Which device delivers shocks to terminate life-threatening arrhythmias?

• A. Implantable cardioverter-defibrillator
• B. Cardiac resynchronization therapy
• C. Left ventricular assist device
• D. Artificial heart

Answer: (A)

An implantable cardioverter-defibrillator is designed to detect dangerous ventricular rhythms and deliver a high-energy shock to reset the heart's electrical activity, restoring a normal rhythm. This is the key way it terminates life-threatening arrhythmias like ventricular tachycardia and ventricular fibrillation, thereby preventing sudden cardiac death. Many ICDs can also use anti-tachycardia pacing to interrupt faster heart rhythms without a shock, but their central purpose is rapid termination of malignant arrhythmias.

Cardiac resynchronization therapy coordinates the timing of contractions between the two ventricles to improve pumping efficiency in certain heart failure patients, not to shock arrhythmias. A left ventricular assist device provides mechanical support to a failing pump, and an artificial heart replaces the heart function entirely—neither is primarily used to terminate malignant arrhythmias with shocks.