×
MedSchool: Ace Your OSCEsThe Medical Company
 
 
 
 
 
GET - On the App Store
View
ECG Basics
 
 

Quality of the ECG Trace

 
 
 
Bookmark

Overview

A poor quality ECG trace can be incredibly difficult to interpret and, more dangerously, may be misinterpreted.

Baseline Wander

This type of interference originates from the interface of the skin and the electrode, and makes interpretation of high amplitude waves (e.g. the T wave or ST segment) difficult. In certain circumstances, baseline wander may mimic life-threatening arrhythmias.
  • Look For

  • Low-frequency variation of the isoelectric line.
  • Baseline Wander
     
  • Causes of Baseline Wander

  • Patient movement - especially respiration
  • Inadequate contact between electrodes and body surface
  • Improper skin preparation
  • Patient sweating

Electrical Interference

This type of interference originates from the power cable, ECG machine, leads or the patient; it makes interpretation of  low amplitude waves (e.g. the P wave) difficult or impossible.
  • Look For

  • High-frequency variation of the isolelectric line.
  • Electrical Interference
     
  • Causes of Electrical Interference

  • Incorrect earthing
  • Other electrical equipment plugged into the same circuit
  • The patient’s muscle activity

Incorrect ECG Lead Placement

Reversal of arm leads (RA and LA)- inversion of lead I (negative P waves and QRS complexes)
Reversal of RA and LL - inversion of lead II (negative P waves and QRS complexes)
Reversal of LA and LL - inversion of lead III (negative P waves and QRS complexes)
Reversal of LA and LL + RA and RL - flattening of lead I (very low frequency waves)
Reversal of RA and RL - flattening of lead II (very low frequency waves)
Reversal of LA and RL - flattening of lead III (very low frequency waves)
Superior misplacement of V1 / V2 - poor R wave progression
No changes will be seen with reversal of LL and RL.
Next Page
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Want more info like this?
  • Your electronic clinical medicine handbook
  • Guides to help pass your exams
  • Tools every medical student needs
  • Quick diagrams to have the answers, fast
  • Quizzes to test your knowledge
Sign Up Now
   
 
 

Snapshot: Initialising...