Fast method to determine the cardiac axis with D1 and D3

Abstract

The cardiac axis is one of the parameters that must be determined in the correct reading and interpretation of the electrocardiogram. Over the years, new formulas have emerged that allow for a more accurate calculation of its value. The goal of this article is to create a quick method for calculating the cardiac axis using leads D1 and D3. Using Microsoft Excel, the inverse tangent formula was adapted for the calculation using D1 and D3. A projection was generated with the different possible values ​​of the derivations. The method that uses D1 and aVF is one of the most popular, however it presents 2 non-measurable points. The first is between 0 and -30 degrees, and the second between the values ​​of 90 and 110 degrees. Although there are proposals with algorithms that use other leads, this article explores an alternative method with D1 and D3 based on the algebraic formula of the inverse tangeta and a mathematical method for the exact calculation of the cardiac axis. A quick method is proposed that maintains the reliability of the algebraic formula to determine if the cardiac axis is within the normal ranges (-30 to 110 degrees).