Electrical phenomena have been observed by humans for more than 2500 years. Thales of Miletus in Greece (sixth century BCE) noted that amber rubbed with wool attracts light objects. In fact, the ancient Greek name for amber is elektron. As early as the end of the sixteenth century, the English physician William Gilbert postulated the relationship between electricity and magnetism. He was followed by Benjamin Franklin, who discovered the lightning rod in about 1750. At the end of the eighteenth century, the Italian Luigi Galvani discovered that electricity in animals is generated via “an electric fluid.” Galvani believed that electrical stimulus preceded muscle contraction. He would become the world’s first electrophysiologist (Rosen 2002; Rosen and Janse 2006).

The electrical activity of the heart was first recorded in the late nineteenth century by Augustus D Waller (Figure 2.1), who in 1887 recorded the curves of electrical activity of the human heart using saline‐filled tube electrodes and the capillary electrometer developed by Gabriel Lippmann (Figure 2.2A,B). The first human ECG was taken to Thomas Goswell, a technician in his laboratory. Initially, he used his dog Jimmy to perform ECG recordings, but was accused of cruelty to animals because of the belts used and the practice of putting the dog’s extremities in saline water. Although Waller was credited with being the first to record the electrical activity of the heart, he did not have much faith in the usefulness of electrocardiography, stating “I do not imagine the electrocardiography is likely to find any very extensive use … just occasionally to record some rare anomaly of cardiac action” (Burch and DePasquale 1964).

In the last years of the nineteenth century, Willem Einthoven (1860–1927) (Figure 2.3) (Einthoven 1912; Snellen 1977; Moukabary 2007; Kligfield 2010) began to study animal action potentials using the capillary electrometer. Because he was dissatisfied with the records obtained, he made several modifications that greatly improved the tracing quality by using differential equations to correct the poor frequency response of the original design (Figure 2.2A). With these modifications, he was able to predict the correct form of the human ECG (Figure 2.2C) and he proved his findings using a string galvanometer developed in 1902.

Einthoven’s string galvanometer (Figure 2.2D) consisted of a silver‐coated quartz filament suspended between the two poles of an electromagnet. The fixed magnetic field created by the electromagnet established a strong constant force moving from one pole to the other. Currents from the heart registered from the surface of the body were conducted through the quartz string, thereby creating a varying magnetic field of force around the long axis of the string. The interaction between the two magnetic fields, one between the poles of the electromagnet and the other depending on the magnitude of the current that flowed through the string, resulted in movements of the string that were recorded as sharp deflections.

The first electrocardiogram recorded using the string galvanometer was published in 1902. The quality of the tracings was undoubtedly very good and similar to today’s tracings (Figure 2.2E). It is interesting to note that because Einthoven’s laboratory was more than a mile from the academic hospital in Leyden, he developed a method for recording the ECG from a distance, which he called “Telecardiogramme.”

Unlike Waller, Einthoven intuited the great potential of electrocardiography, stating that “A new chapter has been opened in the study of heart diseases … by which suffering mankind is helped.” In fact, by 1906, he had already published his first paper presenting normal and abnormal ECGs (Einthoven 1912). 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. Einthoven labeled the detailed wave deflections “PQRST,” instead of using the “ABCD” notations used for the waves taken with the capillary electrometer (Figure 2.2

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