An implantable loop recorder (ILR) is a small device—about the size of a pack of chewing gum—inserted under your skin to record your heart’s electrical activity. The device is implanted on the left side of your chest just below the nipple line. Your doctor will numb the area with local anesthesia and create a small pocket under the skin to hold the device. You can go home the same day, but you may experience bruising and pain in the implant area for a few days. Once implanted, the ILR continuously monitors your heart’s activity. When it detects an arrhythmia, it freezes that portion of the memory to review later. It can be activated when your heartbeat becomes too fast or too slow, or if you trigger it manually to start recording.