1924 Nobel Prize in Physiology or Medicine — Willem Einthoven

What You Will Learn in This Article

You will understand how it became possible to “draw” the electrical activity of the heart onto paper without opening the chest, and why the P-Q-R-S-T designations were chosen for today’s electrocardiogram (ECG/EKG).

Seeing the Heart’s Electricity from the Outside

If you undergo an ECG examination today, several electrodes will be attached to your chest and limbs, and after a few minutes, a familiar waveform will appear on the paper. The P wave, the QRS complex, and the T wave. This is the test used to diagnose myocardial infarction in the emergency room, classify arrhythmias, and monitor heart rhythms.

What makes this test remarkable? It is the fact that it can accurately reconstruct the electrical activity of cells within the heart without opening the chest, inserting needles into the heart, but simply using electrodes on the skin. The electrical signal from each heart cell travels through the body’s resistive tissues (muscle, fat, bone) to reach the skin surface. This faint signal is captured and reconstructed as a waveform, which is the ECG.

Einthoven was the one who brought this technology to the world.

The Zeitgeist — The Height of the Roaring Twenties

In 1924, Europe was recovering and getting back on track:

• The Dawes Plan — A plan to resolve Germany’s reparations problem. American capital flowed into Germany, stabilizing the economy.
• Lenin’s death (January) — Followed by the rise of Stalin.
• Paris Olympics — The first Summer Olympics held normally after the war.
• The Munich Beer Hall Putsch — Hitler’s rise in popularity.

From the perspective of medical history, 1924 was a time when medical devices were becoming standard tools for clinicians. X-rays (1895), the electrocardiogram (prototype in 1902, standardized in 1924), blood chemistry tests, and automated blood pressure monitors. Previously, the physician’s main tools were their hands and a stethoscope, but during this period, quantitative data obtained through machines began to become essential for diagnosis.

When compared to Korean history, 1924 was the year that the first students were admitted to the preparatory course of Keijo Imperial University. In 1926, the undergraduate program was established, marking the birth of the first university in Korea. While the ECG was becoming a clinical standard in Europe, Korea was at the point of having its first university. However, the proportion of Korean students at the time of its founding was very low.

The Man’s Story — A Dutch Physiologist Who Worked with Glass

Einthoven was born in Java (then the Dutch East Indies) in 1860. His father was a physician, and after his father died when he was young, he returned to the Netherlands with his family. He studied medicine in Utrecht and became a professor of physiology at the University of Leiden.

The problem that captured his interest was this: How to accurately record the heart’s electrical activity from outside the body?

Attempts had already been made to measure the heart’s electrical signals. Augustus Waller performed the first ECG on a human in 1887, but the signals were too distorted by the instruments of the time (capillary electrometer) to be clinically useful. The details of the waveform were blurred, and the resolution was not sufficient to diagnose actual heart abnormalities.

Einthoven sought to solve this problem with a completely new device. He invented the string galvanometer.

The principle is beautifully simple:

• A very thin, silver-plated quartz thread is suspended between the poles of a strong magnet.
• When a weak current from the heart flows through this thread, the Lorentz force causes the thread to deflect to the side.
• The shadow of the thread is projected onto a rotating photographic film.
• The movement of the thread is recorded as a waveform on the film.

The precision of this device surpassed all previous instruments. It captured the heart’s electrical signals in the microvolt range without distortion. However, its size was... a massive 300 kg. In early ECG examination rooms, this device occupied an entire room, and a separate room was needed next to it for cooling.

Einthoven was a person who completed his tools by hand. Like Krogh, he was also a person who knew how to build his own experimental equipment, and this skill enabled his discoveries.

Key Achievements — Standardization of Heart Electrical Signals

The Names of P-Q-R-S-T

Einthoven gave names to the different parts of the waveform he obtained with the string galvanometer. Originally, Waller had used A, B, C, and D, but Einthoven created a new nomenclature, starting with P, the middle letter of the alphabet. This was intended to leave room for additional waveforms to be discovered later.

• P wave — Atrial depolarization. The atria prepare for contraction.
• QRS complex — Ventricular depolarization. The ventricles contract.
• T wave — Ventricular repolarization. The ventricles recover in preparation for the next beat.

This nomenclature became the world standard. Today, when you have an ECG done in the emergency room, those names will be exactly what is attached to the waveform.

The CS analogy fits naturally here. The ECG is an oscilloscope that captures signals from a live system using a probe. Just as we attach a probe to a network cable and observe the flow of packets, Einthoven attached a probe to the body’s surface and observed the electrical communication of heart cells. And by assigning standardized names to each part of the waveform, he made it possible for everyone to speak the same language when talking about ECGs.

However, this analogy breaks down here. An oscilloscope probe captures a single signal from a single signal line, but the ECG has to capture and reconstruct the original signal, which has been attenuated and distorted by the body’s tissue as a resistive filter. This is a much more difficult signal processing problem.

Einthoven’s Triangle: Decoding a 3D Heart with 2D Data

Einthoven’s second achievement was the standardization of multiple lead combinations. The heart is a three-dimensional structure, and its electrical activity is also a three-dimensional vector. Observing it from a single angle does not allow you to localize the location of heart abnormalities.

Einthoven defined a standard triangle (Einthoven’s triangle) by attaching electrodes to three points: the right arm, the left arm, and the left leg. He measured the potential difference between different pairs of these three points in three ways (Lead I, Lead II, Lead III) and combined the signals from these three angles to reconstruct the heart’s electrical vector.

His students and successors later expanded this triangle to create today’s 12-lead ECG. The rules we use today to diagnose myocardial infarction, such as “ST elevation in V1-V4 indicates anterior myocardial infarction,” are all based on the expansion of Einthoven’s triangle.

In terms of the CS analogy, this is like combining multiple observation points in a distributed system to reconstruct the original event. A single log cannot tell the whole story, but by synchronizing logs from multiple nodes in time, we can reconstruct the exact state and location of the original event. The ECG is a multi-observation log system for cardiac events.

Quantitative Diagnosis of Arrhythmias and Myocardial Infarction

The clinical impact of the ECG was immediate. Previously, arrhythmias (irregular heart rhythms) were roughly classified by palpation (feeling the pulse) and auscultation (listening with a stethoscope). After the ECG, the exact type of arrhythmia (atrial fibrillation, ventricular tachycardia, complete atrioventricular block, etc.) could be accurately diagnosed from the waveform. Because each type has a different treatment, this accurate classification quickly led to improved treatment outcomes.

The diagnosis of myocardial infarction has also fundamentally changed. It was discovered that a specific pattern called ST segment elevation is a definitive sign of acute myocardial infarction, and the practice of immediately performing an ECG on patients with chest pain in the emergency room began during this period.

Why It Matters

Einthoven’s Nobel Prize was a demonstration of the principle that “invisible activities inside the body can be accurately observed from outside the body.” This principle later led to the development of electroencephalography (EEG, 1929), electromyography (EMG), magnetic resonance imaging (MRI, 1970s), and functional MRI (fMRI, 1990s). All of today’s non-invasive diagnostic devices are based on this principle.

More broadly, it is a symbol of the process by which medicine became a science of tools. Before Einthoven, physicians relied on their own senses (sight, touch, and hearing). After Einthoven, machines that extend and quantify the physician’s senses became essential for clinical practice. This was a fundamental change in clinical medicine.

There is a lesson to be learned here: “When existing tools reach their limits, create new tools.” Einthoven did not try to force the interpretation of Waller’s distorted ECG. Instead, he invented a completely new device based on a different principle. When we encounter a problem today, we should ask ourselves whether a new tool is needed, rather than trying to simply extend existing tools.

Even as you read these words, an ECG is likely being performed in an emergency room somewhere in the world. The names P, Q, R, S, and T attached to the waveform are the letters chosen by a Dutch physiologist in Leiden 100 years ago.

Summary of ECG Signal Acquisition and Interpretation: The depolarization and repolarization processes of heart cells travel through the body’s tissues to reach the skin. Measured using a standard 3-lead or expanded 12-lead system, the combination of waveforms from each lead is used to reconstruct the spatial and temporal changes of the heart’s electrical vector.

→ Experience it through coding: DevBench — Oscilloscope and Signal Profiling → Learn about CS concepts: DryBench — Multi-observation Logs and Event Reconstruction