What is Tetralogy of Fallot?
TOF is one of the most common cyanotic congenital heart defects. It involves four specific heart abnormalities, which together cause oxygen-poor blood to circulate throughout the body.
🔹 The Four Defects in TOF:
- Pulmonary Stenosis: Narrowing of the pulmonary valve, restricting blood flow to the lungs.
- Ventricular Septal Defect (VSD): A hole between the heart’s ventricles, allowing oxygen-poor and oxygen-rich blood to mix.
- Overriding Aorta: The aorta is positioned over both ventricles instead of just the left ventricle, leading to mixed blood flow.
- Right Ventricular Hypertrophy: Thickening of the right ventricle due to increased workload.
Because of these defects, TOF leads to low oxygen levels in the body (cyanosis), which can cause blue-colored skin, lips, and nails.
Causes and Risk Factors
The exact cause of TOF is unknown, but several risk factors may contribute:
- Genetic mutations: Often associated with conditions like DiGeorge syndrome (22q11.2 deletion).
- Chromosomal abnormalities: Increased risk in babies with Down syndrome or Turner syndrome.
- Maternal diabetes: Poorly managed diabetes during pregnancy increases the risk of congenital heart defects.
- Maternal infections (e.g., rubella): Viral infections during pregnancy may contribute to TOF.
- Environmental factors: Exposure to alcohol, smoking, or toxins during pregnancy.
Symptoms of Tetralogy of Fallot
Symptoms of TOF typically appear soon after birth or during infancy and include:
- Cyanosis: Bluish skin, lips, or fingernails due to low oxygen levels.
- Tet Spells: Sudden drops in oxygen levels, causing difficulty breathing, irritability, or fainting.
- Heart murmur: A whooshing sound detected during a heart exam.
- Shortness of breath: Especially during feeding or exercise.
- Clubbing of fingers and toes: Enlargement of fingers/toes due to long-term low oxygen levels.
- Poor weight gain: Babies with TOF often struggle with feeding and growth.
Diagnosis of TOF
Doctors use several tests to diagnose TOF:
- Fetal Echocardiogram: Can detect TOF before birth.
- Pulse Oximetry: Measures oxygen levels in newborns.
- Electrocardiogram (ECG): Checks heart rhythm for abnormalities.
- Chest X-ray: Shows a characteristic boot-shaped heart caused by right ventricular hypertrophy.
- Cardiac MRI: Provides detailed imaging before surgery.
Treatment and Surgery
TOF requires surgical correction to improve oxygen flow. Treatment usually involves:
1. Temporary Treatment (If Needed)
- Prostaglandin Infusion: Keeps the ductus arteriosus open, allowing better oxygen mixing.
- Blalock-Taussig Shunt (Temporary): A bypass procedure to improve blood flow to the lungs until full surgery is possible.
2. Corrective Surgery (Primary Treatment)
The full repair surgery is usually performed between 3 to 12 months of age and involves:
- Closing the VSD (hole in the heart) with a patch.
- Enlarging the pulmonary valve to improve blood flow.
- Realigning the aorta to its correct position.
Most children recover well after surgery, but lifelong cardiac monitoring is needed.
Long-Term Outlook and Follow-Up Care
With early diagnosis and surgery, most children with TOF can lead healthy and active lives. However, long-term care may include:
- Regular heart checkups with a pediatric cardiologist.
- Monitoring for possible arrhythmias (irregular heartbeats).
- Exercise recommendations based on heart function.
- Additional surgeries if complications arise.