The study will try to access the efficacy of atrial pacing, medication and radiofrequency ablation in treating patients with paroxysmal atrial fibrillation and sinus node dysfunction; to identify the response to these treatments in patients with "functional" and organic sinus node dysfunction respectively; to explore the necessity of pacemaker implantation in patients with "functional" sinus node dysfunction. Patients who meet the inclusion criteria will receive pacemaker implantation followed by trial pacing, medication and radiofrequency ablation of AF. Device data will be analyzed to answer the question. And after follow-up of 1 year, lower rate of pacemaker will be set as 40 bpm for patients without AF. The proportion of pacing and patients' tolerance will be analyzed.

Inclusion Criteria:

• Age from 18 - 80 years
• Longest RR interval ≥ 3 seconds in sinus rhythm or when atrial arrhythmia (atrial fibrillation/atrial arrhythmia/atrial flutter) is converted to sinus rhythm (documented by either holter monitor or electrogram).
• Meet the indications of permanent pacemaker implantation in patients with SND according to the 2012 ACCF/AHA/HRS Guidelines for Device-Based Therapy of Cardiac Rhythm Abnormalities.
• Evidence of paroxysmal atrial fibrillation ( two or more symptomatic episodes within 6 months)
• Willing to sigh informed consent

Exclusion Criteria:

• Type II second-degree or three-degree atrioventricular block (in sinus rhythm)
• Intrinsic PR interval ≥ 300 ms in sinus rhythm
• Persistent AF（including long-standing persistent AF）
• Severe structural heart disease(e.g. ischemic heart disease that requires revascularization, rheumatic heart disease that requires valve replacement, cardiomyopathy except hypertensive myocardial hypertrophy)
• Work high above the ground or heavy physical labour
• Malignant ventricular arrhythmias
• New York Heart Association (NYHA) class III or IV
• AF secondary to electrolyte imbalance, thyroid dysfunction, vasovagal reaction or other reversible or non-cardiac causes
• Previous procedures dealing with AF (including radiofrequency ablation and surgical operation)
• Cardiac implantable electronic device implantation history
• Severe hepatic and renal dysfunction(serum creatinine above the upper normal limit of the center, or chronic renal dysfunction ; ALT or AST more than 2 times the upper normal limit of the center, or bilirubin more than 2 times the upper normal limit of the center, or hepatic cirrhosis)
• Contraindication to propafenone/amiodarone/dronedarone(except bradycardia)
• Contraindication to oral anticoagulants
• Women who are pregnant
• Presence of malignant tumor
• Severe coagulation disorder (without any anticoagulation treatment)
• The investigators do not think the patient is eligible for this study
• Patient is unwilling to cooperate with the study procedures

Patients who meet the Eligibility Criteria will be enrolled. The anticipated number of patients is 200.