Exercise Test Feature

The Exercise Test is used to optimize the rate-responsive parameters of the Micra™ Transcatheter Pacing System (TPS) when operating in the VVIR mode. The Exercise Test can be conducted anytime you question whether Rate Profile Optimization (RPO) is providing optimal rate response. Together, the Exercise Test and the Activity Vector Test provide data to help set the Micra device to appropriate rate-response settings for the patient within the most appropriate vector.

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

The Exercis Test is an in-office only test. To access from the Quick Look™ II screen, select Tests -> Exercise

When the device is operating in the VVIR mode, the Exercise Test is used to immediately set the patient’s rate-response settings to appropriate levels. You can conduct an Exercise Test from the programmer to set the rate response for the Lower Rate (LR), Activities of Daily Living (ADL) Rate, and Upper Sensor Rate (UR) ranges. 
  • If Rate Profile Optimization (RPO) is programmed to Off, the Rate-Response parameters remain set to their programmed values
  • When RPO is programmed to On, this feature adjusts the Rate-Response parameters once each day
 
The Exercise Test allows you to evaluate the rate-response settings for the patient and customize the rate-response control parameters:
  • Lower Rate (LR) Setpoint determines the activity counts required to pace at a rate higher than the lower rate
  • ADL Setpoint determines the minimum sensor response to pace at the ADL Rate (i.e., the approximate target rate that the patient’s heart rate is expected to reach during activities of daily living)
  • Upper Rate (UR) Setpoint determines the minimum sensor response to pace at the Upper Sensor Rate, which is at the upper limit of the exertion rate range
Note: The programmed LR Setpoint setting must be lower than the ADL Setpoint setting, and the ADL Setpoint setting must be lower than the UR Setpoint setting.
 
How to Perform an Exercise Test
  1. Select the Duration field on the Exercise Test screen and set the value for the test duration (5 or 20 min).
  2. Select the Vector field and set the value from the list shown. Press [PROGRAM] to program the Vector value selected for the test. Note: Do not change the currently programmed values for LR Setpoint, ADL Setpoint, and UR Setpoint before conducting the exercise test. These values may serve as the baseline to determine whether it is necessary to adjust the rate-response setpoints for the patient, depending on the test results.
  3. Press [START] to start the test. A message window (see below) with a warning appears on the screen that starting another exercise test will overwrite the current test results.
  4. Select [Continue] (see below) to initiate the test in the device or [Cancel] to return to the Exercise Test screen without starting the test.
  5. Once you select [Continue], remove the programming head from the device and instruct the patient on the type of activity to perform, such as hall walk or treadmill walk. During the test, have the patient perform activities that require progressively higher levels of exertion, such as sitting, walking, and vigorous exercise. While the exercise test is in progress, observe the patient’s activity. If the patient is instructed to perform different activities, observe the duration of each.

Retrieving the Exercise Test Data and Adjusting the Rate-Response Setpoints

For each Exercise Test, the device collects and stores the following information, which is displayed on the Exercise Test screen:

  • Start time for the test
  • Programmed activity vector - the activity vector that was selected/programmed as appropriate for the patient’s activity levels
  • Exercise Test duration
  • Activity count data - The activity counts used to calculate the sensor rate are based on the frequency and amplitude of the accelerometer signal
  • Heart rate data
  • Sensor rate data - this is the pacing rate data

  1. When the Test Complete message appears on the Exercise Test screen, reposition the programming head over the patient’s device.
  2. Press [Stop and Retrieve] to collect the test data. The test data is displayed as the Activity Counts graph on the Exercise Test screen.   
Note: You can stop an Exercise Test that is in progress by repositioning the programming head over the device and pressing [Stop and Retrieve] to see the data collected up to that point.
 
The Exercise Test results are shown on the Activity Counts graphs illustrated below. Compare the patient activity count data to the programmed values for LR Setpoint, ADL Setpoint, and UR Setpoint. 
 

Activity Count for LR Setpoint - Patient Sitting Still

 

Activity Count for Upper Rate Setpoint - Patient Walking

 

Activity Count for Upper Rate Setpoint - Patient Vigorously Exercising

If the patient’s resting heart rate is higher than the heart rate while walking, change the vector by which activity is sensed. Refer to the Vector Activity Test feature for more information. 

To adjust a setpoint value, select the corresponding field and set a new value. Then, press [PROGRAM]. Assuming the resting postures generate less activity than the hallway walk, program as follows:

  • LR Setpoint should be a value greater than the highest count while the patient is resting*
  • ADL Setpoint should be set to the highest peaks while walking
  • UR Setpoint should be set to the highest peaks during vigorous exercise
  • If vigorous exercise is not performed, then the following formula can be used to set the UR set point:  1.5 X (ADL Setpoint – LR Setpoint) + ADL Setpoint

*The LR Setpoint should be set to a value above the highest count observed while the patient was stationary in various postures (back, left side, right side, sitting). Refer to the Vector Activity Test.

Exercise Test - Activity Counts

To view the patient’s heart rate, sensor rate, and the device activity during the Exercise Test, press the Activity Counts field and select Rate Graph.

Exercise Test - Rate Graph

You may choose to print the Exercise Test results for the patient’s records.

References

Sources: Medtronic Micra™ Clinician Manual.

Last updated: 
29 Aug 2016