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