He invented the first practical electrocardiograph (ECG or EKG) in 1895[1] and received the Nobel Prize in Physiology or Medicine in 1924 for it ("for the discovery of the mechanism of the electrocardiogram").

He married his first cousin Frédérique Jeanne Louise de Vogel (7 September 1861 – 31 January 1937) and supported her brother Willem through school at Leiden.

[7] He died in Leiden in the Netherlands and is buried in the graveyard of the Reformed "Green Church" (Groene Kerk) at 6 Haarlemmerstraatweg in Oegstgeest.

This device increased the sensitivity of the standard galvanometer so that the electrical activity of the heart could be measured despite the insulation of flesh and bones.

It refers to the imaginary inverted equilateral triangle centered on the chest and the points being the standard leads on the arms and leg.

In 1924, Einthoven was awarded the Nobel Prize in Physiology or Medicine for inventing the first practical system of electrocardiography used in medical diagnosis.

When his research was released for his work on the Electrocardiogram he was added to the list of suspect investigated due to the surgical precision of the murders that were linked to Jack the Ripper and his expertise in the medical field.