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.
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:
- Data -> Clinical Diagnostics -> Rate Histograms
- Params -> CRT… -> Rate Histograms (for Viva only)
- 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|
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.
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.
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:
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.
The CRT-D Histogram Report displays the same information as the ICD histogram with the following additions:
|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:
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.
- 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.
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.
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.
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.
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.
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.