1. Decrease atrial sensitivity, 2. Change the PVAB method
The problem in this case is that FFRWs are present and being marked as an Ab event all the time which is being used in the rate count to trigger MS. To correct this problem the solution must result in eliminating the FFRWs entirely from being sensed and marked as Ab events. From the answers available there are only two options which may achieve this.
1. Decrease atrial sensitivity
A first option to consider if the intrinsic P wave amplitude is large and is notably larger than the FFRW amplitude, is to decrease atrial sensitivity (make the atrial channel less sensitive, increase the threshold value e.g. 0.3 mV 0.6 mV). This may help eliminate FFRWs from being seen and hence not trigger an Ab marker although does risk delaying detection of a true AT/AF episode. If amplitudes are similar this may not be an option as could result in atrial undersensing.
2. Change the PVAB method
In Medtronic devices it is worth understanding the three possible PVAB methods which can be programmed. These are PVAB partial, partial + (already programmed here) and absolute.
- PVAB Partial works by marking atrial events which fall in the programmed PVAB interval (in this case 150ms) as an Ab. Marked events do not affect pacemaker timing cycles but do count towards tachyarrhythmia detection features.
- PVAB Partial + operates in a similar way to PVAB Partial but differs by decreasing the atrial sensitivity (increases the threshold value) after a ventricular event for the duration of the programmed PVAB interval. The sensitivity then gradually returns to the programmed value after the PVAB interval times out. Events are still marked Ab do not affect pacemaker timing cycles but do count towards tachyarrhythmia detection features (as in this case)
- PVAB Absolute is a true blanking period where no atrial events are sensed within the PVAB interval. The atrial channel is completely blind to atrial events within the programmed window and therefore no Ab markers can be allocated.
With the above in mind in this case programming the PVAB method to Absolute could help eliminate the FFRWs being marked. This solution however again is not perfect as caution is advised when selecting the Absolute method as the absolute blanking may reduce the devices ability to sense AT/AF episodes and in ICDs may reduce the ability to discriminate between VT and SVT.
Medtronic ADVISA DR MRITM SURESCANTM A3DR01, ADVISA SR MRITM SURESCANTM A3SR01 Clinician Manual