Importance of geometry in reconstructing endocardial electrograms from noncontact multielectrode cavitary probe data

Solving the inverse problem to reconstruct endocardial electrograms from cavitary probe data requires measuring cavitary electrograms and determining probecavity geometry. To identify the importance of geometry. endocardial electrograms were computed using two geometric models of the endocardium: (1) realistic. and (2) idealized. Endocardial electrograms were computed during pacing and were compared to directly measured electrograms at 8 sites during each paced rhythm. Using realistic geometry. computed electrograms were in excellent agreement with measured electrograms (r = 0.88; error in activation time = 4.7 ms). Whereas, the idealized geometry significantly increased the error in computed electrograms (r = 0.75; error in activation time = 9.9 ms). Therefore. in situ determination of realistic geometry is essential to successfully solve the inverse problem.