What device is implanted under the skin and connected directly to the heart to treat life-threatening arrhythmias, with energy output lower than an external AED?

• A. External defibrillator
• B. Pacemaker
• C. Automatic implanted cardiac defibrillator (AICD)
• D. Cardiac resynchronization therapy device

Answer: (C)

An automatic implanted defibrillator is a device placed under the skin with leads that reach the heart. It continuously monitors the heart rhythm and can deliver a controlled electrical shock to restore a normal rhythm when it detects life-threatening arrhythmias like ventricular tachycardia or ventricular fibrillation. Because the device is inside the body, the energy it uses for defibrillation is lower than what an external AED would deliver, and it can act automatically without someone presenting an external shock. Some AICDs can also provide pacing if the heart rate drops. Other options either refer to devices that are not implanted (external defibrillator) or focus on pacing for slow heart rates (pacemaker) or on heart-failure resynchronization, which isn’t the same thing as treating malignant arrhythmias.