Rythmiq and AV block (1)

Tracing
N° 1
Manufacturer Boston Scientific Device PM Field AV delays, refractory periods management of tachycardia
Patient
  • 81-year-old woman
  • Vitalio dual-chamber pacemaker (Boston Scientific) for episodes of paroxysmal AV block
  • Rythmiq algorithm ON
  • Ventricular pacing < 5%
  • Stored Rythmiq episodes
Graph and trace
  • Atrial sensing and ventricular sensing
  • First dropped P wave
  • VVI backup pacing at a rate 15 bpm (45 bpm, 1333 ms) lower than the lower rate limit (60 bpm)
  • Second dropped P wave
  • Slow ventricular beat (VP-VS interval 170 ms slower than the lower rate limit)
  • Third dropped P wave and VVI backup pacing (45 bpm)
  • 3 slow ventricular beats over the last 11 ventricular beats and the device switches to DDD mode (Rythmiq)
  • Atrial sensing and ventricular pacing
Comments
  • This tracing shows some characteristics of the Rythmiq algorithm
  • When atrioventricular conduction is preserved, the pacemaker operates in ADI(R) mode with VVI backup
  • The device provides AAI(R) pacing at the lower rate limit and/or sensor indicated rate
  • The device provides backup VVI pacing at a rate of 15 bpm slower than the programmed lower rate limit
  • The backup VVI pacing rate is limited to no slower than 30 bpm and no faster than 60 bpm
  • For a lower rate limit < 45 bpm, the VVI Back-up is 30 bpm; for a lower rate limit > 75 bpm, the VVI Back-up is 60 bpm
  • Switch from ADI/VVI backup to DDD mode is not based on the presence of dropped P waves but on the presence of long ventricular beats
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