ECG (Electrocardiogram) was developed first by

The correct option is Willem Einthoven.

An electrocardiogram (ECG) is a medical test that detects and records the electrical activity of the heart over a period of time. This electrical activity is captured by electrodes attached to the skin, which detect the tiny electrical changes on the skin that arise from the heart muscle's electrophysiologic pattern of depolarizing and repolarizing during each heartbeat.

The development of the ECG is credited to the Dutch doctor and physiologist Willem Einthoven. In 1901, Einthoven invented the first practical string galvanometer, which was a major technological breakthrough. This sensitive device allowed the recording of the heart's weak electrical currents with high precision.

For his pioneering work in developing the electrocardiogram and describing the path of electrical impulses through the heart, Willem Einthoven was awarded the Nobel Prize in Physiology or Medicine in 1924. He also assigned the letters P, Q, R, S, and T to the various waves of the ECG, terminology that is still used globally today.