Prevention of Atrial Arrhythmia in Patients Without Atrioventricular (AV) Conduction Disease

Inclusion Criteria: * A pacemaker indication for sinus node dysfunction and/or brady-tachy syndrome OR already implanted for less than three months for the mentioned reasons and supplied with a symphony 2550 DR at time of inclusion AND * A PR interval \<250ms AND * Documented atrial arrhythmia in the past year * Medication for anti-arrhythmic must be stable for at least one month (2 months for amiodarone) prior to enrollment * Patients must have less than two known cardioversions within the last year * Patient has signed a consent form after having received the appropriate information Exclusion Criteria: * Need a replacement pacemaker device * Have an unknown PR interval * Known AV block ≥ 250 ms PR interval * Minor and/or pregnant woman * Patients enrolled in other clinical trials * Patients with sustained ventricular arrhythmia * Patients with severe coronary artery disease (at the discretion of the investigator) * Patients with advanced cardiomyopathy (at the discretion of the investigator) * Patients who have sustained a myocardial infarction or undergone cardiac surgery within the past 30 days * Patients with unstable angina pectoris * Patients whose life expectancy is less than 1 year * Patients who are unlikely to return for required follow-up visits * Patients who present with permanent atrial arrhythmia or those who usually require cardioversion to terminate such arrhythmia and/or * Patients whose physician plans to add or change medical treatment because of AA episodes during the follow-up period. * Patient unable to understand the purpose of the study or refusing to cooperate