What do the generator and leads of a pacemaker do?

A pacemaker has two parts:

• A pulse generator: the battery and circuits that create low-energy electrical pulses. The generator is a little larger than a quarter and less than 1/4 inch thick.

• Leads: thin insulated wires that deliver the electrical pulses to your heart. A single-chamber pacemaker uses one lead to send pulses to the heart’s upper or lower chamber. A dual-chamber pacemaker uses two leads: one in the upper chamber and one in the lower chamber. A biventricular pacemaker has three leads. They are placed in the right upper chamber, right lower chamber, and left lower chamber.