Lead parameters remained stable over time and no lead-related complications were observed (see Table 2). Table 2. Comparison between patients’ characteristics during APP ON phases and APP OFF phases. No differences were found in the number and duration of AF episodes and in the ventricular pacing rate concerning the site of implantation

(RAA DM1 vs. BB DM1 subgroups). Discussion Our clinical experience on a large group of implanted DM1 patients confirmed the data of literature (16) about the high occurrence of paroxysmal AF in patients implantated with PM. Several studies (17-20) have documented that cardiac involvement in Inhibitors,research,lifescience,medical DM1 patients is not limited to the conduction system, as initially supposed, but cardiomyopathy, characterized by progressive selective fibrosis Inhibitors,research,lifescience,medical and scar replacement of initially unaffected areas, facilitating the onset and perpetuation of AF, is a peculiar part of the disease, as it happens for other neuromuscular disorders (21-24). Because one of the causes of AF episodes could reside in the site of stimulation, recent papers (25-30) demonstrate that an alternative stimulation site, i.e the interatrial septum, in the region

of Bachmann’s bundle (BB) is the Inhibitors,research,lifescience,medical atrial site with better sensing and pacing threshold compared with the RAA and presents a low rate of sensing and pacing defects in a long term follow-up. These results were not confirmed by a recent work (31) that, comparing the right atrial appendage and Bachmann’s bundle atrial pacing as sites of stimulation in 30 DM1 patients, Inhibitors,research,lifescience,medical failed to demonstrate a beneficial

effect of BB stimulation in preventing atrial fibrillation. Other studies (32, 33) have shown that atrial preference pacing (APP) may prevent the onset of AF through different mechanisms: prevention of the relative Vorinostat cost bradycardia that triggers paroxysmal AF; prevention of the bradycardia-induced dispersion Inhibitors,research,lifescience,medical of refractoriness; suppression or reduction of premature atrial contractions that initiate re-entry and predispose to AF; preservation of atrioventricular synchrony, Methisazone which in turn may prevent switch-induced changes in atrial repolarization, predisposing to AF. However the efficacy of the automatic atrial overdrive algorithms remains controversial (32-35). The ADOPT Trial (32) demonstrated that overdrive atrial pacing decreased significantly symptomatic AF burden in patients with sick sinus syndrome and AF by 25% and total atrial arrhythmia burden by 26.5%. In the SAFARI trial, Gold et al. (33) showed a statistically significant reduction in the AF burden only in the subgroup of patients with a high AF burden (≥ 6%). In the low AF burden group (≤ 6%), activation of prevention pacing algorithms did not result in the prevention of AF episodes. On the other hand, Ogawa et al.