Tetralogy of Fallot

Recently, in a Holter clinic, I dealt with an 8 year old patient who was on the road to recovery after a diagnosis of congenital defect, Tetralogy of Fallot. As a result, I got hold of the most interesting ECG I have recorded to date.

Background

ToF is a rare congential defect affecting the heart, that results in an insufficiency of oxygenated blood leaving the heart through the systemic circulation. Thus, it is considered a cyanotic disorder.

The disorder affects roughly 5 in 10,000 infants, and has an equal gender distribution.

Generally, four pathologies comprise ToF. Whilst all four are not always present, three can consistently be found. ToF is a progressive disorder, in that each pathology gives rise to the others.

The four principal defects are:

RVH

PVSTEN
L-R: Normal and stenotic PV

 

  • Pulmonary Stenosis
VSD
VSD supplying mixed blood via OvA

 

  • Ventricular Septal Defect
    • Hole in septum, due to malformation, causing oxygenated and deoxygenated blood to mix within cardiac structure
  • Overriding Aorta
    • Aorta is placed over VSD, transporting blood with low O2 content to wider systemic circulation

Cyanotic episodes require immediate correction, before surgical intervention.

  • High flow O2 administration
  • Physical positioning
    • Knees to chest
    • Parent cradling the child will illicit this effect naturally
  • NaCl fluid bolus
  • Vasopressor therapy
    • Increases systemic vascular resistance, shunting blood through pulmonary system.
  • Continuous ECG and SpO2 monitoring

Surgical intervention usually repairs the VSD and addresses pulmonary pathology, often at the same time.

Prognosis for ToF patients is generally very good.

  • Overall outcome improved since surgical treatment has improved
    • Survival of surgery is currently 95-99%
  • 36 year post-surgical survival is currently 96%
  • Patients who undergo surgical treatment are at greater lifelong risk of ventricular arrhythmia
  • Complications can arise as a result of a transannular patch repair, specifically;
    • RV dysfunction
    • Heart block (risk of HB has dropped to around 1%, in recent studies)
    • Heart failure
    • Recurrent or residual VSD

Hx:

  • 8 y/o
  • Previous diagnosis of ToF
    • VSD
    • PV Stenosis
    • Mild RVH
  • Treatment:
  • Transannular patch repair
  • PV Replacement

Medication:

  • Daily:
    • Atenolol
    • Aspirin

This patient was having a 24hr Holter recording to assess cardiac recovery after their most recent procedure; the PV replacement. Physical examination showed a RVOT murmur, whilst echocadiography displayed a mild RVH and PV regurgitation. Left heart functionality has been classed as excellent.

Previous ambulatory study has shown no arrhythmic action, save for that considered normal in a child of this age. No previous ECG recordings were available.

Upon monitor removal, a 12-Lead ECG was performed, the resulting trace was as follows:

ToFECG (2).png

  • Sinus rhythm with BBB morphology
  • Sokolow-Lyon value of 36mV for RVH
  • QRS & ST segment abnormalities in all leads

Ambulatory analysis relating to the most recent study did not differ greatly from previous monitoring, showing occasional sinus arrhythmia and bradycardia, five non-conducted P waves were found, and two of these gave rise to periods of sinus bradycardia. All other instances were gradual onset/offset.

Nocturnal bradycardia reached rates as low as 34bpm.

What does everyone think of this ECG and brief ambulatory report? Let us know by leaving a comment below!

Heart

 

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Published by

Christopher

I'm a qualified clinical physiologist with a keen interest in free open access meducation (FOAMed), pacing and electrophysiology.

2 thoughts on “Tetralogy of Fallot”

  1. Hi, I came across your post and wanted to read bc I have a son who was born with TOF w|an absent Pulmonary valve…he had his 1st surgery 4 months and recently had a 2nd at 15 months which they discovered he has an aneurysm in his lung. The doctors have no information really to go by and wanted to know if this is something you have ever heard of? Thanks for reading my comment 🙂

    Like

    1. Sorry it took so long for me to respond, nsjones17. I don’t personally know, as this TOF isn’t my forté, so I wouldn’t like to guess, but I’ll ask one of my consultants and see if they have any information. I hope that’s ok.

      Like

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