Tetralogy of Fallot

Tetralogy of Fallot is a common syndrome of congenital heart defects. This condition, present in utero, is caused by the narrowing of the pulmonaryartery and a hole between the ventricles of the heart. When the baby is bornand begins to breathe on its own, the baby turns cyanotic, or blue, due to the deoxygenated blood that bypasses the lungs as a result of this deformity.

Each defect acts in combination with the other to create a malfunction of theheart. The problem starts very early in the uterus with a narrowed pulmonaryvalve and a hole between the ventricles. This is not particularly a problemfor a fetus because hardly any blood flows through the lungs until birth. Itis only after birth that the defects pose a problem. The blood that is supposed to start flowing through the lungs cannot easily get there because of thenarrowed valve, however the hole between the ventricles remains open. Becauseof the opening between ventricles, much of the blood that comes back to theheart needing oxygen is sent out without being properly oxygenated. In addition, the right heart has to pump at the same pressure as the left side. Several things follow. First, the baby turns blue (cyanotic) because of the deoxygenated blood that bypasses the lungs. Deoxygenated blood is darker and appearsblue through the skin. Second, the right side of the heart (ventricle) hypertrophies (gets more muscular) from the extra exercise demanded of it. Next, the low oxygen causes the blood to get thicker and clot more easily. Clots inthe veins can now pass through the hole in the heart and directly enter the aorta, where they can do much more damage than in the lungs--such as causing infarcts in the brain. In addition, these anomalies make the lining of the heart more susceptible to infection--endocarditis--which can damage valves and lead to blood poisoning (septicemia).

Tetralogy is a congenital defect with unknown causes. A complete evaluation of the circulation is required, including testing the blood for its oxygen content, ultrasound and x rays of the heart accompanied by a contrast agent to determine the amount of blood flowing in the wrong direction. A search for other birth defects is also necessary, because they tend to happen together.

Correction of the defects are done through surgery. Surgery must be carefullytimed with attention to the progression of the disease process, the size ofthe infant, and the size of the various defects. There are temporary surgicalprocedures that can prolong the time before corrective surgery while the baby grows larger and stronger. During surgery, the pulmonary valve is widened,the ventricular septal defect is closed, and any interim fixes removed. urgical correction has a high rate of success, returning the child to near normalhealth.

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