Efficacy of noncontact mapping in detecting epicardial activation.

The aim of this study is to determine if some of the characteristics of reconstructed unipolar electrograms from the noncontact mapping system can be used to detect epicardial electrical activation in a canine heart. This would help the electrophysiologist know where exactly the origin or the critical point in tissue is located. Following this, arrhythmia can be successfully treated by ablating that part of the tissue of heart. Virtual electrograms were recorded while pacing the right ventricle of an open-chest dog at multiple endocardial and epicardial sites using the commercially available noncontact mapping system (EnSite 3000). The endocardial and epicardial paced virtual electrograms from the juxtaposing sites allow for analyzing systematically the differences in their morphologies. Maximal dV/dt, area under the depolarization curve and latency extracted from unipolar electrograms demonstrated significant difference between epicardial and endocardial pacing sites with a p-value of less than 0.01 in all three cases. The above features were fed to a linear discriminant analysis based classifier and high classification accuracy was achieved. In conclusion, reliable criteria can be proposed to allow for discrimination of an endocardial versus epicardial origin of electrical activation.