Shows the axis of the heart to propagate depolarization that extends into the heart to constrict the myocardium. In fact, the heart axis shows the direction in which most electrical stimuli move. When you read electrocardiograms, the heart axis indicates the direction of propagation of the stimulus. In addition, the direction of the heart axis indicates many disorders and changes in the heart. Usually at least two derivations are required to determine the axis. Algebraic sum is used to calculate the positive and negative of the QRS complex. For example, if the complex has a long R and a short S, count the number of cells occupied by R on the electrocardiogram paper vertically and count it as a positive digit, and count the number of negative cells as a negative digit. We put and then calculate its algebraic sum. If the biphasic complex is one and its size S and Rare exactly equal, the algebraic sum will be zero, which is why in this derivation the electric force is equal on both sides, so it is at the central point. But if the algebraic sum is a positive or negative numerical derivation, that is, the corresponding derivation line is deviated in the positive or negative direction. To determine the axis, it is usually best to see which of the 6 organ derivatives is biphasic, and then find the derivative perpendicular to it, the best lead being the AVF lead perpendicular to the D1 lead or the AVL lead perpendicular to the D2 lead and the AVR lead It is perpendicular to the D3 lead, the most common being the first. Examining an EKG will show that as the location of the positive electrode in the breast derivatives changes sequentially.