ECG of the Week – 4th November 2013 – Interpretation

By | 6 november 2013

Unfortunately I’ve got no clinical information on this case but the ECG looks interesting.




Click to enlarge

A numbered version of this ECG can be found below.

Click to enlarge



Rate:

  • Mean ventricular rate 72 bpm
    • Sinus rate 100bpm
    • Junctional rhythm rate 60 bpm

Rhythm:

  • Two distinct rhythms
    • Complexes # 1,2,6,7,8,12 = Junctional rhythm
      • P wave does precede complex #8 but pr too short for sinus
    • Complexes # 3, 4, 5, 9, 10, 11 = Sinus rhythm

Axis:

  • Normal (55 deg)

Intervals:

  • PR – Normal (~160ms)
    • Complexes # 3, 4, 5, 9, 10, 11
  • QRS – Normal (80ms)
  • QT – 340-360ms

Segments:

  • ST Elevation lead aVR
  • ST Depression upsloping leads II, aVF, V3-6
  • PR Depression leads aVF, V3-6
  • PR Elevation lead aVR

Additional:

  • P-P Interval ~600ms
    • Pause between P waves preceding complex #5 to complex #8 is 3000ms
    • Pause interval 5 x P-P interval
P-P Intervals labelled
Click to enlarge

  • Notching following T wave leads V4-6 ? Atrial vs U wave
  • Prominent T waves leads II, V2-5
  • QRS Morphology almost identical between sinus and non-sinus beats.


Interpretation:

  • Sinoatrial exit block
    • ? 2nd degree type II SA exit block
      • Fixed sinus P-P interval 
      • Pause duration is a multiple of sinus P-P interval 
  • Sinus pause less likely given duration length in relation to P-P interval

Given I don’t have any clinical information on this case there are several potential causes for these ECG findings, including:

  • High vagal tone
  • Drug toxicity especially digoxin
  • Ischaemia
  • Myocarditis
  • Sick sinus syndrome
  • Electrolyte disturbance


References / Further Reading

Life in the Fast Lane

  • Sinoatrial Exit Blocks here
  • Junctional Rhythm here

Textbook

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

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