Whilst the life-giving function of the heartbeat has been known since the Epic of Gilgamesh, it has only been in the last couple of centuries that medical staff have been able to effectively measure its behaviour and detect potential serious issues using medical equipment.
Although a wide range of heart rate monitors exist, the most common and critical of these is the electrocardiogram or ECG, a test that primarily checks for heart conditions, heart disease and other potentially serious health conditions.
The number of lives the ECG has saved is quite possibly incalculable, whilst it has also been adapted for use in fitness and wellness to track workout intensity in real time.
Its most common use is in cardiology clinics and in emergency health settings to track the heart rates of patients in hospital wards and provide an early warning sign of potential anomalies that may require immediate attention.
Whilst there were some early experiments by Alexander Muirhead in 1872, John Burdon-Sanderson with frogs in 1882 and Augustus Waller in 1887, it was in 1895 that Willem Einthoven helped to develop the first ever practical ECG monitor.
By using a string galvanometer, which passed a thin wire through two strong electromagnets, Mr Einthoven had a machine strong enough to detect the electrical current produced by heartbeats without placing electrodes directly on the heart itself.
It was not exactly a flawless machine at first; it weighed 270kg, needed five people to operate it and needed a water-cooling system to stop the electromagnets from overheating, but the principle worked, and many modern ECGs use the same terminology and principles of his string galvanometer.
It was useful in creating an early study on how cardiovascular disorders appeared on electrocardiograms, something that has proven vital for early intervention during cardiac events.
He would win the Nobel Prize for this achievement in 1924, three years before he died at the age of 67.
His legacy lives on in countless heart monitors, which continue to save lives to this day.