Symptoms and Tet Spells: What to Watch For

Recognizing the signs of Tetralogy of Fallot (ToF) and knowing how to respond to a “tet spell” is one of the most important roles a parent or caregiver plays. While the symptoms can be frightening, understanding the mechanics behind them can help you stay calm and take the necessary steps to help your child.

Common Symptoms of ToF

In infants, the symptoms of ToF are caused by low levels of oxygen in the blood. These may include:

• Cyanosis: A bluish tint to the skin, lips, or fingernails, which may get worse when the baby is active ^[1][2].
• Difficulty Feeding: Babies may get tired or turn blue while nursing or bottle-feeding.
• Poor Weight Gain: Because the heart has to work harder, the body burns more energy, which can slow growth.
• Clubbing: Over time, the tips of the fingers and toes may become rounded or “clubbed” due to chronic low oxygen ^[1].
• Heart Murmur: Doctors will usually hear an extra sound in the heart caused by turbulent blood flow ^[3].

Managing Feeding at Home

Because feeding can be exhausting for a baby with ToF, ask your team for guidance on feeding strategies. Common approaches include:

• Pacing: Giving the baby frequent breaks to catch their breath during a feed.
• Smaller, Frequent Feeds: Offering less milk more often so the baby doesn’t burn out.
• High-Calorie Formula/Fortifiers: If your baby is struggling to gain weight, the doctor may recommend fortifying breast milk or using a higher-calorie formula so they get more energy for the same amount of effort.

The “Silent Chest”

Interestingly, infants with ToF often have what doctors call a silent chest ^[1]. In many other heart conditions, a “wet” sounding chest or heavy breathing is a sign of heart failure. Because ToF actually limits blood flow to the lungs, there is no fluid buildup, so the chest sounds clear even when oxygen levels are low ^[1].

Understanding “Tet Spells”

A hypercyanotic spell (or “tet spell”) is a sudden, temporary drop in the amount of oxygen reaching the body ^[4].

Why do they happen?

A spell occurs when the muscle just below the pulmonary valve (the infundibulum) suddenly spasms or tightens ^[4]. This acts like a door slamming shut, making it almost impossible for blood to get to the lungs. Instead, the deoxygenated (blue) blood is forced through the hole in the heart (VSD) and out to the rest of the body ^[4][1].

Common Triggers

Spells are often triggered by things that change blood pressure or make the heart beat faster, such as:

• Hard crying or agitation ^[1]
• Feeding ^[5]
• Bowel movements (straining) ^[5]
• Waking up from a nap ^[6]
• Dehydration or fever

Action Steps: What to Do During a Spell

If you notice your child turning significantly more blue, breathing very deeply and fast (hyperpnea), or becoming unusually sleepy or limp, they may be having a spell. Stay calm—your child can sense your panic.

1. The Knee-to-Chest Position: Immediately pick your baby up and tuck their knees tightly up against their chest ^[1]. If the child is older (a toddler), they may naturally squat on their own ^[1].
2. Soothe Your Child: Try to stop the crying. Use a pacifier, rock them, or speak in a soft, soothing voice.
3. Call for Help: If the spell does not resolve and the child’s color does not improve within 1 to 2 minutes, call 911 or your local emergency services immediately. If possible, have a second person call 911 while you maintain the knee-to-chest position and soothe the baby.

Reporting Resolved Spells

If you perform the knee-to-chest maneuver and your baby’s color quickly returns to normal, you still need to notify your medical team. Call your pediatric cardiologist’s office that same day to report the event. A true spell often indicates that it is time to move forward with surgical planning.

Why the Knee-to-Chest Position Works

It may seem simple, but this position is a powerful mechanical fix. By folding the legs up, you temporarily kink the large arteries in the legs. This increases systemic vascular resistance (the pressure the heart has to pump against to send blood to the body) ^[1][7].

When the pressure in the body goes up, it pushes back against the heart, making it easier for blood to flow through the narrow path to the lungs instead of escaping through the VSD ^[4][1]. This simple movement forces more blood into the lungs to pick up oxygen.

Prevention

While you cannot always stop a spell, there are practical steps you can take at home to minimize the risk:

• Hydration: Ensure your baby is well-hydrated, as dehydration can trigger spells.
• Prevent Iron Deficiency: Ask your doctor to monitor your baby for anemia (low iron). Low iron means the blood carries less oxygen and can make spells worse; your doctor may prescribe iron drops if necessary.
• Medication: If your child has frequent spells, your doctor may prescribe daily medications like beta-blockers to help keep the heart muscle relaxed and prevent the spasms that cause spells ^[8]. Frequent spells are often a sign that it is time to discuss the schedule for surgical repair with your cardiology team.