Tachyarrhythmias:

 

AF

·     Wandering baseline

·     Irregularly irregular QRS

·     Variable amplitude of QRS (∝ ventricular filling)

AFL

·     Classic: sawtooth baseline

·     Real life: hidden in ST segment

·     Often 300 per minute

·     Often fixed conduction interval e.g. 2:1, 3:1

·     Circuit goes up and down -> best seen in inferior leads

SVT

AVNRT:

·     i.e. SVT

·     Narrow complex and regular

·     Rate 150-200

·     May or may not see P waves (retrograde and/or swallowed up)

·     Rx: Valsalva + legs up, adenosine

AVRT:

·     Abnormal pathway between atria and ventricles

·     e.g. WPW (see “Miscellaneous”)

·     Orthodromic: narrow QRS (treated like vanilla SVT anyway)

·     Antidromic: wide QRS (look out!)

VT

·     Monomorphic

·     Polymorphic

o   Torsades: QRS complexes ‘twist’ around the isoelectric line

Broad complex tachycardia

DDx:

·     VT (best to assume)

·     SVT with

o   BBB

o   Accessory pathway

o   Certain anti-arrhythmics

o   Profound hyperkalaemia

Problem:

·     The above look alike

·     Some drugs safe, others lethal

·     Call cardiology for help

Factors suggesting VT: (Brugada criteria)

·     Doesn’t look like a BBB

·     Axis in no-man’s land

·     Very broad complexes

·     AV dissociation

·     Capture beats (occasional normal-looking QRS)

·     Fusion beats (concurrent VT beat and sinus beat -> weird QRS)

VF

·     Why are you doing a 12 lead?