Supraventricular tachycardia

Question 1

What is SVT and what causes it?

Answer 1

• Most common childhood arrhythmia
• HR 250-300 bpm
• Reentry tachycardia: circuit of conduction is set up with premature activation of the atrium through an accessory pathway

Question 2

ECG findings with SVT

Answer 2

• Narrow complex tachycardia
• 250- 300 bpm
• P wave AFTER QRS indicating retrograde activation of the atrium via the accessory pathway
• When in sinus short PR interval
• Myocardial ischemic changes
  
  • T wave inversion in lateral precordial leads
• WPW: short PR interval and delta wave

Question 3

Clinical presentation of SVT

Answer 3

• Poor CO
• Pulmonary oedema
• HF in neonate/ young infant
• Hydrops fetalis and intrauterine death

Question 4

Management of SVT

Answer 4

• RESTORATION OF SINUS RHYTHM
• Circulation and respiratory support: acidosis correction and positive pressure ventilation
• Vagal stimulating manouevere’s (80% successful)
  
  • ​carotid sinus massage
  • cold ice pack to face
• IV adenosine
  
  • ​AV block
  • rapid bolus injection
  • terminates tachycardia by breaking the re-entry between AV node and accessory pathway
• Electrical conversion
  
  • ​synchronised DC shock (0.5- 2 J/kg body weight) if adenosine fails
• Maintenance- resting ECG remain normal but 90% children will have no further attack afterinfancy therefore treatment unsually stopped at 1 year of age
  
  • ​Flecainide
  • Sotalol
  • Digoxin
    
    • no delta wave
    • use propanolol with pre-excitation wave
  • WPW syndrome a
    
    • atrial pacing
    • those risk of relapse –> percutaneous radiofrequency ablation or cryoablation of accessory pathway