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Electrocardiographs

From the Greek, electro (electrical activity), kardio (heart) and graph (to write)

 

Electrocardiography, a truly British invention, is the process of producing an electrocardiogram (ECG), a graph of voltage versus time—a recording of the electrical activity of the heart using electrodes placed on the skin. These electrodes detect the tiny electrical changes on the skin that arise from the heart muscle depolarizing during each heartbeat.

 

The First Human Electrocardiogram

In May 1887 Dr Augustus Desiré Waller, head of the department of physiology at St. Mary’s Hospital London, recorded the first human electrocardiogram at St Mary’s London, using the Waller ECG Train apparatus. It consists of a photographic plate mounted on a toy train. The cardiac potentials were obtained with a Lippman electrometer. A beam of light was shone onto the photographic plate from the capillary electrometer which recorded the electrocardiogram as the “train” moved across the track.

 

Lippman’s Capillary Electrometer

The Lippman Capillary Electrometer, invented by Gabriel Lippman, Berlin, 1873, was the first device to record electrical activity reliably. The capillary tube contains mercury in contact with dilute sulphuric acid. An electric current causes the mercury column to oscillate. The movement is magnified with a telescope and recorded photographically.

 

Thompson’s Galvanometer

The Thompson’s Galvanometer, 1891, by William Thomson, later to become Lord Kelvin, was used in the physiology laboratory of Dr Augustus Waller to record electromotive force from nerves and other sources.

 

In 1901, Waller’s “laboratory tool” was supplanted by the string galvanometer which had been developed in Holland by Einthoven.

 

Image References
Lead covered ECG wires
which connected Thomas Lewis’ ward at University College Hospital to his laboratory in the medical school so his patients could have an electrocardiogram recorded.

 

Original ECG recordings with four-digit patient numbers, made by Thomas Lewis in 1913, annotated by Lewis as showing heart block, atrial flutter and paroxysmal tachycardia.

 

The 1929 portable electrocardiograph was designed and made by the Cambridge Instrument Company. It was the standard equipment in British hospitals until the advent of direct writing machines in the 1950s. This apparatus is rare because it is complete with all its original parts: the cardiographic film; the light shield; the loaded film holder; the patient cable and limb electrodes; the control dial; and the film holders’ light beam slit. The top of the trolley contains the string galvanometer, the camera and the film holders. The lower trolley holds the battery case, the patient cable and the limb electrodes. The light beam with the ECG deflections went through a slit in the white square onto to the roll of film behind it. Three shutters occluded the light beam in sequence and enabled three recordings to be made on one piece of film. These were usually the standard limb leads, and a high voltage tracing could be accommodated by opening two or even three shutters at the same time.

 

As ECG equipment became more compact, portable and affordable, it became a popular instrument for bedside diagnosis.

 

Image References
The direct contact plate electrode, 1930.

 

Contact electrodes held in place by rubber straps.

 

Welsh suction cup electrode, 1932, devise by Rudolph Burger to record the pericardial leads.

 

Portable electrocardiograph. Sanborn Cardiette model, 1935.

 

Portable electrocardiograph designed and manufactured in Britain by the Cambridge Instrument Company, 1938. A string galvanometer produced the electrical signal. The ECG was recorded on a continuous strip of photographic paper.

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