EffectivCRT During AF Feature
Atrial fibrillation often prevents the delivery of optimal CRT therapy due to the irregular conduction to the ventricles. To promote consistent and effective CRT pacing, the EffectivCRT™ During AF feature makes adjustments to the pacing rate based on the morphology of the left ventricular electrogram (LV EGM) following biventricular (Bi-V) or LV-only pacing. For diagnostic information on effective CRT during AF see the EffectivCRT Diagnostic feature.
The EffectivCRT™ During AF features is shipped On in the device.
To program this feature, select Params > Pacing…> CRT
The maximum rate is restricted by the programmed Maximum Rate. This value is the same as the Conducted AF Response Maximum Rate value.
Phases of EffectivCRT™During AF Operation
- For the first 30 beats of EffectivCRT™ During AF operation, the device adjusts the pacing rate based on a beat-by-beat evaluation. The device increases the rate after each sensed or ineffective CRT paced beat and decreases the rate after each effective CRT paced beat. After the initial 30 beat phase, the device alternates between a 10 beat evaluation phase and a 30 second maintenance phase.
- Following the 10 beat evaluation phase, the device adjusts the pacing rate based on the current pacing rate and the number of effective CRT paces delivered during the phase.
- During the 30 second maintenance phase, the device maintains the current pacing rate. If a series of ventricular events occurs with a number of ventricular sensed beats, the device immediately reenters the 10 beat evaluation phase. Otherwise, the device reenters the 10 beat evaluation phase following the 30 second maintenance phase.
Phases of EffectivCRT During AF
- 4 out of 5 Bi-V paced beats are effective and
- 4 out of 5 LV-only paced beats are effective.
Criteria for a Device Check to Pass for EffectivCRT™ During AF
Suspension of EffectivCRT™ During AF Operation
- LV loss of capture is suspected.
- The daily EffectivCRT™ device check, which tests the ability of the device to detect effective CRT pacing under ideal conditions, fails or does not complete successfully at least once in 3 days.
- LV amplitude is less than 0.5 V greater than the last measured LVCM threshold.
- LV amplitude has increased since the last successful daily EffectivCRT™ device check.
- 5 or more beats are paced at the Maximum Rate, at least 4 of the 5 beats indicate ineffective CRT pacing, and the sensor rate is at least 10 bpm below the Maximum Rate.
Evaluation of EffectivCRT™ During AF
- increased effective pacing during AF, from 81% to 88% (p<0.001)
- increased heart rate by 3 bpm, from 77 to 80 bpm (p<0.001)
- patients who were paced less than 80% received the greatest benefit (average absolute increase of 15% effective pacing during AF).
Figure 1: CRTee Study Results: EffectivCRT™
- Mittal S, et al. A Novel Algorithm Increases Effective Left Ventricular Pacing During Atrial Fibrillation in Patients Undergoing Cardiac Resynchronization Therapy: Primary Results of the Randomized CRTee Trial. Presented at ESC Congress 2016.
Source: Medtronic Claria MRI™/Claria MRI™ Quad CRT-Ds Reference Manual