Session P84.4

Modeling the Purkinje Conduction System with a Non Deterministic Rule Based Iterative Method

V Zimmerman, R Sebastian*, BH Bijnens, AF Frangi

Universitat Pompeu Fabra
Barcelona, Spain

The specialized electrical conduction system of the heart guarantees a coordinated excitation and contraction of the ventricles. The electrical impulse, initiated in the sino-atrial node, reaches the His-bundle and rapidly propagates through the whole Purkinje system. Then, the electrical wave fronts enter the myocardium through the Purkinje-myocardium junctions (PMJ) distributed on the ventricular subendocardial walls. Therefore, including the His-Purkinje system in a computational model of the heart is fundamental to obtain realistic electrophysiological simulations, specially for the the study of cases that lead to abnormal ventricular excitation, such as arrhythmias or left bundle branch block. Nevertheless, only a small percentage of computational electrophysiology studies take it into account, and in general are based on 0D or 1D manually delineated fixed models. The method presented allows constructing a Purkinje system automatically for a particular subject. The system is grown using a rule-based algorithm controlled by stochastic and probabilistic decisions that determine the particular structure of the model. A set of user customizable parameters control the final structure. In order to obtain realistic and particularized Purkinje structures, the algorithm controls the PMJ local density, the length of branches, the existence and location of loops and the main growing direction of branches. The construction of the whole structure takes less than 30 s in a 2.4 GHz PC. The Purkinje system is built on an existing segmented ventricular mesh. However, it can be fitted into other ventricular meshes if consistent models are needed. Constrained structures can be generated using patient-specific data such as QRS length, or endocardial activation maps, in order to personalize the model. Geometrically, the system is modeled as a set of lines organized in a tree-like structure, so it can be included in a cardiac electrophysiological solver as a set of cables using a 1D type resolution method. The Purkinje systems obtained closely resemble real photographs and histological diagrams as for example Tawara and Myorburg ones, and can include information on PMJ positioning or density when available.

(Abstract Control Number: 126)