Summary Cardiac Arrest Rhythm Recognition: Differentiating Shockable and Non-Shockable Rhythms for ALSACLS

Cardiac Arrest Rhythm Recognition: Shockable vs
Non-Shockable Rhythms

Introduction

 Differentiating between shockable and non-shockable rhythms is a
critical skill in managing cardiac arrest.
 It guides the appropriate section of the Advanced Life Support (ALS)
algorithm to follow.
 This article reviews the characteristic features of the four main
cardiac arrest rhythms as seen on a defibrillator rhythm strip.

Shockable Rhythms

 Types: Pulseless Ventricular Tachycardia (pVT) and Ventricular
Fibrillation (VF)
 Prognosis: Associated with the best survival outcomes in cardiac
arrest
 Management: High-quality CPR and prompt defibrillation are
essential
 Common Causes: Ischaemic heart disease and acute coronary
syndromes

Ventricular Fibrillation (VF)
 Appearance: Chaotic, disorganised electrical activity with no
identifiable QRS complexes
 Progression: Starts as coarse VF → fine VF → asystole if untreated
 Requires immediate defibrillation


Ventricular Tachycardia (VT)
 Appearance: Regular broad complex tachycardia with rates
typically between 100–300 bpm
 Important to check for a pulse:
o VT with pulse → managed per ALS tachycardia algorithm
o Pulseless VT → treated as cardiac arrest rhythm
 Morphology:
o Monomorphic VT: uniform QRS complexes
o Polymorphic VT: varying QRS morphology (e.g., Torsade de
Pointes)
 Torsade de Pointes:
o Polymorphic VT with sinusoidal QRS rotation