ICD leads are thin, flexible wires that carry electrical signals between the device and the heart. During the implant procedure, the surgeon threads one end of each lead through a vein (usually the subclavian vein, near the collarbone) and guides it into the appropriate chamber of the heart. The tip of the lead is then anchored to the heart wall, either by a small corkscrew-like helix that screws into the tissue, or by tiny tines that grip the tissue passively.
The other end of each lead is connected to the ICD generator, which sits in a small pocket created under the skin near the collarbone. Most ICDs have one, two, or three leads depending on the type of device and what it needs to do.
Over the weeks after implant, tissue grows around the lead tip and anchors it more firmly. This is why activity restrictions in the first few weeks are important: moving the arm on the implant side too vigorously before the leads have settled can dislodge them. Your device clinic will tell you specifically what to avoid and for how long.
You can read more about the implant process and what to expect on our ICD information pages.