13th International Congress
THE "NEW FRONTIERS"
OF ARRHYTHMIAS 1998

January 24-31, 1998
Marilleva, Trento, Italy

S-1

Multisite atrial pacing

D. Gras, P. Ritter, C. Leclercq*, P. Mabo, C. Daubert*.
Centre Chirurgical Val d'Or, Saint Cloud, * University Hospital, Rennes, France

Potential mechanisms for atrial arrhythmia prevention by pacing

Various electrophysiological mechanisms may explain the potential antiarrhythmic effect of permanent atrial pacing. The pacing mode by itself may have a positive effect in atrial arrhythmia prevention. This was clearly shown by a recent randomized prospective study, in patients with sick sinus syndrome, in whom atrial fibrillation occurred less frequently in the AAI mode compared to VVI mode¹. However, this beneficial effect may be related to the maintenance of a physiological atrio-ventricular synchrony as well as atrial pacing itself.

Another basic mechanism is heart rate control which is of particular interest in bradycardia dependent atrial arrhythmias. The role of cardiac pacing is, here, to correct for the arrhythmogenic consequences of bradycardia, as heart rate irregularity and dispersion of refractoriness. In this field the effectiveness of cardiac pacing has been documented several years ago, in the so called vagally-mediated atrial fibrillation². It was further extended to prevention of atrial arrhythmias in the brady-tachy syndrome.

Heart rate control has been also proposed through the use of overdrive pacing. This can be achieved with the use of a sensor by programming hyperchronotropic rate responsive parameters or with a dynamic rate control, obtained with a specific algorithm capable to produce an incremental pacing rate after each atrial premature beats³. The suppression of cycle lenght variation, as during short-long-short cycle phenomenon, by using rate-smoothing algorithms could play a preventive role in atrial arrhythmia initiation. However, the effectiveness of such techniques is not clearly established.

More recently, cardiac pacing techniques using unconventional atrial pacing sites, have been proposed as a means to prevent paroxysmal atrial arrhythmias. The rationale for these new and very promising approaches, is to improve the atrial activation sequences, to preexcite an area involved in a reentrant circuit and/or to lead to a reduction of atrial dispersion of refractoriness^4,5. In some particular patients, multisite atrial pacing could provide an earlier recovery of atrial excitability, therefore eliminating a potential zone of slow conduction that could play a role in the mechanism of atrial arrhythmias.