Correlations between the spread of ventricular activation and map patterns of measured and difference maps.

Three kinds of torso surface isopotential maps (measured, simulated, and difference maps) were delineated at every 1.5 (or 3) msec. during the QRS duration from the 85 unipolar lead ECG's led from the surface of a cylindrical torso model filled with perfusate and containing a canine heart undergoing Langendorff's perfusion. These three maps were compared as to the propagation process of ventricular activation obtained from the same heart and close correlations were found between the spread of ventricular activation and the map patterns of measured and difference maps. The difference map mainly reflected the proximity potential at each instant of ventricular activation in QRS duration and, when used in combination with the measured map, it was useful to estimate the spread of ventricular activation, especially around the stage of epicardial breakthrough of the activation front. It was confirmed that the interpretation of the difference map expressed in the present paper would not be misleading even if applied to a difference map obtained in a human torso model experiment.