What type of device is used to restore a normal heart rhythm by delivering an electric shock?

The device responsible for restoring a normal heart rhythm by delivering an electric shock is the defibrillator. This device is specifically designed to treat life-threatening arrhythmias, such as ventricular fibrillation or pulseless ventricular tachycardia, where the heart beats erratically and is unable to pump blood effectively.

By delivering a controlled electric shock, a defibrillator can reset the heart's electrical system and allow it to resume a normal rhythm. It is often used in emergency situations, particularly in hospital settings or during cardiopulmonary resuscitation (CPR), to prevent cardiac arrest from leading to irreversible damage.

In contrast, a pacemaker is a device that helps to regulate the heart rate through electrical impulses and is not used for immediate emergency intervention like defibrillation. An ECG monitor, or electrocardiogram, is utilized to assess the heart's electrical activity but does not deliver shocks or treat arrhythmias. A cardioversion machine, while similar to a defibrillator in that it can restore rhythm, is typically used in a controlled setting for planned procedures rather than immediate life-threatening situations. Therefore, the primary and most effective device for delivering an electric shock to restore normal heart rhythm in emergencies remains the defibrillator.