Its early incarnations required the patient to plunge both hands and one foot into buckets of salt solution.
The device then produced moving trace on graph paper, monitoring the rhythm of the heart as it pumps blood around the body.
Einthoven was well aware of the potential benefits of the his discovery, writing in 1906 that it would help doctors “to give relief to the suffering of our patients.”
Over the years the ECG became much smaller and monitored the heart’s activity using electrodes placed on the patient’s limbs and chest.
The ECG recording is now best known as the dancing green dot on a computer monitor, accompanied by a regular beeping noise of the kind used for the theme tune of the BBC TV show Casualty.
Einthoven, the son of a doctor, was born on 21 May 1860 in Indonesia (then the Dutch East Indies).
His family returned to the Netherlands when he was still a young boy and he went on to study medicine in Utrecht.
He began his work on the electrical currents of the heart in 1895 and received his Nobel Prize “for the discovery of the mechanism of the electrocardiogram” in 1924. Einthoven died three years later.