Ventricular undersensing and proarrhythmia
Tracing
Manufacturer Boston Scientific
Device PM
N° 2
Patient
- 81-year-old man
- Single-chamber pacemaker (Boston Scientific) for slow symptomatic atrial fibrillation
- Hospitalization for exploration of acute pain of the left hypochondrium
- Two days after admission, while undergoing an abdominal ultrasound, cardiac arrest
- After 10 minutes of cardiac massage and 2 external electric shocks, the patient recovered proper hemodynamics
- Tracing recorded at the time of the episode
Graph and trace
- Ventricular undersensing and pacing on the T wave
- Induction of a fast, polymorphous and spontaneously resolving ventricular arrhythmia
- Ventricular undersensing and pacing on the T wave
- Induction of a VF episode (disorganized ventricular arrhythmia)
- Marked ventricular undersensing of the arrhythmia
Comments
- This tracing is quite rare since it shows the induction of ventricular fibrillation following ventricular undersensing and asynchronous pacing during the ventricular vulnerable period (R-on-T phenomenon)
- This is the more frightened complication associated with ventricular undersensing
- The risk of ventricular fibrillation is very rare outside of circumstances such as myocardial ischemia or metabolic disorder
- This patient underwent 2 electric shocks which allowed termination of the arrhythmia
- The interrogation of the device revealed a drop in impedance associated with a significant rise in the pacing threshold suggestive of lead failure
- A new lead was implanted and the patient was able to be discharged home
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