An Implantable Cardioverter Defibrillator (ICD) is a small device placed inside the body to prevent sudden cardiac death. It continuously monitors heart rhythm. If a dangerous rhythm is detected, it delivers an electric shock. It treats life-threatening arrhythmias. It is recommended for high-risk cardiac patients. The device works automatically. It is implanted under the skin near the chest. It connects to the heart through leads. It improves survival in severe heart disease. It provides long-term cardiac protection.