Congenital heart disease in PEM

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Cyanotic heart disease in acute paeds 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.
  • Fontans like fluid to maintain their passive pulmonary blood flow.

 A six month old presents to ED looking unwell. He has a HR of 170, Sats 60%, RR 70. He is distressed but 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 derrangement in pulmonary or systemic blood flow. We mean one of four things when we talk about congenital heart disease:

  • Not enough pulmonary blood flow
  • Too much pulmonary blood flow
  • Not enough systemic blood flow
  • Not enough coronary artery blood flow

Once you know which of these it is, it helps to manage and troubleshoot.

  • If the child is blue – there is not enough pulmonary blood flow
  • If the child is pink – they may have too much pulmonary blood fow
  • 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 of the well known four elements of:

  • Ventricular septal defect
  • Right ventricular hypertrophy
  • Overriding aorta
  • Pulmonary stenosis

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).

If there is only mild pulmonary stenosis, there will be a normal pulmonary blood flow. These are often called ‘pink tets’ – they have normal sats and for that reason, they may be much older before diagnosis.

But if there is a significant outflow tract obstruction, then 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?

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

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

The increased venous return results in more shunting and the whole cycle gets worse.

We need to break the cycle!

How should we manage a Tet Spell?

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

  • Knees to chest
  • Calm the patient
  • High flow oxygen
  • Morphine and IV fluids
  • If you are still having trouble – go to ketamine (IM or IV)

How is Tetralogy of Fallot repaired?

By six months, the outflow tract obstruction will be definitively repaired in most children. However, some children need a staged repair if the outflow is so tight that they cannot maintain adequate pulmonary blood flow while waiting for a full repair.

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

What's the survival rate and what are the complications?

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

There is a right bundle pattern in the vast majority of post-op patients; some have pulmonary regurgitation or a 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. 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 old presents to 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 eyes sunken, poor capillary refill and tachycardia.

This patient is blue, so there is not enough 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 matter – the point is there is just one ventricle 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 the one ventricle only needs to provide the systemic blood blow (by making the 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 bidrectional 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. Depending on their individual physiology, some children may not be candidates for the full Fontan, and so may only have a hemi-fontan.

Therefore, by two to three years of age, it’s all completed.

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. And 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 the pulmonary blood flow is passive, then it is clearly volume and pressure dependent (to maintain pulmonary flow).

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

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

If intubating a patient post Fontan repair (although 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 – a dehydrated Fontan – we need to give fluids and oxygen (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 sinus rhythm. These patients do not tolerate arrhythmias for long. We just need to work out if it’s not sinus rhythm as the patient will therefore need other interventions. Tachy- and brady-arrhythmias are common and patients can deteriorate quickly if not they are not managed promptly. Look out for junctional rhythms and atrial rhythms.

But, there is the same management as for normal arrhythmias. If the patient is unstable, shock them.

Thromboemobilic 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 when to give oxygen or what 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 i.e. lots of pulmonary blood flow at the expense of the systolic 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 completetion, 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 are – if they are normally 70%, then there is no point trying to get them to 75%.

Fully repaired Fontans like oxygen; but in 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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Tessa Davis is a paediatric emergency registrar from Glasgow and Sydney, but currently living in London. Tessa tries to spend time with her 3 kids in between shifts. @tessardavis | + Tessa Davis | Tessa's DFTB posts

6 Responses to "Congenital heart disease in PEM"

  1. Ken Tegtmeyer
    Ken Tegtmeyer 3 years ago .Reply

    Tessa,

    Very nice resource, but I have a couple comments.

    Tet spells, increased venous return is actually beneficial. One of the problems with a tet spell is the kids are tachycardic. Tachycardia leads to less filling time and a smaller ventricular volume so more blood shunts through the VSD out the aorta. Squatting or knees to chest actually both increases SVR and increases venous return, that’s why giving volume, and increasing preload can be beneficial.

    With regard to ketamine in a tet spell. I’d probably avoid it. The right ventricle is hypertrophied so anything that increases heart rate or strength of contraction can make the outflow obstruction worse. This is why phenylephrine is actually the preferred way to increase SVR. Morphine is preferred over Fentanyl because of its slight myocardial depressant effects, and Propranolol is also used to decrease heart rate and contractility. It’s rarer in first world countries to see kids who are having spells, because generally the first one is a trigger to repair. But, in the past kids prone to spells would be on propranolol to help prevent them.

    There’s a comment in the last section that refers to Tetrology pre-Fontan – Tet’s don’t get Fontan procedures, so I’m not sure what that’s referring to.

    For oxygen: Central Shunt, AP window, BT shunt or modified BT shunt, anything that connects the arterial system directly to the pulmonary artery: Avoid too much oxygen. This includes any child with HLHS who has had a stage one repair (Norwood or Sano)

    For the Glenn, Fontan, Hemi-Fontan or most other things, oxygen is OK.

    The Pediatric Cardiologists I’ve worked with would always want to know EARLY if their kids are showing up in the Emergency Department sick. They can be a valuable resource to avoid disaster.

    • Tessa Davis
      Tessa Davis 3 years ago .Reply

      Thanks for the comments – it’s great to have some discussion on this.

      Tet spells and their effect on venous return.

      My understanding is that increased venous return can be a trigger for the tet spell. For example, crying or straining causes increased venous return which increases right to left shunting which starts off the whole cycle. So the aim is to reduce venous return and squatting does this (as well as increasing SVR). There does seem to be some dispute whether squatting increases or decreases venous return – I can find online sources suggesting both.

      Squatting –> Obstruction of Femoral Arteries –> Increased Peripheral vascular resistance –> Increased LV Afterload –> Increased LV Pressure –> Decreased Right ventricular over Left Ventricular pressure gradient –> Decreased shunting of blood from right ventricle to left ventricle (R to L shunt) through the VSD –> Improved flow to the pulmonary artery –> Better alveolar perfusion –> Better oxygenation –> Decreased symptoms of TOF spell.

      But also,

      Squatting –> Obstruction of Femoral Veins –> Increased pooling of blood in the venous reservoir (high capacity veins) –> Decreased preload –> Decreased Venous Return –> Decreased blood coming back to the right ventricle –> again decreasing the flow across the VSD (RV to LV shunt) (from a USMLE forum)

      Will have a look at the ketamine issue tomorrow and post back here.

    • Tessa Davis
      Tessa Davis 3 years ago .Reply

      The line on Tetratology and Fontan repairs was an error – these were two separate sentences. Thanks for spotting this, I’ve now corrected it in the post.

    • Tessa Davis
      Tessa Davis 3 years ago .Reply

      Ken – I cannot find any evidence to suggest that ketamine should be avoided in a tet spell. It does seem to be part of most guidelines for management.

      I did ask Elizabeth Weinstein about your ketamine/phenylephrine comments. Her general list of options are

      1. Knee to chest
      2. Administer 100% 02
      3. Morphine
      4. Saline bolus
      5. NaHCO3
      6. Phenylephrine
      7. Ketamine
      8. Esmolol gtt
      9. Intubate and sedate

      Essentially she jumps from 4 to 7 for practicality. We don’t see tet spells often and there are too many steps to get through to manage this quickly. In ED we use ketamine regularly so all the staff know the doses. This wouldn’t be the same with phenylephrine – knowing the dose (optimal dose is controversial in tet spells), getting it made up and given would all take longer than getting an giving ketamine. If time is of the essence, ketamine is the most practical to use.

  2. Tim Horeczko
    Tim Horeczko 3 years ago .Reply

    Great post — thank you!

    I really appreciated your thoughtful and helpful approach. As far as Tet spells go, our “understanding” of the pathophysiology may be incomplete, and, as you highlight, there may be a more nuanced model or competing factors vis-à-vis SVR and venous return.

    My thought is, I don’t want people to do too much hand-wringing over this. Identify the pathophysiology in front of you: cyanosis, shock, etc — reverse what you can with the resources you have, provide supportive care, and prepare for rapid subspecialty contact (in house or transfer) as needed.

    Main goals: increase SVR, address the hyperpnea, and reverse the shock —

    In other words, I humbly submit my 3 Cs for a Tet Spell:

    Clamp down (mechanical clamp: squat, knee to chest, prone if tolerates)
    Chill out (sedative: morphine or ketamine)
    Correct the acidosis (supportive care, oxygen, gentle fluids after spell broken)

    Thanks again for a great overview and summary!

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