Brady Episode Detection Feature

Brady Episode Detection is a Medtronic Insertable Cardiac Monitor (ICM) feature that detects slow heart rates. This feature is appropriate for patients experiencing syncope, palpitations, or dizziness which may be symptoms associated with a slow heart rate and/or bradycardia.

This feature can be found in some Medtronic insertable cardiac monitor (ICM) devices. Please go to manuals.medtronic.com or consult with your local Medtronic representative regarding device models available in your geography.

To program this feature in ICMs go to Params -> Brady Detection, which is nominally On.

  1. Select the appropriate Brady Interval (Rate) [1000 ms(60 bpm); 1200 ms(50 bpm); 1500 ms(40 bpm); 2000 ms(30 bpm)]
  2. Select the appropriate Brady Duration (4 beats; 8 beats; 12 beats)

Note: Nominals are in bold; however always consider programming detection values according to patient needs.

The automatic detection and ECG storage of Brady episodes is turned on when you activate Device Data Collection.

An automatically detected Brady episode occurs when the programmed detection criteria are met. The detection criteria are based on the number and rate of the sensed R-waves falling below the programmed detection rate. For example, at nominal values, four consecutively sensed R-waves at a rate of less than 30 bpm would trigger the automatic detection of a Brady episode. The bradyarrhythmia episode ends when one of the following criteria is met:

  • Four consecutive R-waves are detected with a ventricular interval equal to or shorter than the programmed interval.
  • No R-wave is detected during a period of 10 seconds.

In Reveal LINQ™ ICMs with TruRhythm™ Detection, a smart filtering algorithm has been added to enhance the Brady Episode Detection feature. The TruRhythm smart filtering algorithm uses a second filter to process events that are marked as brady sensed beats.  Once a brady sensed beat is detected a second, more sensitive filter is used to evaluate whether the signal is larger than this second filter. A signal that crosses the second filter is considered to be an undersensed ventricular event, and the Brady marker channel is updated to a ventricular sense marker and the false brady beat is eliminated. Rejected brady senses will be marked as a ventricular sensed beat and not stored. The end result is a reduction in the number of false Brady Episode Detections due to the undersensing of PVCs. Reveal LINQ™ ICMs with TruRhythm Detection may be identified by the serial number.  In addition, you will see “Reveal LINQ™ + TruRhythm™” on the pdf heading of all CareLink™ Reports. Consult with your local Medtronic Representative on the change specific to your geography.

Figure 1: First Sensing Filter for Brady Episode Detection

The image above illustrates how the first sensing filter used to detect brady events has the potential to undersense PVCs and result in a false brady episode detection.

Figure 2: Second Sensing Filter Provided with TruRhythm

This image illustrates the use of a second, more sensitive filter provided with TruRhythm that can detect PVCs, note the VS marker.  As a result, the episode is determined to be false and is rejected.

Programming considerations:

  1. Program Brady Detection to "Off" to prevent automatic detection of brady episodes.
  2. Select an interval that represents a heart rate lower than the patient's normal rate at rest.
  3. Select the number of brady intervals that must occur before the episode is classified as a bradyarrhythmia episode.
  4. A Brady episode CareAlert notification may be enabled when monitoring Reveal LINQ ICM patients remotely. The ICM sends a daily wireless audit transmission to the patient's MyCareLink monitor. If Brady detection is programmed "On" in the ICM and the CareAlert for a Brady episode is enabled on the CareLink™ website, a  CareAlert notification will be generated. If the Brady episode is the highest priority event of the day per the Wireless Data Priority setting, the Brady event details will be sent to the CareLink network in the daily wireless audit and displayed on the Event Report. The episode details include 30 seconds of the detected event's ECG. The clinician receives the CareAlert notification based on clinic defined methods.

Viewing Episodes
Stored episodes can be viewed on the 2090 Programmer by opening Episodes and selecting from the Arrhythmia Episodes log. On LINQ Mobile Manger, stored episodes are viewed on the Full Report. Up to 30 Brady episodes will be stored when Brady detection is programmed "On". For each Brady episode, the ECG recording consists of 30 seconds of ECG prior to detection and up to 27 seconds of ECG before the episodes ends. When the log is full, data from the most recent Brady episode will overwrite the oldest stored Brady episode data. The log lists all episodes currently stored in device memory.

The log includes the following summary information:

  • Type of episode – this will say Brady for a Brady event
  • The date, time, and duration of the episode
  • The lowest ventricular rate
  • The median ventricular rate at detection
  • Whether ECG data is available for the episode or text only

For a particular episode, you can display the following information:

  • An interval (or rate) plot
  • A strip chart of the stored ECG (if available)
  • A text summary

Marker channels for Brady episodes are:

  • B: Brady Sense
  • BD: Brady detection (marks the first event in a detected Brady episode)

Episodes and additional reports may also be viewed on the CareLink,website if the patient is enrolled and set up for remote transmissions.

Note: If the patient uses the Patient Assistant while an automatically detected episode is in progress, both episodes are stored. The device records "Symptom (Patient Activated) occurred during episode" in the text of the automatically detected episode.

In the example below, Brady episode detection was programmed to a heart rate of less than 40 bpm, or an interval greater than 1500 ms between sensed R-waves. For each beat that met the Brady criteria, the sense marker is denoted as a 'B.' The Brady duration criteria is programmed to 4 beats, therefore after 4 consecutive 'B' senses, the fourth sensed R-wave is denoted as a 'BD' for Brady Detection. After four consecutive R-waves are detected with a ventricular interval equal to or shorter than the programmed interval, 1500 ms (≥40 bpm), the Brady episode is terminated.

References

Source: Medtronic Reveal LINQ LNQ11 Clinician Manual, TruRhythm™ Detection Algorithms. Medtronic data on file. 2017.

Last updated: 
05 May 2017