Improved activation time assignment of unipolar electrograms from ischemic canine epicardium.

Aims: The present study attempts to develop an objective, statistically based set of criteria for activation time determination from unipolar electrograms (U-EGMs) using a standard of activation related to biophysical theory.

Methods: A high-resolution assembly of U-EGMs obtained from the epicardial surface of the canine postinfarction heart were analyzed in order to achieve the best prediction of local versus distant activation. An activation time standard (ATS) consisted of three properties: (1) propagation of activation, evidenced by a linear temporal shift of waveforms from closely spaced U-EGMs with little or no decay in amplitude; (2) cycle length-dependent changes of those propagating waveforms; and (3) evidence of electrotonic deflections, seen as nonpropagating potentials having decaying amplitude with distance.

Results: A number of U-EGM features were calculated and subjected to analysis by comparing their occurrence with the ATS. A discriminant function analysis incorporating multiple features (Voltage, -dV/dt and Ratio) of major U-EGM deflections improved prediction of activation time of complex fractionated EMGs from ischemic canine epicardium to 90%.

Conclusion: A unique discriminant function based on sound biophysical principles markedly improved prediction of activation time of complex U-EGMs from ischemic canine epicardium. A computerized version of the algorithm could be developed to provide more accurate activation maps for both basic and clinical use.