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Mode Switch

Onset of atrial arrhythmia

  • DDD mode before the switch to DDI: N/1 AV association
  • short AV delay 30 ms
  • maximum pacing rate in the ventricles: 120 bpm

Sustained atrial arrhythmia

  • analysis of groups of 32 consecutive ventricular cycles
  • each ventricular event is labelled as “Normal” or “Suspect”
  • switch to DDI(R) if a minimum % of those cycles are suspect
  • switch to DDI(R) if one of two criteria: primary or secondary criterion
  • once the device switches to DDI(R), the ventricular rate comes “smoothly” to basic rate or sensor rate

 

Suspicion/confirmation phase

Primary criterion (strong criterion)

  • sliding window of 32 ventricular cycles
  • suspicious ventricular cycle: ventricular cycle including at least one Ar
  • during the 32 last cycles, more than 28 suspicious cycles (threshold of 87.5%)
  • switch to DDI(R) after approximately 15 seconds of atrial arrhythmia

 

 

Secondary criterion (weak criterion)

  • in the last 2 sets of 32 ventricular cycles, at least 18 suspicious cycles (threshold of 56%)
  • to ensure mode switch even in case of atrial undersensing
  • switch to DI(R) after approximately 30 seconds of atrial arrhythmia

Switch to DDI(R): dissociation phase

  • the ventricular rate is progressively decreased to reach the Sensor Driven Rate or the Basic Rate

Switch back to DDD(R): re-association phase

  • if no Ar is sensed during the last 12 cycles, the device switches back to DDD
  • if a Ar is sensed within the last 12 cycles, the device resets the counter until having 12 cardiac cycles without Ar
  • when the atrial rate falls below 107 bpm or the maximum tracking rate, whichever is lower, the ventricular pacing rate is accelerated until it reaches the atrial rate
  • when the ventricular rate reaches the atrial rate, the device enters normal AV association in DDD mode