Final answer:
An electrocardiogram (ECG or EKG) is used to record the heart's electrical activity using electrodes on the body, and an electrocardiograph is the machine that processes these readings into a trace that can be analyzed. The number of leads used can vary, providing different levels of detail in heart monitoring, with the Holter monitor being an example of a portable ECG device.
Step-by-step explanation:
The instrument used for recording the electrical activity of the heart by careful placement of electrodes on the surface of the body is called an electrocardiogram (ECG), also known as EKG. An ECG traces the heart's complex electrical signal, providing a detailed picture of heart function, detecting both normal and abnormal heart activity. This diagnostic tool is essential in clinical settings.
The standard electrocardiograph, which is the machine that generates an ECG, may use 3, 5, or 12 leads, with the 12-lead electrocardiograph providing the most comprehensive information about heart activity. Each "lead" refers to the voltage difference between two electrodes, giving insight into different areas and functions of the heart. For continuous and ambulatory monitoring, a person may wear a portable device known as a Holter monitor, which records heart electrical activity typically over a 24-hour period.