Wednesday, 26 July 2017

ECG of the Week - 24th July 2017 - Interpretation

The following ECG is from a 52 yr old female who was referred by her General Practitioner with confusion and abnormal biochemistry results.





Click to enlarge
Rate:
  • Mean rate 66 bpm
Rhythm:
  • Irregular
  • Complexes #1-3, 5-6, 8-10
    • Sinus rhythm
  • Complex #4
    • PVC
  • Complexes #7 & 9
    • Nil convincing preceding P wave
    • Similar morphology as sinus complexes
    • Potential junctional escape during period of sinus arrest / pause
Axis:
  • Normal
Intervals:
  • PR - Normal
    • During sinus conduction
  • QRS - Prolonged (120ms)
  • QT - 520ms (QTc Bazette 565 ms)
    • Calculated in lead II using consecutive sinus complexes
Additional:

  • Absence of typical BBB pattern
  • ST Depression leads II, III, aVF, V3-6
  • Biphasic (down-up) T wave in inferior leads
  • Baseline artifact
  • Notching in ST segment in complexes #6,8,10
  • Precedes period of sinus pause and junctional escape
  • ? Increased sinus automaticity during ventricular refractory period
Interpretation:
  • QT Prolongation
  • ST Depression
  • Increased automaticity
    • PVC, Rhythm disturbance, PJC, possible increased sinus acitivty
Favors hypokalaemia +/- hypomagnesaemia as the likely cause.

What happened ?

The patient's biochemistry results were:
  • Na 131 mmol/L
  • K 2.2 mmol/L
  • Cl 73 mmol/L
  • Bicarb 44 mmol/L
  • Urea 20.3 mmol/L
  • Creat 153 umol/L
Both calcium and magnesium were within normal limits. The patient was on a combination angiotensin II receptor antagonist and thiazide diuretic which was ceased and following electrolyte correction her confusion resolved.

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.