Wednesday, 15 June 2016

ECG of the Week - 13th June 2016 - Interpretation

The following ECG is from a 52yr old male presenting with dysponea.




Click to enlarge

Rate:
  • 96 bpm
Rhythm:
  • Regular
  • P waves difficult to see but likely present
    • Best appreciated in leads I & II
Axis:
  • RAD
Intervals:
  • PR - Unable to adequately identify P wave morphology to measure, suugestion of pr prolongation in lateral leads
  • QRS - Normal (100ms)
Additional:

  • High frequency artefact in all leads
  • Maximal in precordial leads
  • Relative sparring of leads I & aVL 

Interpretation:

  • Significant artefact obscuring the baseline and majority of ECG segments
  • Likely electrical interference from power supply (50Hz AC)
  • Need to check correct line frequency filter, electrode contact and remove obvious potential interfering devices from patient / area


What are the causes of ECG artefact ?

There are multiple causes of ECG artefact and they may relate to the patient, environment or equipment. They include:

  • Patient Factors
    • Implanted devices
    • PPM - Pacing Spikes
    • Nerve stimulators
    • Movement disorders e.g. Parkinson's, essential tremor
    • Rigors
    • Muscle tremor / activity can be related to pain, hypothermia etc.
    • CPR
    • Transport artefact e.g. vehicle movement
  • Environmental
    • Interference from surrounding electronic devices. Relatively rare using newer ECG machines and environmental interferece if usually compounded by incorrect machine filter settings.
  • Equipment
    • Poor lead contact 
    • Damaged cable / connector
    • Filter settings including monitor vs filter mode and main supply hertz filtering



References / Further Reading

Life in the Fast Lane

ECGpedia
Textbook
  • Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.