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QRS axis: Difference between revisions
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This indicates a normal heart axis. Usually, these two leads are enough to diagnose a normal heart axis! A normal heart axis is between -30 and +90 degrees. | This indicates a normal heart axis. Usually, these two leads are enough to diagnose a normal heart axis! A normal heart axis is between -30 and +90 degrees. | ||
*A '''left heart axis''' is present when the QRS in lead I is positive and negative in II and AVF. (between -30 and -90 | *A '''left heart axis''' is present when the QRS in lead I is positive and negative in II and AVF. (between -30 and -90 degrees) | ||
*A '''right heart axis''' is present when lead I is negative and AVF positive. (between +90 and + | *A '''right heart axis''' is present when lead I is negative and AVF positive. (between +90 and +180) | ||
*An '''extreme heart axis''' is present when both I and AVF are negative. This is a rare finding. | *An '''extreme heart axis''' is present when both I and AVF are negative. (axis between +180 and -90 degrees). This is a rare finding. | ||
The largest vector in the heart is from the AV-node in the direction of 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. 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 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. A horizontal line towards the left arm is defined as 0 degrees. | ||
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== Right axis deviation== | == Right axis deviation== | ||
[[Image:rightaxis.jpg|thumb| Right heartaxis]] | [[Image:rightaxis.jpg|thumb| Right heartaxis]] | ||
[[File:E000604.png|thumb|Another example of an ECG with a right heart axis]] | |||
Causes of right axis deviation include: | Causes of right axis deviation include: | ||
*Normal variation (vertical heart with an axis of 90º) | *Normal variation (vertical heart with an axis of 90º) | ||