A Dutch physician and physiologist, Willem Einthoven, developed the first Electro Cardiograph (ECG) Machine. It was a simple string – galvanometer – capable of measuring small changes in electrical potential as the heart contracted and relaxed.
Electrodes were attached to the limbs of the patient. As the string deflected, it obstructed a beam of light and the photographic paper recorded the shadow. As the heart contracts and relaxes repeatedly, Einthoven could record the wave pattern of these impulses. The ECG machine of today looks very different but works on the same principle. Einthoven was awarded the Nobel Prize in 1924 for this discovery.
Willem Einthoven was born on May 21, 1860, in Semarang on the island of Java, in the former Dutch East Indies (now Indonesia). His father was Jacob Einthoven, born and educated in Groningen, The Netherlands, an army medical offcer in the Indies, who later became parish doctor in Semarang. His mother was Louise M.M.C. de Vogel, daughter of the then Director of Finance in the Indies. Willem was the eldest son, and the third child in a family of three daughters and three sons.
At the age of ten, Einthoven lost his father, and his mother decided to return with her six children to Holland, where the family settled in Utrecht.
After having passed the “Hogere Burgerschool” (secondary school), he in 1878 entered the University of Utrecht as a medical student, intending to follow in his father’s footsteps. His exceptional abilities, however, began to develop in quite a different direction. After being assistant to the ophthalmologist H. Snellen Sr. in the renowned eye-hospital “Gasthuis voor Ooglidders”, he made two investigations, both of which attracted widespread interest.
The first was carried out after Einthoven had gained his “candidaat” diploma (approximately equivalent to the B.Sc. degree), under the direction of the anatomist W. Koster, and was entitled “Quelques remarques sur le mecanisme de l’articulation du coude” (Some remarks on the elbow joint).
Later he worked in close association with the great physiologist F.C. Donders, under whose guidance he undertook his second study, which was published in 1885 as his doctor’s thesis: “Stereoscopie door kleurverschil” (Stereoscopy by means of colour variation) – one of Einthoven’s teachers was the physicist C. H. D. Buys Ballot, who discovered the well-known law in meteorology.
That same year, 1885, he was appointed successor to A. Heynsius, Professor of Physiology at the University of Leiden, which he took up after having qualified as general practitioner in January, 1886. His inaugural address was entitled “De leer der specifieke energieen” (The theory of specific energies).
His first important research in Leiden was published in 1892: “uber die Wirkung der Bronchialmuskeln nach einer neuen Methode untersucht, und uber Asthma nervosum” (On the function of the bronchial muscles investigated by a new method, and on nervous asthma), a study of great merit, mentioned as “a great work” in Nagel’s “Handbuch der Physiologie”. At that time he also began research into optics, the study of which occupied him ever since. Some publications in this field were: “Eine einfache physiologische Erklarung fur verschiedene geometrisch-optische Tauschungen” (A simple physiological explanation for various geometric-optical illusions ) in 1898; “Die Accomodation des menschlichen Auges” (The accomodation of the human eye) in 1902; “The form and magnitude of the electric response of the eye to stimulation by light at various intensities”, with W.A. Jolly in 1908. In the first phase of his research career Einthoven probed into various subjects in the fields of vision and respiration but later he restricted himself almost entirely to electrical phenomena in physiology, in particular those related to the heart.
In 1906 he wrote a paper entitled “Het tele-cardiogram” (The tele-cardiogram) in which he stated: “We should first endeavor to better understand the working of the heart in all its details, and the cause of a large variety of abnormalities.
This will enable us, in a possibly still-distant future and based upon a clear insight and improved knowledge, to give relief to the suffering of our patients.” These memorable words have lost nothing of their meaning today and indeed merit serious consideration in view of the increasing pressure to produce early results in research.
Up till now, his talents had not yet been developed to the full. This opportunity came when he began the task of registering accurately theheart sounds, using a capillary electrometer invented by Gabriel Lippmann. It consists of a fine glass tube, with mercury at the bottom and dilute sulphuric acid on top. A change in electrical charge causes the surface tension of the mercury to alter, sending the mercury shooting up or down the tube.
Capillary galvanoscope shown here uses the same principle as theinstrument used by Einthoven, but it has slightly different configuration. A small drop of mercury in the horizontal capillary tube moves under the influence of an electric field applied to the two electrodes. The device is provided with a glass scale for projection.
With this in view, he investigated the theoretical principles of this instrument, and devised methods of obtaining the necessary stability, and of correcting mathematically the errors in the photographically registered results due to the inertia of the instrument. Having found these methods he decided to carry out a thorough analysis of A.D. Waller’s electrocardiogram – a study which has remained classic in its field. However, despite Einthoven’s improvements, the “Lippmann electrometer” failed to satisfy his high standards for accuracy.
Einthoven gradually recognized that far better equipment than was available at the time would be required for successful recording of the electricity developed by cardiac function. The string galvanometer, previously invented and used, among other purposes to amplify electrical signals being transmitted thousands of miles via the transatlantic undersea communications cable, seemed a promising model.
He developed a very sensitive galvanometer using an extremely thin and light weight quartz “string” silvered to reflect a beam of light, which was deflected by the passage of a fluctuating current in a powerful magnetic field. This galvanometer was sufficiently sensitive to detect the extremely small electrical events generated by the heart.
The movable part of a string galvanometer is a microscopic thread of quartz called a “string,” which is suspended vertically in a strong magnetic field. When a minute current is passed through it, the “string” is deflected, or really bent laterally. As the string is supported at both ends, has a very small mass, and moves only a fraction of a millimeter, it has very little inertia, and can record impulses up to many hundred times per minute.
Schematics of a string galvanometer used by Einthoven
These records are obtained by making the string opaque with a coating of silver, placing it in a beam of light which throws a vertical shadow, magnified by a microscope, onto a metal plate in which there is a horizontal slot. This slot allows only a point of shadow to pass through to a moving photographic plate or film, on which the point of shadow writes in a continuous curve.
Einthoven’s string galvanometer
The use of the string galvanometer avoided complex mathematical corrections required upon application of Lippmann electrometer. Although the principle in itself was obvious, and practical applications of it were made in other fields of study, the instrument had to be precisioned and refined to make it usable for physiologists, and this took three years of laborious work. As a result of this, a galvanometer was produced which could be used in medical science as well as in technology; an instrument which was incomparable in its adaptability and speed of adjustment.
Almost immediately the utility of the electrocardiograph was recognized and classic rhythms were soon obtained and published. Several manufacturers began to produce their commercial versions. The Cambridge Scientific Instrument Co., headed by Horace Darwin (Charles’ youngest son), produced a device, shown here in use about a decade and a half after its introduction. The string galvanometer for electrocardiography was superceded by direct writing equipment after the Second World War.
String electrometer manufactured by Leeds & Northrup, Philadelphia
The “string” in this electrometer is a fine wire, connected to the potential to be measured, that passes through the electric field between a pair of electrodes connected to a battery. The deflection of the wire toward one or the other electrode is measured by a microscope and is approximately proportional to the potential on the wire. The sensitivity is varied by changing the tension on the wire and the strength of the field. This form of electrometer has the advantage of compactness, portability, and a wide range of sensitivity.
In Einthoven’s electrocardiographic model the cardiac source is a two-dimensional dipole in a fixed location within a volume conductor that is either infinite and homogeneous or a homogeneous sphere with the dipole source at its center. Einthoven first recognized that because the limbs are generally long and thin, no significant electrocardiographic currents from the torso would be expected to enter them. Accordingly, Einthoven realized that the potential at the wrist was the same as at the upper arm, while that at the ankle was the same as at the upper thigh.
Einthoven consequently assumed that the functional position of the measurement sites of the right and left arm and the left leg corresponded to points on the torso which, in turn, bore a geometric relationship approximating the apices of an equilateral triangle.
He further assumed that the heart generator could be approximated as a single dipole whose position is fixed, but whose magnitude and orientation could vary. The location of the heart dipole relative to the leads was chosen, for simplicity, to be at the center of the equilateral triangle. The signals were obtained from the two arms and left leg (modern Lead I). To enhance conduction, hands and foot were bathed in saline solution with the tubs wired to the input of the electrocardiograph.
Evolution of the electrocardiogram from the electrometer. The upper record was made using the capillary electrometer, the middle record is a “corrected curve,” and the lower record was made using Einthoven’s string galvanometer. (The upper and middle portions of this figure are from Einthoven W: Die galvanometrische Registrirung des menschlichen Elektrokardiogramms, zugleich eine Beurtheilung der Anwendung des Capillar-Elektrometers in der Physiologie. Archiv fur die Gesammte Physiologie des Menschen und der Thiere, 99:473, 1903. The exact source for the lower portion of this figure is unknown because it was not shown in the original figure published in 1903. It did appear in Fishman AP, Richards DW (eds): Circulation of the Blood: Men and Ideas. New York, Oxford University Press, 1964, p 295.
Noticing a recurring pattern of movement, Einthoven named the prominent waves alphabetically, P, Q, R, S, and T: the P-Wave, representing the impulse across the atria to the A/V Node; the QRS representing the impulse as it travels across the ventricles; the T-Wave, representing the repolarization of the ventricles. Why PQRST and not ABCDE? The four deflections prior to the correction formula were labelled ABCD and the 5 derived deflections were labelled PQRST.
The choice of P is a mathematical convention by using letters from the second half of the alphabet. N has other meanings in mathematics and O is used for the origin of the Cartesian coordinates. In fact Einthoven used O ….. X to mark the timeline on his diagrams. P is simply the next letter. A lot of work had been undertaken to reveal the true electrical waveform of the ECG by eliminating the damping effect of the moving parts in the amplifiers and using correction formulae. If you look at the diagram in Einthoven’s 1895 paper you will see how close it is to the string galvanometer recordings and the electrocardiograms we see today. The image of the PQRST diagram may have been striking enough to have been adopted by the researchers as a true representation of the underlying form. It would have then been logical to continue the same naming convention when the more advanced string galvanometer started creating electrocardiograms a few years later.
Scientific co-workers in Einthoven’s laboratory during World War I (probably 1916 or 1917). Standing from left to right: W.F. Einthoven (son), Hugenholtz (later general physician in Leiden), Waar (later general physician in The Hague), Flohil (later general physician in the east of Holland) Bijtel (later ear specialist in Amsterdam). Sitting: W. Einthoven (left) and Bergansius (physicist). The whole group is gathered around an installation of the string galvanometer (the instrument itself is on the pillar behind Einthoven).
Einthoven then, with P. Battaerd, took up the study of the heart sounds, followed by research into the retina currents with W.A. Jolly (begun earlier with H.K. de Haas). The electrocardiogram itself he studied in all its aspects with numerous pupils and with visiting scientists. It was this last research which earned him the Nobel Prize in Physiology or Medicine for 1924. In addition to this the string galvanometer has proved of the highest value for the study of the periphery and sympathetic nerves.
Einthoven possessed the gift of being able to devote himself entirely to a particular field of study. (His genius was actually more orientated towards physics than physiology.) As a result he was able to make penetrating inquiries into almost any subject which came within the scope of his interests, and to carry out his work to its logical conclusion. Einthoven was a great believer in physical education.
In his student days he was a keen sportsman, repeatedly urging his comrades “not to let the body perish”. (He was President of the Gymnastics and Fencing Union, and was one of the founders of the Utrecht Student Rowing Club.) His first study on the elbow joint resulted from a broken wrist suffered while pursuing one of his favourite sports, and during the somewhat involuntary confinement his interest was awakened in the pro- and supination movements ofthe hand and the functions of the shoulder and elbow joints.
The string galvanometer has led countless investigators to study the functions and diseases of the heart muscle. The laboratory at Leiden became a place of pilgrimage, visited by scientists from all over the world. For this, suffering mankind has much to owe to Einthoven.
In electrocardiography the string galvanometer is the most reliable tool. Although it has been superseded by portable types and by models utilizing amplification techniques used in radio communication (Einthoven has always mistrusted the use of condensers, fearing the distortion of curves), cardiograms from the string galvanometer have remained the standard of reference in numerous cases to this day.
Einthoven was a member of the Dutch Royal Academy of Sciences, the meetings of which he hardly ever missed. He frequently took part in the debates himself, and his sharp criticism frequently found weaknesses in many a lecture.
Willem Einthoven married in 1886 Frederique Jeanne Louise de Vogel, a cousin, and sister of Dr. W.Th. de Vogel, former Director of the Dienst der Volksgezondheid (Public Health Service) in the Dutch East Indies. There were four children: Augusta (b. 1887), who was married to R. Clevering, an engineer; Louise (b. 1889), married to J.A.R. Terlet, pastor emeritus; Willem (1893-1944) – a brilliant electro-technical engineer who was responsible for the development of the vacuum model of the string galvanometer and for its use in wireless communication, and who was Director of the Radio Laboratory in Bandung, Java; and Johanna (b. 1897), a physician.
The photo shows Willem Einthoven and his wife in 1924. Standing behind them Mrs. Eitnhoven’s sister, Mrs de Voogd, who joined them on their journey to America. For the two ladies this was mainly an independent trip. Einthoven was here in his happy old age.
Portraits of Willem Einthoven
In the remaining years of his life, problems of acoustics and capacity studies came within the sphere of his interests. The construction of the string phonograph (1923) could be considered as a consequence of his string galvanometer.
“Electrocardiograms” and Willem Einthoven – Time chart
Dutch physiologist Willem Einthoven sees Waller demonstrate his technique at the First International Congress of Physiologists in Bale. Waller often demonstrated by using his dog “Jimmy” who would patiently stand with paws in glass jars of saline.
Willem Einthoven introduces the term ‘electrocardiogram’ at a meeting of the Dutch Medical Association. (Later he claims that Waller was first to use the term). Einthoven W: Nieuwe methoden voor clinisch onderzoek [New methods for clinical investigation]. Ned T Geneesk 29 II: 263-286, 1893.
Einthoven, using an improved electrometer and a correction formula developed independently of Burch, distinguishes five deflections which he names P, Q, R, S and T. Einthoven W. Ueber die Form des menschlichen Electrocardiogramms. Archfd Ges Physiol 1895; 60: 101-123.
Clement Ader, a French electrical engineer, reports his amplification system for detecting Morse code signals transmitted along undersea telegraph lines. It was never intended to be used as a galvanometer. Einthoven later quoted Ader’s work but seems to have developed his own amplification device independently. Ader C. Sur un nouvel appareil enregistreur pour cables sous-marins. C R Acad Sci (Paris) 1897; 124: 1440-1442.
Einthoven invents a new galvanometer for producing electrocardiograms using a fine quartz string coated in silver based on ideas by Deprez and d’Arsonval (who used a wire coil). His “string galvanometer” weighs 600 pounds. Einthoven acknowledged the similar system by Ader but later (1909) calculated that his galvanometer was in fact many thousands of times more sensitive. Einthoven W. Un nouveau galvanometre. Arch Neerl Sc Ex Nat 1901; 6: 625-633.
Einthoven publishes the first electrocardiogram recorded on a string galvanometer. Einthoven W. Galvanometrische registratie van het menschilijk electrocardiogram. In: Herinneringsbundel Professor S. S. Rosenstein. Leiden: Eduard Ijdo, 1902: 101-107.
Einthoven discusses commercial production of a string galvanometer with Max Edelmann of Munich and Horace Darwin of Cambridge Scientific Instruments Company of London.
Einthoven starts transmitting electrocardiograms from the hospital to his laboratory 1.5 km away via telephone cable. On March 22nd the first ‘telecardiogram’ is recorded from a healthy and vigorous man and the tall R waves are attributed to his cycling from laboratory to hospital for the recording.
Einthoven publishes the first organised presentation of normal and abnormal electrocardiograms recorded with a string galvanometer. Left and right ventricular hypertrophy, left and right atrial hypertrophy, the U wave (for the first time), notching of the QRS, ventricular premature beats, ventricular bigeminy, atrial flutter and complete heart block are all described. Einthoven W. Le telecardiogramme. Arch Int de Physiol 1906; 4: 132-164 (translated into English. Am Heart J 1957; 53: 602-615).
Thomas Lewis publishes a classic textbook. The mechanism of the heart beat. London: Shaw & Sons and dedicates it to Willem Einthoven.
Einthoven addresses the Chelsea Clinical Society in London and describes an equilateral triangle formed by his standard leads I, II and III later called ‘Einthoven’s triangle’. This is the first reference in an English article with the abbreviation ‘EKG’. Einthoven W. The different forms of the human electrocardiogram and their signification. Lancet 1912; 1: 853-861.
Willem Einthoven wins the Nobel prize for inventing the electrocardiograph.
Ernstine and Levine report the use of vacuum-tubes to amplify the electrocardiogram instead of the mechanical amplification of the string galvanometer. Ernstine AC, Levine SA. A comparison of records taken with the Einthoven string galvanomter and the amplifier-type electrocardiograph. Am Heart J 1928; 4: 725-731.
Emanuel Goldberger increases the voltage of Wilson’s unipolar leads by 50% and creates the augmented limb leads aVR, aVL and aVF. When added to Einthoven’s three limb leads and the six chest leads we arrive at the 12-lead electrocardiogram that is used today.
Willem Einthoven died on the 28th of September,1927, after long suffering. The picture shows grave of Willem Einthoven, his wife and his son; on both sides of it the graves of Mrs Einthoven’s relatives. At the back the Green Church in Oegstgeest. It was built on the site of a wooden chapel reputed to have been consecrated by St. Willibrord in the 8th century. In the 11th century the (tuff stone) church was built, subsequently destroyed in the war againts Spain and rebuilt in the 17th century on the old foundations.
Willem Einthoven is honored on the purple stamp from his native Netherlands.