Definition
Cyanotic heart defects are typically congenital heart defects, or birth defects of the heart. The normal heart has four chambers. Blue or deoxygenated blood returning from the body is pumped by the right ventricle through the pulmonary artery to the lungs. Red or oxygenated returning from the lungs is pumped by the left ventricle back out to the body (see normal heart anatomy and normal blood flow).
Most cyanotic heart defects involve what is termed a right to left shunt. This means that blood from the right side of the heart, either the right atrium or right ventricle, bypasses the lungs and travels directly back out to the body. This usually involves a hole in either the atrial or ventricular septum, as well as some type of obstruction to blood entering the lungs. Relatively common cyanotic heart defects that are classified as right to left shunts include tetralogy of Fallot, tricuspid atresia, pulmonary atresia, and severe forms of Ebstein's anomaly of the tricuspid valve.
Other cyanotic heart defects may be classified as parallel circulations. The most common heart problem in this group is transposition of the great arteries. In this situation, blood never appropriately mixes but instead travels in parallel circuits, one to the body and one the lungs.
Cause
The cause of cyanotic heart defects, as is the case with most congenital heart defects, remains unknown. Genetic factors may play a large role, although this is still being clarified.
Signs and Symptoms
The most common sign associated with cyanotic heart defects is cyanosis, a blue discoloration of the skin because of lack of oxygen in the blood. This may be noticed immediately after birth in cases of severe cyanosis, for example with transposition of the great arteries. With mild cyanosis, it may be somewhat difficult to appreciate. Some infants with tetralogy of Fallot may not be identified for several weeks after birth or even later.
Rapid breathing, or tachypnea, may also be a symptom associated with cyanotic heart defects. A lower than normal oxygen concentration in the bloodstream may stimulate the body to breathe faster.
Diagnosis
Most cyanotic heart defects are identified through the use of an echocardiogram. Sound waves are used to visualize the structures of the heart. The presence of a right to left shunt as seen in tetralogy of Fallot or tricuspid atresia can easily be visualized. In some instances a cardiac catheterization may be necessary to better clarify the heart anatomy.
Treatment
Most all cyanotic heart defects ultimately require surgery for definitive treatment. Prior to surgery, medication may be necessary to stabilize the patient. In patients with severe cyanosis, a medication called prostaglandin may be used to keep the ductus arteriosus open to allow blood to enter the lungs. Surgery for cyanotic heart defects may often initially involved placement of a shunt as a means for blood to enter the lungs (Blalock Taussig shunt). This often is followed by either definitive repair or further palliation, such as seen with a Fontan procedure.
Prognosis
Fortunately the prognosis for patients with cyanotic heart defects in this day and age is good. Almost all can successfully be addressed with different surgical techniques. The overall survival rate for patients with cyanotic heart defects continues to improve.