Tachycardias

Question 1

Differentials

Answer 1

• Atrial (AF, atrial flutter, atrial tachycardia)
• SVT
• VT
• VF

Question 2

Management of Tachycardias

Answer 2

Question 3

Definition of VT

Answer 3

• Sustained VT is a ventricular rhythm faster than 100bpm lasting at least 30 seconds or requiring termination earlier due to haemodynamic instability. VT is defined as a wide complex tachycardia (QRS ≥120ms) that originates from one of the ventricles, and is not due to aberrant conduction.

Question 4

Signs and Symptoms of VT

Answer 4

• Tachycardia
• Hypotension
• Weak pulse
• Syncope/presyncope
• Airway compromise
• Chest discomfort
• Dyspnoea.

Question 5

ECG Features of VT

Answer 5

• Wide complex tachycardia (QRS ≥120ms)
• HR ≥100bpm

Question 6

ECG Features of VF

Answer 6

• Arrhythmic
• Fibrillatory baseline >300bpm
• Erratic undulations with indiscernible QRS complexes
• No atrial P waves

Question 7

Pathophysiology of atrial flutter

Answer 7

• Electrical signal recirculates in a self-perpetuating loop due to an extra electrical pathway
• Signal goes round and round the atria without interruption and every second lap is conducted due to the long refractory period of the AV node

Question 8

Pathophysiology of SVT

Answer 8

• Electrical signal re-enters the atria from the ventricles
• This signal travels through the AV node again causing another ventricular contraction
• Self-perpetuating loop

Question 9

WPW Syndrome

Answer 9

• Extra electrical pathawy connecting atria and ventricles (often called Bundle of Kent)
• Definitive management is radioablation of the acessory pathway

Question 10

ECG features of WPW

Answer 10

• Short PR interval (<0.12s)
• Wide QRS complex (>0.12s)
• Delta wave which is a slurred upstroke on the QRS

Question 11

Torsades de pointes

Answer 11

• HR usually >200
• Varying shape and size of QRS
• QTc prolongation
• Treat with:
  
  • IV magnesium
  • Synchronised DC cardioversion
  • Stop all precipitants