Tetralogy spells (tet spells)

A tetralogy or ‘tet’ spell (also known as a cyanotic spell, or hypercyanotic spell) describes a short period when a child’s skin, nails and lips turns a little blue or grey. They are caused by a rapid drop in the amount of oxygen in the blood. Children who have heart conditions such as Tetralogy of fallot are most likely to experience a tet spell.

During a tet spell it becomes harder for the heart to pump blood into the lungs. This means oxygen-poor (blue) blood from the right ventricle will instead travel an easier route through the ventricular septal defect (hole in the heart) and into the left side of the heart where it is pumped out to the brain and body. This reduces the amount of oxygen in the blood going around the body. This cycle will continue unless the spell is recognised and stopped.

Signs and symptoms

The main signs and symptoms of tet spells include:

• Pale or blue/grey skin, nails and lips
• Cool and clammy skin
• Irritability/tiredness/floppy body (but awake)

What causes a tet spell?

Tet spells can be spontaneous or triggered by certain events such as prolonged crying and episodes of exertion such as during feeding or even pooing. Illness can also trigger a tet spell. If your baby has a fever and is not hungry or feeding, contact your cardiac care coordinator or GP for advice.

What to do if your child is having a tet spell

If you think your baby or child is having a tet spell, try to calm them down to prevent it from getting worse.

Place your baby’s knees on their chest (see pictures below which show how to do this). This helps increase blood flow to the lungs. Toddlers and older children may prefer to squat.

When to seek help

• If you cannot stop a tet spell by trying the strategies outlined above, call Triple Zero (000) and ask for an ambulance. If your baby becomes blue, floppy and unresponsive before an ambulance arrives, you should perform CPR.
• If it’s not an emergency but you have any concerns, contact your GP or call 13 HEALTH (13 43 25 84) and speak to a registered nurse.

If your child is taken to emergency for treatment of a tet spell, tell their cardiac team at your child’s next appointment.

Developed by Queensland Paediatric Cardiac Service, Queensland Children's Hospital.

Resource ID: FS239. Reviewed: December 2023.

Disclaimer: This information has been produced by healthcare professionals as a guideline only and is intended to support, not replace, discussion with your child’s doctor or healthcare professionals. Information is updated regularly, so please check you are referring to the most recent version. Seek medical advice, as appropriate, for concerns regarding your child’s health.