Ambulatory ECGs are often extremely useful, but what happens if your symptoms occur only periodically? If the symptoms are severe enough for a patient, it is possible to implant a small recorder under the skin, which can monitor the heart for the duration of its batteries (up to 3 years). This can automatically record heart rhythm problems, or the patient can ‘auto-activate’ the device when they have their symptoms. This can then be downloaded wirelessly to determine if there was a heart rhythm problem at the time. The latest devices are only an inch long and a few millimetres thick, and are injected under the skin under local anaesthetic. The whole procedure lasts only a few minutes. They can then be removed at a later date once the diagnosis has been made and treated.