From a laboratory to the wearables: a review on history and evolution of electrocardiogram / Del laboratorio a la práctica: una revisión sobre la historia y evolución del electrocardiograma

The development of electrocardiography, one of the top scientific breakthroughs of the 20th century, occurred in the field of cardiology. The history of the ECG began long before its invention, with the advent of the study of electricity in the medical field. The idea of electrophysiology and Waller's initial recording of the ‘electrogram’ encouraged Willem Einthoven to develop new string galvanometers and turn this remarkable physiologic occurrence into a vital clinical recording tool. It has progressed from Einthoven's innovation to wearable technology. In the first part of the 20th century, a number of inventive people achieved a remarkable succession of discoveries and advancements that led to the development of the 12-lead ECG as we know it today. It went further than that. The evolution of science and technology over the years has allowed for continual development in terms of usefulness, ranging from five operators to one operator meant to record the ECG trace, and mobility, ranging from around 300 Kg to roughly around 1 Kg. Electrocardiographs in minimized form now exist thanks to the modern era of digitalization. We will go over the significant processes in the development of the ECG in this article. (AU)

El desarrollo de la electrocardiografía, uno de los principales avances científicos del siglo XX, se produjo en el campo de la cardiología. La historia del ECG comenzó mucho antes de su invención, con el advenimiento del estudio de la electricidad en el campo médico. La idea de la electrofisiología y el registro inicial del "electrograma" de Waller animó a Willem Einthoven a desarrollar nuevos galvanómetros de hilo y convertir este acontecimiento fisiológico notable en una herramienta de registro clínico vital. Ha progresado desde la innovación de Einthoven hasta la tecnología portátil. En la primera parte del siglo XX, varias personas ingeniosas lograron una notable sucesión de descubrimientos y avances que condujeron al desarrollo del ECG de 12 derivaciones tal como lo conocemos hoy. Fue más allá que eso. La evolución de la ciencia y la tecnología a lo largo de los años ha permitido un desarrollo continuo en términos de utilidad, que va desde cinco operadores a un operador destinado a registrar el trazo de ECG, y la movilidad, que va desde alrededor de 300 kg hasta aproximadamente 1 kg. Los electrocardiógrafos en forma minimizada ahora existen gracias a la era moderna de la digitalización. Repasaremos los procesos significativos en el desarrollo del ECG en este artículo. (AU)

[The Discovery of the Cardiac Atrioventricular Node by Sunao Tawara and Ludwig Aschoff]. / Die Entdeckung des AV-Knotens des Herzens durch Sunao Tawara und Ludwig Aschoff.

Already in 1664, the Danish anatomist and naturalist Niels Stensen proved that the heart is a muscle. But for a long time it remained unclear what triggered the heart contractions.The Dutch physiologist Willem Einthoven registered the electrical processes in the contraction of the heart muscle and thus provided the first electrophysiological basis of cardiac muscle activity. Since 1903, Sunao Tawara was assistant to Ludwig Aschoff in Marburg. Both left Marburg in 1906: Tawara went back to Japan and Aschoff to Freiburg. In 1905, Tawara discovered the connections of the His' bundle to the AV node and the Purkinje fibers. At that time, there was no thought of a functional interpretation. Tawara discovered a kind of "knot" that linked to the adjacent myocardial cells, as well as the "Tawara thighs", which frayed and went into structures known as Purkinje fibers. Tawara detected the tree-like structure he had discovered as a muscle-fiber system that controlled the arousal of the heart's musculature. Thus the old dispute between myogenic and neurogenic arousal of the heart was decided in favor of the myogenic excitation conduction. The atrioventricular node described by Tawara was given the eponym "Aschoff-Tawara node". Tawara's groundbreaking work on the conduction system was the basis for the discovery of the sinus node and the interpretation of the heart's electrophysiology.

Conduction in cardiac tissue. Historical reflections.

Two hypotheses have been proposed to explain propagation of the action potential in heart. According to the gap junction hypothesis local short-circuit currents pass from the proximal depolarized cell to the distal inactive cell via gap junctions and are responsible for the depolarization of the distal cell. In the ephapse hypothesis the depolarization of the proximal cell generates an electrical field in the narrow cleft between cells resulting in depolarization beyond threshold of the distal cell. Measurements of length constant, free diffusion of 42 K, local currents between cells, existence of high-conductance gap junctions led to the conclusion that heart muscle is a functional syncytium. Propagation of the action potential, however, is not uniform but anisotropic and discontinuous; it can be also unidirectional. These findings are strong arguments in favor of the gap junction thesis. They do not exclude, as predicted by theoretical calculations, that in conditions of an abnormal fall in gap junction conductance ephaptic conduction takes over. In this last case, definitive experimental confirmation is still required. See also: https://doi.org/10.14814/phy2.13861 & https://doi.org/10.14814/phy2.13862.

[Hugo von Ziemssen poster award 2015]. / Hugo-von-Ziemssen-Posterpreis 2015.

Prize winner: Herr Dr. Stefano Bordignon, for the poster presentation "The SCAR-AF study: electroanatomial scar distribution and left atrial conduction delay in patients undergoing pulmonary vein isolation".