Wednesday, 30 August 2017

ECG of the Week - 28th August 2017 - Interpretation

This ECG is from an 86 yr old male referred by his General Practitioner with worsening renal failure. He has a history of atrial fibrillation with bradycardia for which he had a PPM inserted. His medications include metoprolol.



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Rate:
  • Mean ventricular rate ~24 bpm
Rhythm:
  • Irregular ventricular rhythm
  • No visible P waves
  • Irregular pacing spikes mean rate of 43 bpm
  • No evidence of capture
Axis:
  • Normal
Intervals:
  • QRS - Prolonged
Additional:

  • ST depression with T wave inversion leads II, III, aVF

Interpretation:

  • Pacemaker failure to capture
  • Underlying marked slow atrial fibrillation

Causes of pacemaker failures

In broad terms there is either a problem with the pacemaker signal generator, the connection to the patient or the patient. These can be further expanded:


  • Signal generator problems
    • End-of-life
    • Battery failure
    • Programming issue
    • Over or under sensing
  • Connection between unit and patient
    • Lead fracture
    • Lead malposition
    • Lead migration
    • Lead fibrosis
  • Patient factors
    • Progression of underlying disease
    • Ischaemia
    • Electrolyte / acid-base disturbance
    • Drug toxicity

What happened ?

The patient had moderate renal failure with a normal potassium. CXR showed no lead abnormality and lead placement appeared unaltered. His metoprolol was ceased and the pacemaker threshold was reprogrammed with resultant 100% capture.

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.