Ventricular undersensing

N° 1
Manufacturer Boston Scientific Device PM Field Sensing
  • 80-year-old man
  • Vitalio pacemaker (Boston Scientific) for sinus dysfunction
  • Episodes classified as Rythmiq in the device memory
Graph and trace
  • Ventricular undersensing
  • Ventricular backup pacing as a result of this undersensing
  • Second ventricular backup pacing
  • Ventricular undersensing and ventricular backup pacing
  • Switch to DDD mode (RYTHMIQ)
  • This tracing illustrates a case of ventricular undersensing revealed by the presence of a RYTHMIQ switch
  • Ventricular undersensing is followed by backup pacing and switch to DDD mode
  • A good quality ventricular sensing, atrial sensing and atrial pacing is required for the RYTHMIQ algorithm to work properly
  • Recording an EGM in case of switch to DDD allows the diagnosis of even intermittent dysfunctions
  • Traditionally, unlike ICDs, pacemakers functioned with a fixed and stable sensitivity throughout the cardiac cycle
  • Modern pacemakers allow the programming of an ICD-like adaptive sensitivity (variable sensitivity levels according to the amplitude of the R wave or the sensed P wave with progressive increase in sensitivity during the cardiac cycle)
  • In Boston ScientificTM pacemakers, the 2 options are available: fixed sensitivity or adaptive sensitivity (automatic gain control, AGC)
  • The type of sensing method used (AGC or Fixed) must be the same for both leads
  • Atrial and ventricular sensitivity values can be programmed independently
  • If sensing is programmed on AGC, the nominal sensitivity value is 0.6 mV for the ventricle and 0.25 mV for the atrium
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