Identifying uncertainty in epicardial activation maps

Epicardial activation maps in surviving infarct regions are derived by: (1) choosing a specific activation time at each recording site and (2) interpolating the data so that contours can be drawn representing the activation wavefronts. Concentrating on the latter problem, the spatial autocorrelation function (SAF) was calculated to evaluate the smoothness or regional correlation of activation times obtained at neighboring recording sites. Low values of the SAF would imply discontinuities (dead tissue) in the underlying data. These represent faults and traditional methods of interpolation cannot be applied as they would assume an activation time over dead tissue. Hence, contour generation must map around these faults. Another approach for defining uncertainty is to examine ambiguous electrograms and choose either the earliest or latest activation times. Two activation maps are created which can be differenced to form an isopachous map. This isopach then depicts the region of uncertainty. These methods have been used in a data set of 17 dogs with four day-old infarcts. The presence and extent of the uncertainty region have a corresponding influence on the visualization of the map and its interpretation.<
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