The role of pacemaker therapy in the prevention of atrial fibrillation.

Atrial fibrillation (AF) has been recognized, with increasing concern, as a potentially disabling illness, occurring either as a symptom of many cardiac diseases or as an isolated disorder. It can independently contribute to mortality and morbidity and may have serious prognostic importance in acute or chronic cardiac disease. In patients with symptomatic drug refractory atrial fibrillation, ventricular rate control by atrioventricular nodal ablation or modification commonly results in pacemaker implantation. The concept of AF prevention by pacemaker therapy has been introduced in patients with bradycardia-tachycardia syndrome or vagally mediated bradycardia-dependent AF. In patients with sick sinus syndrome, atrial pacing has proved to be more effective than VVI pacing in maintaining the electrical stability of the atrium in long-term follow up. Recently, the development of new techniques of atrial pacing employing pacing at two atrial sites may improve the effectiveness of the AF prevention by pacemaker therapy. Dual-site right atrial pacing using overdrive stimulation activates simultaneously the high right atrium and the left atrium via the ostium of the coronary sinus. Two main mechanisms have been proposed to explain the favourable effect of this technique. One is the suppression of atrial premature beats initiating AF by the overdrive pacing. The second is the alteration of atrial activation pattern by preexcitation of the area of the coronary sinus ostium which permits earlier recovery of excitability in sites of atrial conduction delay. The combination of drug therapy and pacing is essential for effective AF control. We have hitherto studied 30 patients with single- and dual-site pacing. Single-site pacing was performed at the high right atrium or coronary sinus ostium. The dual-site pacing mode increased the arrhythmia-free intervals, decreased patients' arrhythmia-related symptoms and anti-arrhythmic drug use as compared to the period preceding institution of pacing and incrementally over conventional high right atrial pacing alone. A multicentre randomized trial, Dual-site Atrial Pacing for Prevention of Atrial Fibrillation (DAPPAF), evaluating three pacing modes (dual-site, single-site and support pacing), is now in progress.