Wednesday, 27 April 2016

ECG of the Week - 25th April 2016 - Interpretation

The following ECG is from an 89 yr old male who presented to the Emergency Department complaining of dizziness.


Click to enlarge

Rate:
  • 54 bpm
Rhythm:
  • Sinus arrhythmia
Axis:
  • LAD (-73 deg)
Intervals:
  • PR - Prolonged(~280ms)
  • QRS - Prolonged (~150ms)
  • QT - 480-500ms (QTc Bazette 450-470 ms)
Segments:
  • Discordant ST depression leads I, aVL, V1-2
  • Concordant ST depression lead V4
Additional:
  • RBBB Morphology
  • Broad P wave with notching 
  • T wave inversion leads I, aVL, V1-4
Interpretation:
  • PR Prolongation
  • Bifasicular block
    • RBBB with LAFB
So it's a trifasicular block ?

Many people refer to the combination of bifasicular block with a 1st or 2nd degree AV block as a 'trifasicular block', this term is obviously incorrect as a block of all three fasicles should result in complete heart block. 
Further to the inaccurate nature of the term the AHA 2009 Recommendations for the Standardization and Interpretation of the Electrocardiogram specifically recommended the term 'trifasicular block' not be used due to the variation in anatomy and pathology producing the pattern.
On this surface ECG it isn't possible to tell whether all three fasicles are affected as the pr prolongation may be due to disease at the AV node, the left posterior fasicle, or the His bundle. 
Those patients with bifasciular block, pr prolongation and a history of syncope or likely arrhythmia, should be referred to cardiology team for telemetry, review of current medications, and consideration for PPM insertion.
The AHA 2008 guidelines for PPM insertion are clear that an incidental bifasicular block with pr prolongation in the asymptomatic patient does not warrant PPM insertion (LoE: B, Class III recommendation).


References / Further Reading

Life in the Fast Lane

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