The main difference is the number of leads threaded down into the heart from the implanted device.

• For single-chamber pacing, either the right atrium (upper chamber) or the right ventricle (lower chamber) is paced. Only one pacing lead is used.
• For dual-chamber pacing, both the right atrium and right ventricle are paced. This requires two pacing leads. One lead is placed in the right atrium, and the other lead is placed in the right ventricle.

Doctors will take condition, disease state, and other factors into consideration to choose which type of device is most appropriate for each case.