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

1. Select the appropriate Pause Duration (1.5 sec; 3 sec; 4.5 sec)

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

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

The device detects a pause (asystole) episode when the interval between two sensed events exceeds the programmed Pause Duration. A sensed event could be a ventricular sense, escape time-out, or an over range ECG signal noise. However, f the sensitivity is programmed to 0.025 mV, 0.035 mV, or 0.050 mV and the sensed R-waves preceding the suspected pause show evidence of diminishing amplitude, the suspected pause episode is rejected because of probable undersensing. This is known as the Diminishing R-waves rejection rule. The TruRhythm update added an additional exception rule which is explained further in this document.

Diminishing R-waves rejection rule
This rejection rule was created to identify diminishing R-waves before detection of a Pause event and thereby help prevent false pause detection. This rule is only active if sensing is programmed to 0.025, 0.035, or 0.050 mV. Prior to a pause, a "Low Signal Evidence" counter is incremented thanwhen the R-wave amplitude is between the minimum sensing threshold and twice the minimum sensing threshold (2 x sensing floor), and decremented when R-wave amplitudes are above twice the minimum sensing threshold. The counter range is 0-10. Once the counter reaches a count of 10, it holds at 10. Once an R-wave is sensed again (R-wave amplitude above twice the sensing floor), it decrements by 1. Pause detection is rejected if the "“Low Signal Evidence" counter is greater than 0 on the beat prior to the V sense interval that represents the long pause. The episode rejection marker is

In the example above, the R-waves are decreasing in size and eventually become undersensed by the device. With each diminishing R-wave falling in the window between the sensing floor and twice the sensing floor (35 – 70 µV in this example) the "Low Signal Evidence" counter. Since the "Low Signal Evidence" counter is greater than 0, in this case it is a count of 2 on the beat prior to the V sense that represents the beginning of the pause, the Pause detection is rejected  

A pause episode terminates after 12 ventricular sensed events have occurred.

In Reveal LINQ™ ICMs with TruRhythm™ Detection, a smart filtering algorithm has been added to enhance the Pause Episode Detection feature. The TruRhythm Smart Filtering algorithm uses a second filter to process events that are marked as a Pause after being processed through the current pause and pause rejection algorithm. Once a pause episode is detected, the second filter re-evaluates the signal in the detection window to identify smaller R-waves. If smaller R-waves are present and they cross the second filter the pause episode is rejected through this algorithm and will be marked with an asystole rejection marker. This results in a reduction in the number of false pause detections due to PVCs and low amplitude R-waves. Devices 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 Pause Episode Detection

This image illustrates how the sensing filter used to detect a pause, has the potential to undersense small R-waves and result in a false pause 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 small R-waves.  As a result, the episode is determined to be false and is rejected.

Programming considerations:

1. Program Pause Detection to "Off" to prevent automatic detection of Pause episodes.
2. Select the length of the pause interval that must occur before the episode is classified as a pause episode.
3. A Pause 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 Pause detection is programmed "On" in the ICM and the CareAlert notification for a Pause episode is enabled on the CareLink™ website a CareAlert notification will be generated. If the detected Pause episode is the highest priority event of the day according to the Wireless Data Priority setting, the Pause event details will be displayed in the Event Report. The episode details include 30 seconds of the detected event's ECG. The clinician is notified of 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 through the Full Report. Up to 30 pause episodes will be stored when Pause detection is programmed "On". For each pause episode, the ECG recording consists of 30 seconds of ECG prior to detection and up to 27 seconds of ECG before the episode ends. When the log is full, data from the most recent pause episode may overwrite the oldest stored pause 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 Pause for a Pause event
• The date, time, and duration of the episode
• 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 Pause episodes are:

• A
  D: Pause (asystole) detection (marks the first event in a detected Pause episode)
   
• A
  D: Asystole rejection (marks a pause that is determined to not be asystole)

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, the settings for Pause detection are programmed to greater than 3 seconds. After 3 seconds without a ventricular sensed event, the device denotes a pause episode has been detected with an 'AD' marker. The detected pause episode is 6 seconds in duration. After twelve consecutive R-waves are detected the Pause episode is terminated.