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.

Click to enlarge

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

• Pacemaker Normal Function
• Pacemaker Malfunctions

Textbook

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