To evaluate whether atrial fibrillation (AF) therapies in Guidant Pulsar Max II or Insignia Plus DR have an effect on the occurance of AF in patients with no prior history of AF

This multi-centre, randomized, cross-over, prospective study will evaluate the occurrence of AF with AF pacing therapies programmed on (APP and VRR) and with AF therapies programmed off (APP and VRR) in patients with no known prior history of AF (all patients have a pacing indication). The occurrence of AF as well as time to first event and AF burden (frequecy and duration).

Inclusion Criteria:

• No prior history of AF or atrial flutter, primary indication of SSS or AV block for dual chamber pacemaker, confidentiality agreement signed and dated before implant, available for follow-up at the study centre where they were enrolled at the protocol defined intervals, willing and capable of participating in all testing associated with the study, on stable regime of arrhythmia management drugs.

Exclusion Criteria:

• Documented history of AF or atrial flutter, clinically significant ventricular arrhythmias, < 18 yrs old, life expectancy < 1 year or expectation of heart transplantation during the study period, likely to or have received a mechanical tricuspid valve during the study, enrolled in other cardiovascular studies, women who are pregnant, inability or refusal to sign Patient Confidentiality Agreement, inability or refusal to complete the follow-up schedule at the study centre in which they were enrolled, exhibit arrhythmias due to reversible cause eg, digitalis toxicity, hypoxia, transient electrolyte imbalance, acute myocardial infarction or electrocution.