The Electrocardiograph 1903 – Monitoring Heart Rhythm

Electrocardiography (ECG) uses devices that monitor the heart's electrical activity through electrodes placed on the body. By observing the traces obtained over time, physicians can often diagnose abnormal heart rhythms that may be caused by heart damage, hormone and electrolyte imbalances, or other factors.

In 1887, the British physiologist Augustus D. Waller became the first person to record the heart's electrical activity from a person's skin using the Lippmann electrometer, a device containing a column of mercury in a thin glass tube. The mercury's movement changed slightly with the heart's electrical activity. However, the device was impractical because of friction in the moving mercury and its sensitivity to external vibrations. 

The Dutch physician and physiologist Willem Einthoven was aware of Waller's work. In 1901, he began developing a new, ultrasensitive string galvanometer to monitor the heart. These devices used a thin electrical sensing needle suspended between magnetic poles. Because the heart's electrical activity is very weak, Einthoven's lightweight needle consisted of an extremely fine, silver-coated filament.

Einthoven was one of the first to promote the clinical use of electrocardiography, but his first version weighed 600 pounds (272 kg) and required five operators. The patient immersed both arms and the left leg in buckets of salt solution, which served as electrodes to conduct current from the skin surface to the string. In 1903, Einthoven identified various waves, still recognized today, in the electrocardiogram (the recorded electrical trace):

• The P wave characterizes the activity of the heart's atria, while 
• the QRS wave complex and the T wave characterize the heart's ventricular activity. 

For his work, Einthoven received the 1924 Nobel Prize.

Today, in addition to electrocardiographs, which have become portable, different approaches can be used to examine the heart, such as echocardiography, which uses sound waves.

About the Article Image: Einthoven's electrocardiograph, weighing 272 kg

Historical Figures Mentioned in the Article: Augustus Desiré Waller (1856–1922), Willem Einthoven (1860– 1927)

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