Light, portable and an integral part of the cardiac diagnostic process, it is hard to imagine that the first electrocardiograph machine weighed some 270 kg.
Today, it is among the simplest and most common of tests used by a specialist when seeking to diagnose a heart condition; a system that checks the heart’s rhythm and electrical activity via sensors attached to the skin to detect the electrical signals produced by the heart as it beats and then offers an instant print-out.
Yet as with many medical tests that are routine today, it was years in development and the gap between invention, clinical implementation, and recognition can be measured in decades.
The man regarded as the father of modern electrocardiography, Willem Einthoven, is credited with inventing the first practical electrocardiogram in the first few years of the 20th century. Yet it was not until 1924 that he received the Nobel Prize in Physiology or Medicine—3 years before his death aged 67 years on 29 September 1927—for inventing electrocardiography for use in medical diagnosis.
An eminent Dutch doctor and physiologist, he was born in May 1860 in Semarang on Java in the Dutch East Indies (now Indonesia), the son of Louise Marie Mathilde Caroline de Vogel and Jacob Einthoven, an army medical officer and later a parish doctor in Semarang. Einthoven’s father died when he was only 6, and 4 years later—in 1870—his mother returned to the Netherlands with her six children and settled in Utrecht.
Intent on following in his father’s footsteps, Einthoven entered the University of Utrecht as a medical student in 1878, receiving his medical degree in 1885 and was appointed Professor of Psychology at the University of Leiden in 1886, after having qualified as a general practitioner.
Einthoven, who married one of his cousins Frédérique Jeanne Louise de Vogel in 1886, and had four children, was a keen sportsman and a firm believer in physical education.
In his role at Leiden, he conducted research, initially focusing on the function of bronchial muscles and optics, and in particular geometric-optical illusions and the form and magnitude of the electric response of the eye to stimulation by light at various intensities. But towards the end of the 19th century, his interest shifted to a device that would accurately measure and record the electrical impulses of the heart.
While it had been long known that the beating heart produced electrical current, the instruments of the late 19th century were still not able to accurately measure and record this.
As early as 1786, Italian physician and physicist Dr Luigi Galvani from the University of Bologna first noted that electrical current could be recorded from skeletal muscles and the electrical activity of the heart was first demonstrated in 1842.
In 1887, Augustus D. Waller of St Mary’s Medical School in London made the first human recording, showing simultaneous electrometer and cardiograph tracings of an electrical activity preceding every heartbeat. Whilst this was the first electrocardiogram, the tracings with this apparatus were heavily damped.
Inspired by the work of Waller, Einthoven set about designing a new type of instrument in the early 1890s and further refined the capillary electrometer.
To adjust for inertia in the capillary system, he implemented a mathematical correction, which resulted in the various deflections that we see today, PQRST, though Einthoven never fully explained why he chose this sequence of letters.
The term ‘electrocardiogram’ used to describe these wave forms is believed to have been first coined by Einthoven at the Dutch Medical Meeting of 1893.
Beginning in 1901, he successfully developed a string galvanometer with very high sensitivity, which he used in his electrocardiograph and yielded the first high-quality electrocardiograms in 1902, followed by publication of a more detailed description the following year. These prototypes of a string galvanometer used a thin filament of conductive silver-coated quartz fibre suspended between the poles of an electromagnet. An image of the string, magnified 600 times, was projected onto a photographic plate.
In the opening lines of his Nobel lecture of 11 December 1925—entitled ‘The strong galvanometer and the measurement of the action currents of the heart’—Einthoven clearly described the equipment and how it worked. ‘The string galvanometer’, he explained, ‘consists of a thin thread conducting the electric current which is stretched as a string in a magnetic field. The thread, as soon as the current passes through it, is displaced from its position of equilibrium in a direction at right angles to the direction of the lines of magnetic force. The amount of displacement is proportional to the strength of the current passing through the thread, so that this current can be easily and accurately measured’.
Eventually, Einthoven produced a galvanometer which could be used in medical science, was adaptable and comparable in its speed of adjustment and did not involve complex mathematical corrections and calculations.
How this early electrocardiogram worked was that 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, forming a continuous curve showing the movement of the string.
The original machine to achieve this was cumbersome. It required water cooling for the powerful electromagnets, needed five people to operate, and weighed some 270 kg. Yet it worked. The 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.
As the string galvanometer electrocardiograph became available for clinical use, improvements were made to make it more practical. Einthoven was able to reduce the number of electrodes from Waller’s five to three and the resulting three leads were used to construct Einthoven’s triangle, named after the imaginary inverted equilateral triangle, centred on the chest and the points being the standard leads on the arms and leg (first outlined to the Chelsea Clinical Society in London in 1912).
In electrocardiography the string galvanometer became a most reliable tool, superseded by portable types and by models utilizing amplification techniques used in radio communication. This apparatus was the standard equipment until direct writing instruments came into use 50 years later.
Although he was not a physician, Einthoven—who became a member of the Royal Netherlands Academy of Arts and Sciences in 1902—was one of the first to recognize that the electrocardiogram would be important in the diagnosis of heart disease.
Over the years, the electrocardiogram (ECG)—or EKG as it was known by Einthoven—led to smaller, portable devices that were technically advanced. Today, there is the prospect of smartphone-based ECG recorders, but much of what the inventor laid down in terms of terminology using an ECG remains.
After his development of the string galvanometer, Einthoven went on to describe the electrocardiographic features of a number of cardiovascular disorders.
By 1905, Einthoven had begun transmitting electrocardiograms from the hospital to his laboratory 1.5 km away via telephone cables and on March 22 that year the first ‘telecardiogram’ was recorded from a ‘healthy and vigorous man’, with the tall R waves displayed attributed to his cycling from the laboratory to the hospital for the recording. In 1906, Einthoven published the first organized presentation of normal and abnormal electrocardiograms recorded with a string galvanometer. As the string galvanometer electrocardiograph became available for clinical use, improvements were made to make it more practical.
In 1924, Einthoven was awarded the Nobel Prize in Physiology or Medicine for the invention of the first practical electrocardiogram. Following Einthoven’s development of a practical galvanometer for recording ECGs, considerable interest in electrocardiography followed with a number of advances being made.
A key figure in the field was Sir Thomas Lewis of University College London, who between 1908 and 1920 made important contributions in the understanding of mechanisms of arrhythmias and spread of excitation, bringing the device to the bedside and further applying it to clinical medicine. The work of Lewis, and the advances he made, was recognized by Einthoven who formally acknowledged Lewis’ contribution in his Nobel lecture as someone who has ‘played a great part in the development of electrocardiography’.
‘It is my conviction’, stated Einthoven, ‘that the general interest in the ECG would certainly not be so high nowadays if we had to do without his work, and I doubt whether without his valuable contribution I should have the privilege of standing before you today’.
During the first three decades of the 20th century, the three-lead electrocardiogram usage expanded especially after improvements were made to make it more portable, leading to the evolution of the 12-lead electrocardiogram and seeing its weight reduced to a few kilograms and a machine able to be operated by only one person.
Today, some 12 decades after its introduction, the ECG remains the most commonly used cardiovascular laboratory procedure and a technique and tool which plays a critical role as a non-invasive, cost-effective method to evaluate arrhythmias and ischaemic heart disease.
Items and images associated with the work of Willem Einthoven and his discovery of the mechanism of the electrocardiogram can be seen at the Rijksmuseum Boerhaave in Leiden (www.rijksmuseumboerhaave.nl). Described as the Netherlands’ treasure chamber of science and medicine, it showcases the major discoveries in the history of science in the Netherlands, the researchers behind them and the impact of their discoveries on modern life with a collection spanning five centuries of research and innovation.
Professor Antoni Bayés de Luna is Senior Investigator Cardiovascular ICCC-Program, Research Institute Hospital de la Santa Creu, Sant Pau, Barcelona, Spain; Emeritus Professor of Cardiology, Autonomous University of Barcelona; and Honorary Director Cardiac Department, St Pau Hospital, Barcelona.
His interest past and present is in clinical cardiology, especially clinical electrocardiography. He has written hundreds of papers on the subject and is the author of books on Clinical Electrocardiography in nine different languages. He is currently devoted to studying the relation of advanced interatrial block (A-IAB) and atrial fibrillation and stroke, that has been named ‘Bayés Syndrome’.
He explained how Willem Einthoven had become dissatisfied with the records obtained with capillary electrometer, so began to work on a sensitive galvanometer in 1900, with a preliminary paper describing the galvanometer appearing in 1901.
Professor Bayes de Luna continued: ‘Einthoven’s first major, and often quoted, paper about ECG appeared in 1903. Initially, this work attracted little attention. Even the great classic, “Le Télécardiogramme”, published in 1906, was received with only a moderate degree of interest’.
That changed with publications in 1908 and 1912 where he explained the scheme of the equilateral Einthoven triangle which was a key point to understand the frontal plane ECG leads.
He added: ‘Einthoven was besieged by visitors and correspondence from people all over Europe, who wanted to see or learn about the new instrument. The quality of the tracings was undoubtedly very good and similar in quality to today’s tracings’.
Einthoven, he said, intuited the great potential of electrocardiography, saying that ‘A new chapter has been opened in the study of heart diseases… by which suffering mankind is helped’.
Professor Bayés de Luna said: ‘With this new technique, the recording of ECG curves had a high fidelity and sensitivity and represented an undistorted, directly readable graphic record of the electrical activity of the heart’.
The diagnostic technique introduced by Einthoven more than 100 years ago was soon manufactured by the Cambridge Scientific Instrument Company, founded by Horace Darwin, younger son of the great biologist Charles Darwin and the first to officially commercialize ECG machines.
‘Today’s ECG tracings are no better in quality from a morphological point of view than the ones recorded by Einthoven more than a century ago, although now the ECG is usually recorded digitally and the devices are much smaller’, he added. ‘Although the ECG can now be recorded over a long period (Halter device) it is interesting to remember that Einthoven was already able to record the ECG from a distance. The ECG may be now even be recorded holding the device with two hands or even on a watch. In any case, the ECG remains, presumably forever, the ‘gold standard’ technique most used in everyday practice in cardiology, and possibly general medicine, throughout the world and will surely continue forever.
‘With hindsight, it is clear that the Nobel Prize Einthoven received in 1924 was very well deserved. He had a fascinating and creative personality added to his genius. He only looked for the truth’.
Conflict of interest: none declared.
