Left axis deviation (LAD)
Also calledLAD · left axis deviation · left QRS axis deviation
Definition
A mean frontal-plane QRS axis of -30 degrees or beyond (that is, -30 to -90 degrees). It is recognized when the QRS is positive in lead I and net negative in aVF, with lead II turning net negative being the key marker that the axis has passed -30 degrees. Marked left axis deviation (-45 to -90 degrees) is often associated with left anterior fascicular block, and left axis deviation may also accompany left ventricular hypertrophy.
Clinical noteLead II going net negative, not merely aVF, is what confirms true LAD rather than a normal but leftward axis.
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
- Meek S, Morris F. ABC of clinical electrocardiography. Introduction. I: Leads, rate, rhythm, and cardiac axis. BMJ. 2002;324(7334):415-418. doi.org/10.1136/bmj.324.7334.415
- Hancock EW, Deal BJ, Mirvis DM, et al. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part V: electrocardiogram changes associated with cardiac chamber hypertrophy. Circulation. 2009;119(10):e251-e261. doi.org/10.1161/CIRCULATIONAHA.108.191097
Last reviewed 2 October 2026. Every definition in the EKG Dictionary cites the guideline, consensus statement or original paper it comes from.