An electrocardiogram (ECG or EKG abbreviated from the German Elecktrokardiogramm) is a graphic produced by an electrocardiograph, which records the electrical activity of the heart over time. ‘Analysis’ of the various waves and normal vectors of depolarization and depolarization yields important diagnostic information.

•It guides therapy and risk stratification for heart patients

•It helps detect electrolyte disturbances. It allows for the detection of conduction abnormalities.

•It is used as a screening tool for ischemic heart disease during a cardiac stress test.

•It is occasionally helpful with non-cardiac.

In 1856 Kollicker and Mueller discovered the electrical activity of the heart when a frog sciatic nerve/gastrocenemius preparation fell onto an isolated frog heart and both muscles contracted synchronously. Alexander Muirhead attached wires to a feverish patients’ wrist to obtain a record of the patient’s heartbeat, while studying for his DSc (in electricity) in 1872 at St. Bartholomew’s Hospital. This activity was directly recorded and visualized using a Lippmann capillary electrometer by the British physiologist John Burdon Sanderson. The first to systematically approach the heart from an electrical point-of-view was Augustus Waller, working in St. Mary’s Hospital in Paddington, London. His electrocardiograph machine consisted of a Lippmann capillary electrometer fixed to a projector. The trace from the heartbeat was projected onto a photographic plate which was itself fixed to a toy train. This allowed a heartbeat to be recorded in real time. In 1911 he still saw little clinical application for his work.

The breakthrough came when Willem Einthoven, working Leiden. The Netherlands used the string galvanometer invented by him in 1901, which was much more sensitive than the capillary electrometer that Waller used. Einthoven assigned the letters P, Q.R, S and T to the various deflections and described the electrocardiographic features of a number of cardiovascular disorders. In 1924, he was awarded the Noble Prize in Medicine for his discovery.