Two-dimensional generator function for the vector cardiogram for use in volume conduction models of the thorax
An electrocardiogram (ECG) measures the electrical activity of the heart on the surface of the skin. Volume conduction models of the thorax can be designed to simulate such measurements. However, to drive such simulations a generator function is required to describe the electrical activity of the heart. Although such simulations, varying in complexity, are discussed in literature, there is a need for a simplified, though comprehensive approach that can be used as a concise introduction to this topic, or for cases where one is primarily interested in first-order approximations of this problem. In this article an overview of the vector interpretation of the ECG, also known as a vector cardiogram (VCG), is presented in the two-dimensional frontal plane of a human. The derivation of the equivalent electric dipole (i.e. the cardiac vector) from the VCG, which can be used as a current-source generator function for volume conduction model simulating the ECG, is discussed. A procedure for implementing such a volume conduction model with the finite element technique, using this simplified two-dimensional generator function, is discussed and the results are presented. The general features observed in recorded ECG leads agree with those predicted by this simple model.