The Role of the Crista Terminalis in Atrial Flutter and Fibrillation: A Computer Modeling Study

Abstract

Although atrial fibrillation is a common arrhythmia, the underlying mechanisms are incompletely understood. Recent studies have determined the role of the crista terminalis in the mechanisms of a simpler arrhythmia, atrial flutter. We hypothesize that as transverse coupling across the crista terminalis increases, the activation pattern that results is less like typical atrial flutter and more like atrial fibrillation. 6480 Van Capelle elements were coupled in an icosahedron, simulating the right atrium. Atrial simulations were created which incorporated no heterogeneity, heterogeneous coupling, heterogeneous effective refractory periods, and both heterogeneous coupling and effective refractory periods. When the entire crista terminalis was uncoupled, typical atrial flutter occurred. When transverse coupling allowed activation to propagate across the crista terminalis, the flutter cycle length decreased (p<0.0001). In addition, when heterogeneity was present, both the coefficient of variation of cycle length and the number of activation wavelets increased (p<0.0001). Thus, a more rapid reentrant circuit in the superior right atrium drove fibrillatory activity in the remainder of the atrium, as predicted by the "mother wavelet hypothesis." While awaiting in vivo validation, our study indicates that transverse coupling along the crista terminalis may play an important role in the development of atrial fibrillation from atrial flutter.

Modeling Atrial Arrhythmias: Impact on Clinical Diagnosis and Therapies

“…5(d)], in agreement with noncontact mapping data in humans [56]. Ellis et al reported occurrences of atrial flutter in a simplified computer model of the right atrium when transverse connections in the crista terminalis were uncoupled [42]. This observation was confirmed by Vigmond et al in a more realistic canine atrial model with reduced transverse coupling in the crista terminalis [31].…”

Mathematical Approaches to Understanding and Imaging Atrial Fibrillation

“…Furthermore, PMs have been found to play a role in the conversion between AF and flutter by anchoring spiral waves. 90,92 Modeling studies 43,52, 91,93 have implicated the highly anisotropic conduction and longer APD in the crista terminalis in setting up the conditions for reentry generation. Using anatomical models of the rabbit RA and of the pig RA appendage, respectively, both based on histological reconstructions, studies by Aslanidi et al 49 and Zhao et al 48 demonstrated that because electrotonic coupling transverse to fibers in the crista terminalis is weak, high-frequency pacing at the border between the crista and PMs results in a reduced safety factor, leading to unidirectional block and subsequent generation of reentry.…”

Evaluation of Ablation Patterns Using a Biophysical Model of Atrial Fibrillation

“…6,9,22 Elaborate atrial models already published take into account conduction bundles and evaluate normal propagation or atrial arrhythmias with simulations lasting a few seconds. 6,9,22 For example, Harrild et al developed an anatomically accurate three-dimensional model of human atria, used for the simulation of sinus rhythm. 9 Vigmond et al developed a model of canine atria (3.3 cm wide) including Bachmann's bundle, crista terminalis and pectinate muscles.…”

“…Our single layer cell model does not include anisotropic fast-conducting regions, fiber orientation, crista terminalis and pectinate muscles, which may all play a role during AF. 6,16 A version of our model incorporating some of these aspects has been developed 3 at the expense of an increased complexity and computational load. The inclusion of such details needs further validated data.…”