ECG of the Week - 13th October 2014 - Interpretation

This ECG is from a 45 yr old female. She presented with abdominal pain and vomiting. Investigations revealed an acute small bowel obstruction. Prior to admission to the ward a 'routine' ECG was performed and is below.
Check out the comments from our original post here.

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Rate:

• Mean ventricular rate ~78 bpm

Rhythm:

• Regularly irregular
• Repeating pattern of sinus complex followed by two ventricular complexes

Axis:

• Sinus complexes: Normal
• Ventricular complexes: Left axis deviation

Intervals - Sinus Complexes:

• PR - Normal (140ms)
• QRS - Normal (80ms)
• QT - 380ms

Intervals - Ventricular Complexes:

• QRS - Prolonged (120-140ms)
• QT - 360 ms

Segments:

• Minor ST elevation sinus complex in lead V6
• Ventricular complexes show appropriate ST segment and T wave discordant change

Additional:

• Notching in terminal portion of ventricular QRS best seen in leads aVL and aVF ? native atrial activity - thanks to Ken for spotting this.

Interpretation:

Benign arrhythmia which will likely resolve once the underlying bowel obstruction has resolved. 
Causes could include:

• Electrolyte abnormality
• Acid/base disturbance
• High vagal tone secondary to pain and nausea
• Drug toxicity pending a review of the patient's usual medication

References / Further Reading

Life in the Fast Lane

• Premature ventricular complexes
• Accelerated Idioventricular rhythm 

Textbook

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