Clinical implantable electronic devices, such as permanent pacemaker, implantable cardioverter defibrillator and cardiac resynchronization therapy are used in current daily practice for patients with bradycardia, ventricular arrhythmia, or heart failure. The rapid progress of permanent pacemaker function is growing to replace human's degenerating electrophysiology of heart.

The ability of physical work is an important cornerstone of quality of life. In daily activities, rate response to higher rate is importance for patients with bradycardia who can not accelerate their heart rate. And rate-adapting pacing of permanent pacemaker is a design to increase heart rate pacing according to physical activity or emotional activity. Patients with rate-adaptive pacing will get more cardiac output and overcome the physical activity such as stair climbing. But there are few studies to evaluate whether the rate-adaptive pacing of permanent pacemaker will improve the quality of life in people with bradycardia. The aim of this study is to compare turn-on with turn-off this function (DDDR vs DDD) whether rate-adaptive pacing will improve quality of life in patients with permanent pacemakers.

Inclusion Criteria:

• sick sinus syndrome for permanent dual-chamber pacing
• pacemakers are implanted for ≥30 days with no complications.

Exclusion Criteria:

• (1) patient or legal representative could not provide written informed consent
• (2) unwillingness or inability to return for follow-up visits or reason to believe that adherence to follow-up visits wound be irregular,
• (3) current or scheduled enrollment in other, conflicting studies,
• (4) concomitant disease or other medical condition likely to result in death within 6 months, and