Which device measures the electrical activity of the heart?

The device that measures the electrical activity of the heart is the ECG machine. An electrocardiogram (ECG) records the electrical signals that trigger each heartbeat, providing important information regarding the heart's rhythm and function. By placing electrodes on the skin at specific locations, the ECG machine can detect and display the electrical signals in a graphical form, helping healthcare professionals diagnose various cardiac conditions, monitor heart function, and assess responses to treatment.

In contrast, a pulse oximeter measures the oxygen saturation level in the blood and does not provide information about electrical activity. A ventilator assists patients with breathing but does not monitor heart activity either. Defibrillators, while essential in treating certain heart conditions, particularly those that involve life-threatening arrhythmias, are used to deliver an electrical shock to restore a normal rhythm rather than measure any electrical activity.