Atrial Mechanical Sensing for Micra AV

The Micra™ AV Transcatheter Pacing System (TPS) has new atrial sensing features to allow for optimization of parameters to provide AV synchrony. These include automatic atrial sensing features, Atrial Sensing Setup, and Manual Atrial Mechanical Test.

The automatic atrial sensing features adjust over time for improved atrial mechanical sensing. These features include Auto A3 Threshold, Auto A3 Window End, and Auto A4 Threshold.

Atrial Sensing Setup assesses atrial activity during post-operative recovery and establishes the key AV synchrony parameters in Micra AV. Atrial Sensing Setup measures the accelerometer signals in the A3 and A4 window for each vector and programs the parameters related to atrial contraction and detection with patient-specific values for Vector, Min/Max Auto A3 Window End, and initial values for A3 Threshold, A3 Window End, and A4 Threshold.

The Manual Atrial Mechanical (MAM) Test is a press and hold test designed to allow for assessment and adjustment of atrial sensing parameters.

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

Auto A3 Threshold is nominally programmed On with a programmable A3 Threshold value. To program this feature, go to Params -> A3 Threshold.

 

Auto A3 Window End is nominally programmed On with a programmable A3 Window End value and Min/Max A3 Window End. To program this feature, go to Params -> A3 Window End.

 

Auto A4 Threshold is nominally programmed On with a programmable A4 Threshold value and programmable Min Auto A4 Threshold value. To program this feature, go to Params -> A4 Threshold.

 

Auto A3 Threshold and Auto A3 Window End features are available in VDD and VDI mode and function when the device is operating in VDD and VDI mode. Auto A4 Threshold feature are available in VDD mode and function when the device is operating in VDD mode.

Atrial Sensing Setup is nominally programmed On/Restart after implant. Atrial Sensing Setup is available in VDD mode and operates in both VDI and VDD modes during Atrial Sensing Setup. To program this feature, go to Params -> Atrial Parameters -> Atrial Sensing Setup.

 

The Manual Atrial Mechanical (MAM) Test is available in all modes and runs in VDD, VDI, or ODO mode. To access the MAM test, go to Tests -> Manual Atrial Mechanical.

If the Auto A3 Threshold is programmed On, the device automatically adjusts the A3 Threshold to be above the A3 signal to prevent oversensing of the A3 signal. It also allows the occasional sensing of the A7 summation.

If the Auto A3 Window End is programmed On, the device will automatically adjust the A3 Window End within the programmed upper and lower limits using the Max A3 Window End and Min A3 Window End. Auto A3 Window End adjusts the A3 Window End to be between the A3 signal and A4 signal over time. It is indicated by a fuchsia-colored VE marker.

If the Auto A4 Threshold is programmed On, the device will automatically adjust the threshold to be below the A4 signal to allow detection of the A4 signal and prevent undersensing of the A4 signal. The Auto A4 Threshold will not lower the A4 Threshold below the programmable Min Auto A4 Threshold value.

When programmed to On/Restart, Atrial Sensing Setup enters the Scheduled state. After telemetry has been removed, Atrial Sensing Setup enter the In Progress state, VDI mode with a Lower Rate of 50bpm. During the In Progress state, the device collects atrial sensing data and then makes final adjustments to the atrial sensing parameters in both the VDI and the VDD operating pacing modes. The data collection and adjustment of parameters takes about 30 min from the removal of telemetry. If permanent or temporary parameters are programmed, the patient becomes active, or the patient has a high or variable ventricular rhythm during Atrial Sensing Setup, the device discontinues the attempt to return to the In Progress state. Atrial Sensing Setup will try for approximately 4 hours to successfully complete. After approximately 4 hours, Atrial Sensing Setup completes with a status of unsuccessful.

The MAM test collects ECG, accelerometer waveform, markers, and marker intervals from the Live Waveform. The signals collected from the Live Waveform are then displayed as separate cardiac cycle images. The images can be arrowed through to select the cardiac cycle image that is ideal for observing and adjusting atrial sensing parameters. An ideal cardiac cycle image has the P-wave in diastole, where the A3 signal and the A4 signal are clearly identifiable. The A3 Window End, the A4 Threshold, and the A3 Threshold values are superimposed on top of the rectified accelerometer signal displayed on the cardiac cycle image. Once the parameters have been adjusted, the test can be repeated to temporarily test the new values. If the new values are effective, they can be programmed from the MAM test screen.

 
  1. The MAM test displays the A3 Window End value in relation to the rectified accelerometer waveform. When the A3 Threshold value is changed in the MAM test, the A3 Threshold line on the display moves to the new value.
  2. The MAM test displays the A3 Window End value in relation to the rectified accelerometer waveform. When the A3 Window End value is changed in the MAM test, the A3 Window End line on the display moves to the new value.
  3. The MAM test displays the A4 Threshold value in relation to the rectified accelerometer waveform. When the A4 Threshold value is changed in the MAM test, the A4 Threshold line on the display moves to the new value.

References

Sources 

Micra™ AV MC1AVR1, Reference Manual

Last updated: 
23 Jan 2020