Tetralogy of Fallot (patient information)
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. ; Associate Editors-In-Chief: Priyamvada Singh, MBBS 
Tetralogy of Fallot (fuh-LOE) is a rare condition caused by the combination of four heart defects that are present at birth. These defects, which affect the structure of the heart, cause oxygen-poor blood to flow out of the heart and into the rest of the body. Infants and children with tetralogy of Fallot usually have blue-tinged skin because their blood doesn't carry enough oxygen. Tetralogy of Fallot is often diagnosed during infancy or soon after. However, tetralogy of Fallot may not be detected until later in life, depending on the severity of the defects and symptoms. With early diagnosis followed by appropriate treatment, most children with tetralogy of Fallot live relatively normal lives, though they'll need regular medical care and may have restrictions on exercise. 
What are the symptoms of Tetralogy of Fallot?
Tetralogy of Fallot symptoms vary, depending on the extent of obstruction of blood flow out of the right ventricle and into the lungs. Signs and symptoms may include:
- A bluish coloration of the skin caused by blood low in oxygen (cyanosis)
- Shortness of breath and rapid breathing, especially during feeding
- Loss of consciousness (fainting)
- Clubbing of fingers and toes — an abnormal, rounded shape of the nail bed
- Poor weight gain
- Tiring easily during play
- Prolonged crying
- A heart murmur
- Tet spells
- Sometimes, babies with tetralogy of Fallot will suddenly develop deep blue skin, nails and lips after crying, feeding, having a bowel movement, or kicking his or her legs upon awakening. These episodes are called "Tet spells" and are caused by a rapid drop in the amount of oxygen in the blood. Toddlers or older children may instinctively squat when they are short of breath. Squatting increases blood flow to the lungs. Tet spells are more common in young infants, around 2 to 4 months old.
What are the causes of Tetralogy of Fallot?
Tetralogy of Fallot 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). 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 is rare, but it is the most common form of cyanotic congenital heart disease. Patients with tetraology of Fallot have a higher incidence of major non-heart congenital defects. The cause of most congenital heart defects is unknown. Many factors seem to be involved. Factors that increase the risk for this condition during pregnancy include:
- Alcoholism in the mother
- 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).
Who is at highest risk?
While the exact cause of Tetralogy of Fallot is unknown, several factors may increase the risk of a baby being born with this condition. These include:
- A viral illness in the mother, such as rubella (German measles), during pregnancy
- Maternal alcoholism
- Poor nutrition
- A mother older than 40
- A parent with tetralogy of Fallot
- Babies who are also born with Down syndrome or DiGeorge syndrome
How to know you have Tetralogy of Fallot?
If you or you're baby have any of the symptoms listed above. Contact your doctor if you are unsure.
When to seek urgent medical care
Seek medical help if you notice that your baby has the following symptoms:
- Difficulty breathing
- Bluish discoloration of the skin
- Passing out or seizures
- Unusual irritability
- If your baby becomes blue (cyanotic), immediately place your child on his or her side and pull the knees up to the chest. This helps increase blood flow to the lungs. Call 911 or your local emergency number immediately.
Surgery to repair Tetralogy of Fallot is done when the infant is very young. Sometimes more than one surgery is needed. When more than one surgery is used, the first surgery is done to help increase blood flow to the lungs. Surgery to correct the problem may be done at a later time. Often only one corrective surgery is performed in the first few months of life. Corrective surgery is done to widen part of the narrowed pulmonary tract and close the ventricular septal defect.
Diseases with similar symptoms
- Down Syndrome
- DiGeorge Syndrome
Where to find medical care for Tetralogy of Fallot
Directions to Hospitals Treating Tetralogy of Fallot
Prevention of Tetralogy of Fallot
There is no known prevention.
What to expect (Outlook/Prognosis)
Most cases can be corrected with surgery. Babies who have surgery usually do well. Ninety percent survive to adulthood and live active, healthy, and productive lives. Without surgery, death usually occurs by the time the person reaches age 20. Patients who have continued, severe leakiness of the pulmonary valve may need to have the valve replaced. Regular follow-up with a cardiologist to monitor for life-threatening arrhythmias (irregular heart rhythms) is recommended.