An implantable heart rhythm monitor or implantable loop recorder is a cardiac device which is placed under the skin of the chest. This device continuously monitors the heart rhythm for up to three years and records the heart rhythm when any abnormalities are detected. An implantable loop recorder is implanted when an abnormal heart rhythm (arrhythmia) is suspected and the usual tests (i.e. electrocardiogram, 24-hours ECG monitoring) have failed to detect it. However, it cannot deliver any therapy. It is just used for making the diagnosis.