Electrical axis

From CardioWiki

Electrical axis of the heart is a term used in cardiology and functional diagnostics, reflecting the electrical processes taking place in the heart.

The direction of the electric axis of the heart shows the total value of the bioelectric changes that occur in the cardiac muscle with each contraction. The heart is a three-dimensional organ, and in order to calculate the direction of electric axis, cardiologists represent the thorax in the form of a coordinate system.

Each electrode, when electrical axis is recorded, detects bioelectric excitation occurring in a specific part of the myocardium. If you project the electrodes onto a conditional coordinate system, you can calculate the angle of the electric axis, which will be located where the electrical processes are the strongest.

Electrical axis is indicated as the alpha angle. It can have a normal, horizontal or vertical position. Moreover, in a lean person, the axis of the heart is more vertical relative to the average values, while in an over-weight person the axis is more horizontal. The electric axis of the heart can deviate under various pathological conditions. For example, a conduction disorder (block) can shift it to the right or to the left.

Electrical axis.jpg

The values of electric axis in degrees from -180 to 180:

  • From -180 to -90 - Extreme axis deviation
  • From -90 to -45 - Moderate left axis deviation
  • From -45 to -15 - Mild left axis deviation
  • From -15 to 15 - Horizontal axis position
  • From 15 to 85 - Normal axis position
  • From 85 to 105 - Vertical axis position
  • From 105 to 180 - Right axis deviation

You can find out your electrical axis of the heart at home using the ECG Dongle [1].