QRS axis: Difference between revisions

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[[Image:hartas2.jpg|thumb|The heartaxis indicates the average direction of the depolarization wave. A normal heartaxis, the picture shows an example, is between -30 and +90 degrees. In this example, the heartaxis is +45 degrees.]]
[[Image:hartas2.jpg|thumb|The heartaxis indicates the average direction of the depolarization wave. A normal heartaxis, the picture shows an example, is between -30 and +90 degrees. In this example, the heartaxis is +45 degrees.]]
[[Image:hart_axis.png|thumb]]
[[Image:hart_axis.png|thumb]]
[[Image:einthhartas.png|thumb|Heartaxis from the original publication of Einthoven. Reprinted from The Lancet, March 30 1912, Einthoven W., ''The Different Forms of The Human Electrocardiogram and Their Signification'', 853-861, 1912, with permission from Elsevier]]
<flashow>http://nl.ecgpedia.org/images/b/bc/Normal_SR_vector.swf|height=300px</flashow>
 
When you average all electrical signals from the heart, you can indicate the direction of the average electrical depolarization with an arrow (vector). This is the heartaxis. Especially a change of the heartaxis or an extreme deviation can be an indication for pathology.
When you average all electrical signals from the heart, you can indicate the direction of the average electrical depolarization with an arrow (vector). This is the heartaxis. Especially a change of the heartaxis or an extreme deviation can be an indication for pathology.
 
*Largest QRS deflection in lead I: the electrical activity is directed to the left (of the patient)
<i>For example:</i>
*Largest QRS deflection in lead AVF: the electrical activity is directed down.
 
*Biggest QRS deflection in lead I: the electrical activity is directed to the left (of the patient)
*Biggest QRS deflection in lead AVF: the electrical activity is directed down.
 
This indicates a normal heartaxis. Usually, these two leads are enough to diagnose a normal heartaxis!
This indicates a normal heartaxis. Usually, these two leads are enough to diagnose a normal heartaxis!


The biggest vector in the heart is from the AV-node in the direction of the ventricular depolarization. Under normal circumstances, this is directed left and down.(towards leads I and AVF). The position of the QRS vector is given in degrees. See the figure, the middle of the figure is the AV-node. A horizontal line towards the left arm is defined as 0 degrees.
The largest vector in the heart is from the AV-node in the direction of the ventricular depolarization. Under normal circumstances, this is directed left and down.(towards leads I and AVF). The position of the QRS vector is given in degrees. See the figure, the middle of the figure is the AV-node. A horizontal line towards the left arm is defined as 0 degrees.


A normal heartaxis is between -30 and +90 degrees.
A normal heartaxis is between -30 and +90 degrees.
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:When all extremity leads are biphasic, the axis is directed to the front or back, in a transverse plane. The axis is than '''undetermined'''.
:When all extremity leads are biphasic, the axis is directed to the front or back, in a transverse plane. The axis is than '''undetermined'''.
{{clr}}
{{clr}}
==Abnormal heartaxis==
==Abnormal heartaxis==
<div style="float:right">
<div style="float:right">

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