Which statement best describes an implantable cardioverter-defibrillator (ICD)?

• A. Prevents sudden cardiac death
• B. Paces the ventricles
• C. Replaces heart function
• D. Detects abnormal rhythms and delivers shocks

Answer: (D)

An implantable cardioverter-defibrillator is designed to monitor the heart’s rhythm and intervene when a dangerous fast rhythm occurs. It continuously senses the electrical activity and, if it detects ventricular tachycardia or ventricular fibrillation, delivers a high-energy shock to reset the heart to a normal rhythm. Some ICDs can also provide pacing support if the heart rate drops, but the defining feature is detecting malignant rhythms and delivering shocks to terminate them, which helps prevent sudden cardiac death. It does not replace heart function, and it is not simply a pacemaker, though some devices combine pacing and defibrillation capabilities.