Tetralogy of Fallot (TOF): Echocardiography
S. Vishalini
Cardiac Technician, Kauvery Heart City Hospital, Trichy
Introduction
Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart disease, it present at birth. In the normal heart, there are two atria and two ventricles. Blood comes back from the body from the superior vena cava (SVC) and inferior vena cava (IVC) to the right atrium through the tricuspid valve to the right ventricle. The ventricle contracts and blood is pumped through the pulmonary valve to the pulmonary arteries out to the lungs where the blood is oxygenated. Blood returns from the lungs by the pulmonary veins to the left atrium. It then travels from the left atrium through the mitral valve to the left ventricle. The left ventricle contracts, sending blood through the aortic valve through the aorta and out to the body.
Tetralogy of Fallot (TOF)
It includes four cardiac abnormalities:
- Ventricular septal defect (VSD): There is an opening in the wall between the 2 lower chambers of the heart (right and left ventricles).
- Overriding of aorta: The artery that connects the heart left ventricle to body circulation is abnormally positioned directly over the VSD.
- Pulmonary Stenosis: A narrowed or stiffened pulmonary valve means the pulmonary artery has trouble sending enough blood from the heart to the lungs.
- Right Ventricular Hypertrophy: The right ventricle becomes thicker and more muscular than normal as a result of working harder to pump blood through the narrow pulmonary valve.
Symptoms
The most common symptom of TOF is cyanosis, which is when the skin, lips and nail beds are blueish in color. Cyanosis is the result of too much oxygen-poor blood being pumped through the body.
Other symptoms of tetralogy of Fallot at birth may include:
- Difficult or rapid breathing
- Fatigue
- Fussiness
- Heart murmur
- Trouble feeding or gaining weight
Pathophysiology of the Tetralogy of Fallot
The pressure in the right ventricle is higher than in the left ventricle due to the pulmonary stenosis.
This causes a right to left shunt, in which blood flows from the right ventricle into the left ventricle through the ventricular septal defect.
The blood with low oxygen concentration from the right ventricle mixes with the oxygen-rich blood of the left ventricle. This mixed blood is sent to the systemic circulation, causing cyanosis.
The severity of the pulmonary stenosis will be directly proportional to the magnitude of the right to left shunt and the cyanosis, and it is inversely proportional to the pulmonary blood flow.
Electrocardiogram changes of TOF
An ECG may be helpful in the diagnosis of tetralogy of Fallot. Findings on ECG suggestive of tetralogy of Fallot include,
- Right axis deviation
- Right ventricular hypertrophy
- Wide QRS
- Right bundle branch block.
Impression
ECG showing right axis deviation with right ventricular hypertrophy.
Echocardiogram
Two- Dimensional echocardiography and doppler studies usually make the diagnosis and quantitate the severity of TOF.
Impression
Echocardiogram showing VSD, overriding of aorta, and right ventricular hypertrophy.
Echocardiographic evaluation
- Evaluate the etiology and severity of pulmonary regurgitation.
- Identify right ventricular outflow tract obstruction and its level, causes and severity.
- Assess the presence and severity of tricuspid regurgitation.
- Rule out residual atrial or ventricular septal defects.
- Evaluate left ventricular size & function.
- Assess the presence and severity of aortic regurgitation.
- Use doppler echocardiography to estimate right ventricular systolic and pulmonary artery pressure.
Diagnosis
Babies may also be diagnosed with tetralogy of Fallot after birth if doctors note they have abnormal oxygen levels. Additional tests after birth to confirm that your baby has tetralogy of Fallot may include:
- Electrocardiogram: A test that records the electrical activity of your baby’s heart using small sensors placed on the chest.
- Echocardiogram: A sound waves create an image of the internal structure of the heart.
- Cardiac MRI: A three-dimensional image that shows the heart’s abnormalities
- Cardiac catheterization: A thin tube (catheter) is inserted into the heart through a large vein in the leg, and guided to the heart to see internal structures and potentially treat any narrowing or blockages.
Treatment
All babies who have tetralogy of Fallot need surgery to fix the heart and improve blood flow. A heart surgeon, called a cardiovascular surgeon, does the surgery. The timing and type of surgery depends on the baby’s overall health and specific heart problems.
Surgery used to treat tetralogy of Fallot
Temporary surgery, also called temporary repair
Some babies with tetralogy of Fallot need a temporary surgery to improve blood flow to the lungs while waiting for open-heart surgery. This type of treatment is called palliative surgery. A surgeon places a tube called a shunt between a large artery that comes off from the aorta and the lung artery. The tube creates a new path for blood to go to the lungs. This surgery may be done if a baby is born early or if the lung arteries are not fully developed. The shunt is removed during open-heart surgery to treat tetralogy of Fallot.
Open-heart surgery, called complete repair
People with tetralogy of Fallot need open-heart surgery to completely fix the heart.
A complete repair is usually done in the first year of life. Rarely, a person may not have surgery in childhood if tetralogy of Fallot goes undiagnosed or if surgery is not available. These adults may still benefit from surgery. A complete repair is done in several steps, The surgeon patches the hole between the lower heart chambers and repairs or replaces the pulmonary valve. The surgeon may remove thickened muscle below the pulmonary valve or widen the smaller lung arteries.
After complete repair, the right lower chamber won’t need to work as hard to pump blood. As a result, the right chamber wall should go back to its usual thickness. The oxygen level in the blood goes up. Symptoms typically get better.
Follow-up care of TOF
A Patient who have had surgical repair of tetrology of fallot, will require lifelong care by a cardiologist. Patient will need to carefully follow their doctor’s advice, including continuing any prescribed medications and in some cases, limiting exercise.
Post-operative Evaluation
- Evaluation of VSD repair
- Residual shunting
- Right ventricular size and contractility
- Right ventricular outflow tract for residual stenosis
- Severity of pulmonary regurgitation
Post – Operative Patient case report
Baby. Vijay Balaji is a 10-year male who has undergone Intra cardiac repair for tetralogy of fallot . An echocardiogram was performed, which showed no residual VSD, no significant RVOT obstruction, and good biventricular function
Echo image
Echocardiogram after repair of Tetralogy of Fallot (TOF) from the parasternal long axis (PLAX) view showing the patch which was used to close the ventricular septal defect. The aortic over-ride is no more present.
Conclusion
TOF is a congenital heart defect that results in decreased blood flow to the lungs and it is successfully repaired by surgery in infancy, allowing most patients a normal lifestyle. Lifelong follow-up is important to watch for problems such as an abnormal heart rhythm, leaking of the pulmonary valve, or poor function of the right ventricle.
S. Vishalini
Cardiac Technician