Mode swith during an episode of AF

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Tracing N° 1
Medtronic Devices: PM Field: Management of atrial arrhythmias
Patient

Same patient as for tracing 1 of pacing mode chapter; the patient is in AV block; he underwent pacemaker interrogation 3 days after device implantation; programming of various pacing modes and recording of the tracings; DDD mode programming.

Graph and trace

Tracing 1a: the first channel is lead I of the surface ECG with the markers superimposed, the second shows the time intervals, the third is lead III and the last channel is lead II;

  1. atrial and ventricular paced rhythm (AP-VP);
  2. atrial extrasystole outside the refractory period with ventricular pacing (AS-VP);
  3. another atrial extrasystole;
  4. acceleration and disorganization of the atrial rhythm; the atrial events labeled AS are conducted to the ventricle, the atrial events in the refractory period (AR) are blocked;
  5. mode switch (MS); indeed, out of the 7 previous consecutive atrial intervals, at least 4 are shorter than the programmed interval of rate detection;
  6. slowing of the paced ventricular rate after switch to DDIR mode;

Tracing 1b: the episode of AF lasted 2 minutes before spontaneous conversion; new tracing in DDD mode at 60 bpm;

  1. rhythm sensed in the atrium and paced in the ventricle (AS-VP);
  2. frequent atrial extrasystoles sensed outside the refractory period and ventricular pacing (ASVS);

Tracing 1c: change of programming to MVP mode at 70 bpm;

  1. regular paced atrial and sensed ventricular rhythm AP-VS; elimination of the atrial extrasystoles;
Comments

2 factors are determinant in the management of atrial arrhythmias in recipients of cardiac pacemakers: fallback must be systematically programmed to prevent rapid ventricular pacing during abnormal acceleration of the atrial rhythm; algorithms can be implemented to alleviate the arrhythmia burden.

This tracing illustrates important points:
1) an Adapta pacemaker switches mode for episodes of atrial arrhythmias based on the following criteria: out of 7 consecutive intervals, 4 are shorter than the programmed rate detection interval (in this case 175 bpm);
2) the efficacy of the various pacing algorithms in lowering the arrhythmia burden varies depending on the patient and remains to be confirmed in a large population.

The tracings recorded in this patient are, nevertheless, promising. The episode of AF began with an atrial extrasystole, sensed with any pacing mode with a backup rate at 60 bpm. An increase in the backup rate to 70 bpm and the programming of the MVP mode completely suppressed the atrial extrasystoles. The suppression of the trigger, known to initiate episodes of atrial arrhythmias, might lower the arrhythmia burden and, in this patient, highlights the particular benefit of programming an algorithm that stabilizes the atrial rhythm, promotes atrial pacing, and eliminates the compensatory pauses occurring after atrial extrasystoles. The efficacy of this type of algorithm remains to be confirmed in a large population.

Theoritical features / Basic concepts

General points Automatic mode switch for atrial arrhythmias   GENERAL POINTS The management of cardiac pacemaker recipients who present with episodes of atrial arrhythmias is complex because of the risk of run away of ventricular pacing by tracking of a rapid atrial rhythm. From a continuous analysis of the atrial rhythm, mode switch causes the automatic transition from an atrial tracking DDD or VDD, to a non-atrial tracking DDI pacing mode. The fallback algorithm prevents ventricular pacing at high rates, synchronized to the rates of atrial arrhythmias. An ideal mode switch algorithm combines the following characteristics: rapid onset to avoid rapid ventricular pacing during the initial phase of sensing of the arrhythmia ability to return rapidly to a synchronous mode at the end of the...