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 degrees0
*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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