# How to determine the "argument" of the electrical axis of the ECG from aVF ＆ VI

This question is a continuation of the following question;
Is the definition of aVF consistent with Novosel’s formula?

Unfortunately, the article at the following URL is written in Japanese, but its statement can be summarized as follows; https://www.kango-roo.com/learning/1705/

To determine the "argument" of the electrical axis of the ECG, the aVF reading should be entered on the VF axis and the I st induction reading on the I st axis, as shown in the figure below, and the angle should be measured with a protractor.

Here, the English translations of the figure legends in the figure above are as follows;

• For the left panel: I st. induction　is -1.0 and aVF induction　is 1.0 .
• For the left panel: I st. induction　is 2.0 and aVF induction　is -3.0 .

However, the website of the British Physiological Society has a Novosel's formula, as follows;

https://www.physoc.org/magazine-articles/trigonometry-of-the-ecg/

>To be recorded on the VF axis must be ”aVF/0.85.”

Which method is correct? Or, what would be the correct way to do it?

This question is a continuation of the following question. Is the definition of aVF consistent with Novosel’s formula?

Unfortunately, the article at the following URL is written in Japanese, but its argument can be summarized as follows; https://www.kango-roo.com/learning/1705/

To determine the "argument" of the electrical axis of the ECG, the aVF reading should be entered on the VF axis and the I induction reading on the I axis, as shown in the figure below, and the angle should be measured with a protractor.

However, the website of the British Physiological Society has a Novosel's formula, which is as follows.

To be recorded on the VF axis must be ”aVF/0.85.”

Which method is correct? Or, what would be the correct way to do it?

To myself 10 hours ago, stumbling through the most rudimentary cardiology course in medical school.

The resource you cite is designed for nurses who are not comfortable with EKGs. They are the ones who understand at least the answers to the following questions.

Is the definition of aVF consistent with Novosel’s formula?

Ten hours ago you understood at least that the questions and the math were different - that aVF, VF, and heart vectors were defined by the medical community, not by mathematicians - but that was not enough.

In case you are wondering, I am not a nurse, I am not a doctor yet, I am in the process of trying the most rudimentary course, and I am a very beginner who barely understands the question I just asked.

It is very presumptuous of me to be so dismissive, but I will assume that you understand the rudiments of the relationship between aVF, VF, and heart vectors. If you don't, please refer to the Q&A I have just given you.

In summary, let me just summarize my conclusion,

And, to emphasize again,

Hy is not equal to either VF or aVF.

And,

when you want to find the heart vector, it is perfectly OK to plot I induction in the x direction, but you should not write aVF or VF in the aVF direction.

-If you really want to use aVF to obtain ECG vector, you must multiply the value of aVF by 1.16, and ** -If you really want to use VF to obtain ECG vector, you musts multiply the value of VF by 1.73, and **

This is the principle argument.

But this is a medical problem. It is not a mathematical problem. If you really knew what it meant, you would not make fun of the following problem. You are wisely aware of that. You are wisely aware of this and are asking a very good question.

Read the PR interval, etc. from the given ECG

If you have asked this question, you will recognize the crucial difference between medicine and mathematics. That is,

quickness to use in the field rather than accuracy.

In other words, this question asks how lax a professional would work in the field.

That's why you asked the question you just did. How accurate do professionals work?

Maybe, but while it is important to understand the theory properly in a basic course, maybe if you can't notice that the average electrical axis vector is wrong by eyeballing it, you won't be able to talk about it in the field.

I guess accurate analysis can be done slowly after the treatment is over. At least when an urgent decision is needed.

However, I am not a professional at all, so I can't give you crap based on my professional experience. So, instead, I will try to mathematically estimate how serious this "mistake" is with my knowledge of high school mathematics.

If you have H_y=aVF

(which is theoretically wrong), you have written the ECG values on a piece of graph paper. The declination of this wrong Heart vector is written as θ'.

Normal range of the correct mean electrical axis (not to be confused with the common Heart vector)
-30° ≤ θ ≤ +110° So, let us assume that this is
-30°≤θ' ≤ +110°
If this is mistakenly assumed to be
-30°≤θ' ≤ +110°,

Then,

-33.8° = 360*(arctan(1.16tan(6.28(-30/360))))/6.28 107.3 = 180+360*(arctan(1.16tan(6.28(110/360))))/6.28

I am not competent to judge whether this error should be considered serious or not, but perhaps the advantage of being able to make an immediate decision by reading only the aVF and I produced by the machine won out over the hassle involved, whether using the six-axis coordinate system or Novocel's formula.

Of course, the author of the article you cited may have simply misunderstood, lol.

Only someone with clinical experience would know what the temperature is in that area.