How many electrodes are used as part of a 12 lead ECG?

In a standard 12-lead ECG, 10 electrodes are used. This configuration includes 6 limb electrodes and 4 precordial electrodes. The limb electrodes are placed on the wrists and ankles, which contribute to the monitoring of the heart's electrical activity from different angles. The precordial electrodes, placed on the chest in specific locations, provide additional views of the heart’s electrical activity along the horizontal plane.

The term "12 lead" refers to the 12 different views or leads that are obtained from the configuration of these electrodes. Each lead represents a different angle of the heart's electrical activity, which is crucial for diagnosing various cardiac conditions.

While it might seem intuitive to connect the number of electrodes directly to the number of leads, the important distinction is that the 10 electrodes produce 12 leads due to the way the electrical signals are derived from the combinations of the electrodes.