Rythmiq and AV block (2)

N° 2
Manufacturer Boston Scientific Device PM Field AV delays, refractory periods management of tachycardia
  • 81-year-old woman
  • Vitalio dual-chamber pacemaker (Boston Scientific) for episodes of paroxysmal AV block
  • Rythmiq algorithm ON
  • Lower rate limit: 60 bpm
  • Ventricular pacing < 5%
  • Stored Rythmiq episodes
Graph and trace
  • Atrial sensing and ventricular sensing (sinus tachycardia)
  • Dropped P wave
  • Slow ventricular beat (VS-VS interval 1288 ms, 288 ms slower than the lower rate limit)
  • Second dropped P wave and second slow ventricular beat
  • Third dropped P wave and third slow ventricular beat
  • 3 slow ventricular beats detected over the last 11 beats
  • Switch to DDD mode
  • Atrial sensing and ventricular pacing
  • This tracing shows other characteristics of the Rythmiq algorithm
  • 2 types of ventricular beats are considered to be long: a paced ventricle and a sensed ventricular event with an interval greater than 150 ms relative to the programmed lower rate limit or current rate response  
  • If a lower rate of 60 bpm (1000 ms) is programmed, a ventricular interval between 1150 ms (1000 + 150 ms) and 1333 ms (60-15 bpm) does not result in pacing but is considered slow by the device
  • If 3 ventricular beats are considered slow (intrinsic or paced) in a rolling window of 11 consecutive ventricular beats, the device automatically switches to DDD(R) mode
  • 20 seconds of EGM are stored when the device switches to DDD(R) mode
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