EffectivCRT Diagnostic Feature

Optimal CRT therapy requires a high percentage of effective biventricular (Bi-V) or LV-only pacing. However, device counters that indicate the percentage of Bi-V or LV-only pacing do not indicate whether the pacing was effective at successfully capturing the heart. Ineffective CRT pacing can be caused by several factors, such as the presence of AT/AF, AV intervals that are too long, inadequate LV pacing output, delayed LV activation, LV/RV electrode proximity, or atrial or right ventricular undersensing.
The EffectivCRT™ Diagnostic feature determines the percentage of effective CRT pacing by evaluating the morphology of the LV pacing cathode to RVcoil EGM. It provides data about the effectiveness of CRT pacing on the Quick Look™ II screen, Rate Histograms, Cardiac Compass™ Trends, and EffectivCRT™ Episodes.  Visit the EffectivCRT™ During AF feature for more information.

EffectivCRT™ Diagnostic is automatically On, no setup or programming is required. 
To access EffectivCRT™ Diagnostic data select Data>Clinical Diagnostics>EffectivCRT™ Episodes> (Open Data).  
The EffectivCRT™ Diagnostic feature determines the percentage of effective CRT pacing by evaluating the morphology of the LV pacing cathode to RVcoil EGM. EffectivCRT™ Diagnostic data collection automatically occurs when all of the following conditions are met:
  • the EffectivCRT™ device check, which evaluates the ability of the device to detect effective CRT pacing under ideal conditions, was successful at least once since implant
  • the device check is run 30 minutes after implant and then daily at 01:00
  • the LV Amplitude is less than 8.00 V
  • the V. Pacing is LV→RV or LV, or AdaptivCRT is enable
  • the LV Amplitude was not increased and LV Pace Polarity or LV Pulse Width was not changed since the last successful EffectivCRT™ daily device check
If the above conditions are not met, data is not collected. Data collection begins once the conditions are met following the next EffectivCRT™ daily device check.
When the data collection conditions are met, the EffectivCRT™ Diagnostic feature analyzes 100 consecutive ventricular events every hour and determines the percentage of effective CRT pacing. If Ventricular Safety Pacing [VSP] events and/or Ventricular Sense Response [VSR] are noted in the 100 consecutive ventricular events, they are ignored and not evaluated. When EffectivCRT™ Diagnostic is collecting data, the device switches the EGM3 source to the LV to RVcoil EGM. For a ventricular event to be counted as effective, the LV cathode to RV coil EGM needs to start with a negative deflection. The image below shows 100% ventricular pacing with 50% effective pacing.  All 6 events are classified as biventricular events.  The first three ventricular events are ineffective because the tissue is paced but not captured as shown with the positive EGM deflection. The last three beats are effective because the tissue is paced and captured shown with a negative deflection. 

Device Check 

For EffectivCRT™ Diagnostic to function, the Device Check must pass. If Left Ventricular Capture Management™ (LVCM) has increased the LV amplitude or pulse width or if the LV parameter has been manually reprogrammed, then the diagnostic will not run until the next Device Check passes. The criteria for passing a device check are: 4 of 5 Bi-V paced beats, or 4 of 5 LV-only paced beats are effective. 


Once the criteria are met and data is collected, the EffectivCRT™ Diagnostic displays the percentage of effective CRT pacing as subset of the Total Percent Ventricular Pacing (Total VP). 
Medtronic CRT devices without the EffectivCRT™ Diagnostic feature show the Total VP, which includes all fully paced, fusion, pseudofusion, non-captured paced, and ventricular paced with sensed beats.  Medtronic CRT device with EffectivCRT™ Diagnostic provides the percent pacing that is determined to be effective based on EGM morphology evaluation. 


To evaluate the effectiveness of CRT pacing, review the Quick Look II™ screen, Rate Histograms Report, Cardiac Compass Trends™, and EffectivCRT™ Episodes. 
In this example the Quick Look II screen shows a discrepancy in Total Pacing versus Effective Pacing. An Observation message will appear when Effective Pacing is < 90%. 
The Rate Histograms Report shows the amounts of Effective and Ineffective pacing, Since Last Session, Prior to Last Session, and specific to the time in AT/AF.  See the EffectivCRT™ During AF feature to learn more.
The Cardiac Compass™ Trends illustrate the amount of time for Effective and Ineffective Pacing. Note in this example the decrease in Total Pacing and Effective Pacing correlates with the times of higher AT/AF total hours per day. 
The EffectivCRT™ episodes show the LV to RV Coil EGM of EffectivCRT™ episodes. During the EffectivCRT™ Diagnostic analysis, the device creates an EffectivCRT™ Episode record when all of the following occur:
  • 8 consecutive ventricular events are sensed beats, safety paces, VSR paces, LV-only paces or bi-ventricular paces without effective CRT pacing
  • at least 5 of those events are LV-only or biventricular paces without effective CRT pacing
Each episode shows when ineffective pacing occurred. There will only be one episode per 100 beats collected. Each episode will display the following data:
  • the date and time of the episode (note that data collection begins 25 min after the hour)
  • the median atrial and ventricular beats per minute at the time of the episode
  • an indication of whether an atrial tachyarrhythmia or atrial fibrillation (AT/AF) was present
  • a 10 s strip chart of EGM
  • event markers
  • an indication of whether each ventricular pace, excluding Ventricular Safety Pacing  (VSP) and Ventricular Sense Response (VSR) paces, was effective (Y) or ineffective (N)
The episode list shows the date and time the episode occurred, as well as the average atrial and ventricular rate. 
Each episode will show the LV to RVcoil EGM as well as atrial and ventricular markers. A "Y" (yes) or "N" (no) to indicate if pacing was effective will also be annotated. The paced beats shown in this example are annotated as “N” and therefore determined to be ineffective. Sensed beats are not analyzed so will not be marked with a Y or N. 
The OLÉ CRT study was a prospective, multi-center, observational study to evaluate the percent effective CRT being delivered to a typical CRT cohort and compare the percent V pacing from the same 24 hour period. 
Enrolled patients underwent an inclusion visit, an in-office visit and a 24-hour monitoring with a custom Holter which could simultaneously record device EGMs and surface ECG. The investigators found that in 18% of the patients, device-reported percent V pacing overestimated effective CRT pacing by 3%. Although the percent pacing was high, the device EGMs and surface ECG on the holter monitor recordings did not confirm effective pacing.1
Figure 1:  3/57 patients had virtually NO effective pacing, whereas the % V pacing was > 90%


Watch the recorded version of our February 6, 2017, webcast with Dr. Suneet Mittal to learn more about how implanters are using the new EffectivCRT Diagnostic feature with our therapeutic algorithms to optimize therapy to meet CRT patients'...


  1. Hernandez-Madrid A, Facchin D, Klepfer RN, et al. Device pacing diagnostics overestimate effective CRT pacing results of the holter for efficacy analysis of CRT study (OLÉ CRT study). Heart Rhythm. Published online January 17, 2017, DOI: http://dx.doi.org/10.1016/j.hrthm.2017.01.022.

Sources: Medtronic Claria MRI™/Claria MRI™ Quad CRT-Ds Reference Manual

Last updated: 
23 Feb 2017