Congenital heart disease in the ED

Tessa Davis Ā· Published 5 December 2013 Ā· Updated 30 April 2026

Clinical

Cyanotic heart disease in acute paediatrics is a nightmare. How much oxygen to give? How much fluid to give? How quickly can Google explain a Stage II Fontan?

Elizabeth Weinstein gave an amazing talk at the AAEM Scientific Assembly about managing cyanotic heart disease in the acute setting. Here’s my summary.

Bottom Line

If in doubt – aim for sats of 80-85% – this may not be ideal but it is unlikely to cause a big problem and the patient won’t be too hypoxic.

Give fluid in lots of 10ml/kg and go slowly.

Fontan-like fluid to maintain their passive pulmonary blood flow

A six-month-old presents to the ED looking unwell. He has an HR of 170, Sats of 60%, and RR 70. He is distressed, but his chest sounds are clear. Mum says he has ‘some sort of heart condition’ but doesn’t know the details.

Essentially all patients with cyanotic heart conditions have some derangement in pulmonary or systemic blood flow. We mean one of fourĀ things when we talk about congenital heart disease:

Once you know which of these it is, it helps with management and troubleshooting.

If the child is blue – there is not enough pulmonary blood flow

If the child is pink – they may have too much pulmonary blood flow

if the child is grey – there is not enough systemic flow

You realise that your patient is having a Tet Spell.

What is Tetralogy of Fallot?

Tetralogy of Fallot accounts for 10% of cyanotic heart disease – it is the most common cause of cyanosis in children over eight months. It comprises the well-known four elements:

How sick is a patient with Tetralogy of Fallot?

The baseline status of a patient with Tetralogy of Fallot depends on the degree of pulmonary stenosis (or pulmonary outflow obstruction).

There will be normal pulmonary blood flow if there is only mild pulmonary stenosis. These are often called ‘pink tets’ – they have normal sats, so they may be much older before diagnosis.

However, if there is a significant outflow tract obstruction, the patient is hypoxic, usually with sats in the 70s. Normal sats in children with TOF may range from 70-100% on room air, depending on the degree of the outflow tract obstruction.

What happens in a Tet Spell?

If systemic vascular resistance drops, the patient’s baseline status will change. This change causes oxygenated blood to beĀ preferentially shunted from the right side of the heart through the ventricular septal defect to the left side of the heart (rather than passing through the outflow obstruction).

A Tet Spell can be preceded by an innocuous event (e.g. crying). The event results in a drop in systemic vascular resistance, leading to increased shunting from the right side of the heart to the left.Ā This results in falling pO2, rising CO2, and a falling pH. All of these increase pulmonary vascular resistance and stimulate the respiratory centre (and consequently increase venous return).

Increased venous return leads to greater shunting, and the cycle worsens.

We need to break the cycle!

How should we manage a Tet Spell?

We need to increase systemic vascular resistance, decrease venous return, or reduce pulmonary vascular resistance. The best management plan is:

How is Tetralogy of Fallot repaired?

Most children with outflow tract obstruction will be definitively repaired by 6 months. However, some children require staged repair if the outflow is so tight that they cannot maintain adequate pulmonary blood flow while awaiting a full repair.

The staged repair involves a Blalock-Taussig shunt (a man-made ductus arteriosus). This involves a subclavian artery-pulmonary artery tube graft and allows pulmonary blood flow to be maintained (in the presence of an obstructive lesion) until the patient is big enough for a definitive repair.

What’s the survival rate, and what are the complications?

Survival is 86% at 30 years, but the patients do have complications along the way.

There is a right bundle ECG pattern in most post-op patients; some have pulmonary regurgitation or recurrent stenosis. Right ventricular dysfunction is common (so bear in mind that it is easy to volume overload these patients as they get older).

Sudden cardiac death is a real risk (4% at 25 years post-op) – and this risk is thought to increase if the QRS is >180ms, so watch out for a wide QRS.

Arrhythmias happen, too. Many patients have complex ventricular ectopics, but we rarely see ventricular tachycardia.Ā Atrial arrhythmias are very common, specifically intra-atrial re-entrant tachycardia (a fibrillation/flutter hybrid). In Tetralogy of Fallot, in particular, we see a wide-complex tachyarrhythmia, which is often difficult to distinguish from ventricular tachycardia.

A six-year-oldĀ presents to the ED with vomiting and diarrhoea. Grandma says she had a ‘fountain’ operation when she was younger. She takes aspirin every day and needs antibiotics for dental procedures. Her sats are 70%, RR 30, and she has sunken eyes, poor capillary refill and tachycardia.

This patient is cyanotic, indicating insufficient pulmonary blood flow. There are also signs of systemic hypoperfusion.

What is a Fontan procedure?

A Fontan repair is for children with a functionally univentricular heart (this could be TA, hypoplastic right/left heart, but it doesn’t matterā€”the point is that just one ventricle is working). This accounts for 10% of complex congenital heart disease.

Fontan knew that one ventricle wasn’t enough. So, he developed a repair so that only one ventricle needs to provide systemic blood flow (by making pulmonary blood flow passive).

The IVC and SVC connect directly to the pulmonary artery (bypassing the right heart completely). Therefore, pulmonary blood flow is passive, and the ventricle is only responsible for systemic flow.

This is done as a staged repair:

Stage I (hemi-fontan or bidirectional Glenn). This is carried out at four to nine months. The SVC is connected to the pulmonary artery.
Stage II is carried out 12-24 months later (a full Fontan). This connects the IVC to the pulmonary artery.Ā 

Depending on their physiology, some children may not be candidates for the full Fontan, and so may only have a hemi-Fontan. Therefore, it’s all completed by two to three years of age.

The pulmonary blood flow is passive; the systemic blood flow is by the one ventricle.

Survival post-Fontan is excellent – 85% at 20 years post-op.

Some patients need a Blalock-Taussig shunt before Stage I. Those with only a right ventricle need surgery to make it a left ventricle before they proceed with the staged Fontan (this is a Norwood procedure).

What’s a Norwood procedure, and what happens afterwards?

The Norwood procedure essentially connects the single ventricle to the systemic circulation.

Patients following a Norwood procedure are unstable and at risk of sudden death (15%). They are very sensitive to fluid and oxygen (it’s easy to kill them) – so BE CAREFUL!

Back to Fontan – should we give fluids or not?

In a Fontan, if pulmonary blood flow is passive, it is clearly volume- and pressure-dependent (to maintain pulmonary flow).

So – dehydration is bad. A dry Fontan is a dead Fontan,Ā as it cannot maintain pulmonary blood flow or cardiac output. This patient will become increasingly hypoxic, but if we rehydrate them, the hypoxia resolves.

Low blood pressure and intrathoracic pressure are problems, too. Routine respiratory illnesses can cause huge problems (due to intrathoracic pressures), so there is a low threshold for admission.

If intubating a patient post-Fontan repair (though generally try to avoid this), remember: intrathoracic pressure is bad. Therefore when ventilating: use a low PEEP (<5); low volume; and low rate (to allow PBF). Ketamine is good for induction as it maintains haemodynamic status.

In this case, we need to give fluids and oxygen to a dehydrated Fontan (a fully repaired Fontan likes oxygen).

The patient comes back again a few months later as he is tired.

In Fontan’s, arrhythmias occur at slower heart rates (usually low 100s) than in Tetralogy of Fallot, so it can be difficult to distinguish an arrhythmia from a sinus rhythm. These patients do not tolerate arrhythmias for long. We just need to determine whether it’s not sinus rhythm, as the patient will therefore need other interventions. Tachy- and bradyarrhythmias are common, and patients can deteriorate quickly if they are not managed promptly. Look out for junctional rhythms and atrial rhythms.

However, the same management applies to normal arrhythmias. If the patient is unstable, shock them.

Thromboembolic disease (3-20%) is a real problem, too, so think of this.

Most will develop some degree of myocardial depression as they get older (not clinically seen) so it is easy to volume overload them. Give fluid, but don’t go nuts. 20ml/kg is too much – give 10ml/kg and go slowly but continue until you reach your goal.

How can we know sats to aim for?

In cyanotic congenital heart disease, there are usually mixing lesions. How much goes to the lungs and how much goes to the body is a tight balance (and easy to unbalance).

Vasodilating the pulmonary vasculature can tip the balance, increasing pulmonary blood flow at the expense of systemic blood flow. Be careful of pulmonary overcirculation and cardiovascular collapse.

If a child has a shunt or a partially repaired complex lesion,  then sats are likely to be 75-85% (e.g. BT shunts; Norwood; Stage I Fontan).

Tetralogy of Fallot patients have sats of 70-100% on room air depending on the degree of outflow obstruction.

A child who has had a Fontan completion, the sats will be 95-100% (but they can drop as the patient gets older).

The best tip is to ask the family what the normal sats areā€”if they are normally 70%, then there is no point trying to get them to 75%.

Fully repaired Fontan-like oxygenation, but with Norwood and central shunts, it is easy to get pulmonary overcirculation.

Be careful in children with newly diagnosed cyanotic heart disease, i.e. neonates starting on PGE. Oxygen will hasten closing the duct (so aim for 85% sats)

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