Basics: Difference between revisions

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[[Image:nsr.png|thumb| A short ECG registration of normal heart rhythm (sinus rhythm)]]

[[Image:Normaal ecg.jpg|thumb| An example of a normal ECG. ''Click on the Image for an enlargement'']]

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  An ECG is a registration of the heart's electric activity.

Just like skeletal muscles, the heart is electrically stimulated to contract. This stimulation is also called ''activation'' or ''excitation''. Cardiac muscles are electrically charged at rest. The inside of the cell is negatively charged relative to the outside (resting potential). If the cardiac muscle cells are electrically stimulated they depolarize (the resting potential changes from negative to positive) and contract.

As the impulse spreads through the heart, the electric field changes continually in size and direction. The ECG is a graphical visualisation of these electric signals in the heart.

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[[Image:conduction_system_en.png|thumb]]

[[Image:ECG_principle_slow.gif|thumb|The electric discharge of the heart, first slowly]]

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[[Image:PQRS_origin_en.png|thumb| 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]]

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[[Image:Einthoven.gif|thumb|[[w:Einthoven|Willem Einthoven (1860-1927), the founder of the current ECG]]]]

[[Image:einthECG1.png|thumb|ECG from Eindhoven's first publication. ''Pfügers Archiv March 1895, page 101-123'']]

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[[Image:ECGelectrodes.jpg|thumb|click on the Image for an enlargement]]

Electric activity going through the heart, can be measured by external (skin)electrodes. The electrocardiogram (ECG) registers these activities from these electrodes which have been attached on diffrent places on the body. In total, twelve leads are calculated using ten electrodes.

Using these 10 electrodes, 12 leads can be derived. There are 6 extremity leads and 6 precordial leads.

[[Image:ECGafleidingen.jpg|thumb]]

The extremity leads are:

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The precordial, or chestleads, '''(V1,V2,V3,V4,V5 and V6)''' 'observe' the depolarization wave in the frontal plane

''Example'': V1 is close to the right ventricle and the right atrium. Signals in these areas of the heart have the largest signal in this lead. V6 isthe closest to the laterale wall of the left ventricle.

In case of an inferior wall infarct, extra leads may be used:

#In a right side ECG, V1 and V2 remain on the same place.V3 to V6 are placed on the same place but mirrored on the chest. So V4 is in the middle of the right clavicle. On the ECG it should be marked that it is a ''Right sided ECG''. V4R (V4 but right sided) is a sensitive lead to diagnose right ventricular infarction.

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<biblio>

#Dubois Du Bois-Reymond, E. ''Untersuchungen uber thierische Elektricitat''. Reimer, Berlin: 1848.