Mode Switching for Micra AV

The Micra™ AV Transcatheter Pacing System (TPS) device includes two mode switching features to further optimize pacing therapy. The two mode switching features are Activity Mode Switch and AV Conduction Mode Switch.

The Activity Mode Switch feature is designed to provide appropriate rate support during patient activity. The device switches to a rate-responsive mode (VDIR) when it detects high activity and a low Ventricular rate.

The AV Conduction Mode Switch feature is designed to limit the amount of RV pacing and maximize device longevity by disabling atrial sensing during mode switch. The device aims to detect AV conduction by periodically dropping into VVI-40 (VVI+ mode) to check for intact AV conduction.

This feature can be found in Micra™AV Transcatheter Pacing System. Please go to manuals.medtronic.com or consult with your local Medtronic representative regarding device models available in your geography.

Activity Mode Switch and AV Conduction Mode Switch are nominally programmed On. Both mode switches are available in the VDD mode and function when the device is operating in the VDD mode.

To access the Activity Mode Switch parameter in pacemakers, go to Params -> Mode Switch -> Activity Mode Switch. To access the AV Conduction Mode Switch parameter in pacemakers, go to Params -> Mode Switch -> AV Conduction Mode Switch.

 

 

The Activity Mode Switch feature is designed to provide appropriate rate support during patient activity. Patient activity can result in atrial oversensing, which can cause the ventricular pacing rate to be lower than the optimal rate for the activity. This feature monitors the device’s target pacing rate for the given activity input as determined by Rate Response.

When both of the following conditions occur, the device mode switches to the VDIR mode and begins providing therapy at the Sensor Rate indicated by Rate Response:

  1. The target pacing rate is greater than or equal to the programmed ADL Rate, signifying that patient activity is occurring.
  2. The target pacing rate is significantly higher than the current ventricular rate, signifying a loss of appropriate rate support.

When the Sensor Rate returns to a rate below the programmed ADL Rate (indicating that patient activity has ceased), the device mode switches to the VDD mode.

The AV Conduction Mode Switch feature aims to detect intact conduction by periodically dropping into VVI-40 (VVI+ mode) to check for intact conduction. If the intrinsic rate is above 40 bpm, the device stays in the VVI+ mode. When the intrinsic rate drops below 40bpm, the device switches back to the VDD mode. The first conduction check is up to one minute after switching to the VDD mode. If the device detects AV block shortly after switching to the VVI+ mode, the time between conduction checks double (2, 4, 8…. min up to a maximum of 8 hours).

 
  1. Conduction Check + Low Sensor Rate (patient at rest)
  2. Low Ventricular Rate + High Activity (needs rate support)
  3. Ventricular Pacing (AV Block)
  4. Sensor Rate < ADL Rate (activity ceased)

References

Sources 

Micra™ AV MC1AVR1, Reference Manual

Last updated: 
23 Jan 2020