Vp suppression (AAI-DDD mode)

The AAI-DDD mode – Vp suppression (Biotronik) has been designed to allow pacing in ADI mode with permanent monitoring of atrioventricular conduction and switching to DDD mode when the pacemaker detects an alteration in conduction.

 

Switch from ADI to DDD

There are 3 switching criteria corresponding to the different degrees of atrioventricular block (first-degree AV block, second-degree AV block, third-degree AV block and ventricular pause).

 

1) second-degree AV block

The pacemaker switches to DDD mode when X (nominal 3, programmable 1-4) out of 8 atrial (spontaneous or paced) events are blocked (not followed by a spontaneous QRS).

  • the more the value is decreased, the more frequent the switches
  • the device does not switch to DDD after a single dropped atrial activity when the programming is set to nominal (3)

 

2) third-degree AV block

The pacemaker switches to DDD mode when 2 consecutive spontaneous or paced atrial activities are blocked (not followed by a spontaneous QRS).

  • this parameter is not programmable

 

3) ventricular pause

The pacemaker switches to DDD mode when the interval between 2 sensed ventricular activations exceeds 2 seconds.

  • this parameter is not programmable

 

Switch from DDD to ADI

During the DDD activity, the device systematically scans to determine whether there is an intrinsic ventricular signal (Vs continuity search):

  • when the device is operating in DDD mode, it searches for the presence of an underlying intrinsic rhythm every 30 seconds and subsequently spaces the latter (1, 2, 4, 8, 16 … 128 minutes, up to 20 hours) if the search is inconclusive (persistence of impaired atrioventricular conduction)
  • the AV delay is extended to 450 ms for 8 cycles (identical duration for spontaneous or paced atrial activity)
  • the search is successful and the device switches to ADI mode if the set number of ventricular cycles (nominal value 6) has been sensed consecutively within 8 cycles

Search Time Interval Scheme: 30 sec. > 1 min. > 2 min. > 4 min. > 8 min. > 16 min. > 32 min. > 64 min. > 128 min. > 20 hr.

 

During this search:

  • no blocked P wave
  • increased risk of PMT
  • risk of 2/1 block if the search occurs during exercise

 

To avoid iterative alternations between DDD and ADI mode, the device switches permanently to DDD until 24:00 h of the same day if more than 15 switches/hour are observed.

 

Programmable parameters

The Vp-Suppression feature provides the following programmability:

 

 

Parameter Range Default
Pacing suppression after x consecutive Vs 2..(1)..8 6
Pacing support after x / 8 cycles without Vs 1..(1)..4 3

 

Statistics Vp-suppression

No EGM is automatically recorded as a result of switching from ADI mode to DDD mode.

Different statistics are available:

  • 240 day trend of duration in ADI(R)
  • Count of successful switches to the ADI(R)
  • Count of total Vs searches