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ECG Explanation

The ECG (sometimes called EKG), is short for electrocardiogram. The ECG is one of the most common and important tests done in hospital today.

ECG Explanation

The ecg works on the fact that heart muscle is stimulated by bio-electricity to contract. A normal heart will project this electricity across your chest in a predictable way with a predictable healthy signature.

The ecg electrocardiogram has twelve connected electrodes. Each 'lead' acts like one camera angle capturing the path the electricity takes from your pacemaker to the rest of your heart. By looking at the results of each lead a trained observer can put their patterns together in their mind as a three dimensional view of heart activity. Each event in the production of a heart beat makes a characteristic electrical signature.

ecg machine picture
child ecg picture

Above left is a photograph of a portable ECG machine. And right, you can see how it's connected. There are four 'limb' straps (1) placed around each of your wrists and each ankle. The bulbs (2) are then connected across your chest in a predetermined order and a 'trace' of electrical activity drawn by the machine as below.

ECG Q waves
Normal ECG Reading
ECG T-waves


normal ecg



Certain electrical patterns are read by health practitioners to help diagnose a variety of abnormalities such as abnormal blood chemistry, arrhythmia misfiring, and of course, heart attacks. ECG Q waves and inverted ECG T waves are two diagnostic wave forms seen in old and new heart attacks respectively.

Doctors and nurses learn to 'read' ecg's by learning basic patterns to look for. They fine tune their interpretations through experience reading hundreds or thousands of ECGs over a career. Typically a doctor reads an ecg the way you'd scan a magazine article looking for obvious things that jump off the page then zoom in for greater detail.

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    Last Updated:
    April 22 2016
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