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How to Read ECG Electrocardiogram

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

The electrocardiogram works on the fact that heart muscle is stimulated to contract by electricity and that a normal heart will project this electricity across your chest in a predictable way.

The ecg electrocardiogram has twelve connected electrodes. Each 'lead' acts like one camera angle capturing the path the electricity takes across your chest. By looking at all the printouts of the ecg a trained observer can put them together his/her mind into a three dimensional view of heart activity. Each event in the production of a heart beat makes a characteristic shape or 'signature' on the ecg reading.

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 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 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 heart attacks and new heart attacks respectively.

Doctors learn to 'read' ecg's by learning these basic patterns to look for, and then fine tune their interpretations through experience reading hundreds to thousands of ECGs. Typically a doctor reads an ecg the way you'd scan a magazine article looking for obvious things that jump off the page, then in more detail from the upper left corner down to the lower right corner.

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    Last Updated:
    December 15 2013
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