Tetrology Of Fallot
Tetralogy of Fallot is a congenital heart defect, meaning that it is present in an infant from birth. A combination of four abnormalities in the heart allow 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.
Tetralogy of Fallot is a combination of four heart defects that are apparent at birth. These are:
ventricular septal defect (a hole in the wall between the heart's two pumping chambers)
pulmonary stenosis (a partial blockage of the outflow tract from the right heart)
overriding aorta (the main artery coming from the left heart is out of position)
- right ventricular hypertrophy (the pumping chamber on the right side is abnormally muscular and thickened)
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 as well. Not getting enough oxygen can cause vital organs to fail.
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 has one of the following conditions:
- a viral illness such as rubella during pregnancy
- poor prenatal nutrition
- age of 40 years or older
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 an unborn child at higher risk for this disease, such as alcohol.
How is the condition diagnosed?
After a complete history and physical exam are done, a variety of imaging tests can confirm the diagnosis.
An electrocardiogram (ECG) 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 (CXR) 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 an X-ray of the heart performed after a dye has been injected.
Long Term Effects
What are the long-term effects of the condition?
Unless the child's heart can be surgically repaired, tetralogy of Fallot is fatal.
What are the risks to others?
Tetralogy of Fallot is not contagious, and poses 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.
Open heart surgery is done to close the hole in the septum, remove extra heart muscle, and open or repair 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, the arteries that 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. Like any surgery, repair of a tetralogy of Fallot can be complicated by bleeding, infection, or reactions to anesthesia. In addition, this repair can have additional complications:
an infection of the inner lining of the heart called infective endocarditis
development of an abscess, or pus-filled cavity, in the brain
further damage to the pulmonary valve
Restoring normal blood flow may trigger:
problems in the left ventricle of the heart, which pumps oxygen-rich blood into the body
problems with 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 and can prove fatal later,
What happens after treatment for the condition?
After surgery, improvements should be seen in the symptoms linked to low-oxygen levels, such as cyanotic spells, and 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 healthcare professional are scheduled regularly to check that the heart is healing properly and that there are no new symptoms. Testing may need to be repeated to ensure that heart disease is not worsening. People who have had tetralogy of Fallot should take antibiotics before any future surgery or dental work in order to help them avoid serious heart infections. Any new or worsening symptoms should be reported to the healthcare professional.
Merck Manual, 1999
Current Medical Diagnosis and Treatment, 1996
Harrison's Principles of Internal Medicine, 1991