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100 Years Ago: The innovation that Defined Cardiology

Image Citation: [1]


Written by Ava Grave de Peralta ’28

Edited by Joanna Sohn ’28


If you’ve ever stepped foot in a hospital, or even seen one on TV, you’re likely familiar with the beeping, squiggly line moving across the screen of a patient’s heart monitor. This iconic wave has become the symbol of heart health, but have you ever wondered what that spikey line really means?


One hundred years ago this October, the 1924 Nobel Prize in Physiology or Medicine was awarded to Dutch physician Willem Einthoven for his development of the electrocardiogram, or EKG, which has stood the test of time as the most commonly used cardiovascular test today [2].


EKGs detect and graph changes in the electrical signals produced by a patient’s heart. By illuminating abnormalities in these electrical wave patterns, the EKG was the first noninvasive diagnostic test to allow doctors to observe and diagnose heartbeat irregularities, ultimately leading to the birth of the cardiology field [2].


It may seem strange to think about electricity constantly moving through our organs, since we don’t feel these electric signals like we do the shock of a metal door handle. However, electric signaling is an essential method of cellular communication used by our muscle cells. Each beat of our hearts is controlled by an electric signal that travels through the heart muscle to tell the atria and ventricles (the four chambers of the heart) to contract, allowing blood to circulate through the body [3].


The first record of this electrical activity was observed in human skeletal muscle by Italian physician Dr. Luigi Galvani in 1786 [4]. Other seminal discoveries soon followed, including the association of electric current with each heartbeat noted by Dr. Carlo Matteucci in 1842. These advances paved the way for Augustus Waller’s first recording of body surface voltage changes created by the heart using a capillary electrometer, the precursor to Einthoven’s string galvanometer that would soon transform the practicality of electrocardiology [4].


Einthoven’s string galvanometer, invented in 1901, records electrical activity of the heart by photographing the movements of a wire between two poles of a magnet. The wire ends are connected to sensors on the patient’s forearms, allowing the electrical impulses of the heart to travel through the wires and generate a wavelike pattern on the resulting image [5].


With the sensitivity allowed by the string galvanometer, Einthoven developed the first practical electrocardiograph, the machine that performs EKGs. He coined the term “elektrokardiogramm” from the Greek roots for electric, heart, and writing, and this German spelling of the term popularized the abbreviation EKG [6]. Einthoven’s EKG standardized the three-electrode triangle that is still used today, with early versions utilizing leads in the right arm, left arm, and left leg [4]. However, these first electrodes were not the small gel stickers you might find in hospitals, but rather consisted of buckets of electrolyte-rich saline in which the patient’s arms and legs were immersed [2].


Figure 1: A,B. Early recordings with EKG using saline leads (Einthoven W. Arch International Physiol 1906;4:132). C. One of Einthoven’s EKG recordings from 1903-4 (Einthoven W. Arch International Physiol 1906;4:132) [2].


Thanks to Einthoven’s adjustment calculations, an EKG consists of a distinct pattern with three sections: the P wave, QRS complex, and T wave. The P wave is the first peak in the pattern and shows the electrical impulse from the atria, the top chambers of the heart. Next, the QRS complex is a group of three waves that represents the electrical impulse spreading through the ventricles, the lower chambers of the heart. Finally, the T wave illustrates that the electrical impulse is no longer spreading [3]. By comparing the wave pattern of a patient’s EKG to the wave pattern of a healthy heartbeat, doctors can identify heartbeat irregularities, or arrhythmias [3]. This newfound ability to objectively identify heart disease, rather than relying on reported symptoms and patient histories, ultimately led to the establishment of a new field of medicine called cardiology [7].


Figure 2: The QRS complex between the P wave and T wave illustrates the flow of electric charge during a normal heartbeat [3].


As the 20th century progressed, new observations linking electrocardiographic signals with both cardiac and noncardiac diseases expanded the influence of the EKG beyond just identifying arrhythmias [7]. As the number of diseases identifiable from an EKG continued to grow, ranging from arrhythmias to noncardiac conditions including liver disease, rules were defined to correlate electrocardiographic criteria with specific diseases. In the 1970s, innovations in computing technology allowed electrocardiographic machines encoded with this identification criteria to generate the first diagnostic reports  [7].


Today, developments in technology such as machine learning offer exciting new frontiers in EKG analysis. Machine learning-based approaches to analyzing electrocardiographic data potentially allow for the identification of conditions that are not reliably recognized by human technicians. In addition, these artificial intelligence EKGs may be able to identify individuals at high risk for developing a disease, surpassing capabilities of current standard tests [7].


With EKG testing still saving lives over a century after its invention, and technological innovations rapidly expanding its influence, Willem Einthoven’s elektrokardiogramm is here to stay.


References

  1. Electrocardiogram -12 Lead EKG [Internet]. Blue Apple Health; Available from: https://www.blueapplehealth.com/services/portfolio-of-tests/12-lead-ekg

  2. Fisch C. Centennial of the string galvanometer and the electrocardiogram. Journal of the American College of Cardiology. 2000;36(6):1737–45. Figure 4, Recording leads I and II, An ECG recorded by Einthoven in 1903–4.

  3. Institute for Quality and Efficiency in Health Care (IQWiG). In brief: What is an electrocardiogram (ECG)? In: InformedHealth.org [Internet] [Internet]. National Library of Medicine; 2006. Available from: https://www.ncbi.nlm.nih.gov/books/NBK536878/. Figure 1, The QRS complex between the P wave and the T wave in a normal heartbeat.

  4. AlGhatrif M, Lindsay J. A brief review: history to understand fundamentals of electrocardiography. J Community Hosp Intern Med Perspect. 2012;2(1).

  5. Aitchison R, Aitchison P, Wang E, Kharasch M. A review of cardiopulmonary resuscitation and its history. Disease-a-Month. 2013;59(5):165–7.

  6. Smith Haghighi A. Is there a difference between an ECG and an EKG? Medical News Today [Internet]. 2023; Available from: https://www.medicalnewstoday.com/articles/ecg-vs-ekg

  7. Friedman P. The Electrocardiogram at 100 Years: History and Future. Circulation. 2024;149(6):441–413.


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