Comparison of AAIsafeR and DDD Modes in Non-selected Patients

1 Purpose In patients with sinus node dysfunction (SND), the use of AAI mode is rare. In paroxysmal high-degree or complete atrio-ventricular (AV) block, paroxysmal vagally-mediated bradycardia, single chamber atrial pacemakers are contraindicated although ventricular support is only rarely needed. As a result, these patients are usually exposed to an unnecessary high proportion of ventricular pacing due to the programming of the system to DDD mode for preventive safety reasons. This drains the pulse generator battery, and more importantly has long-term adverse effects on ventricular function in a subset of vulnerable patients, leading to left ventricular (LV) asynchrony, mitral regurgitation and increased left atrium (LA) size. The deleterious effects of right ventricular (RV) pacing, which increased heart failure (HF) morbidity/mortality, atrial fibrillation (AF) and related adverse events have been highlighted in several large clinical studies. Limiting RV pacing in non-dependant patients is therefore desirable. The Symphony DR 2550 cardiac pacemakers (SORIN Group, Montrouge, France) offer a new pacing mode that automatically switches from AAI(R) mode to DDD(R) or DDI(R) in event of severe atrioventricular conduction disorder, returning spontaneously to AAI(R) mode as soon as the spontaneous AV conduction has resumed. This particular mode is called the AAIsafeR2(R). The objective of this study is three-fold: to demonstrate that AAIsafeR2 mode (i) reduces the percentage of ventricular pacing in patients with a spontaneous AV conduction and (ii) prevents atrial arrhythmias by improving atrial hemodynamics and (iii) improves the long-term hemodynamic status of implanted patients in comparison to the "standard" DDD mode, set with long AV Delays (DDD Long AVD). The scientific soundness lying in this study is a proposal of an optimal programming of dual-chamber pacemakers (PM) with regard to the preservation of spontaneous AV conduction.