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How Do EKG Machines Work?

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The electrocardiograph machine, or EKG, is one of the most common medical machines found in hospitals today, and is an essential tool for keeping doctors and nurses updated on the status of their patients. The EKG interprets electrical signals produced by the heart over time, capturing them and recording them via electrodes attached to the skin.

If you have ever stayed at a hospital overnight under constant monitoring, you’ve probably seen one of these EKG machines, though you might not have noticed it amidst the multitude of wires and flashing buttons surrounding your bed. Nonetheless, it played a crucial role in keeping you alive and in a stable condition. But how does an EKG machine actually work? To understand exactly what this device is and what it does, some background information on the name of the device itself could be of good use.

Background and Etymology

The term EKG is an abbreviation of the original German word “elektrokardiogramm”. Its etymology derives from the Greek words, electro, meaning having to do with electrical activity; cardio, meaning heart; and graph, meaning “to write”.

The first breakthrough in EKG technology was made by the Dutch scientist Willem Einthoven, who in 1903 developed series of prototype string galvanometers that he used to build the first ever EKG machine. Before Einthoven, scientists were aware that the heart produced electrical signals, but they had no way of recording them without attaching electrodes directly to the heart. Einthoven’s 600 lbs machine was the first to allow recording of the heart’s electrical impulses via non-invasive method. Though many advances to the EKG have been made since Einthoven’s time, the core concepts are still the same and the letters which he assigned to the heart’s various electrical deflections (P, Q, R, S and T) are still used today.

The Heart

To understand how an EKG can record a person’s heart impulses through his or her skin, it can prove helpful to think of the human body as a large sack of salt water. That is, a natural conductor of electricity.

The human heart is a pump made up of four chambers. The two upper chambers are the atria, and the two lower ones are called ventricles. The body’s natural electric current causes the heart muscles to contract and pump blood through the heart’s chambers and throughout the body. To measure the sympathetic electrical impulses that lead to heart contractions, an EKG technician attaches electrodes to selected parts of the patient’s torso, directly on the skin. Small pads are placed between the skin and the electrodes to improve electrical conductivity and to function as buffers to reduce patient discomfort. These electrode leads must be placed at very specific points in the body, which are more directly connected to specific kinds of cardiac electrical signals.

These electrodes are extremely sensitive. In order to measure heart muscle activity, they have to be able to detect incredibly minute changes in potential energy on the body’s skin. These changes are communicated through electrical signals measuring only about 1mV (millvolt) or less.

There are three different electrical waves that are recorded by the EKG machine, which are represented in a digital graph, which can be printed out on paper for closer analysis. This line graph is what most people associate with electrocardiographs, as it is commonly referred to and shown in medical dramas and films.

EKG readings are helpful in determining whether a patient is likely to suffer a heart attack before it actually happens. It can also detect past heart attacks and pinpoint irregularities in the heart’s rhythm and activity.