SYSTEMS OF PROTECTION OF DUAL-CHAMBER PAC EMAKERS AGAINST ATRIAL ARRHYTHMIAS

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 ra tes leading to non-physiological rapid ventricular paced responses. Th e unquestioned benefits of DDD pacing in terms of mortality and morbid ity has led to the conservation of this mode in such situations, but w ith various systems of protection. Initially, limitation of the maximu m frequency and programming a long atrial refractory period were propo sed, but these measures were contrary to the physiological vocation of DDD pacing. Similarly, DDI and DDIR pacing, which do not ensure synch ronisation on spontaneous P waves, were suggested, but in some cases t here was loss of atrio-ventricular syn chronism in sinus rhythm. There fore, the manufactures developed ''fallback systems'' allowing program ming of physiological pacing in patients with paroxysmal atrial arrhyt hmias. The aims of these systems are : 1) to detect atrial arrhythmias ; 2) to change the pacing mode when the arrhythmias is detected for ve ntricular 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 drawbacks, their main indication s and possible future developments.