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 Electrocardiograph (ECG) machines measure the heart’s electrical activity using electrodes placed on the skin. Information about heart activity is produced as visual wavy lines called ‘traces’. During the 20th century, ECG diagnosed heart conditions.

Until the late 1800s, medical scientists could only record heart activity by directly examining the heart. It was not possible on a living patient. In 1887, British physiologist Augustus Waller discovered it was possible to record heart activity from the skin’s surface. He used an instrument called a capillary electrometer to trace heart signals onto photographic plates.

Dutch physiologist Willem Einthoven was inspired by Waller’s experiments. In 1902 he developed an instrument to record traces of the heart’s activity. His string galvanometer was critical to the manufacture of early electrocardiograph machines in 1908.

Early ECG machines were cumbersome and hard to use. Einthoven’s first machine required five people to operate. The person monitored had to place each limb in a bucket of salt water, so it was impractical for patient use. Improvements such as electrodes attached to the skin’s surface meant machines became smaller, portable and more reliable.

Physiologists such as Thomas Lewis helped ECG machines gain acceptance in hospitals during the 1920s. Computerised ECG machines now enable continuous heart monitoring.



R Bud and D J Warner, (eds.), Instruments of Science, An Historical Encyclopaedia (London: Science Museum, 1998)

S Barron, The development of the electrocardiograph: with some biographical notes on Professor W. Einthoven (London: Cambridge Instrument Co, 1952)

J Burnett, ‘The origins of the electrocardiograph as a clinical instrument’, Medical history supplement, 5 (1985), pp 53-76 A D Waller, The electrical action of the human heart (London: University of London Press, 1922)

Z Cope, ‘Augustus Desiré Waller (1856-1922)’ Medical history 17 (1973), pp 380-385

The graphic method [article]: [a history of the electrocardiograph and its predecessors]
Kuhfield, Albert W. Rittenhouse. - Vol.9, no.3. - p.89-96. 1995

T Lewis, The soldier's heart and the effort syndrome ( London: Shaw, 1918)

T Lewis, ‘Electro-cardiography and its importance in the clinical examination of heart affections’ Reprinted from the British Medical Journal, January 22nd, 1912, p.1421-1423, June 29th, 1912, p.1479-1482, July 13th, 1912, p.65-67"

S Serge Barold, ‘Willem Einthoven and the Birth of Clinical Electrocardiography a Hundred Years Ago’, Cardiac Electrophysiology Review, 7 (2003), pp 99-104


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