Tetralogy of Fallot (TOF) and Hypercyanotic Spells factsheet

Introduction

Tetralogy of Fallot (TOF) is a rare condition where a baby is born with four different congenital heart defects.

Congenital heart defects are differences in how the heart develops during pregnancy. They can affect various parts of the heart, like the:

aorta – The largest blood vessel, responsible for carrying oxygen-rich blood from the heart to the rest of the body.
atria – the two top chambers of the heart that receive the blood flowing in
pulmonary arteries – blood vessels that carry oxygen-poor blood from the right side of the heart into the lungs
ventricles – the two bottom chambers of the heart that pump the blood back through the body.

Heart defects can change how blood and oxygen flow through the lungs, heart, and body. Children with TOF usually don't have enough blood flowing to their lungs. This means the blood pumped from the heart to the rest of the body doesn't have enough oxygen to keep them healthy.

The four congenital heart defects that cause TOF are:

Ventricular septal defect (VSD)

A hole between the two lower ventricles allows oxygen-poor and oxygen-rich blood to mix, reducing blood flow to the lungs.

Pulmonary stenosis

The valve or flap connecting the right ventricle to the pulmonary artery is thicker than usual, making the pathway smaller and forcing the heart to work harder to pump blood to the lungs.

Right ventricular hypertrophy

The muscle wall of the right ventricle is thicker than usual, making the pathway smaller and forcing the heart to work harder to pump blood to the lungs. The heart is a muscle, so the harder it works, the thicker it becomes.

Overriding aorta

The aorta is larger than usual and sits slightly different, starting at the left and part of the right ventricle. This means oxygen-poor blood gets pumped back through the body.

Signs and symptoms

The signs and symptoms of TOF can be different, depending on how severe it is.

They can include:

cyanosis - a bluish colour in the skin, lips, tongue, and nails
shortness of breath and rapid breathing, especially during feeding or exercise
poor weight gain
fatigue - getting very tired easily
irritability and crying more than usual
heart murmur - a whooshing sound in the heart caused by the force of blood flow
fainting
clubbing of finger and toenails - an abnormal, rounded nail bed shape.

Diagnosis

TOF can be diagnosed:

during pregnancy, using ultrasound scans of the baby's heart
at birth, if the baby has the blue colour of cyanosis
in the first few weeks after birth when other signs or symptoms are noticed.

A child specialist doctor called a paediatrician, will check your baby in the hospital after birth.

If they think your baby has a heart condition, they will order tests and scans like:

hyperoxia test - your baby breathes in 100% oxygen for ten minutes before their blood is taken to check the oxygen levels
pulse oximeter - a small sensor clipped onto your baby's fingertip, toe, or ear to measure blood oxygen levels
electrocardiogram (EKG) - measures the heart's electrical activity
echocardiogram- an ultrasound that provides a detailed picture of the heart’s structure and how blood is moving around the heart
chest X-ray - using radiation to get an image of the heart's structure
cardiac catheterisation - a thin, flexible tube is inserted through a vein into the heart to give information about the structure, blood pressure, and blood oxygen levels.

Treatment

Your baby will be referred to a heart specialist (cardiologist) for treatment and management of TOF.

TOF is treated with surgery to repair the heart defects. Surgery is usually done soon after birth, depending on how severe the defects are and your child’s:

symptoms
overall health
weight.

Your child’s doctor will discuss the most appropriate surgery and the timing with you.

Temporary surgery

Temporary surgery is done in babies who are too small for complete surgery. The aim is to improve blood flow to the lungs until the baby can have a complete repair.

In temporary surgery, the doctor may insert a:

stent - a tiny wire mesh tube that holds open the part of the heart that carries blood from the right ventricle to the lungs
shunt - a small tube between the aorta and the pulmonary artery that allows more blood to travel to the lungs for oxygen.

The stent and shunt will usually stay in place until the complete repair surgery. Temporary surgery for TOF is a closed-heart procedure, meaning the surgeon does not open up the chest.

Complete repair

Complete repair of TOF is usually done around 4-6 months of age or when your baby is strong enough for surgery.

It involves:

closing any holes or gaps with a patch
widening the narrow areas of the ventricles and arteries
removing the stent or shunt from the previous surgery.

Complete repair of TOF requires open heart surgery, which means the surgeon opens up the chest to repair the heart.

Management

Hypercyanotic spells

Hypercyanotic or "Tet" spells happen when the oxygen levels in your child's blood drop quickly.

During these spells, your baby will:

have a sudden deep blue or grey colour in their skin, nails, and lips that lasts for several minutes
seem floppy or unwell
cry for longer periods
breathe more deeply and quickly.

Hypercyanotic spells can happen when your child is:

crying
feeding
upset
waking up early in the morning.

These spells are rarely life-threatening and commonly happen in babies between two and six months.

Hypercyanotic spells can be distressing, but they will generally get better when your child feels comforted and settled.

Generally, it is normal for a baby to have a slight blue tinge when crying or cold. It is usually not a hypercyanotic spell if:

their skin colour only changes while crying, feeding, or upset
their skin returns to normal after they stop crying
they otherwise seem well.

See your local doctor if you are worried or unsure about hypercyanotic spells.

Supporting your baby through a hypercyanotic spell

Help your baby recover by:

picking them up and soothing them to lower their heart rate and the amount of oxygen they are taking in
cuddling them with their knees tucked up against their chest to increase blood flow to the lungs.

Supporting your toddler or older child through a hypercyanotic spell

Toddlers and older children sometimes squat down during a spell, which can help increase the amount of blood getting to their lungs.

Soothe and comfort your child and support them if they need help raising their knees against their chest.

Your child’s skin and nail colour should slowly return to normal as they settle. Let your child’s cardiologist know when the spell happened and the trigger.

Call triple zero (000) for an ambulance if your baby is having a spell and:

not settling
not returning to normal
still having difficulty breathing.

Long-term complications of TOF

Most babies who have a complete TOF repair recover well after surgery. Your child will need regular check-ups with their cardiologist throughout their life to make sure they are healthy, growing well, and managing any complications from the condition.

Complications may include:

holes in the wall between the ventricles that can continue to leak after surgery
a larger than average right or left ventricle that doesn’t work properly
arrhythmias - irregular heartbeats
coronary artery disease – where substances in the blood build up inside the artery, making the inside stiff and narrow
enlargement of the ascending aorta – where a bulge forms in the aorta, causing it to become weak and at risk of tearing.