Cardiac monitor implant. X-ray of a section through the chest of a 53-year-old female patient with an implantable loop recorder (ILR, insertable cardiac monitor, upper right). This implant is roughly the size of a USB key. It is implanted under the skin (subcutaneous) and used to record the heart's electrical activity in order to help diagnose heart issues in patients with unexplained recurrent episodes of palpitations or loss of consciousness (fainting, syncope) and for long-term monitoring in patients at risk of atrial fibrillation.