On 21st May, Google Doodle celebrates the birth of Willem Einthoven, the Nobel Prize-winning Dutch physiologist who pioneered electrocardiography—a quick, painless, and effective method of studying the rhythms of the heart and diagnosing cardiovascular disease.

Born on the island of Java (now Indonesia) on this day in 1860, Einthoven grew up aspiring to follow in the footsteps of his father who had been both a doctor and military medical officer. By 1886 he had become a professor of physiology at the University of Leiden, focusing on optics, respiration, and the heart.

Willem Einthoven

In 1889, Einthoven attended the First International Congress of Physiologists, where he watched a demonstration of a device known as the “Lippmann capillary electrometer” recording the electrical activity of the human heart. After analyzing the results, Einthoven recognized the need for a more accurate device, and began work on his string galvanometer, based on the technology used to amplify signals along underwater cables.

Balancing a fine string of quartz coated in silver between the two poles of a magnet, Einthoven’s invention precisely measured variations in electrical current. In 1901 he announced the first version of the string galvanometer, and soon published the world’s first electrocardiogram or ECG, a printed record of a human heartbeat. Einthoven studied the ECG patterns, identifying five “deflections” of normal heart function, learning how to interpret deviations that signal circulatory problems and heart disease.

Einthoven’s groundbreaking research won him the 1924 Nobel Prize for Physiology or Medicine. Today, ECG machines are still used in hospitals all over the world, and while the technology has evolved greatly, they still work according to the same basic principles and techniques developed by Einthoven, who is now remembered as the father of modern electrocardiography.

Einthoven’s Work

Before Einthoven’s time, it was known that the beating of the heart produced electrical currents, but the instruments of the time could not accurately measure this phenomenon without placing electrodes directly on the heart. Beginning in 1901, Einthoven completed a series of prototypes of a string galvanometer.

This device used a very thin filament of conductive wire passing between very strong electromagnets. When a current passed through the filament, the magnetic field created by the current would cause the string to move. A light shining on the string would cast a shadow on a moving roll of photographic paper, thus forming a continuous curve showing the movement of the string.

The original machine required water cooling for the powerful electromagnets, required five people to operate it and weighed some 270 kilograms. This device increased the sensitivity of the standard galvanometer so that the electrical activity of the heart could be measured despite the insulation of flesh and bones.

Although later technological advances brought about better and more portable EKG devices, much of the terminology used in describing an EKG originated with Einthoven. His assignment of the letters P, Q, R, S and T to the various deflections are still used.

The term Einthoven’s triangle is named after him. It refers to the imaginary inverted equilateral triangle centered on the chest and the points being the standard leads on the arms and leg.