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Patient
67-year-old man implanted with a dual-chamber pacemaker for complete atrioventricular block; recording of this tracing during the consultation;
Trace
Onset is atrial pacing and ventricular pacing (DDD mode); programming of MVP mode (Managed Ventricul Pacing, specific to Medtronic devices); atrial pacing not followed by spontaneous QRS; on the following cycle, atrial pacing and ventricular pacing with a short AV delay (80 ms); this short AV delay on the cycle following the blocked P wave is the signature feature of the MVP mode; identical sequence (blocked atrial pacing, atrial pacing and ventricular pacing with short AV delay); return to DDD mode with programmed AV delay (switching when 2 out of 4 atrial activities are blocked);
Trace
Confirmation on the EGMs with initially the DDD mode followed by programming of the MVP mode (programming successful); the intervals show the AV delay: after a blocked atrial pacing, AV delay at 80 ms on the following cycle;
Exergue
Each manufacturer proposes a specific mode to reduce the percentage of ventricular pacing, each with its specificities. A blocked P wave may correspond to a normal functioning for Medtronic, Biotronik, Boston Scientific and Sorin dual-chamber pacemakers but not for St. Jude Medical devices.
This tracing shows the specificities of the MVP mode for Medtronic pacemakers. It is essential to understand its operating principles so as not to be surprised by the presence of blocked P waves which could suggest a dysfunction.