[Protection systems of dual-chamber pacemakers against atrial arrhythmia]

The incidence of atrial arrhythmias may be as high as 10% in patients paced in the DDD mode carrying the risk of tracking of rapid atrial rates leading to non-physiological rapid ventricular paced responses. The unquestioned benefits of DDD pacing in terms of mortality and morbidity has led to the conservation of this mode in such situations, but with various systems of protection. Initially, limitation of the maximum frequency and programming a long atrial refractory period were proposed, but these measures were contrary to the physiological vocation of DDD pacing. Similarly, DDI and DDIR pacing, which do not ensure synchronisation on spontaneous P waves, were suggested, but in some cases there was loss of atrio-ventricular synchronism in sinus rhythm. Therefore, the manufactures developed "fallback systems" allowing programming of physiological pacing in patients with paroxysmal atrial arrhythmias. The aims of these systems are: 1) to detect atrial arrhythmias; 2) to change the pacing mode when the arrhythmias is detected for ventricular pacing not synchronised on the P wave (VVIR or DDIR modes); 3) to revert to the initial mode of pacing when the arrhythmia is over. This paper describes the different specialised algorhythms currently available, with their advantages and draw-backs, their main indications and possible future developments.