aVL

aVL stands for augmented voltage left arm and refers to one of the three augmented limb leads used in the standard electrocardiogram (ECG). It is derived from the left arm electrode as the positive input, with the reference terminal formed by averaging the potentials of the other two limb electrodes (the Wilson central terminal). The term “augmented” indicates that the signal from the single positive electrode is amplified to improve visibility.

In the frontal plane, aVL views the heart from the left shoulder, producing information mainly about the high lateral wall of the left ventricle. Its axis is approximately -30 degrees, making it sensitive to electrical activity directed toward the left arm and less so to other regions. Clinically, aVL is interpreted in conjunction with the other limb leads (I, II, III, aVR, aVF) and the chest leads to localize abnormalities.

Normal values typically show a small to moderate R wave in aVL, with the Q wave depending on patient-specific anatomy. The lead is particularly useful for assessing lateral wall involvement. Elevation of the ST segment in aVL can indicate lateral myocardial ischemia or infarction, especially when seen with concurrent ST elevation in leads I and V5–V6. Conversely, ST depression in aVL may accompany ischemia elsewhere or reflect reciprocal changes to ST elevation in other leads. Pathologic Q waves in aVL may suggest a prior lateral infarct.

As with all ECG leads, accurate interpretation of aVL depends on proper electrode placement and correlation with clinical context and findings in other leads.