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Basics

65 bytes added, 07:41, 30 May 2009
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==The ECG represents the sum of the action potentials of millions of cardiomyocytes==
[[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.{| class="wikitable" align="rightcenter" width=385px font-size="70%"
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[[Image:Hart_cells_en.png|thumb|left|The heart consists of approximately 300 trillion cells]][[Image:cells_in_rest_en.png|thumb|left|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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==The different ECG waves==
[[ImageFile: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:Qrs-shapes.png|thumb| Example of the different QRS configurations]]
Using these 10 electrodes, 12 leads can be derived. There are 6 extremity leads and 6 precordial leads.
===The Extremity Leads===
[[ImageFile:ECGafleidingen.jpg|thumb|left|200px]]
The extremity leads are:
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{{:Technical Problems}}
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==References==
<biblio>
#Kligfield pmid=17322457
</biblio>
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==External links==
*[http://www.ecglibrary.com/ecghist.html An extensive history of the ECG]
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[[nl:Grondbeginselen]]
[[Category:ECG Course]]
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