Definition Tetrology of Fallot is a congenital heart defect. A combination of four abnormalities in the heart allows oxygen-rich and oxygen-depleted blood to mix. The resulting low-oxygen blood then circulates through the body.
What is going on in the body? Normally, the right side of the heart pumps oxygen-poor blood to the lungs. Once enriched by oxygen, this blood returns to the left side of the heart to be pumped to tissues throughout the body. A wall called the septum separates the two sides of the heart.
Tetrology of Fallot is a combination of four heart defects apparent at birth. These defects allow the blood supplies to mix so that the blood sent to cells throughout the body is low in oxygen. Blood flow to the lungs is decreased, too. Not getting enough oxygen can cause vital organs to fail.
What are the signs and symptoms of the condition? Infants with this condition usually have a heart murmur heard at birth, or shortly thereafter. They have a bluish-purple colour to the skin, a condition called cyanosis. The child is cyanotic because the blood circulating through the body does not have enough oxygen. Between the ages of 2 months and 2 years children with tetrology of Fallot may experience "blue" spells. These spells may be brought on by crying, straining to have a bowel movement, or fever.
A child who has tetrology of Fallot tends to develop slowly, eat poorly, and grow slowly. He or she may get short of breath, especially when exercising. A change in the shape of the fingertips called clubbing is another sign of this condition.
What are the causes and risks of the condition? The cause of tetrology of Fallot is unknown. However, a baby is more likely to be born with tetrology of Fallot if the mother:
What can be done to prevent the condition? Many times nothing can be done to prevent the disease. However, it may help if a pregnant woman avoids certain factors known to put a foetus at higher risk for this disease, such as alcohol.
How is the condition diagnosed? After a complete history and physical examination are done, a variety of imaging tests can confirm the diagnosis.
An electrocardiogram traces electrical activity in the heart muscle. It usually reveals enlargement in the muscles of the right ventricle of the heart, which pumps blood to the lungs.
A chest x-ray shows a characteristic boot-shaped heart of fairly normal size.
An echocardiogram uses sound waves to see a hole in the wall between the two sides of the heart. Narrowing of the pulmonary valve through which blood must pass on its way to the lungs can also been seen with this test.
Angiography provides detailed images of the structural defects in the heart and the degree to which blood flow is blocked. Angiography is a x-ray of the heart performed after a dye has been injected.
What are the long-term effects of the condition? Unless the child's heart can be surgically repaired this condition is fatal. Treatment may be affected by complications, such as:
an infection of the inner lining of the heart called infective endocarditis
development of an abscess, or pus-filled cavity in the brain
What are the risks to others? There are no risks to others.
What are the treatments for the condition? Cyanotic spells usually respond to oxygen, morphine, and the knee-to-chest position. These spells are usually a sign that surgery is needed.
Sometimes an injection of a hormone called prostaglandin E can help improve blood flow through the lungs. This is done until surgery can repair the problem.
Full surgical repair closes the hole in the septum, removes extra heart muscle, and opens or repairs the pulmonary valve. This surgery is recommended as early as possible in nearly all cases. It can be done only if the child has well-developed pulmonary arteries. These arteries carry blood to the lungs. If they are not well developed, temporary surgery may be done to increase blood flow to the lungs. This will give a child some time until the arteries develop more and full repair can be done.
What are the side effects of the treatments? Prostaglandin E can stop a child's breathing. It should be used in a setting where resuscitation equipment is available.
There are possible side effects with any surgery. These include bleeding, infection, and reactions to the drugs used to control pain.
Other problems can arise after surgery. Restoring normal blood flow may trigger problems in:
the left ventricle of the heart, which pumps oxygen-rich blood out into the body
the pulmonary valve
conduction problems, or problems with the electrical activity of the heart
insufficient blood flow to the pulmonary artery, which sometimes occurs despite surgery. That can prove fatal later on.
What happens after treatment for the condition? After surgery, improvements should be seen in:
symptoms linked to low-oxygen levels, such as cynanotic spells
the child's tolerance of exercise
However, heart function is not fully normal. A variety of problems called heart blocks and, rarely, sudden death can occur years after surgery.
How is the condition monitored? Visits to the doctor are scheduled regularly to check that the heart is healing properly and there are no new symptoms. Testing may need to be repeated to ensure that heart disease is not worsening.
People who have had this condition should take antibiotics before any future surgery or dental work. This will help them avoid serious heart infections.
Author: Eric Berlin, MD Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
