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2 bytes added, 19:58, 8 May 2009
Undo revision 8798 by Odesk1 (Talk)
|nextpage=Rate
|nextname=Step 1: Heart Rate
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{{authors|
|mainauthor= [[user:Vdbilt|I.A.C. van der Bilt, MD]]
|moderator= [[user:Vdbilt|I.A.C. van der Bilt, MD]]
|editor=
}}
}}
==How do I begin to read an ECG?==
==The ECG represents the sum of the action potentials of millions of cardiomyocytes==
{| class="wikitable" align="right" width=385px font-size="70%"
| This movie shows the contraction of a single (rabbit) heart cell. The glass electrode measures the electrical current in the heart cell (with the[[w:Patch_clamp|patch-clamp method]]). The electrical signal is written in blue and shows the actionpotential. ''Courtesy of Arie Verkerk and Antoni van Ginneken, AMC, Amsterdam, The Netherlands''.
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|<flashow>http://nl.ecgpedia.org/images/5/50/Single_cardiomyocyte.swf|height=350px|width=400px</flashow>
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| This movie shows the contraction of a single (rabbit) heart cell. The glass electrode measures the electrical current in the heart cell (with the[[w:Patch_clamp|patch-clamp method]]). The electrical signal is written in blue and shows the actionpotential. ''Courtesy of Arie Verkerk and Antoni van Ginneken, AMC, Amsterdam, The Netherlands''.
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[[Image:Hart_cells_en.png|thumb|leftright|The heart consists of approximately 300 trillion cells]][[Image:cells_in_rest_en.png|thumb|leftright|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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