12 lead ECG

• permanent right ventricular pacing
• programming of the MVP mode
• first blocked atrial activity
• atrial pacing and ventricular pacing with a short AV delay
• second blocked atrial activity
• atrial pacing and ventricular pacing with a short AV delay
• atrial and ventricular pacing with the programmed AV delay

EGM recorded simultaneously: the first line corresponds to lead II on which the event markers are added, the second line corresponds to the ventricular bipolar EGM, the third line corresponds to the atrial bipolar EGM lead and the fourth line corresponds to a far-field EGM with inter-ventricular and atrio-ventricular intervals

• DDD mode followed by programming of the MVP mode (programming successful)
• 2 blocked non consecutive atrial activities
• the intervals show the AV delay: after a blocked atrial pacing, AV delay at 80 ms on the ensuing cycle

Comments

• there is extensive evidence demonstrating the deleterious effect of prolonged right ventricular pacing on left ventricular function
• different strategies and algorithms have been designed by device manufacturers to mitigate unnecessary ventricular pacing without inducing symptoms or compromising safety
• 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 Microport dual-chamber pacemakers
• it is essential to understand the operating principles so as not to be surprised by the presence of blocked P waves which could suggest a dysfunction; it is not uncommon to be called by a nurse who considered a tracing with blocked P wave as abnormal
• this tracing shows the specificities of the MVP mode for Medtronic pacemakers
• the MVP mode tolerates that a single atrial activity is blocked; the device provides an emergency ventricular pacing pulse 80 ms after the next atrial activity

if 2 atrial activities out of 4 are blocked like shown in this tracing, the device switches to DDD mode.