Which diagnostic tool records the electrical activity of the heart over time?

Which diagnostic tool records the electrical activity of the heart over time?

• A. Echocardiogram
• B. Electrocardiogram (EKG)
• C. MRI
• D. X-ray

Answer: (B)

The main idea is recognizing a tool that captures the heart’s electrical signals as they occur over time. An electrocardiogram records this activity by using skin electrodes to pick up the tiny electrical voltages generated with each heartbeat and graph them as a trace over time. This continuous recording shows the timing and shape of the heart’s electrical events—the P wave, the QRS complex, and the T wave—so clinicians can detect irregular rhythms, blocks in conduction, or ischemic changes. It’s specifically about electrical activity, not the heart’s structure or anatomy. In contrast, an echocardiogram uses ultrasound to visualize heart chambers and valves, MRI uses magnetic fields to image detailed anatomy (and can assess function), and X-ray mainly shows structure like heart size and lungs. None measure the heart’s electrical activity over time the way an electrocardiogram does.

The main idea is recognizing a tool that captures the heart’s electrical signals as they occur over time. An electrocardiogram records this activity by using skin electrodes to pick up the tiny electrical voltages generated with each heartbeat and graph them as a trace over time. This continuous recording shows the timing and shape of the heart’s electrical events—the P wave, the QRS complex, and the T wave—so clinicians can detect irregular rhythms, blocks in conduction, or ischemic changes. It’s specifically about electrical activity, not the heart’s structure or anatomy.

In contrast, an echocardiogram uses ultrasound to visualize heart chambers and valves, MRI uses magnetic fields to image detailed anatomy (and can assess function), and X-ray mainly shows structure like heart size and lungs. None measure the heart’s electrical activity over time the way an electrocardiogram does.