Extremitätenableitungen

Extremitätenableitungen, commonly referred to as limb leads, are a set of ECG leads used to record the heart’s electrical activity from the limbs. They provide information about the heart’s activity in the frontal plane and are essential for constructing the standard 12-lead electrocardiogram, alongside the chest (precordial) leads V1–V6. The extremities leads include three bipolar leads (I, II, III) and three augmented leads (aVR, aVL, aVF).

Placement and derivation: Electrodes are placed on the wrists or forearms and on the ankles or lower legs, with a ground or neutral electrode on a separate limb. Lead I measures the potential difference between the left arm and right arm, Lead II between the left leg and right arm, and Lead III between the left leg and left arm. The augmented leads are derived from the same limb potentials but referenced to the Wilson central terminal, an average of the limb signals, resulting in aVR, aVL and aVF. Together, these leads offer six frontal-plane views of cardiac electricity.

Purpose and interpretation: The extremitätenableitungen help assess the cardiac axis, rhythm disturbances, conduction abnormalities, ischemia or infarction patterns, and chamber enlargement when interpreted in conjunction with the precordial leads. They are influenced by electrode placement, patient movement, and impedance, so proper skin preparation and consistent calibration are important. Standard ECG calibration typically uses a paper speed of 25 mm/s and a sensitivity of 10 mm/mV.

Clinical use: In routine ECGs, the limb leads contribute to arrhythmia detection, axis assessment, and broad ischemic or structural insights, forming an integral part of the 12-lead ECG and guiding further diagnostic steps.