ECG of the Week 28th July 2021 – Interpretation

You are reviewing the ECG of a 65 year old man who has presented with a one week history of chest tightness and shortness of breath. He has a background history of Type 2 Diabetes and had x2 coronary stents 5 years prior.


  • Rate: 84
  • Rhythm: Sinus rhythm (p wave most easily seen in V2 where artefact is less obstructive)
  • Axis: Normal (0-90)
  • Morphology: low amplitude interference seen throughout all leads, relative sparing of V2
  • Intervals: PR160 QRS 80
  • Summary: Normal ECG with interference.

Causes of interference or artefact:

  • Patient Factors: PPM or other implanted devices, movements disorders eg PD, rigors, muscle activity for other reasons eg pain or hypothermia, poor pad contact due to hair or moisture.
  • Lead Factors: pads poorly placed or misplaced, damaged or misconnected leads
  • ECG machine Factors: inappropriate gain settings, electrical artefact from power supply
  • Printing Factors: low ink, paper malaligned, printer head tracking
  • External Factors: ie external surroundings causing interference (rare with newer machinery)

Clinical Relevance in this patient:

  • At Joondalup the commonest cause of interference is due to artefact from the power supply (solved with turning off the plug and relying on battery power to print an ECG) – but in this instance the artefact remained
  • This patient had a spinal cord stimulator which was the cause for the interference seen.

Further Reading -Online

ECG of the Week from Dr Larkins Blog 26th June 2017 – and ECG showing artefact from an implantable neuro-stimulator


Further Reading – Textbook:

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