Wednesday, 28 December 2016

ECG of the Week - 26th December 2016 - Interpretation

The following ECG is from a 36 yr old male who presented with chest pain and dysponea.





Click to enlarge
Rate:
  • 54 bpm
Rhythm:
  • Regular
  • Sinus rhythm
Axis:
  • Right axis deviation / Inferior
Intervals:
  • PR - Normal (~160ms)
  • QRS - Normal (80ms)
  • QT - 480ms (QTc Bazette 455 ms)
Segments:

  • Nil change in interpretable leads

Additional:

  • Significant high frequency baseline artifact
    • Maximal in precordial leads
    • Obscures P wave, T wave, PR segment, ST segment and baseline
  • P inversion aVL 
    • Pattern not consistent with lead reversal
    • Normal P wave axis in other leads

Interpretation:

  • High frequency artifact
  • Unable to fully interpret ECG due to artifact but likely normal


Troubleshooting artifact

There are multiple factors that can generate artifact during the ECG recording / printing process including:

  • Patient factors
    • Habitus - very thin or obese patients, paediatric patients
    • Poor pad contact due to hair
    • Poor pad contact due to moisture - sweating, immersion etc.
    • Movement artifact - tremor, resp pattern, agitation, shivering, rigor
  • Lead factors
    • Poor pad contact
    • Pad misplacement
    • Damaged lead or lead connection
  • ECG Machine Factors
    • Inappropriate settings of gain or filtering modes
    • Electrical artifact from power supply
  • Printing factors
    • Low ink
    • Print head tracking
    • Paper alignment
  • External factors
    • Electrical interference from other devices - mobile phones, diathermy, computers etc.
An awareness of these factors and a systemic approach to addressing each point in the recording process, from patient to printer, is important in addressing recording problems such as artifact and lead malpositioning. 


References / Further Reading

Textbook

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