Einthoven directed much of his research to the development and perfection of recording instruments. His most famous work was in connexion with his string galvanometer, a perfection of the instrument invented by J. S. C. Schweigger, of Halle.

In 1924 Einthoven was awarded the Nobel Prize in Physiology or Medicine for "for his discovery of the mechanism of the electrocardiogram."  See also No. 842.

First description of Einthoven's string galvanometer that recorded electrical changes occurring in the human heart. Includes the first illustration of an EKG (ECG) recording. Modern electrocardiography became a reality through his work, and the string galvanometer finally displaced the capillary electrometer in the measurement of the electric current produced by the contracting heart. See also No. 840.

This paper includes the first published ECG tracing of atrial fibrillation. See W. Bruce Fye, "Tracing atrial fibrillation - 100 years," New Eng. J. Med., 355 (2006) 1412.

Phonocardiography.