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No comprehensive cardiac examination would be complete without performing an electrocardiogram (ECG or EKG). More than 100 years old, the electrocardiograph machine remains the simplest, least expensive, and most valuable tool in cardiology. It’s easy to take this bedside instrument for granted. So, before we teach you how to use this vital medical tool, let’s take a trip back through history.

The electrocardiograph was first developed in the latter part of the nineteenth century and was the most sophisticated medical device of its time. Even so, not all physicians of that era realized its utility and the lasting success of the ECG as a clinical tool was by no means certain. It was only through a series of brilliant experiments and enhancements did the electrocardiograph reach its full potential as a diagnostic instrument.


The potential for living tissue to contain an electric current was recognized in antiquity. Aristotle observed that the electric ray incapacitated its prey with a shock from an organ located in its pectoral fin. Roman physicians in the first century A.D. used such electrically charged sea creatures to treat the pain of headache and acute gout. This phenomenon remained a curiosity of nature until 1787 when Luigi Galvani of the University of Bologna observed that the leg muscle of a frog would contract when stimulated by an electrostatic apparatus. A debate ensued as to whether the frog’s muscle was able to react only to an outside influence or whether the electricity was present in the muscle itself. Galvani believed the latter and eventually demonstrated that the stimulating electrical source originated within the living tissue. Galvani’s nephew, Giovanni Aldini later expanded on his uncle’s theories with a series of sensational experiments of his own. In 1803 at the Royal College of Surgeons in London, Aldini applied an electrical stimulus to the limbs of an executed criminal, causing the deceased man’s muscles to contort.


Many historians believe that Aldini’s experiments were the inspiration for Mary Shelley’s Frankenstein.

By the 1870s, experiments demonstrated that the muscular pumping of the heart was related to an intrinsic electrical impulse. Instruments of the time did not have the capability to further explain the phenomenon, but this launched the search for an acceptable recording device of the heart’s electrical current.


Two men, Augustus D. Waller of London and Willem Einthoven of Leiden pioneered the path to the modern electrocardiograph machine (Figure 1-1). In 1887, Waller used an instrument called a capillary electrometer to take the first surface measurement of the heart’s electrical activity that did not require opening the chest and exposing the beating heart. He first termed the recording an “electrogram” and later, a “cardiogram.”

Figure 1-1.

Augustus D. Waller (left) and ...

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