Sequential changes in the difference maps of potential distributions and the extent of myocardial infarctions

Surface isopotential maps were recorded immediately before and 1 week after production of myocardial infarctions in 15 dogs. Difference maps were made by subtracting pre-infarction maps from time-equivalent post-infarction maps, and the electrophysiological basis of the difference maps was examined. The dogs were classified into 4 groups according to the location and extent of the infarction. Difference maps of these groups displayed an area with significant surface potential defects due to infarction. These changes were observed during specific phases of ventricular activation and in specific portions of the chest surface, depending on the location and extent of the infarction. These findings were well accounted for by the hypothesis that difference maps reflect the loss of activation fronts as a result of the infarction.