Pacing in DDD mode

N° 8
Manufacturer Medtronic Device PM Field Pacing Modes

Same patient as in tracing 1.

Graph and trace

Programming in DDD mode 60 beats/minute;

  1. atrial sensing and ventricular pacing (AS VP); the AV delay on spontaneous atrial activity is 120 ms;
  2. atrioventricular pacing; the AV delay on paced atrial activity is 150 ms;
  3. during the alternation between AS-VP and AP-VP, the interval between the 2 VPs is 30 ms longer than the programmed value corresponding to the base rate; these additional 30 ms correspond to the difference between spontaneous AV delay and paced AV delay.

The basic principle of the DDD mode is to synchronize ventricular pacing with atrial sensing (triggered functioning) or pacing. Spontaneous atrial or ventricular activity respectively inhibits atrial or ventricular pacing (inhibited functioning). This mode allows maintaining an atrial synchrony for low sinus rates up to high rates (maximal tracking rate limit). Any atrial sensing outside the refractory period or atrial pacing result in an AV delay with ventricular pacing in the absence of spontaneous ventricular sensing.

The programming of the DDD mode hence appears satisfactory in this patient. However, follow-up would probably show a percentage of ventricular pacing close to 100%. This would therefore correspond to a functioning deemed normal and appropriate. ODO analysis nevertheless revealed that this patient had correct AV conduction. One of the priorities of the programming of a pacemaker is to avoid unnecessary right ventricular pacing. This avoids heavy battery consumption and prolongs the life of the device and, above all, avoids right ventricular pacing which is associated with short, medium and long term effects with adverse effects on hemodynamics, on ventricular remodeling and on the onset of atrial arrhythmias. Indeed, right ventricular pacing induces an asynchronous interventricular and intraventricular activation and relaxation sequence. A high percentage of ventricular pacing in a patient with preserved AV conduction should alert the physician at the time of interrogation and elicit a discussion regarding the use of specific algorithms.

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