The role of the crista terminalis in atrial flutter and fibrillation: A computer modeling study

Although atrial fibrillation is a common arrhythmia, the underlying mechani sms are incompletely understood. Recent studies have determined the role of the crista terminalis in the mechanisms of a simpler arrhythmia, atrial fl utter. We hypothesize that as transverse coupling across the crista termina lis increases, the activation pattern that results is less like typical atr ial Butter and more like atrial fibrillation. 6480 Van Capelle elements wer e coupled in an icosahedron, simulating the right atrium. Atrial simulation s were created which incorporated no heterogeneity, heterogeneous coupling, heterogeneous effective refractory periods, and both heterogeneous couplin g and effective refractory periods. When the entire crista terminalis was u ncoupled, typical atrial Butter occurred. When transverse coupling allowed activation to propagate across the crista terminalis, the flutter cycle len gth 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 a trium, as predicted by the "mother wavelet hypothesis." While awaiting in v ivo validation, our study indicates that transverse coupling along the cris ta terminalis may play an important role in the development of atrial fibri llation from atrial flutter. (C) 2000 Biomedical Engineering Society. [S009 0-694(00)00107-7]