No. Sleeping on the same side as your ICD will not damage the device or dislodge the leads once the implant has healed. The device is sealed in a durable titanium case designed to withstand normal physical activity, including sleeping positions.
In the first few weeks after implantation, you may find that sleeping on the implant side is uncomfortable as the area is still healing and tender. During this period, sleeping on the opposite side or on your back is generally more comfortable and avoids pressure on the wound. Once the incision has healed, you can sleep in whatever position feels comfortable.
If you experience ongoing discomfort or pain when lying on the device after the wound has fully healed, mention it at your next clinic appointment. Persistent discomfort can occasionally indicate that the device position needs to be reviewed.