## QRS AXIS DETERMINATION

During ECG interpretation, cardiacÂ Axis, or direction of electrical impulses, may be normal (physiologic) or abnormal (pathologic), suggesting abnormal cardiac conductivity. Although every deflection obtained on the ECG will have an axis, we will focus on the ventricular axis. When we think of our cardiac monitoring lead placement, we have to understand cardiacÂ Vectors, which is the […]

## Cardiac Axis Determination – Part 6

By now you can predict the QRS axis in the frontal plane within 15 degrees as long as you have an equiphasic (or isoelectric) lead in the frontal plane. So what constitutes a normal QRS axis? What is a left axis deviation? A right axis deviation? If you don’t have a copy of the hexaxial […]

## Cardiac Axis Determination – Part 5

In Part 4 I promised that I’d show you a fascinating relationship between the standard 12-lead ECG and the hexaxial reference system. You will recall that to use the hexaxial reference system, you find the most equiphasic (or isoelectric) lead in the frontal plane (first 6 leads of the 12-lead ECG) and look for the […]

## Cardiac Axis Determination – Part 4

By now you should have a fairly good grasp of how the hexaxial reference system is derived from the first 6 leads of the 12 lead ECG. Before we break down the finished diagram, let’s look at the hexaxial reference system laying on top of the patient’s anterior chest, with the arrows and leads in […]

## Cardiac Axis Determination – Part 3

In Part 2 we discussed the heart’s mean electrical vector and how Einthoven’s Triangle (leads I, II, and III) can be redrawn to form the first 3 spokes of the hexaxial reference system. Essentially, we ended up with a shape like the one on the right. When leads I, II, and III are drawn this […]

## Cardiac Axis Determination – Part 2

In Part 1, we looked at Einthoven’s Equilateral Triangle and Einthoven’s Law, and I told you that it was the key to understanding the formation of the hexaxial reference system. But before we delve further into the hexaxial reference system (the instrument we’ll be using to calculate the heart’s QRS axis) we need to address […]