Atrial fibrillatory cycle length: computer simulation and potential clinical importance.

Atrial fibrillatory cycle length (AFCL) is generally accepted as a surrogate marker for local refractoriness. In this study, a computer model and clinical data on human subjects undergoing catheter ablation for paroxysmal and persistent AF were used to determine the clinical potential of AFCL. Simulations were performed in a biophysical computer model of AF, induced from eight simultaneously active focal sources. Atrial fibrillatory cycle length persistence and termination were assessed in response to successively switching off the involvement of the eight sources. Electrophysiological data were obtained from 178 subjects undergoing catheter ablation of AF. Atrial fibrillatory cycle length, measured in the atria appendages using automated monitoring software, was studied to determine its clinical correlation, the complexity of the ablation procedure, and the AF termination success rate. Computer simulations showed an inverse relationship between the number of sources participating in AF maintenance and AFCL. Clinical data demonstrated a strong relationship between duration, degree of ablation, and AFCL, with shorter AFCL associated with more extensive ablation to terminate AF. Atrial fibrillatory cycle length was prolonged exponentially at each stage, with a critical cycle length of approximately 200 ms for AF conversion. Atrial fibrillatory cycle length is inversely associated with the number of sources participating in AF maintenance observed in the computer model. In addition, AFCL is an important predictor of baseline duration of the arrhythmia, type of AF, and ease of catheter ablation therapy to terminate AF.