The aim of this study is to test the impact of the managed ventricular pacing (MVP) mode and atrial preventive and antitachycardia pacing therapies on the reduction of a composite clinical outcome composed of any death, permanent atrial fibrillation, and cardiovascular hospitalizations.

Kristensen et al. reported that AAIR pacing reduces atrial fibrillation (AF) development compared to DDDR pacing in sinus node disfunction patients.

Several authors have shown that, in patients with intact AV conduction, unnecessary chronic RV pacing can cause detrimental effects such as AF, left ventricular (LV) dysfunction and congestive heart failure. These findings arose the hypothesis that the non-physiologic nature of ventricular pacing may result in electrophysiological and LV remodeling changes that have potentially deleterious long-term effects.

The MVP mode, present in the Medtronic pacemaker EnRhythm, provides atrial based pacing with ventricular backup. It operates in true AAI(R) mode, it provides ventricular backup in case of a single conduction loss and converts to DDD(R) mode in case of persistent loss of AV conduction.

Aim of this study is to test the impact of the MVP pacing mode and atrial preventive and antitachycardia pacing therapies on the reduction of a composite clinical outcome composed by any death, permanent AF, cardiovascular hospitalizations.

Inclusion Criteria:

• Class I/Class II indications for dual chamber pacing
• Previous implant of an EnRhythm dual chamber implantable pulse generator (IPG) since maximum 2 weeks
• History of atrial arrhythmias (at least one electrocardiogram [ECG] or Holter documented episodes in the last 12 months)

Exclusion Criteria:

• Less than 18 years of age
• Pregnancy
• Unwilling or unable to give informed consent or to commit to follow-up schedule
• Medical conditions that preclude protocol required testing or limit study participation
• Enrolled or intend to participate in another clinical trial during the course of this study
• A life expectancy of less than 2 years
• Patient is a candidate for an implantable cardioverter defibrillator (ICD) or cardiac resynchronization therapy (CRT) device implant
• Anticipated major cardiac surgery within the course of this study
• Permanent III degree AV-block or history of AV node ablation
• History of permanent AF (as defined below)
• AF ablation (left pulmonary veins) or other cardiac surgery < 3 months
• Prior implant of defibrillator device or pacemaker (apart from EnRhythm IPG implanted within two weeks)
• Uncontrolled hyperthyroidism