• Patients mode preference
  
• Specific symptom scale
  

• Evaluation of rate irregularity indicators and patient's symptoms
  
• Number of patients that should undergo atrioventricular nodal (AVN) ablation
  
• Number of patients that should undergo drug therapy in combination with pacing to stabilize heart rate
  
• Potential discomforts of pacing algorithm for heart rate stabilization
  

The RARE PEARL is a multicenter prospective, randomized, double-blinded, crossover study.

Prior entering the study the patient should be informed and should give his written consent. Besides he/she should meet all selection criteria. The Investigator has to check that all selection criteria are satisfied. Then the patient undergoes pacemaker implantation, receiving a pacemaker model C20 SSIR or T20 SSIR (or later). The ventricular lead must be bipolar independently of the manufacturer.

After pacemaker implantation, a 45 days Stabilization Period is necessary to stabilize leads and drug therapy.

At the end of the stabilization period the patient is randomized to have VRS algorithm switched either ON or OFF. The 1° Study Phase ends after 2 months. Then a cross-over takes place: VRS algorithm is switched respectively OFF or ON and the 2° Study Phase is started. Also the 2° Study Phase ends after 2 months.

The randomization will be centralized: randomization lists will be generated and managed by the sponsor. Because the patients will undergo a QoL questionnaire at each crossover phase, they will have to be blinded about the status of their VRS setting. Similarly, also the co-investigators administering the QoL questionnaires have to be blinded about the status of VRS setting. Only the principal investigator knows if the VRS algorithm is ON or OFF. The principal investigator will be instructed not to inform the patient and the co-investigators administering QoL questionnaire about the setting until after the end of the study.

The co-investigator(s) responsible for QoL questionnaire should not perform the patient follow-up at 1° and 2° Study Phase, otherwise the patient is automatically excluded from the study.

After the cross-over period (2 + 2 months) a Free Therapy Phase (3° Phase) starts. Device settings and drug therapy are left to the physician’s discretion.

One year after implantation a final follow-up is scheduled. The study ends and the pacemaker can be programmed according to the physician’s discretion.