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Indications, Safety, and Warnings

Rate Histograms Feature

The Rate Histograms Report is based on the atrial and ventricular event data stored by the device. The Rate Histograms Report presents heart rate data in 3 types of histograms: atrial rate, ventricular rate, and ventricular rate during AT/AF. It also presents data about the patient’s conduction status. The report includes data from the current and previous collection periods. Data storage for the Rate Histograms Report is automatic; no setup is required.

Information about heart rates recorded between patient sessions can help you to monitor a patient’s condition to assess the effectiveness of therapies. The histograms can be used as an aid for evaluating rate response parameter settings and chronotropic incompetence. For CRT patients, the pacing percentages can be used to assess how often the patient is receiving cardiac resynchronization therapy. In Claria™ CRT-D devices, the EffectivCRT™ Diagnostic provides information on effective or ineffective CRT pacing. For Insertable Cardiac Monitors (ICM) patients, Rate histograms provide information about the heart rates recorded between patient sessions, or at timed intervals, and can be used to monitor the effectiveness of rate or rhythm control therapies.

This feature can be found in some Medtronic Pacemaker, ICD, CRT-P, CRT-D, and 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.

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Rate Histograms are available without any programming. For legacy ICD and CRT devices, as well as Advisa MRI™, Revo MRI™ and EnRhythm™ pacemakers, the report is available in a printed format. To print, select Reports -> Available Reports… -> Rate Histograms -> Print or Data -> Clinical Diagnostics -> Rate Histograms -> Print Now.

In Claria™, Viva™, Evera™, Advisa MRI pacemakers and Micra™ transcatheter pacing system (TPS) , the Rate Histograms can also be viewed on the programmer:

  1. Data -> Clinical Diagnostics -> Rate Histograms
  2. Params -> CRT… -> Rate Histograms (for Viva only)
  3. Data -> Diagnostics -> Rate Histogram (for Micra)

 

 

For Adapta™, Versa™ and Sensia™ pacemakers, the histograms will automatically print in the Initial Interrogation Report (Reports -> Available Reports -> Initial Interrogation Report). Short- and long-term atrial and ventricular histograms can also be viewed on the programmer from the Quick Look™ ll screen by clicking the Quick Link next to Pacing.

For Insertable Cardiac Monitors, the report is only available in a printed format. To print, select Reports -> Available Reports...-> Rate Histograms.

Depending on the type of device you are interrogating, you will be able to view and print different histograms. Rate histograms are also viewable on the CareLink™ Network when remote monitoring is utilized. The following table describes the histograms that can be printed from different device types.

Device Type Rate Histograms
Pacemaker

The Rate Histogram data is based on the ventricular and/or atrial event data stored by the device since the last patient follow-up session. Rate Histograms show what percentage of the rate events (sensed and paced) counted during the monitoring period fall into each 10 bpm segment in the range of 40 ppm to 180 ppm. (The “< 40” ppm group also includes events occurring below 40 ppm; the “180 >”ppm group also includes events occurring above 180 ppm.) Ventricular Rate Histograms display the recorded number of single PVCs and PVC runs. Atrial Rate Histograms display the number of PAC runs.

All pacemakers have Long-term heart rate histograms represent data collected since the last follow-up (available for viewing on the programmer and in the Initial Interrogation Report).

Adapta/Versa/Sensia also have Short-term heart rate histograms that represent data collected over the last 3 to 6 days (available for viewing on the programmer).

In Adapta/Versa/Sensia DR devices the V. Rate During Atrial Arrhythmias graph can be accessed through Data -> Graphs and Tables. This graph is also printed on the Initial Interrogation Report.

For Advisa DR devices, the V. Rate During Atrial Arrhythmias graph is part of the Cardiac Compass™ Trends.
ICD

Rate Histograms show the percentage of time that the device was pacing and sensing in 10 bpm segments within the range of 40 bpm to 220 bpm. Rates slower than 40 bpm are included in the “< 40” range; rates faster than 220 bpm are included in the “> 220” range.

The following information is provided on the Rate Histograms Report:

  1. % of Time – This section shows the patient’s conduction status as the percentage of the total time that the device paced or sensed during the collection period. The percentages are calculated from the daily counts of AS-VS, AS-VP, AP-VS, and AP-VP event sequences. Note that the AS-VP % in Viva™ and Evera™ devices includes all ventricular paced events (even if preceded by an atrial refractory (AR) event).
  2. Atrial Rate Histogram – This histogram shows the rate distribution of atrial sensed and paced events. The histogram also indicates if the percentage of atrial senses that may be due to far-field R wave (FFRW) sensing is 2% or greater.
  3. Ventricular Rate Histogram – This histogram shows the rate distribution of ventricular sensed and paced events.
  4. Ventricular Rate During AT/AF Histogram – This histogram shows ventricular sensed and paced events that occurred during detected atrial arrhythmias, and the total time in AT/AF. This histogram may be used to monitor the effectiveness of ventricular rate control therapy and drug titration.
CRT-P

The CRT-P Histogram Report displays the same information as the ICD histogram report with the exception of the V. Rate During AT/AF Histogram. This information is available in the Cardiac Compass™ Report.

The CRT-P report also shows the percentage of all ventricular events delivered by the Ventricular Sense Response (VSR) feature. Note that the VP % includes all ventricular paced events (RV or Bi-V). If the device is programmed to BiV pacing, and RV and LV capture are confirmed, the total VP % is an indicator of how much cardiac resynchronization therapy the patient is receiving.
CRT-D

The CRT-D Histogram Report displays the same information as the ICD histogram with the following additions:

  • The CRT-D report shows the total VP % and total VS %. Note that the VP % includes all ventricular paced events (RV or Bi-V). The total VP % is an indicator of how much cardiac resynchronization therapy the patient is receiving if ventricular capture has been confirmed.
  • The CRT-D report also shows the percentage of all ventricular events delivered by the Ventricular Sense Response (VSR) feature. The total ventricular pacing value is key in assessing how much CRT therapy the patient is receiving. The ventricular sense response pace percentage indicates how often a ventricular pace was triggered in response to a ventricular sensed event. The VSR paces are not considered a ventricular sense because the device actually paced; it is not considered a ventricular pace because it is not a true biventricular pace. The percentage of ventricular sensing provides information on how often the patient is losing CRT therapy.
  • The sum of the VP, VS, and VSR percentages represents 100% of the time in the session.
  • Beginning with the Viva XT CRT-D device model, the CRT Pacing section is included in the histogram report. The CRT Pacing section details how often ventricular pacing was delivered in Bi-V and in LV through AdaptivCRT™ pacing. These percentages are a breakdown of the total ventricular pacing percentage. This breakdown provides information on how often the patient is leveraging Adaptive LV pacing. Typically, Bi-V and LV add up to 100% of the total delivered ventricular pacing. A value less than 100% may occur if right-ventricle-only pacing occurs due to operation of a pacing feature that takes priority over AdaptivCRT, such as Ventricular Safety Pacing, Atrial Capture Management™, Ventricular Capture Management, or VVI backup. If AdaptivCRT pacing is programmed to Adaptive Bi-V or Nonadaptive CRT, the LV pacing percentage will be zero.
  • Devices with the EffectivCRT™ Diagnostic feature provide the percentage of effective and ineffective CRT pacing indented from the V Pacing.
Insertable Cardiac Monitor

The Rate Histograms report is based on a continuous recording of ventricular rates in the period after the last patient session. The Rate Histograms report presents heart rate data in 2 types of histograms:

  1. Ventricular Rate Histogram - shows the rate distribution of ventricular events as the percentage of total time. The histogram shows 20 rate ranges, rates slower than 40 bpm are included in the <40 bpm range and rates faster than 220 bpm are included in the >220 bpm range. This histogram is labelled Ventricular Rate out of AF on CareLink.
  2. Ventricular Rate During AT/AF Histogram - shows ventricular events that occurred during automatically detected AT/AF episodes. The histogram shows 9 rate ranges that are each 20 bpm wide. Rates slower than 80 bpm are included in the <80 bpm range; rates faster than 220 bpm are included in the >220 bpm range. The information includes the total time that the patient spent in AT/AF (AT/AF burden). This histogram may be used to monitor the effectiveness of ventricular rate control therapy and drug titration. This histogram is labelled, Ventricular Rate in AF on CareLink.

Both reports includes data from the current (since last session) collection period. Rate histograms are viewable on Carelink based on time intervals of 30 days, 90 days or 14 months.


Considerations:

  • Rates may occur below the lower rate for various reasons:
    • PVCs can cause rates below the lower rate when a ventricular sense restarts the VA timer.
    • Due to A-A timing, rates can be recorded in low rate ranges when the atrial rate (paced or sensed) is at or near the lower rate and intermittent conduction occurs. For example, when an AP-VS sequence is followed by an AP-VP sequence and atrial pacing is at the lower rate, the V-V interval will exceed the lower rate interval because the PAV is longer than the intrinsic AV conduction time.
    • Sleep function causes the lower rate to decrease to the programmed sleep rate.
    • Single chamber hysteresis causes lower rates to search for intrinsic conduction.
    • NCAP can cause lower rate because an AR event delays the next A. pace for 300 ms.
  • Different device types interpret events in the rate bins differently:
    • Pacemakers – The histogram will include a bar for rate ranges if there are one or more beats in a rate bin. To find out how many beats are actually in each rate bin (eg. 10 beats in the 40-50 bpm bin), click on the print button from the histogram screen, select “Graph and counter data” and then select print.
    • ICDs and CRT-P/CRT-Ds – Several beats need to occur in a rate range for a bar to be shown on the histogram.

Rate Histogram examples for each device type are provided below.

Pacemaker
The histogram shows that the patient has a low percentage of atrial pacing and minimal ventricular pacing. This indicates that the patient needs some atrial pacing support but has intact AV conduction. The heart rate distribution appears appropriate but patient age, activity level, and symptoms should be taken into consideration.

ICD
The patient’s heart rate histogram shows a high percentage of atrial pacing and low percentage of ventricular pacing. The rate distribution is similar in the prior and last sessions with a slightly better distribution in the last session. The ventricular rate during AT/AF appears controlled with almost exclusively all ventricular pacing.

CRT-P
The patient’s heart rate histogram shows primarily atrial and ventricular pacing (appropriate for a CRT patient).

In the last 6 months the ventricular sensing has increased to 11.6%. This could be further investigated by looking at the Cardiac Compass™ and reviewing the patient’s arrhythmia history. The patient’s heart rate distribution appears appropriate but patient age, activity level, and symptoms should be taken into consideration.

 

CRT-D
Below is an example of a Rate Histogram Report for a patient with a Claria MRI™ CRT-D device. \ The “Since Last Session” data shows there was 91.2% total Ventricular Pacing of which 87.4% was Effective and 3.9 % Ineffective. Remember that the total VP + VSR Pace + VS = 100%. In addition, percent Bi-V and LV pacing percentages are listed. AdaptivCRT allows the device to pace adaptive Bi-V and/or LV only depending on programmed parameters.  The Rate Histograms illustrates the Bi-V pacing and LV pacing percentages. Prior to, and Since Last Session, the patient was adaptive Bi-V paced 89.9% and adaptive LV paced 10.1%.

Notice in the image below, the time in AF specifically reports the percentages of Effective and Ineffective V. pacing during atrial episodes.

Insertable Cardiac Monitors – Reveal LINQ
The histograms show that the patient had less than one day out of 10 days in AT/AF. While not in AT/AF, the heart rate distribution appears appropriate. However, patient age, activity level, and symptoms should be taken into consideration. The ventricular rates while in AT/AF are mainly above 100 bpm and the patient’s physician should be advised.

References

Sources: Medtronic Micra™ Clinician Manual, Medtronic Adapta™/Versa™/Sensia™ Reference Guide; Medtronic Consulta™ CRT-P Clinician Manual;Medtronic Protecta™ XT DR Clinician Manual; Medtronic Claria MRI™/Claria MRI™ Quad CRT-Ds Reference Manual, Medtronic Protecta™ XT CRT-D Clinician Manual; REVEAL LINQ™ Clinician Manual.

Last updated: 
21 Apr 2017