An implantable cardioverter-defibrillator (ICD) is a small device placed inside the body to monitor and treat irregular heartbeats, known as arrhythmias. It continuously checks the heart's rhythm and can deliver electrical shocks to restore a normal heartbeat if it detects a dangerous condition. This device is especially important for people at risk of sudden cardiac arrest. The ICD is usually implanted under the skin near the collarbone during a minor surgical procedure. It connects to the heart with thin wires called leads. Patients with an ICD can lead active lives, but they should follow their doctor's advice on activities and regular check-ups to ensure the device works properly.