ECG of the Week - 21st May 2018 - Interpretation

This ECG is from a 42yr old female who presented complaining of palpitations following an elective procedure in general anaesthetic earlier that day.

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Rate:

• 66 bpm mean ventricular rate

Rhythm:

• Two distinct rhythms
• Complexes #1-3 and #11
• Sinus
• Rate 60 bpm
• Normal QRS width
• Complexes #4-10
• Non-sinus
• Rate 63 bpm
• QRS Prolonged
• AV dissociation
• Atrial activity buried in QRS

Axis:

• Unable to determine due to rhythmm change

Intervals for sinus complexes:

• PR - Normal (~160ms)
• QRS - Normal (80ms)
• QT - 400ms

Intervals for non-sinus rhythm:

• QRS - Prolonged (120ms)

Additional:

• Non-specific conduction delay not typical BBB
• No evidence of fusion or capture during non-sinus rhythm

Interpretation:

• Episode of accelerated idioventricular rhythm (AIVR)

What happened ?

The are a number of potential causes of AIVR in patients including:

• Ischaemia
• Post-reperfusion
• Drug toxicity / effect especially digoxin and other anti-arrhythmics
• Athletic heart
• Electrolyte abnormalities
• Structural cardiac disease
• Myocarditis

AIVR occurs when the rate of the ectopic ventricular pacemaker exceeds that of the sinus node. This patient was observed in the Emergency Department and normal biochemistry and negative biomarkers. The episodes of AIVR resolved and were felt to be secondary to volatile anaesthetic and she was discharged with out-patient cardiac follow-up.

References / Further Reading

Life in the Fast Lane

• Accelerated Idioventricular Rhythm 

Textbook

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