Einthoven, Willem (1860-1927) was a Dutch physiologist who founded electrocardiography. An electrocardiograph is an instrument used to diagnose heart disorders. Each time the heart beats, it produces electrical currents. These currents are responsible for the rate and pattern of contraction of the heart. An electrocardiograph picks up and records these currents.

Einthoven was born on May 21, 1860, in Semarang, Java (in what was then the Dutch East Indies and is now Indonesia). In 1866, Einthoven's father died, and four years later, his mother moved the family to Utrecht, the Netherlands. After graduating from high school, Einthoven enrolled in medical school at the University of Utrecht. He received his Ph.D. degree in medicine in 1885. He then became professor of physiology at the University of Leiden. He remained at the university for the next 42 years.

About 1903, Einthoven invented a new instrument called the string galvanometer and with it developed an improved method for measuring the electrical changes that take place in the body upon the contraction of the heart. While using his string galvanometer, Einthoven was able to detect and identify a number of different kinds of electrical waves associated with a beating heart. Eventually, he demonstrated that some of these waves result from contractions and electrical changes in the atria of the heart, and others from contractions and electrical changes in the ventricles. He published a description of his string galvanometer in 1909. In this work, he outlined a method for using the instrument to record heart action using combinations of electrode placement. The string galvanometer made possible the first valid and reliable electrocardiogram, thus giving doctors one of the most valuable tools for the study of heart disease. Einthoven received the 1924 Nobel Prize in physiology or medicine for “his discovery of the mechanism of the electrocardiogram.” After winning the award, he continued to work to perfect his string galvanometer throughout the rest of his career. Einthoven was elected to foreign membership in the British Society in 1926. Einthoven died on Sept. 28. 1927, in Leiden.