Over the last decade, atrial fibrillation (AF) and heart failure (HF) have emerged as new epidemics.During the same period, there has been an increase in the use of implantable devices for cardiac pacing or defibrillation, which in turn can promote or worsen both AF and HF because of possible deleterious effects of chronic right ventricular (RV) pacing itself.In pts with sinus node dysfunction (SND) AAI pacing was associated with a reduction in mortality, AF and HF occurrence when compared with VVI pacing.