What is Tetralogy of Fallot?
Tetralogy of Fallot is an uncommon cardiac combination which is actually a combination of four heart defects. It is a congenital defect which is present at birth. These defects cause the heart to function poorly resulting in poor oxygen supply to the other parts of the body. It also damages the structure of the heart. Tetralogy of Fallot causes the skin of the affected child to cyanotic at birth as there is not enough supply of oxygen to the parts of the body. Tetralogy of Fallot is normally diagnosed immediately at birth or within a few days after birth, although in some cases where the symptoms and signs are very mild it may remain undetected until much later in life. If Tetralogy of Fallot is diagnosed and treated early, children affected by it go on to live a normal healthy life even though they will need frequent checkups to check the status of the defects and the status of the heart and will have to take precautions while doing certain activities.
What Causes Tetralogy of Fallot?
Tetralogy of Fallot occurs at the time of development of the heart in the fetus. Studies point to lack of proper nutrition on the part of the mother, viral infections or even genetic predisposition to some cases of Tetralogy of Fallot even though why it occurs is still a matter of ongoing research. As stated, there are four defects that combine together to form Tetralogy of Fallot. These defects are as follows:
Pulmonary Valve Stenosis: In this condition, there is stenosis of the pulmonary valve of the heart. This stenosis results in reduced blood flow to the lungs.
Ventricular Septal Defect: This is a condition in which there is a hole in the wall of the ventricles of the heart. Because of this hole, the deoxygenated blood mix with the oxygenated blood hence impairing the smooth flow of oxygenated blood to the heart resulting in weakening of the heart.
Overriding Aorta: This is a condition in which there is a slight shift of the aorta from its normal position to the right of it positioning itself right over the ventricular septal defect causing numerous complications.
Right Ventricular Hypertrophy: This condition is caused due to excessive strain being put on the muscles of the heart which makes the walls of the right ventricle to become thick and get enlarged which over a period of time makes the heart weak and eventually causes heart failure.
What are the Risk Factors for Tetralogy of Fallot?
There are certain risk factors which predisposes a child to have Tetralogy of Fallot. These risk factors include:
- Viral illness during pregnancy may cause the fetus to develop Tetralogy of Fallot
- Abuse of alcohol and other substances during pregnancy
- Not eating enough food leading to malnutrition. This is commonly found in the third world countries and is rare in the United States.
- If a woman becomes pregnant after the age of 40 then it predisposes the fetus to developing Tetralogy of Fallot
- If there is a parent with Tetralogy of Fallot then there is a high likelihood that the child will also have Tetralogy of Fallot.
What are the Symptoms of Tetralogy of Fallot?
Symptoms caused due to Tetralogy of Fallot are variable and depend on the severity of the defect and how much blood is the right ventricle able to pump into the lungs. Some of the symptoms of Tetralogy of Fallot are:
- Cyanotic skin
- Syncopal episodes
- Failure to thrive
- Inadequate weight gain
- Easy fatigue
- Easy irritability
- Heart murmur.
How is Tetralogy of Fallot Diagnosed?
Immediately after birth if the color of the skin of the baby is bluish then the physician may immediately suspect a cardiac defect. This may be further confirmed if there is a heart murmur present. In order to confirm the diagnosis of Tetralogy of Fallot, the physician may order the following tests:
Chest X-ray: This may virtually confirm the presence of Tetralogy of Fallot as it will show an enlarged ventricle and the shape of the heart will look like that of a boot.
Blood Test: A complete blood count will be taken which in Tetralogy of Fallot will show increased RBCs in blood.
Pulse Oximetry: This is a test done to measure the amount of oxygen present in the blood.
Electrocardiogram: This test shows the heartbeat in the form of electrical impulses. This test can show whether there is any abnormality in the rhythm of the heart and whether the heart is functioning normally.
Echocardiogram: This test makes use of ultrasound waves to look at the functioning of the heart. This test can accurately identify any abnormality of the functioning of the heart.
Cardiac Catheterization: This is a minimally invasive test in which a catheter is inserted in the heart through the leg. This test accurately measures the pressure that is exerted on the chambers of the heart.
How is Tetralogy of Fallot Treated?
There is only one way to treat Tetralogy of Fallot and that is by surgical procedure. There are two types of surgical procedures which are done to treat Tetralogy of Fallot which are intracardiac repair and temporary surgery.
Open Heart Surgery to Treat Tetralogy of Fallot: This procedure is done before the child is one year of age. This is a form of open heart surgery in which the surgeon will make an incision over the chest and go into the heart and place a patch over the right ventricle to close the ventricular septal defect. Next, the surgeon will repair the stenosed pulmonary artery to restore normal blood flow through it. Once the Tetralogy of fallot is virtually repaired the symptoms of the child significantly come down.
Temporary Surgery to Treat Tetralogy of Fallot: This is a surgical procedure which infants need to undergo before the actual open heart procedure. Hence it is called as temporary procedure. In this procedure, the surgeons create a bypass between the stenosed pulmonary artery and the aorta by placing a shunt. This restores normal supply of blood passing through the pulmonary artery. When the open heart surgery is done and the stenosis is repaired this shunt is removed by the surgeons.
Postsurgery, most infants do not have any symptoms and live normally but in some cases there have been certain complications reported in the form of pulmonary regurgitation or arrhythmia. In some cases, even after the repair normal blood flow is not restored and further surgical procedures may be required. In some cases the pulmonary valves may be irreparable and will require a mechanical valve to be placed. Apart from these complications, as inherent with any surgical procedure there is a risk of bleeding, infection, injury to the adjacent structures etc. In some cases complications may continue throughout the child's adolescence and into the adulthood which will require frequent follow up and investigations due to tetralogy of Fallot.