Friday, 3 July 2015

ECG of the Week - 29th June 2015 - Interpretation

This week's ECG case is from an 83yr old male who presented to the Emergency Department with several days of atypical chest pain with negative serial biomarkers. He had no relevant past medical history and was on no medication. The first ECG was taken on arrival to the Emergency Department the second ECG was perform when it was noted his heart rate has decreased suddenly. The patient remained asymptomatic during this period with normal conscious level, normal blood pressure and no chest pain or dysponea.
Check out the comments from our original post here.



ECG on arrival to the ED
Click to enlarge

Rate:
  • 54 bpm
Rhythm:
  • Regular
  • Sinus rhythm
Axis:
  • LAD (-90 deg)
Intervals:
  • PR - Prolonged (~360ms)
  • QRS - Prolonged (120ms)
  • QT - 480ms 
Additional:

  • Lead V1 rsR' morphology
  • T wave in leads V2-3 relatively large compared with QRS voltage


Interpretation:


  • Bifascicular block (RBBB + LAFB) with PR Prolongation

So it's a trifasicular block ?

Well yes and no.

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. .
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) - as in our case here.


What happened next ?

Our patient was noted to have a bradycardia and a repeat ECG was performed - he remained completely asymptomatic during this episode.

ECG with heart rate change
Click to enlarge

Rate:
  • Atrial rate ~75 bpm Ventricular rate of ~38 bpm
Rhythm:
  • 2:1 AV Block
  • Regular ventricular complexes
  • Note the finally complex only partial seen at the end of the ECG occur much sooner than anticipated
Axis / Intervals / Additional:

  • As in 1st ECG
Interpretation:
  • Bifascicular block (RBBB + LAFB) with 2:1 AV Block
What happened next ?

The patient was admitted under the cardiology team on telemetry and had no further episodes of 2:1 block, this episode captured here was short lived and spontaneously resolved. Given the patient remained asymptomatic through-out he was discharged for out-pt surveillance / follow-up.

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.