63-year-old man with a history of paroxysmal atrial fibrillation; full right bundle branch block pattern on the electrocardiogram; 3 episodes of sudden syncope; electrophysiological study with HV interval measurement at 82 ms; implantation of an Adapta dual-chamber pacemaker; the 2 leads are well positioned with normal pacing impedance, proper sensing and satisfactory pacing thresholds; 3 days after implantation, pacemaker control; programming of various pacing modes and recording of tracings; for this first tracing, programming in ODO mode.
On this tracing and the following tracings, the first line corresponds to lead I on which the event markers are added, the second line corresponds to the intervals (interatrial, interventricular and atrioventricular), the third line corresponds to lead III and the fourth to lead II;
- sinus rhythm properly detected by the pacemaker; AS-VS intervals; wide QRS;
- early atrial extrasystole blocked without conduction to the ventricle;
- slightly delayed atrial extrasystole with conduction to the ventricle with prolongation of the PR interval;
- atrial bigeminism.
In ODO mode, no pacing is possible; this mode is therefore to be avoided in pacemaker-dependent patients; on the other hand, sensing occurs in the designated chambers. This mode of pacing thus enables an analysis of the spontaneous rhythm of the patient with concomitant visualization of the electrocardiogram and event markers. This is a sensitivity test mode. The ODO mode can be programmed temporarily in non-pacemaker-dependent patients with an MRI-compatible pacemaker who are scheduled for an MRI. The ODO mode of these compatible MRI pacemakers allows avoiding the possible reversion of a conventional ODO mode to a VVI mode. Obviously, one must not forget to re-monitor and reprogram the pacemaker after the examination.