Several major organizations have developed electrode identification systems, primarily for cardiac monitoring (ECG) and brain wave recording (EEG). The two most widely used ECG systems come from the American Heart Association (AHA) and the International Electrotechnical Commission (IEC), while the International Federation of Clinical Neurophysiology (IFCN) established the standard system for EEG electrodes. Additional standards bodies, including the Association for the Advancement of Medical Instrumentation (AAMI) and the American National Standards Institute (ANSI), have contributed labeling and performance requirements that shape how electrodes are identified in clinical use.
ECG Electrodes: AHA vs. IEC Color Coding
The two dominant systems for identifying ECG electrodes use entirely different color schemes, which can cause confusion when clinicians move between regions or equipment. The AHA/AAMI system is standard in North America, while the IEC system is used across Europe and much of the rest of the world. Both systems label the same electrode positions on the body but assign different colors and naming conventions to each one.
For a basic 3- or 5-lead ECG, the AHA system labels the limb electrodes as RA (Right Arm, white), LA (Left Arm, black), RL (Right Leg, green), LL (Left Leg, red), and V (Chest, brown). The IEC system uses single-letter labels instead: R (Right, red), L (Left, yellow), N (Neutral, black), F (Foot, green), and C (Chest, white). Notice that the same color can mean completely different things depending on the system. Red is the left leg electrode under AHA but the right arm electrode under IEC. White is the right arm in AHA and the chest in IEC.
For a full 12-lead ECG (which uses 10 physical electrodes), both systems share the same color assignments for the six chest electrodes: red, yellow, green, blue or brown, orange or black, and violet or purple, numbered V1 through V6 (AHA) or C1 through C6 (IEC). The limb leads keep the same divergent color codes as the basic setup. This partial overlap, where the chest leads mostly align but the limb leads do not, makes it especially important for healthcare workers to know which system their equipment follows.
EEG Electrodes: The 10-20 System
For brain wave monitoring, the IFCN developed what’s known as the International 10-20 System, which has been the global standard for scalp electrode placement since the 1950s. Rather than using color codes, this system identifies each electrode by a letter and number combination. The letter indicates the brain region: F for frontal, T for temporal, C for central, P for parietal, and O for occipital. The number indicates laterality, with odd numbers on the left side of the head, even numbers on the right, and “z” (for zero) along the midline.
The “10-20” name refers to how electrode positions are calculated. Distances between anatomical landmarks on the skull are measured, and electrodes are placed at intervals of 10% or 20% of those distances. This proportional approach means the system scales to any head size, from neonates to adults. For newborns, a modified version of the montage focuses more heavily on the central and temporal regions, since most neonatal brain activity occurs there.
Extended versions of this system, sometimes called the 10-10 or 10-5 systems, add more electrode positions between the original ones for higher-density recordings used in research or surgical planning. These follow the same naming logic but introduce additional letter-number combinations to cover the extra sites.
Standards for Electrode Labeling and Safety
Beyond the identification systems used in clinical practice, regulatory bodies have established formal standards that govern how electrodes are labeled, packaged, and tested. ANSI and AAMI jointly publish the EC12 standard, which sets minimum labeling, safety, and performance requirements for disposable ECG electrodes used in diagnostic and monitoring applications. The U.S. Food and Drug Administration recognizes this as a consensus standard, meaning manufacturers who comply with it can streamline their regulatory submissions. The FDA’s recognition is partial, excluding certain provisions around pre-attached leadwire safety, but the core labeling and performance criteria apply.
Implanted Electrode Identification
For implanted devices like deep brain stimulation (DBS) leads, identification works differently. Rather than external color codes, each electrode is a small metal contact on a thin lead wire inserted into the brain. These contacts are numbered sequentially along the lead, and clinicians test each one individually during a process called monopolar screening to find the most effective stimulation point. Conventional DBS leads have four contacts, but newer directional leads split each contact into multiple independent segments, significantly increasing the number of possible stimulation configurations.
Localizing these contacts after surgery relies on specialized software tools that merge preoperative MRI scans with postoperative CT images. One widely used open-source toolbox called Lead-DBS maps the electrode positions into a standardized brain atlas, allowing clinicians and researchers to pinpoint exactly which brain structures each contact sits near. This kind of identification is less about naming conventions and more about precise spatial mapping within an individual patient’s anatomy.