The question may be asked, "Why are these details about map generation important?" Most of the theories regarding cardiac activation and arrhythmogenesis are derived from the visual examination of contour maps. However, there has been very little attention given to the creation of these maps. Even if the problems of selecting activation times from the electrograms are solved, the validity of the mapping assumptions has not been critically examined. It is quite possible to generate visually different maps, all correct according to their mathematical basis, from the same data sets. Hence, differences of interpretation concerning a particular activation sequence may in fact be due to different algorithms used in contour generation rather than the underlying pathophysiology.

The methods used to generate a contour map should be examined in greater detail as it applies to cardiac mapping. Investigators must become cognizant of various methods and the strengths and weaknesses of these approaches. Until that time, the conclusions drawn from contour maps should be tempered so that investigators can develop the technical skills to deal with the problems associated with the data presentation. Various mapping approaches will change the interpretation of the data, and greater care must be taken in presenting the methods used and the impact these methods have on interpretation.

The interpolation of activation times is perhaps the greatest possible source of error in creating activation maps from infarcted regions of the heart. Because there can be dead or nonactivating regions, one can never assign a valid activation time to such regions due to the discontinuity of activation that this implies. A more accurate method would be to consider interpolating the isopotential data, as there are no discontinuities. The role of the spatial autocorrelation function would provide a level of confidence when dealing with uncertain data.

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