Which of the following tests measures the electrical activity of the heart?

The electrocardiogram (ECG) is a test that specifically measures the electrical activity of the heart. It does this by placing electrodes on the skin that detect the electrical impulses produced by heart cells as they contract and pump blood. The resulting tracing provides valuable information about the heart’s rhythm, the size and position of the heart chambers, and any potential abnormalities in the heart’s electrical system.

In contrast, Doppler ultrasound primarily assesses blood flow and can help visualize blood movement through blood vessels by using sound waves. Echocardiography utilizes ultrasound to create images of the heart, allowing for the assessment of heart structure and function, but it does not focus on electrical activity. Electrophysiological studies (EPS) are specialized tests that investigate the electrical system of the heart to assess arrhythmias but are more invasive and not the primary method for measuring routine electrical activity.

Understanding the unique roles of these tests helps clarify why the electrocardiogram is the most direct measure of the heart's electrical activity among the listed options.