A Three-Dimensional Human Atrial Model with Fiber Orientation. Electrograms and Arrhythmic Activation Patterns Relationship
The most common sustained cardiac arrhythmias in humans are atrial tachyarrhythmias, mainly atrial fibrillation. Areas ofcomplex fractionated atrial electrograms and high dominant frequency have been proposed as critical regions formaintaining atrial fibrillation; however, there is a paucity of data on the relationship between the characteristics of electrograms and the propagation pattern underlying them. In this study, a realistic 3D computer model of the human atriahas been developed to investigate this relationship. The model includes a realistic geometry with fiber orientation,anisotropic conductivity and electrophysiological heterogeneity. We simulated different tachyarrhythmic episodes applying both transient and continuous ectopic activity. Electrograms and their dominant frequency and organization index valueswere calculated over the entire atrial surface. Our simulations show electrograms with simple potentials, with little or nocycle length variations, narrow frequency peaks and high organization index values during stable and regular activity as theobserved in atrial flutter, atrial tachycardia (except in areas of conduction block) and in areas closer to ectopic activity duringfocal atrial fibrillation. By contrast, cycle length variations and polymorphic electrograms with single, double andfragmented potentials were observed in areas of irregular and unstable activity during atrial fibrillation episodes. Our resultsalso show: 1) electrograms with potentials without negative deflection related to spiral or curved wavefronts that pass overthe recording point and move away, 2) potentials with a much greater proportion of positive deflection than negative inareas of wave collisions, 3) double potentials related with wave fragmentations or blocking lines and 4) fragmentedelectrograms associated with pivot points. Our model is the first human atrial model with realistic fiber orientation used toinvestigate the relationship between different atrial arrhythmic propagation patterns and the electrograms observed atmore than 43000 points on the atrial surface.