Atrial undersensing

N° 4
Manufacturer Abbott Device PM Field Sensing
  • 69-year-old woman
  • AssurityTM + DR pacemaker (Abbott) for complete atrioventricular block
  • Episodes of paroxysmal AF
Graph and trace

Tracing 4a

  • DDD mode 60 beats/minute
  • Undersensing of atrial arrhythmia
  • Asynchronous atrial pacing followed by effective ventricular pacing


Tracing 4b

  • Same patient and recording of a HVR episode (high ventricular rate)
  • Sinus rhythm with atrial undersensing
  • Asynchronous atrial pacing
  • Premature ventricular contraction not detected because falling in the post-atrial ventricular blanking period
  • Ventricular pacing at the end of the AV delay
  • Fast ventricular arrhythmia spontaneously terminating after 5 seconds
  • These tracings illustrate a case of atrial undersensing during sinus rhythm and during an episode of AF
  • In this patient, undersensing of atrial arrhythmia is responsible for inefficient and unnecessary atrial pacing thereby increasing energy consumption and reducing battery performance
  • Atrial arrhythmias are not counted thus skewing the data in terms of arrhythmia burden rendering the device memory unreliable for assessing the efficacy of antiarrhythmic therapy or for initiating anticoagulant therapy
  • The second tracing shows undersensing of sinus activity leading to the occurrence of asynchronous atrial pacing
  • A PVC falls within the post-atrial ventricular blanking period, and is not sensed; ventricular pacing is delivered in the ventricular vulnerable period with induction of a VT  
  • Atrial undersensing can be proarrhythmogenic at the atrial stage but also, although more rarely, at the ventricular stage
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