biomedicalephemera:

Ever had an electrocardiogram (EKG/ECG)? Be grateful you didn’t have to get one back when it was first developed!

Though a significant amount of the “electro-medicine” that arose during the age where electricity was a “mysterious power” was complete quackery, this is one development that was a true boon to cardiology, and medicine in general.

Constructed by Cambridge Scientific Instrument company in 1911, this EKG machine [bottom illustration] was built to the specifications of one William Einthoven, who developed the string galvanometer in 1903, to measure the electrical currents produced by the heartbeat.

Prior to Einthoven’s time, it was known that the heart produced electric currents, but there was no way to measure them that didn’t involve putting electrodes directly on the heart. I don’t mean right over the heart, on the breastbone - the chest had to be opened to actually measure this phenomenon. Einthoven’s device made it possible to measure the electric currents given off by the heart despite the insulation of fat and skin, and thus made it possible to measure the heartbeat without actually opening someone up.

The string galvanometer worked by using a thin conductive wire passing between powerful electromagnets. When a current passed through the filament, the electromagnetic field would cause the string to move, and form the familiar heartbeat pattern (or not, if their heart is impaired). A light shining on the string would cast a shadow on a moving roll of photographic paper, forming a continuous curve showing the movement of the string [see top illustration].

The original machine required water cooling for the powerful electromagnets, required 5 people to operate it and weighed some 600 lb. Despite the advances made in technology and design, the concept of today’s electrocardiograms is almost identical to the machines that earned Einthoven the 1927 Nobel Prize. Advances in cardiovascular treatment and surgery mean that discrepancies in the results of the EKG readout can be addressed, as opposed to just known to exist, but we still read the same P, Q, R, S, and T waves that were named by him, and still use “Einthoven’s Triangle” - the equilateral triangle that the electrical leads are placed in.

Top: Initial concept work of William Einthoven. Diseases of the Heart and Aorta. Arthur Douglass Hirschfelder, 1912.

Bottom: 1911 ECG Machine. A Brief History of Electrocardiography - Progress through Technology, Christoph Zyweitz.