AXIS OF HEART ON ECG
The axis of the heart in the ECG is the main direction of the overall electrical conductions of the heart. It is very easy to assess the QRS axis which is the electrical depolarization of the ventricles. Since the total mass of the ventricles represents 90% of the total mass of the heart assessing the QRS axis can give us the knowledge of almost all of the heart problems. The QRS axis can be easily observed at the lead-II column because the lead II is fixed very near to the ventricles. This column is separately mentioned at the bottom as the last column in the ECG paper
P-axis may give us some figures for the problems in the atrium only which is 1/8 that of the heart problems.
Hence we are going to concentrate more on the QRS axis in the following article.
P-axis may give us some figures for the problems in the atrium only which is 1/8 that of the heart problems.
Hence we are going to concentrate more on the QRS axis in the following article.
Normally all the electrical activities of the heart are directed towards -30 degrees to +90 degrees in a quadrant as shown in the diagram below:-
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| Fig-1 |
In the above diagram (Fig-1) the circle has been divided with two crossed pairs of diameters perpendicular to each other to form 4 main quadrants.
For the illustrative purposes these 4 quadrants have been subdivided into sub-quadrants with 30 degrees radians each.
In Fig-1 if the axis (Yellow) is shifted to the left (-30 to -90) then it is known as Left Access Deviation (LAD) which indicates that there are problems in the left ventricle such as hypertrophy or a fascicular block.
Similarly if the axis is shifted to the right side then it is known as Right Access Deviation (RAD) which indicates there are problems in the right ventricle.
Normal ECG:- In the above circle (Fig-1) the leads I, II, and aVF lie in the normal yellow region. Hence in the ECG graph if the QRS complex is positive in the lead-I and II column and aVF column then we can confirm that the ECG is normal with normal ventricular depolarization and the axis of the electrical activities are normal.
Abnormalities:- In the above circle aVL lies on the quadrant between -30 to -90 degrees.
Hence in the ECG columns of lead-I and aVL shows positive QRS and column aVF shows negative QRS then there is LAD which indicates there are problems in the left ventricle.
Similarly if column I shows negative QRS, and the columns of aVF and the III-lead shows positive QRS then there is RAD.
If both column I and aVF shows negative QRS then there is an indeterminate axis which means extreme deviation.
See the above graph. When you have received your ECG report you may notice on your ECG graph which will look like the one shown above. (Fig-2)
Descriptions as follows:-
1)I-column:-This shows the deflection QRS by the I-bipolar electrode or lead
2)II-column:-This shows the QRS axis deflected in the II-bipolar electrode or lead
3)III-column:- This shows the QRS-axis deflected in the III-bipolar electrode or lead.
4)aVR column:-This shows the QRS deflection at the aVR-unipolar lead.
5)aVL-column:-This shows the QRS axis deflected at the aVL-unipolar lead.
6)aVF-column:-This shows the QRS axis deflected at the aVF-unipolar lead
7)V-1 column: This shows the QRS deflection at the 1st chest lead
8)V-2-column:- This shows the QRS deflection at the 2nd chest lead.
9)V-3-column:-This shows the QRS deflection at the 3rd chest lead.
10) V-4-column:-This shows the QRS deflection at the 4th chest lead.
11)V-5-column:-This shows the QRS deflection at the 5th chest lead.
12)V-6-column:-This shows the QRS deflection at the 6th chest column.
Continued next...
For the illustrative purposes these 4 quadrants have been subdivided into sub-quadrants with 30 degrees radians each.
In Fig-1 if the axis (Yellow) is shifted to the left (-30 to -90) then it is known as Left Access Deviation (LAD) which indicates that there are problems in the left ventricle such as hypertrophy or a fascicular block.
Similarly if the axis is shifted to the right side then it is known as Right Access Deviation (RAD) which indicates there are problems in the right ventricle.
Normal ECG:- In the above circle (Fig-1) the leads I, II, and aVF lie in the normal yellow region. Hence in the ECG graph if the QRS complex is positive in the lead-I and II column and aVF column then we can confirm that the ECG is normal with normal ventricular depolarization and the axis of the electrical activities are normal.
Abnormalities:- In the above circle aVL lies on the quadrant between -30 to -90 degrees.
Hence in the ECG columns of lead-I and aVL shows positive QRS and column aVF shows negative QRS then there is LAD which indicates there are problems in the left ventricle.
Similarly if column I shows negative QRS, and the columns of aVF and the III-lead shows positive QRS then there is RAD.
If both column I and aVF shows negative QRS then there is an indeterminate axis which means extreme deviation.
How to be Familiar With ECG Columns
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| Fig-2 |
See the above graph. When you have received your ECG report you may notice on your ECG graph which will look like the one shown above. (Fig-2)
Descriptions as follows:-
1)I-column:-This shows the deflection QRS by the I-bipolar electrode or lead
2)II-column:-This shows the QRS axis deflected in the II-bipolar electrode or lead
3)III-column:- This shows the QRS-axis deflected in the III-bipolar electrode or lead.
4)aVR column:-This shows the QRS deflection at the aVR-unipolar lead.
5)aVL-column:-This shows the QRS axis deflected at the aVL-unipolar lead.
6)aVF-column:-This shows the QRS axis deflected at the aVF-unipolar lead
7)V-1 column: This shows the QRS deflection at the 1st chest lead
8)V-2-column:- This shows the QRS deflection at the 2nd chest lead.
9)V-3-column:-This shows the QRS deflection at the 3rd chest lead.
10) V-4-column:-This shows the QRS deflection at the 4th chest lead.
11)V-5-column:-This shows the QRS deflection at the 5th chest lead.
12)V-6-column:-This shows the QRS deflection at the 6th chest column.
Continued next...
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