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
