This study aims to determine whether increasing atrial base rate pacing to achieve at least 75-80% atrial pacing in patients with sick sinus syndrome undergoing the implementation of dual-chamber pacemaker can be useful to prevent or decrease the atrial fibrillation during 6 months follow-up duration.

Inclusion Criteria:

• Sick sinus syndrome patients having dual-chamber pacemaker
• Having paroxysmal AF defined as at least 2 episodes of AHR/AMS >190 b/min lasting >6 minutes
• Having normal atrioventricular conduction

Exclusion Criteria:

• Other clinical indications for pacing except sick sinus syndrome (bradycardia-tachycardia syndrome)
• History of acute coronary syndrome
• Significant heart valve disease
• Chronic AF before randomization
• Overt heart failure
• Malignancy
• Any reasons for antiarrhythmic medication use
• Inability to follow patients every 3 months