Fallot's Tetralogy

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Fallot’s Tetralogy: A Complex Congenital Heart Defect


Fallot’s tetralogy, named after the French physician Etienne-Louis Arthur Fallot who first described it in 1888, is a congenital heart defect characterized by four distinct abnormalities:

  1. Ventricular septal defect (VSD): A hole in the wall (septum) separating the right and left ventricles.
  2. Pulmonary artery stenosis: Narrowing or obstruction of the pulmonary artery, which carries blood from the right ventricle to the lungs.
  3. Overriding aorta: The aorta, which carries oxygenated blood to the body, is positioned abnormally and straddles both the right and left ventricles.
  4. Right ventricular hypertrophy: Thickening of the right ventricle in response to the increased workload associated with pulmonary artery stenosis.

Fallot’s tetralogy is a relatively rare heart defect, occurring in approximately 5-10 per 100,000 live births. It is more common in males than females, and the severity of the condition can vary widely.


The primary abnormality in Fallot’s tetralogy is the VSD, which allows oxygen-poor blood from the right ventricle to mix with oxygenated blood from the left ventricle. This leads to a condition known as cyanosis, where the skin, lips, and nail beds appear bluish due to low oxygen levels in the blood.

The combination of VSD and pulmonary artery stenosis creates a significant obstruction to blood flow from the right ventricle to the lungs. As a result, the right ventricle has to work harder to pump blood through the narrowed artery, leading to right ventricular hypertrophy.

Overriding aorta further exacerbates the problem by allowing some oxygenated blood from the left ventricle to be diverted into the right ventricle, worsening the cyanosis.

Clinical Manifestations

Symptoms of Fallot’s tetralogy can range from mild to severe, depending on the severity of the defect. Common clinical manifestations include:

  • Cyanosis, especially when crying or feeding
  • Difficulty breathing and shortness of breath
  • Frequent episodes of bluish spells, known as “tet spells”
  • Failure to thrive
  • Clubbing of fingers and toes
  • Fatigue and exercise intolerance
  • Squatting (knee-to-chest position) to improve blood flow to the lungs


Fallot’s tetralogy can be diagnosed through a combination of physical examination, echocardiography, and cardiac catheterization.

  • Physical examination: The doctor may listen to the heart for a characteristic “machinery-like” murmur and check the skin for cyanosis.
  • Echocardiography: This ultrasound imaging technique provides detailed images of the heart, allowing the doctor to visualize the VSD, pulmonary artery stenosis, and overriding aorta.
  • Cardiac catheterization: This minimally invasive procedure involves inserting a thin tube (catheter) into the heart through a blood vessel in the groin. It allows the doctor to measure blood pressure and oxygen levels in different chambers of the heart, and to confirm the presence and severity of the defects.


Treatment for Fallot’s tetralogy typically involves surgical repair, which is usually performed during the first year of life. The goal of surgery is to correct the defects and restore normal blood flow through the heart and lungs.

The most common surgical approach is the Blalock-Taussig shunt, which creates a temporary connection between the pulmonary artery and the aorta. This shunt improves blood flow to the lungs and relieves cyanosis.

In a more definitive surgery, known as complete repair, the VSD is closed, the pulmonary artery is widened, and the aorta is repositioned over the left ventricle. Complete repair typically restores normal heart function.


With timely diagnosis and treatment, most children with Fallot’s tetralogy can live full and active lives. The prognosis depends on the severity of the defect and the timing of surgical intervention.

Surgical repair significantly improves survival and reduces the risk of complications, including stroke, heart failure, and sudden cardiac death. However, some individuals may require additional surgeries or interventions later in life.


Untreated Fallot’s tetralogy can lead to serious complications, including:

  • Brain abscesses
  • Endocarditis (infection of the heart valves)
  • Heart failure
  • Pulmonary hypertension
  • Sudden cardiac death


Advances in surgical techniques and medical management have significantly improved the outlook for children with Fallot’s tetralogy. With early diagnosis and appropriate treatment, most individuals can achieve normal growth, development, and life expectancy.


There is no known way to prevent Fallot’s tetralogy. However, genetic counseling may be recommended for families with a history of the condition.


Fallot’s tetralogy is a complex congenital heart defect that requires specialized care and treatment. With prompt diagnosis and surgical intervention, the majority of individuals with Fallot’s tetralogy can live full and active lives. Ongoing follow-up care is essential to monitor for any potential complications and ensure optimal heart health.

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