Which device is used for restoring heart rhythm through electrical shock?

The defibrillator is specifically designed to restore normal heart rhythm during critical situations, such as cardiac arrest or certain arrhythmias. It delivers an electrical shock to the heart, which can reset the electrical activity and allow for a normal heartbeat to resume.

In contrast, a pacemaker is a device used to regulate the heartbeat of patients with bradycardia (slow heart rate) by sending electrical impulses to the heart but does not administer shocks for the purpose of restoring rhythm. A cardiac monitor is used to observe and display the heart's electrical activity but lacks the capability to treat arrhythmias directly. A stethoscope, while important for listening to heart sounds, does not provide any electrical intervention at all. Therefore, the defibrillator is the only device among the options that directly restores heart rhythm through the application of electrical shock.