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:

• Right Ventricular Hypertrophy

 

• Pulmonary Stenosis

 

• 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:

• 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!