Introduction: : Ablation of complex fractionated atrial electrograms (CFAEs) is an important adjunctive therapy in atrial fibrillation (AF). The underlying substrate is poorly understood. Autonomic nervous system modulation appears to influence the complexity characteristics of atrial electrograms EGMs). This study sought to examine the histological substrate of CFAEs in chronic AF patients.
Methods: We stained 24 biopsies taken from the pulmonary vein-left atrium junction and right atrial appendage from 8 chronic AF patients and 4 sinus rhythm patients undergoing mitral valve surgery using trichrome, and antibodies to tyrosine hydroxylase and cholineacetyltransferase (ChAT). Local EGMs were recorded from the same sites using a bipolar recording catheter before samples were taken.
Results: A total of 48 slices have been analyzed. In AF patients, the myocardium was disorganized and the intercellular space was occupied by abundant interstitial fibrosis. Sympathetic nerve twigs and parasympathetic nerve densities were present. There was a significant association between AF and EGMsduration and deflections (p=.035, and p=.04, respectively). In AF, EGMs duration correlated positively with the amount of fibrosis (r=.149, p=.017), and the number of EGM deflections was positively related to the ChAT nerve density (p=.007).
Conclusions: Fibrous tissue and parasympathetic nerve structures in the atria may account for the substrate of CFAEs and serve as potential targets of chronic AF ablation.