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QRS axis: Difference between revisions
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→How do you determine the electrical heartaxis
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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]] | ||
<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) | |||
*Largest QRS deflection in lead AVF: the electrical activity is directed down. | |||
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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 | 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"> | ||