Although trained in medicine, Willem Einthoven was always very much interested in physics, and his greatest contributions to science involve the application of physical principles to the development of new instruments and techniques in physiological studies. One such instrument, the string galvanometer, made possible the first valid and reliable electrocardiogram, thereby providing physicians with one of their most valuable tools for the study of cardiovascular disorders. For his invention of the string galvanometer, Einthoven was awarded the Nobel Prize for Physiology or Medicine in 1924.
Einthoven was born on May 21, 1860, in Semarang, Java, in what was then the Dutch East Indies and is now Indonesia. His father, Jacob Einthoven, was a physician in Semarang. When Jacob died in 1866, his wife, Louise M. M. C. de Vogel, returned to her native Holland with her six children, Willem included. The family settled in Utrecht, where young Willem attended local grammar and high schools. Upon graduation from high school in 1879, he enrolled in the medical program at the University of Utrecht. Six years later, Einthoven received his Ph.D. in medicine, having written his doctoral thesis on the use of color differentiation techniques in spectroscopic analysis. He was immediately offered an appointment as professor of physiology at the University of Leiden, a job he actually began after passing his final state medical examinations on February 24, 1886. Einthoven would remain at his post at the University of Leiden for the next forty-two years until his death in 1927. Also in 1886, Einthoven was married to Frédérique Jeanne Louise de Vogel, a cousin, with whom he would father four children: a son and three daughters. Perhaps the most significant feature of Einthoven's career is the way he made use of his interest in--and knowledge of--physics in his study of physiological problems. The research for which he is best known involved the detection of the association between electrical currents and the beating human heart. Physiologists in the 1880s knew that each contraction of the heart muscle is accompanied by electrical changes in the body, but no precise quantitative data existed for this phenomenon. At that time, the only equipment available to measure electrical charges in the body was not sensitive enough to detect the minute changes in potential difference--the amount of energy released--associated with a heartbeat. The most commonly used device, a capillary electrometer, made use of the rise and fall of a thin column of mercury in a glass tube. Unfortunately, the measurement process of such an instrument took place too slowly to determine actual changes in potential difference resulting from muscular contractions.
Around 1903, Einthoven invented an improved method for measuring such changes: the string galvanometer. Einthoven's new instrument consisted of a very thin quartz wire suspended in a magnetic field. An electric current, even one as small as those associated with muscular contraction, caused a deflection of the wire. By focusing a moving picture camera on the wire, Einthoven could obtain a visual record of the movement of the wire as it was displaced by electrical currents from the heart.
As a result of his research, Einthoven was able to detect and identify a number of different kinds of electrical waves associated with a beating heart, waves that he originally labeled as P, Q, R, S, and T waves. He was eventually able to show that some of these waves result from contractions and electrical changes in the atria and others from contractions and electrical changes in the ventricles of the heart.
Einthoven published a complete description of his string galvanometer in 1909 as Die Konstruktion des Sitengalvanometers. In this work, he outlined a method for using the galvanometer to record heart action using three combinations of electrode placement: right hand to left hand, right hand to left foot, and left hand to left foot. Such arrangements of the electrodes could be used, he showed, to locate the position of the heart and to detect any abnormalities in its function.
In Nobel Prize Winners, Einthoven's biographer points out that the invention of the string electrode "revolutionized the study of heart disease." For his accomplishment, Einthoven was awarded the Nobel Prize for Physiology or Medicine in 1924. Interestingly enough, the basic principles of electrocardiography, while first developed by Einthoven, were also derived independently a short time later by the English physicians Sir Thomas Lewis, Sir William Ogler, and James Herrick.
Einthoven continued to refine, develop, and extend the applications of his string galvanometer throughout the rest of his career. For example, later in his life he modified the device so that it could be used to receive long-distance radio telegraph signals and to measure changes in electric potential in nerves. He was also very popular as a lecturer and made a number of trips to Europe and the United States to talk about his work. Among the many honors Einthoven received was his election as an honorary member of the Physiological Society in 1924, and his induction into England's prestigious Royal Society two years later in 1926.
Einthoven died in Leiden, Netherlands, on September 28, 1927. His obituary in the periodical Nature spoke of the "grace, beauty, and simplicity of his character." Although he left few students or disciples behind, Einthoven's impact on the development of electrocardiography was profound.
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