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.