. There are several causes of RTLS, including a congenital cardiac anomaly called Tetralogy of Fallot.
Left-to-right shunts (LTRS), also called late cyanotic congenital heart disease, are more common than right-to-left shunts. They do not cause cyanosis from birth, but they may gradually cause overload with associated hypertrophy of the right ventricle and pulmonary hypertension.
If pressure in the right heart becomes higher than in the left, a reversal may occur, to produce a right-to-left shunt. This reversal allows poorly oxygenated blood to enter the systemic circulation, producing late cyanotic congenital heart disease (Eisenmenger’s syndrome). Although there are several causes, left-to-right shunts often involve defects of the ventricular or atrial septa.
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