Evaluation of the SafeR Mode in Patients With a Dual Chamber Pacemaker Indication

Inclusion Criteria: * Patient primo-implanted with a Symphony 2550 or Reply DR for less than 1 month according to the official guidelines. * Patient implanted for sinus node dysfunction (including bradycardia-tachycardia syndrome) or 2nd, advanced or 3rd degree intermittent or allegedly permanent AV block. * Patient implanted with a bipolar right atrial lead and a right ventricular lead * Patient has signed a consent form after having received the appropriate information Exclusion Criteria: * Patient with permanent AF * Patient suffering from sustained ventricular arrhythmias * Patient with congenital complete heart block * Patient with vasovagal syncope, carotid sinus syndrome * Patient with AV node ablation * Patient having suffered from a myocardial infarction within the last month * Patient suffering from severe aortic stenosis * Patient suffering from unstable angina pectoris * Patient is not able to understand the study objectives and protocol or refuses to co-operate * Patient is not available for scheduled follow-up * Patient has a life expectancy less than one year * Patient is included into another clinical study * Patient is minor, this is \< 18 years * Patient is a pregnant woman * Any patient with a contra-indication for the device labeling