What does an electrocardiogram or ECG record?

An electrocardiogram (ECG) records the electrical activity of the heart. This diagnostic tool measures the electrical impulses that trigger heartbeats, reflecting how the heart is functioning in real time. The ECG provides vital information about the rhythm, rate, and overall electrical activity of the heart muscle. Medical professionals use this data to diagnose various conditions, such as arrhythmias, heart attacks, and other cardiac abnormalities.

In contrast, the other options pertain to different physiological functions or systems. The electrical activity of the brain is measured by an electroencephalogram (EEG), which is distinct from an ECG. Blood flow, whether through the brain or elsewhere in the body, is assessed using other techniques like Doppler ultrasound or angiography, rather than an ECG. Sounds produced by the heart, such as heartbeats, are typically evaluated through auscultation with a stethoscope rather than through an ECG. Thus, understanding that an ECG exclusively monitors cardiac electrical activity is crucial for recognizing its role in medical diagnostics.