Normally, blood returns from the body and flows through the heart and lungs. It will then leave the heart with enough oxygen to supply the body's tissues.
Cyanotic heart disease causes the child's skin to look blue (cyanotic/cyanosis) due to deoxygenated blood bypassing the lungs and entering the systemic circulation. This bluish color is most often seen on the lips, fingers, and toes, or during exercise. Some heart defects cause major problems immediately after birth. Others cause few, if any, problems until adulthood.
Congenital heart defects that may cause cyanosis include:
Tetralogy of Fallot (ToF)
Coarctation of the aorta
Critical pulmonary valvular stenosis
Ebstein's anomaly
Hypoplastic left heart syndrome
Interrupted aortic arch
Pulmonary valve atresia
Pulmonic stenosis with an atrial or ventricular septal defect
Some forms of total anomalous pulmonary venous return
Total anomalous pulmonary venous return
Transposition of the great vessels
Tricuspid atresia (a deformity of the tricuspid heart valve)
Truncus arteriosus
Tetralogy of Fallot (TOF) is a congenital heart defect is the most common cause of blue baby syndrome. It is classified as a cyanotic heart defect because the condition causes low oxygen levels in the blood. This leads to cyanosis (a bluish-purple color to the skin). Patients with tetraology of Fallot have a higher incidence of major non-heart congenital defects.
The classic form of tetralogy includes four related defects of the heart and its major blood vessels:
Ventricular septal defect (hole between the right and left ventricles)
Narrowing of the pulmonary outflow tract (the valve and artery that connect the heart with the lungs)
Overriding aorta (the artery that carries oxygen-rich blood to the body) that is shifted over the right ventricle and ventricular septal defect, instead of coming out only from the left ventricle
A thickened muscular wall of the right ventricle (right ventricular hypertrophy)
At birth, infants may not show signs of cyanosis. However, later they may develop sudden episodes (called "Tet spells") of bluish skin from crying or feeding.
Tetralogy of Fallot results in low oxygenation of blood due to the mixing of oxygenated and deoxygenated blood in the left ventricle via the VSD and preferential flow of the mixed blood from both ventricles through the aorta because of the obstruction to flow through the pulmonary valve. This is known as a right-to-left shunt. The primary symptom is low blood oxygen saturation with or without cyanosis from birth or developing in the first year of life. If the baby is not cyanotic then it is sometimes referred to as a "pink tet". Other symptoms include a heart murmur which may range from almost imperceptible to very loud, difficulty in feeding, failure to gain weight, retarded growth and physical development, dyspnea on exertion, clubbing of the fingers and toes, and polycythemia.
Children with tetralogy of Fallot may develop "tet spells". The precise mechanism of these episodes is in doubt, but presumably results from a transient increase in resistance to blood flow to the lungs with increased preferential flow of desaturated blood to the body. Tet spells are characterized by a sudden, marked increase in cyanosis followed by syncope, and may result in hypoxic brain injury and death. Older children will often squat during a tet spell, which increases systemic vascular resistance and allows for a temporary reversal of the shunt.
Surgery to repair the defects in the heart is usually performed between 3 and 5 years old. In more severe forms, surgery may be indicated earlier. In most cases the heart can be surgically corrected and the outcome is good.
Causes
The cause of most congenital heart defects is unknown. Many factors seem to be involved.
Cyanotic heart diseases may be caused by:
Chemical exposure
Genetic and chromosomal syndromes, such as Down syndrome, trisomy 13, Turner syndrome, Marfan syndrome, Noonan syndrome, and Ellis-van Creveld syndrome
Infections (such as rubella) during pregnancy
Poorly controlled blood sugar levels in women who have diabetes during pregnancy
Some prescription and over-the-counter medications and street drugs used during pregnancy
Factors that increase the risk for this condition during pregnancy include:
Alcoholism in the mother
Diabetes
Mother who is over 40 years old
Poor nutrition during pregnancy
Rubella or other viral illnesses during pregnancy
There is a high incidence of chromosomal disorders in children with tetralogy of Fallot, such as Down syndrome and DiGeorge syndrome (a condition that causes heart defects, low calcium levels, and immune deficiency).
Symptoms
Clubbing of fingers (skin or bone enlargement around the fingernails)
Cyanosis, which becomes more pronounced when the baby is upset
Difficult feeding (poor feeding habits)
Failure to gain weight
Passing out
Poor development
Squatting during episodes of cyanosis
