Pacing in MVP mode (first version)

The observation of the deleterious effect of right ventricular pacing led to the development of an AAI platform automatically switching to DDD mode in the presence of an atrioventricular block and vice versa when conduction is restored. The functioning of the MVP mode has moreover been modified on the latest dual-chamber pacemaker platforms.

These different tracings allow defining the various characteristics of the first version of the MVP mode:

1. on the first tracing, the major advantage of this algorithm appears obvious. Indeed, with respect to the previous tracing, the programming of this algorithm allows reducing the percentage of pacing from 100 to 0%. In the long term, this should prove beneficial in terms of ventricular remodeling and occurrence of atrial arrhythmia. Analysis of the percentage of ventricular pacing is thus an important follow-up component in a patient with sinus dysfunction, in an attempt to minimize the occurrence of any unnecessary pacing. Note that on this tracing, the PR interval is relatively prolonged (around 300 ms on paced P wave). For patients with a long PR, both at rest and during exercise, in this version of the MVP mode, the pacemaker remains in ADI mode without switching to DDD mode. In the presence of symptoms associated with PR prolongation on exertion, programming in DDD mode would probably be desirable;
2. on the second tracing, the occurrence of a single blocked atrial activity is not sufficient to incur switching in DDD mode. Ventricular safety pacing occurs 80 ms after the ensuing paced atrial activity. The maximum ventricular pacing interval tolerated by the pacemaker corresponds to half the programmed minimum rate. In order to avoid too long pauses, it is therefore advantageous not to program a minimum rate that is too low;
3. on the third tracing, the switching to DDD mode occurs upon repeated interruption of atrioventricular conduction. For the first version of the algorithm, if a ventricular event is missing in 2 of the 4 most recent A-A intervals, the device identifies an AV conduction loss and switches to DDD mode. This provides ventricular safety pacing in response to deficient ventricular events. This relatively fast switching in DDD mode allows avoiding the succession of pauses and of non-optimal AP-VP pacing sequences due to short AV delay;
4. the last tracing shows the first verification of AV conduction, 1 minute after switching to DDD mode. During this verification, the device switches to ADI pacing mode during one interval. If the next A-A interval includes a sensed ventricular beat (as in this example), the sensing control was successful. The device remains in ADI pacing mode. If the ensuing A-A interval does not include a sensed ventricular beat, the conduction control fails and the device returns to DDD mode. Only one blocked P wave can be tolerated during this search. The interval between each conduction control is doubled (2, 4, 8 ... minutes to a maximum of 16 hours).