Atrial fibrillation and sensing failure
81-year-old man implanted with an Adapta dual-chamber pacemaker for atrial disease with sinus dysfunction and episodes of paroxysmal atrial fibrillation; routine examination.
Tracing 29a: the first line corresponds to lead I with the superimposed markers, the second line to the ventricular EGM and the last line to the intervals;
- rapid atrial rhythm with spontaneous conduction (AR-AS-VS);
- atrial undersensing period;
- certain atrial activities outside the refractory periods are followed by a paced ventricle (AS-VP);
- better atrial sensing and switching to DDIR (MS) mode;
- spontaneous ventricles;
Tracing 29b: tracing recorded a few seconds after the preceding tracing;
- wide range of atrial undersensing;
- switching to DDD mode (MS);
- reappearance of a paced ventricle (VP) by exit from the fallback mode (due to the absence of sensed atrial signal).
The proper functioning of mode switching implies proper sensing of the arrhythmic atrial signals. Their amplitude is very often reduced comparatively to the amplitude of the signals of sinus origin. It is therefore difficult to predict the proper sensing of atrial arrhythmias from the measurement of sinus rhythm signals. In this patient, this intermittent sensing is responsible for repeated alternations between synchronous mode (DDD) and fallback mode (DDIR) and an unnecessary and energy-intensive ventricular pacing. There is sometimes inhibition by the QRS, sometimes ventricular pacing synchronized with an atrial sensing.
In this patient, atrial sensing was programmed to the maximum of the capacities of the device leaving no possibility for optimization. A programming in DDIR mode thus appears appropriate in this patient with atrial disease since it allows atrial pacing when the patient is in sinus rhythm and avoids the problems of erratic ventricular pacing by absence of switching when the patient is in AF.