Einthoven triangle
Also calledEinthoven's triangle · Einthoven triangle of leads · Einthoven's triangle of leads
Definition
A model that places the right-arm, left-arm and left-leg electrodes at the corners of an equilateral triangle with the heart at its center. The three standard limb leads (I, II and III) form its sides, and the voltage in each is proportional to the projection of the heart's electrical vector on that side. Einthoven's law states that lead II equals lead I plus lead III at every instant. The law follows from Kirchhoff's law and does not depend on the exact geometry of the triangle, so the three limb leads hold only two independent signals. The model underlies the use of the limb leads to estimate the frontal-plane (QRS) axis.
Sources
- Kligfield P, Gettes LS, Bailey JJ, et al. Recommendations for the standardization and interpretation of the electrocardiogram: part I: the electrocardiogram and its technology. Circulation. 2007;115(10):1306-1324. doi.org/10.1161/CIRCULATIONAHA.106.180200
- Batchvarov VN, Malik M, Camm AJ. Incorrect electrode cable connection during electrocardiographic recording. Europace. 2007;9(11):1081-1090. doi.org/10.1093/europace/eum198
- Malmivuo J, Plonsey R. Bioelectromagnetism: principles and applications of bioelectric and biomagnetic fields. New York: Oxford University Press; 1995. Chapter 15, 12-lead ECG system. doi.org/10.1093/acprof:oso/9780195058239.001.0001
Last reviewed 2 October 2026. Every definition in the EKG Dictionary cites the guideline, consensus statement or original paper it comes from.