Cardiac axis
Also calledQRS axis · mean electrical axis · mean QRS axis · electrical axis · frontal plane axis · mean frontal plane axis
Definition
The mean direction of ventricular depolarization in the frontal plane, expressed in degrees on the hexaxial reference system. It is estimated from the QRS deflections in the limb leads: most simply from leads I and aVF (both positive means an axis between 0 and +90 degrees), or by finding the limb lead with the most equiphasic QRS, since the axis lies perpendicular to it; a second lead then shows which way along that perpendicular it points, because leads within 90 degrees of the axis record a positive QRS and leads facing away from it record a negative one. The normal adult range is -30 degrees to +90 degrees.
Sources
- Surawicz B, Childers R, Deal BJ, Gettes LS. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part III: intraventricular conduction disturbances. Circulation. 2009;119(10):e235-e240. doi.org/10.1161/CIRCULATIONAHA.108.191095
- Gao Q, Dai Z, Hu Y, et al. A new method to determine the QRS axis: QRS axis determination. Clin Cardiol. 2020;43(12):1534-1538. doi.org/10.1002/clc.23477
Last reviewed 2 October 2026. Every definition in the EKG Dictionary cites the guideline, consensus statement or original paper it comes from.