EKG and Axis

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Specializes in Medsurg/Critical Care.

This is one thing I don't understand about EKG analysis. Most of the nurses I ask in the unit really act as if axis is insignificant and none have been able to explain it to me.

I found this little site... http://www.ecglibrary.com/axis.html...and it describes using leads I and aVF to determine axis. But what am I looking for in these leads?

Forgive my stupidity and thank you in advance.

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Specializes in CVICU, ICU, RRT, CVPACU.
This is one thing I don't understand about EKG analysis. Most of the nurses I ask in the unit really act as if axis is insignificant and none have been able to explain it to me.

I found this little site... http://www.ecglibrary.com/axis.html...and it describes using leads I and aVF to determine axis. But what am I looking for in these leads?

Forgive my stupidity and thank you in advance.

Axis deviation is unimportant to people who dont understand it or cant explain it to you:D. There is a great book entitled "12-lead ECG for Acute and Critical Care Providers" and semiar by a national speaker/Paramedic named Bob Page. It explains axis and axis deviation in depth and is VERY interesting if you ever get the chance to go to it.

Axis is the direction of electrical impulses as they travel through the heart muscle. The impulses and direction can tell us different things about the severity of the patients condition and help with treatment. We use leads I, II, and III to determine axis. Try to visulize lead I at the Left Atrium, Lead II at the apex of the heart and Lead III near the right ventricle. Normally impulses start in the SA node and and travels down the septum toward lead II causing an upward deflection in the QRS. If the electrical impulse deviates from this and moves more toward the left side of the heart (left axis deviation) it causes a more positive deflection of the QRS in lead I (left heart leads) and a more negative deflection in the leads that the impulse is moving away from, which in this case would be leads II and III (apex and right heart). In arrhythmias such as V-Tach you have an Extreme right axis deviation. Simply reverse it. If you have a right axis deviation you show the electrical impulse moving toward lead III and away from Lead I and II. This would show a positive deflection in lead III and more of a negative deflection in Leads II and I.

Differentiating between Right and Left axis deviations can help to diagnose a number of things accoding to Page. A right axis deviation can indicate:

  • Posterior Hemiblock
  • Right Vent hypertrophy or enlargement
  • Cor pulmonale, or right heart failure
  • PE
  • Arrhythmias

Left Axis Deviation:

Pathalogic

Inferior MI

WPW type A

LVH

HERE is a great link for understanding axis. I hope this helps you a little and doesnt make you more confused.

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Specializes in ER/ICU/Flight.

not stupid at all...and you have linked to a very good website.

the axis can be insignificant but it is important to understand what it means. axis refers to the electrical pathways of the heart, relating to right, left or normal.

know the normal qrs complex for each lead, like it says on the website, you first look at I and aVF and you are looking for the deflection of the qrs. they should both be positive (+ ve) as opposed to - ve. look for the deflections and follow the guide on that website.

among the causes listed on the webpage for different kinds of deviation, the big danger is having an extreme right axis deviation (or erad) because you have what's called a bi-fascicular block, meaning both the anterior and posterior fascicles are blocked as they pass through to the ventricles. these fascicles are located just above the bundle of his. a bi-fascicular block is more likely to degenerate into a high-grade av block (mobitz II, or 3* avb).

i've seen patient's with erad labeled on their telemetry as having a normal sinus rhythm just because there's an upright p for each qrs, rate 60-100, regular rhythm and those don't necessarily make for an NSR!

hope this helps somewhat, and i'm sure many people much smarter than me will probably chime in and explain it much better.

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Specializes in ER/ICU/Flight.

sorry, i hadn't seen joeyzstj's posting.

bob page is one of the most dynamic speakers in the country and his 12 lead course is better than any i've ever sat through.

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Specializes in Medsurg/Critical Care.

Thanks for all the information. I have to sit down and absorb it all...and I'll let you know if I have any other questions.

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Another thing to add, there are 4 quadrants with axis deviation: normal is both deflections (QRS) in lead I and aVF are positive; right axis deviation would be if lead I is downward and the QRS in aVF is postive; Left axis deviation is if lead I is positive and lead aVF is negative; and indeterminate is BAD and that is when both are negative. An easy way to remember this is to but both thumbs up: Left thumb will be lead I and Right thumb will be aVF. Ok, now if lead one is upright (QRS) then you put you left thumb up and if lead aVF is downright you put your right thumb down... you are left with the left thumb up and this left axis deviation. Clearly, this is only good for a memory jogger and you should understand it in more depth than this. Another thing to keep in mind is with normal axis deviation there is a portion of it (30 degrees) that is questionable and could be normal or abnormal. Good luck with learning this. It is pretty interesting. The idea is that the electrical impulse moves from the SA node through the internodal pathways to the AV node down the bundle of his and bundle branches (Right and Left). Left bundle branch bifurcates into anterior and posterior hemiblocks. Contraction should occur from the septum to the ight ventricle and when the Left ventricle contracts the septum normally moves a little inward and helps the Left ventricle push about blood better. When you have a block, this is decreased and causes a less of contraction as well as some eventual valvular issue and subsequent heart failure. Good luck it is all very interesting.

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