Progress towards Model-based Estimation of the Cardiac Electromechanical Activity from Ecg Signals and 4d Images

We present recent advances on a 3D numerical modeling of the myocardium which couples electrical and biomechanical models. The long-term objective is to simulate a realistic contraction of the heart from both electrical measurements (typically the ECG) and geometrical measurements (typically provided by medical imaging). This realistic contraction should provide useful quantitative parameters for the diagnosis and also for guiding some new forms of therapy. Our modeling is based on a multiscale analysis ranging from microscopic to macroscopic scales, and integrates a priori information on the overall geometry and on the fiber directions extracted from specific medical imaging techniques (e.g. dtMRI). The FitzHugh-Nagumo equations are solved along with a constitutive law based on the Hill-Maxwell Rheological model, on which a data assimilation analysis is done. In medical image analysis, we believe that this new generation of physics-based deformable models will be useful to provide a more robust quantitative interpretation of temporal series of cardiac images. Résumé. Nous présentons ici nos avancées sur la modélisation du myocarde couplant des modèles électriques et biomécaniques. L’objectif à long terme est de simuler la contraction du cœur à partir de mesures ECG et d’images médicales, afin de fournir des outils d’aide au diagnostic. Notre modèle se base sur une étude multiéhelle des phénomènes et des données anatomiques extraites d’images médicales. La partieélectrique repose sur le modèle de FitzHugh-Nagumo et la partie mécanique reprend le formalisme de Hill-Maxwell avec une nouvelle loi de comportement, sur laquelle de l’assimilation de données est réalisée. En imagerie médicale, nous pensons que ce nouveau type de modèles devrait permettre une interprétation plus robuste des séquences temporelles. Introduction The knowledge of the heart function has greatly improved on the nanoscopic, microscopic and mesoscopic scales during the last decades, thus a global integrative work of this organ becomes conceivable [17]. It is the objective of our multidisciplinary project ICEMA1 to build a generic dynamic model of the beating heart and a procedure to automatically adjust the parameters to any specific patient from relatively easy-to-access measurements: ECGs (electrocardiograms) and time sequences of volumetric medical images [1]. Once the 1 Epidaure Research Project, INRIA Sophia-Antipolis, BP 93, 06902 Sophia-Antipolis, France 2 Mathematics Laboratory, Nantes University, France 3 Macs Research Project, INRIA Rocquencourt, France 4 Sosso Research Project, INRIA Rocquencourt, France 1Images of the Cardiac ElectroMechanical Activity, a collaborative research action between different INRIA projects and Philips Research France, http://www-rocq.inria.fr/who/Frederique.Clement/icema.html c © EDP Sciences, SMAI 2003 154 SERMESANT ET AL. generic model is adapted to a specific patient, it becomes possible to derive a set of quantitative and objective parameters useful for clinicians and physiologists.