ECG of the Week - 10th August 2015 - Interpretation

This ECG is from a 70 year old male who presented to the Emergency Department complaining of feeling light-headed and dizzy. Past medical history or hypertension, diabetes, chronic atrial fibrillation and chronic renal failure on dialysis. His medications included metoprolol but no digoxin.
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Rate:

• 36 bpm

Rhythm:

• Irregular
• Nil consistent atrial activity
• Possible atrial activity in ST segment of 2nd complex and after T wave of 3rd complex

Axis:

• LAD

Intervals:

• QRS - Normal (100ms)
• QT - 480ms (QTc Bazette 375 ms)

Additional:

• T waves leads V3-5 appear prominent and peaked

Interpretation:

• Slow atrial fibrillation
• Broad differentials including:
• Drug toxicity
• Sinus node dysfunction
• Hypothermia
• Electrolyte abnormalities
• Ischaemia

In this case the major concerns were hyperkalaemia and drug toxicity from beta-blocker.

What happened ?

The patient had taken an extra metoprolol dose earlier in the day ! Venous blood gas revealed a potassium of 7.0 mmol/L.
Further beta-blocker medication was withheld and hyperkalaemia was treated with calcium gluconate and insulin / dextrose therapy prior to planned dialysis later in the day. 
Following ED treatment of hyper-k the patients heart rate improved to ~50 bpm and he made an uneventful recovery.

References / Further Reading

Life in the Fast Lane

• Hyperkalaemia
• Hyperkalaemia - Case Study

Textbook

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