Wednesday, 13 December 2017

ECG of the Week - 11th December 2017 - Interpretation

The following ECG is from a 68 yr old male who presented with a history of dizziness and pre-syncope.



Click to enlarge
Rate:
  • 60 bpm
Rhythm:
  • Regular
  • Sinus rhythm
Axis:
  • Left axis deviation
Intervals:
  • PR - Prolonged (~220=240ms)
  • QRS - Prolonged (160ms)
Additional:
  • RsR' Pattern leads V1-2

Interpretation:

  • Bifascicular block with pr prolongation
    • RBBB
    • LAFB

Many people refer to the combination of bifascicular block with a 1st or 2nd degree AV block as a 'trifascicular block', this term is obviously incorrect as a block of all three fascicles 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 'trifascicular 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 fascicles are affected as the pr prolongation may be due to disease at the AV node, the left posterior fascicle, or the His bundle.
The AHA 2008 guidelines for PPM insertion are clear that an incidental bifascicular block with pr prolongation in the asymptomatic patient does not warrant PPM insertion (LoE: B, Class III recommendation) but in the setting of syncope are an indication for PPM insertion.

Given history of near syncope this patient needs cardiology referral was consideration of PPM insertion.

What happened ?

During admission the following ECG was recorded:


Click to enlarge
The patient has now developed complete heart block with a bradycardic escape rhythm with distinctly different QRS morphology from his earlier ECG. There are also prominent T waves in all leads with deep T inversion in the infero-lateral leads. The patient had normal electrolytes and negative cardiac biomarkers. The T wave abnormalities likely reflect the abnormal ventricular repolarisation from the escape rhythm couple with cardiac T wave memory. The patient underwent an uneventful PPM insertion and was discharged shortly afterwards. 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.