Which diagnostic test records the electrical activity of the heart?

Electrocardiography is the procedure that records the electrical activity of the heart. This test is crucial in diagnosing various cardiac conditions, as it captures the timing and strength of electrical signals as they travel through the heart, ultimately facilitating the assessment of its rhythm and functioning.

In contrast, a CT scan is primarily used for imaging structures within the body, providing cross-sectional views of organs, and is not focused on electrical activity. Ultrasound uses sound waves to produce images of organs and tissues, which can include heart structures but does not provide a direct measure of electrical activity. A venogram is a specific type of imaging test used to visualize veins after injecting a contrast dye, primarily focused on venous circulation, and does not evaluate heart electrical activity at all.

Thus, electrocardiography stands out as the correct choice because it is specifically designed to measure and visualize the heart's electrical patterns, making it essential in medical evaluations of heart health.