Abstract
When first learning how to read ECGs, the electromotive force generated by the heart (R wave) can be represented by the vector force, and we analyze the direction of the electrical axis according to Einthoven's triangle. Moreover, Wilson introduced zero potential electrode-merging tree limb lead signals, and developed unipolar chest leads. However, Wilson's zero potential is not a true zero potential, electrically speaking. We must be aware that surface ECGs are essentially the measurement of the voltage difference between indirect and bipolar electrodes. This article summarizes the mechanisms of normal and abnormal surface ECG from the above viewpoints.
