What are devices made of a conductive material to pick up the electrical activity of the heart; sensors?

• A. Electrodes
• B. Precordial leads
• C. Holter monitor
• D. Bundle of His

Answer: (A)

Electrodes are the sensors that pick up the heart's electrical activity. They’re made of conductive material (often silver/silver chloride) and are placed on the skin, usually with a conductive gel to improve contact. As the heart muscle depolarizes and repolarizes, tiny electrical voltages appear on the body surface; electrodes detect these voltages and feed them to the ECG machine to create a tracing of the heart’s rhythm and conduction. Some electrodes are placed in specific chest positions (precordial leads) to view the heart from different angles, but they are all types of conductive sensing pads. In contrast, a Holter monitor is a portable device that records ECG over time, and the Bundle of His is a part of the heart’s internal conduction pathway, not a sensor.