Evaluation of Atrial Fibrillation Occurrence in Sick Sinus and Complete Atrioventricular Block Patients After Pacemaker Implantation (AF-pacemaker Study)

Inclusion Criteria: * Age: 18-80 years * Patients eligible for the indications for permanent pacemaker implantation in accordance with 2016 revised Korean indication guideline on cardiac pacemaker implantation * Estimated percentage of atrial pacing \>40% under sinus rhythm (LR≥60bpm, close hysteresis and rest rate) * Estimated percentage of ventricular pacing \>40% under sinus rhythm (LR≥40bpm, DDD pacing, close hysteresis and rest rate) * Patients who are willing to sign the informed consent. * Patients who are willing to receive the implantation and post-operative follow-up. Exclusion Criteria: * Persistent or permanent AF * Severe hepatic and renal insufficiency (AST or ALT ≥ three times of normal upper limit; SCr \> 3.5 mg/dl or Ccr \< 30ml/min) * Thyroid gland dysfunction * Pregnancy * Malignant tumor * Severe organic heart disease (such as moderate to severe mitral regurgitation, dilated cardiomyopathy, hypertrophic cardiomyopathy, severe heart valve disease) * Life expectancy \< 12 months * Patients unable or unwilling to cooperate in the study procedures.