Patients with a history of paroxysmal AF who received an AT501 pacemaker for the treatment of bradycardia will be randomized to having both the prevention and therapy algorithms "ON", both "OFF" or having only the therapy algorithms "ON". They will be followed every 3 months for 1 year, then every 6 months for an 2 additional years. Recurrence and frequency of AF will be determined over time based on data retrieved from the device at each follow-up visit.