Introduction Atrial fibrillation AF is a highly

Introduction Atrial fibrillation (AF) is a highly prevalent atrial arrhythmia that affects approximately 10% of individuals older than 75 years of age and tends to increase in prevalence with advancing age [1–3]. Although AF itself is not life threatening, it is a risk factor for stroke, and the AF-associated stroke mortality rate is high [4–6]. Antiarrhythmic agents are usually effective for treating AF; however, some cases are refractory to pharmacological agents. Although various treatments for AF such as catheter ablation have been used, perfect rhythm control is not easily achieved. An atrial overdrive pacing algorithm for the prevention of AF was initially reported by Murgatroyd et al. in 1994 [7], and other alternative pacing algorithms have since been developed, including post-premature atrial contraction (PAC) and post-exercise response algorithms and atrial overdrive pacing [8–10,33]. Although many clinical trials have been conducted, the usefulness of AF control algorithms has remained a walk through of debate during the past 20 years [8–16]. Additionally, none of the pacemaker guidelines includes an AF suppression algorithm as a standard programming feature for AF prevention in pacemaker patients. The stated reason is that pacemaker-embedded AF suppression algorithms have not demonstrated unequivocal clinical efficacy. In this review, we summarize the previous clinical trials, characterize the efficacy of atrial pacing for AF prevention, and discuss the practical clinical applications of this algorithm.
Prevalence and impact of AF in clinical practice AF is the most common arrhythmia worldwide, and its prevalence increases with age; AF occurs in approximately 10% of the general population older than 75 years of age [1–3]. The prevalence of sick sinus syndrome or atrioventricular block, which requires pacemaker implantation, also increases with age [17,18]. Asymptomatic AF episodes are detected in approximately 10% of pacemaker recipients, an higher incidence than that observed in the general population [19–21]. AF poses a significant risk of stroke and systemic thromboembolism. Stroke resulting from a large cerebral infarction consequent to a left atrial appendage thrombus is the most severe complication of AF and is associated with a high mortality rate [22,23]. Annually, AF is responsible for 20% of all strokes. Strong evidence suggests that anticoagulant therapy could reduce the annual incidence of stroke in patients with AF; therefore, AF patients should certainly be treated with anticoagulation agents to prevent stroke [24]. However, anticoagulation therapy is underused in clinical practice because of the difficulty associated with drug administration and the risk of bleeding complications [25]. Nevertheless, AF prevention should be given the utmost priority.
Benefit of dual-chamber pacing for AF prevention Several studies have demonstrated that dual-chamber pacing, through which ventricular pacing can be minimized, is superior to single-chamber ventricular pacing in terms of reducing the incidence of AF [26–31]. Atrial (atrial–atrial interval; AAI) and physiologic pacing (dual-chamber pacing, dual-chamber sensing, dual response, and rate-adaptive; DDDR) avoid atrioventricular dyssynchrony, which is associated with increased atrial pressure. The Mode Selection Trial (MOST) study [32] demonstrated a linear increase in the risk of AF up to cumulative ventricular pacing rates of approximately 80–85% in the DDDR and ventricular pacing, ventricular sensing, inhibition response and rate-adaptive (VVIR) modes (Fig. 1). Nielsen et al. [33] compared the AAI and DDDR modes by observing changes in the left atrial (LA) diameter and left ventricular fractional shortening (LVFS). In the DDDR mode, the LA diameter increased significantly (p<0.05) and the LVFS decreased significantly (p<0.01) [33]. Additionally, AF occurred significantly less often in the AAI mode. Therefore, by increasing the atrial stress associated with ventricular dyssynchrony, ventricular pacing might increase the risk of AF even when AV synchrony has been preserved. A large, randomized trial conducted by Connolly et al. [29] reported a significantly lower annual incidence of AF in the physiologic pacing group (5.3%) than in the ventricular pacing group (6.6%).