This will depend on which type of device is being implanted and which condition the device is used to address.

• A cardiac resynchronization therapy (CRT) device will have three leads.
• An implantable cardioverter defibrillator (ICD) will have one or two leads.
• A pacemaker will have one or two leads.
• Leadless pacing and insertable cardiac monitors (ICMs) don't have any leads.