The cause of most congenital heart defects is unknown. Multiple factors seem to be involved. Prenatal factors associated with higher than normal risk for this condition include maternal rubella or other viral illnesses during pregnancy, poor prenatal nutrition, maternal alcoholism, mother over 40 years old, and diabetes.

There is a higher incidence of tetralogy of Fallot in children with Down syndrome (a common genetic disorder which results from having an extra 21st chromosome).

Tetralogy of Fallot is classified as a cyanotic heart defect because the condition causes insufficiently oxygenated blood to be pumped to the body, which leads to cyanosis (a bluish-purple coloration to the skin).

The classic form of Tetralogy includes 4 defects within the heart structures:

• Ventricular septal defect (hole between the right and left ventricles)
• Narrowing of the pulmonic outflow tract (tube that connects the heart with the lungs)
• An aorta (tube that carries oxygenated blood to the body) that arises from both ventricles, rather than exclusively from the left ventricle
• A thickened muscular wall of the right ventricle (right ventricular hypertrophy)

There is flow of deoxygenated (blue) blood into the general body circulation and decreased blood flow to the lungs.

At birth, infants may not show the signs of the cyanosis, but later may develop sudden frightening episodes of bluish skin from crying or feeding (called "Tet spells"). Tetralogy of Fallot occurs in approximately 5 out of 10,000 infants.

• Difficult feeding (poor feeding habits)
• Failure to gain weight
• Poor development
• Cyanosis which becomes more pronounced during periods of agitation
• Passing out
• Sudden death
• Clubbing of fingers (skin or bone enlargement around the finger nails)
• Squatting during episodes of cyanosis

A physical examination with a stethoscope almost always reveals a heart murmur.

Tests:

• EKG (elctrocardiogram) showing the thickening of the right ventricle muscle
• CBC showing increased red blood cells
• Chest x-ray showing a "boot shaped" heart and dark lungs
• Cardiac catheterization
• Echocardiogram for the definitive diagnosis

Surgery to repair the defects in the heart is always performed relatively early in life. Sometimes a preliminary surgery to create increased blood flow to the lungs is done before definitive corrective surgery. Corrective surgery widens the narrowed pulmonary valve, and the ventricular septal defect is closed.

Parents of children with tetralogy of Fallot can be assisted in coping with the symptoms of the disease. Some interventions to consider include:

• If a child does become blue, the parent should immediately place the child on his/her side and put the knees up to the chest, calm the baby and seek medical attention
• Feeding the child slowly
• Giving smaller, more frequent meals
• Decreasing the child's anxiety by remaining calm
• Minimizing crying by trying to anticipate the child's needs
• Recruiting others to care for the child to prevent parental exhaustion and burn-out

• Delayed growth and development
• Seizures during periods of insufficient oxygen