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==The ECG represents the sum of the action potentials of millions of cardiomyocytes== | ==The ECG represents the sum of the action potentials of millions of cardiomyocytes== | ||
{| class="wikitable" align=" | [[Image:Hart_cells_en.png|thumb|right|The heart consists of approximately 300 trillion cells]] | ||
[[Image:cells_in_rest_en.png|thumb|right|In rest the heart cells are negatively charged. Through the depolarization by surrounding cells they become positively charged and they contract.]] | |||
[[Image:Ion_currents_en.png|thumb|During the depolarization sodium-ions stream inwards the cell. Subsequently the calcium-ions stream into the cell. These calcium-ions give the actual muscular contraction. Finally the potassium-ions stream out of the cell. During the repolarisation the ion concentration is corrected. On the ECG, an action potential wave coming towards the electrode is shown as a positive (upwards) signal. Here the ECG electrode is represented as an eye.]] | |||
The individual [[action potential|action potentials]] of the individual cardiomyocytes are averaged. The final result which is shown on the ECG is actually the average of trillions of microscopic electronical signals. | |||
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|<flashow>http://nl.ecgpedia.org/images/5/50/Single_cardiomyocyte.swf|height=350px|width=400px</flashow> | |<flashow>http://nl.ecgpedia.org/images/5/50/Single_cardiomyocyte.swf|height=350px|width=400px</flashow> | ||
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{{clr}} | {{clr}} | ||
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==The different ECG waves== | ==The different ECG waves== | ||
[[ | [[File:PQRS_origin_en.png|thumb|left|200px|The origin of the different waves on the ECG]] | ||
[[Image:Epi_endo_en.png|thumb| The QRS complex is formed by the sum of the electric avtivity of the inner (endocardial) and the outer (epicardial) cardiomyocytes]] | [[Image:Epi_endo_en.png|thumb| The QRS complex is formed by the sum of the electric avtivity of the inner (endocardial) and the outer (epicardial) cardiomyocytes]] | ||
[[Image:Qrs-shapes.png|thumb| Example of the different QRS configurations]] | [[Image:Qrs-shapes.png|thumb| Example of the different QRS configurations]] | ||
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Using these 10 electrodes, 12 leads can be derived. There are 6 extremity leads and 6 precordial leads. | Using these 10 electrodes, 12 leads can be derived. There are 6 extremity leads and 6 precordial leads. | ||
===The Extremity Leads=== | ===The Extremity Leads=== | ||
[[ | [[File:ECGafleidingen.jpg|thumb|left|200px]] | ||
The extremity leads are: | The extremity leads are: | ||
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{{clr}} | {{clr}} | ||
{{:Technical Problems}} | {{:Technical Problems}} | ||
{{box| | |||
==References== | ==References== | ||
<biblio> | <biblio> | ||
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#Kligfield pmid=17322457 | #Kligfield pmid=17322457 | ||
</biblio> | </biblio> | ||
}} | |||
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==External links== | ==External links== | ||
*[http://www.ecglibrary.com/ecghist.html An extensive history of the ECG] | *[http://www.ecglibrary.com/ecghist.html An extensive history of the ECG] | ||
}} | |||
[[nl:Grondbeginselen]] | [[nl:Grondbeginselen]] | ||
[[Category:ECG Course]] | |||