This post is an answer to the ECG Case 333
- 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 in leads II, III, aVF
Interpretation
- Pacemaker failure to capture
- Underlying marked slow atrial fibrillation
What happened next ?
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.
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
