Principal Factor Waveforms of the Thoracic QRS Complex

High-speed, high-fidelity recordings from 150 to 180 systematically spaced points over the thoracic surface of both a dog and a man have yielded detailed maps of QRS waveforms. With the aid of digital computer analysis, these waveforms have been resolved into the minimum number of mathematically uncorrelated waveforms necessary for adequate resynthesis of all the original QRS complexes. Under the conditions imposed by the experimental design, seven (in the dog) and eight (in the man) such waveforms, or principal factors, were found. Maps were constructed for both the contribution of each principal factor to the various regions of the chest and also for the degree of reproducibility of the original waveforms by successive addition of the principal factors. The first three factors accounted for an average of 92.8% of the available information on the chest in the dog and 85.4% in the man. A resynthesis of over 99% of the information was achieved for both subjects when all remaining principal factors were also employed. This necessity for more than three factors or generating functions for reproduction of all the known surface potentials was interpreted as strong support to the equivalent multipole concept of the electrocardiographic generator. In addition, the reduction of total surface information into a compact set of waveforms of specified distribution opens an experimental avenue to the examination of such concepts in living subjects.