The ECG and Electrolyte Abnormalities

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INTRODUCTION

  • Various electrolyte disorders can result in abnormalities to the resting ECG ranging to clinically significant arrhythmias
  • Hyperkalaemia is the commonest abnormality that can lead to significant arrhythymias
  • General factors that predict deterioration are conduction abnormalities, QT changes and frequent ectopic beats
  • Treatment of arrhythmias typically follow ACLS guidelines in combination with correction of the abnormality

Resting ECG Changes

P wave PR Interval QRS duration ST segment T wave QT interval Other
↓K Flat/ Inverted  ↑

 

U wave
↑K +/0 ←→ Peaked Sine wave
↓Ca

 

↑Ca ←→

→←

Abrupt upslope

Flat/Inverted/Biphasic

 ↑ QRS size
↓Mg ←→ ←→

→←

Peaked

Flat/Wide/Inverted

 

 

U wave
↑Mg
↑Li Flat Flat

 

Arrhythmias

  Bradyarrythmias Tachyarrythmias
↓K Sinus Bradycardia
1o/2o AV block
 Asystole
AF
PAT
SVT
PACs
PVCs
VT
VF
↑K 2o/3o AV block
Asystole
Broad complex tachycardia

VF

↓Ca Sinus Bradycardia Torsade de pointes
↑Ca 2o/3o AV block
Asystole
 SVT
VT
↓Mg PACs
PVCs
AF
MAT
SVT
PVCs
VT
Torsade de Pointes
VF
↑Mg 3o AV block
Asystole (diastolic arrest)
↑Li Sinus/Bradycardic arrest (rare)

 

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