What is Tetralogy of Fallot?

What are the 4 defects found in tetralogy of Fallot?

Tetralogy of Fallot or ToF is characterised by four distinct but related heart defects that affect the blood flow through heart and lungs and also the distribution of oxygen throughout the body.

In a healthy heart, the blood travels to the lungs to collect oxygen and returns to the heart, which is then pumped to the rest of the body, but in case of Tetralogy of Fallot the amount of blood reaching the lungs reduces drastically leading to less oxygen rich blood pumped through the body causing the baby to turn blue or Cyanosis. The usually seen four defects of the heart found in Tetralogy of Fallot are:

Pulmonary Stenosis: Pulmonary Stenosis is a condition where the pulmonary valve (opening that connects right ventricle to pulmonary artery) thickens and becomes stiff making it difficult for blood to pass through from the right ventricle to the pulmonary artery. As a result the pulmonary artery carries less blood to lungs to soak up oxygen which is then sent back to heart to pump to the rest of the body.

Pulmonary stenosis causes the right ventricle to work extra hard to pump blood through the thickened valve leading to heart stress, wall thickening and even heart failure in some cases. In some rare cases, babies with ToF could also have pulmonary atresia where the pulmonary valve or the opening to pulmonary artery is poorly formed or completely absent and the baby may need surgery to correct this.

Ventricular Septal Defect (VSD): Ventricular septal defect is a hole in the septum that separates the left and the right ventricle causing the oxygen poor blood from right ventricle to mix with oxygen rich blood in the left ventricle.

Overriding Aorta: Overriding aorta is a congenital defect where the aorta is sitting over the ventricular septal defect instead of the left ventricle causing oxygen poor blood from right ventricle to enter aorta along with the oxygen rich blood from left ventricle, this purple blood is then pumped throughout the body causing complications like cyanosis, irregular heart rhythm or even heart failure.

Enlargement (Hypertrophy) of Right Ventricle: The right ventricular walls thicken as a result of the immense stress put on it by the heart defects like pulmonary stenosis, ventricular septal defect and overriding aorta.

Related: Ventricular Septal Defects

Down Syndrome

What are Congenital Heart Defects

Tetralogy of Fallot Causes

Although the exact cause of Tetralogy of Fallot is unknown, it is believed that certain risk factors could increase the chances of having a baby with ToF:

1. Baby born with Down or DiGeorge Syndrome.

2. Family History

3. Viral Infections during pregnancy like Rubella

4. Other factors like use of medication, recreational drugs, drinking alcohol, smoking, or poor maternal diet during pregnancy.

5. Advanced maternal age, above 40.

Tetralogy of Fallot Symptoms

The symptoms of Tetralogy of Fallot vary from being mild, moderate to severe based on the extent of the defect, but in any case without right medical attention and treatment the symptoms get worse with time.

1. Cyanosis: Most babies develop a blue or purple tint of the skin due to low oxygen levels in blood.

2. Tet Spells: Babies with Tetralogy of Fallot can experience sudden spells lasting few minutes to hours triggered by exertion due to feeding, crying or pooping. These spells cause oxygen levels in body to drop leading to skin, nails, tongue and lips to turn blue or grey.

3. Clubbing: Cyanosis over time causes skin and nails to enlarge with curved nails.

4. Heart Murmurs

5. Easily getting tired or Sleeping excess

6. Difficulty Feeding

7. Difficult breathing or Rapid breathing

8. Limp body

9. Irritability

10. Difficulty gaining weight

11. Seizures, Convulsions

12. Dizziness

13. Seeming unconscious, not responding to the parent's voice

14. Restlessness

15. Temporary loss of movement of one side of the body

Tetralogy of Fallot Complications

Tetralogy of Fallot could lead to other complications evident immediately or over time

1. Irregular heart rhythm

2. Increased red blood cells

3. Infection (Endocarditis) of the heart valves, lining caused by bacteria

4. Heart Failure

5. Sinusitis

6. Blood clots

7. Brain abscess: Pus filled bacterial cavity in the brain that causes serious complications

8. Pulmonary Valve Regurgitation: Leaking blood even after surgical correction of the valve

9. Aortic Root Dilation: Swelling of aorta due to increased blood flow from ventricular septal defect tampering the pressure dynamics in the heart

10. Tetralogy of Fallot when left untreated could develop serious life threatening complications leading to even death.

Tetralogy of Fallot Diagnosis

1. During Pregnancy: The doctor performs an ultrasound called anomaly scan to see whether all the major organs are developing as they should, In case of Tetralogy of Fallot, the doctor could detect issues with the heart and may ask for a foetal echocardiogram to assess the heart further.

2. After Birth: Babies with Tetralogy of Fallot may start showing symptoms within minutes to first few weeks of life like blue tinted skin, fast breathing, sweating, difficulty to feed, heart murmurs, etc. and the doctor may ask for an echo to confirm the same.

3. Physical Exam: Doctors may hear a murmur during physical exam and may ask for more tests to confirm. The murmur usually get obvious at around 3-6 weeks of age.

Tetralogy of Fallot Testing

There are multiple tests that can be used to detect Tetralogy of Fallot as listed below:

• Pulse Oximeter: Device that is put on the baby's toe to monitor oxygen saturation levels. It is very effective in detecting low oxygen levels which is a key symptom of Tetralogy of Fallot.

• Echocardiogram - Most commonly used form of test as it uses sound waves to form the image of the heart and see it's functioning. It is quick, painless, non-invasive and accurate, hence preferred form of testing.

• Chest X-Ray - Tetralogy of Fallot can cause structural changes to the heart which can be seen on x-rays. The technician may also inject a substance in the blood that highlights the circulation and any defects on the x-ray.

• Electrocardiogram - or ECG uses multiple sensors stuck to your child's chest to measure electrical activity of the heart that shows up as a wave or graph on the screen that can be printed. Any structural changes or issues with the heart, the wave patterns change this helps doctors to assess the extent of impact of Tetralogy of Fallot.

• CT Scan - X-ray images of the chest / heart are processed by a computer to form a 3D image of the heart to see any structural changes and impact of ToF on the heart. An injectable substance is used to highlight on the screen and help with images.

• Cardiac Catheterization - The doctor inserts the catheter device from your upper thigh into the major blood vessel to look in your heart to see the defects. Not commonly used unless the doctor suspects a blood clot, blood vessel damage, high blood pressure in the lungs or an enlarged heart that needs a closer look.

Tetralogy of Fallot Treatment

Symptoms get worse with time if left untreated, all babies/children with Tetralogy of Fallot need surgery for correcting their defects and proper functioning of the heart. Your healthcare provider might treat the symptoms with medicines to increase oxygen levels until surgery.

Your doctor may also teach you to manage tet spells causing difficulty for your baby to breathe by making them sit in a squat position or by bringing their knees close to their chest.

Tetralogy of Fallot Surgery

Based on the baby's condition and age your surgeon will take a call on when to do the surgery. More often the surgery is done between the age of 3 to 6 months of age.

• Temporary Surgery: If the baby is weak, too small or has other complications, the surgeon may do a temporary fix with a shunt to help blood flow to the lungs and relive the symptoms so the child can grow till the complete operation could be done to fix all the defects.

• Complete Repair Surgery: Once the baby is well and strong enough for the surgery, your surgeon will fix all the four defects:

  • Pulmonary valve widening or replacement

  • Widening the passage of right ventricle to the pulmonary artery

  • Patching the Ventricular Septal Defect

  • Removing the thickened tissue from the right ventricle

Tetralogy of Fallot Life Expectancy

Advances in science, technology and skilled doctors have made it possible for someone with Tetralogy of Fallot to lead active and full filling lives post surgery with life expectancy getting similar to general population. In some cases the patients may develop complications post surgery or later in life and may need follow up surgery/ies (like pulmonary valve replacement) and medications to manage the condition. Based on the patient's age at surgery, type of repair done, complications and other influencing factors that are specific to each patient the life expectancy may vary.

Everyone with Tetralogy of Fallot surgery may need to continue to see their doctor from time to time to ensure their heart is working as it should and no other complications have developed.