Med in Small Doses - Ventricular Tachyarrhythmias


This post is on some common and important Ventricular Tachyarrhythmias (e.g. Ventricular Fibrillation). See Cardiac Arrhythmias for a complete overview. A Quick Guide to ECG will also give you tips on how to approach an ECG.

Typically Board Complex (QRS>0.12)

General Approach to the acute management of Ventricular Tachyarrhythmias is ACLS or Advanced Life Support (ALS). VF & pVT are both shockable rhythms.



VF (V-fib)
Most serious. Cardiac Output = 0.
VF is a medical emergency that requires prompt BLS interventions.


Key ECG Features
  • Irregular rhythm
  • No measurable rate
  • Loss of P Waves  
  • No discernible QRS complex

VF via ECGPedia

VT
Most common cause is myocardial ischaemia or scarring following an AMI. Pulseless VT is a major threat to life.

Key ECG Features
  • QRS Regular (occasionally slightly irregular) and wide (>0.12s)
  • Ventricular rate = 150 - 250 bpm
  • P Waves do link up with QRS Complexes
  •  Hard to seperate QRS Complex and T Waved

VT via ECGPedia

Ventricular tachycardia: treatment LAMB:
L idocaine
A miodarone
M exiltene/ Magnesium
B eta-blocker

Consider DC Cardioversion (repeat up to 3 times).

Pulseless VT: Commence ALS. Early defibrillation is the priority.

Torsades
Torsades de pointes, or simply torsades, is a French term that literally means "twisting of the points." Wikipedia

Can progress to VF.


Key ECG Features
  • Regular (mostly)
  • Rotation of the heart's electrical axis by at least 180°
  • Ventricular rate = 150-300 bpm


Torsades adapted from Wikipedia


RFs: FLASH
F Familial Long QT syndrome
L eft Ventricular Hypertrophy
A cidoisis / Antiarrhythmics (Class III)
S low heart rate / SAH
H ypos (e.g. Hypokalemia, Hypocalaemia, Hypomagnesaemia, Hypothermia)


Tx: Withdrawal of the offending agent, infusion of Mg2+ sulfate, antiarrhythmic drugs, and electrical therapy as needed.

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