Substrate of complex fractionated atrial electrograms： evidence by pathologic analysis

Background Ablation of complex fractionated atrial electrograms （CFAE） is an important adjunctive therapy in atrial fibrillation （AF）. The present study was to elucidate the substrate underlying CFAE. Methods Nine adult mongrel dogs were involved in the present study. AF was induced through rapid atrial pacing with vagosympathetic nerve stimulation, CFAE was recorded during AF. Ablation was performed at CFAE sites. Based on the location of the ablation scar, the atrial specimens were divided into CFAE and non-CFAE sites. Serial sections of the atrium were stained respectively with hematoxylin-eosin （HE） and the general neural marker protein gene product 9.5 （PGP9.5）. We compared the characteristics of the myocardium and the ganglionated plexus （GPs） distribution between the CFAE and non-CFAE sites. Results The myocardium of non-CFAE sites was well-organized with little intercellular substance. However, the myocardium in the CFAE site was disorganized with more interstitial tissue （（61.7±24,3）% vs, （34.1±9,2）%, P 〈0,01 ）, G Ps in the CFAE site were more abundant than in non-CFAE sites （（34.45±37.46） bundles/cm2 vs, （6.73± 8.22） bundles/cm2, P〈0.01）. Conclusion The heterogeneity Of the myocardium and GPs distribution may account for the substrate of CFAE and serve as a potential target of ablation.

Effect of ablation of complex fractionated atrial electrogram on vagal modulation in dogs

Background Clinical observations have shown that the complex fractionated atrial electrogram （CFAE） associates with ganglionated plexus activity in the cardiac autonomic nervous system. This study aimed to investigate the impact of CFAE ablation on vagal modulation to atria and vulnerability to develop atrial fibrillation （AF）. Methods Ten adult mongrel dogs were involved. Cervical sympathovagal trunks were decentralized and sympathetic effects were blocked. CFAE was color tagged on the atrial 3-dimensional image and ablated during AF induced by S1S2 programmed stimulation plus sympathovagal trunk stimulation. Atrial effective refractory period （ERP） and vulnerability window （VW） of AF were measured on baseline and at vagal stimulation at 4 atrium sites. Serial tissue sections from ablative and control specimens received hematoxylin and eosin staining for microscopic examination. Results Most CFAE areas were localized at the right superior pulmonary quadrant, distal coronary sinus （CS~） quadrant, and proximal coronary sinus （CSp） quadrant （21.74%, separately）. Sinus rhythm cycle length （SCL） shortening did not decrease significantly after ablation at the sites, including right atrial appendage, left atrial appendage, CSd, and CSp （P 〉0.05）. ERP shortening during vagal stimulation significantly decreased after ablation （P 〈0.01）; the VW to vagal stimulation significantly decreased after ablation （P 〈0.05）. The architecture of individual ganglia altered after ablation. Conclusions CFAE has an autonomic basis in dogs. The decreased SCL and ERP shortening to vagal stimulation after CFAE ablation demonstrate that CFAE ablation attenuates vagal modulation to the atria, thereby suppressing AF mediated by enhanced vagal activity. CFAE ablation could suppress AF mediated by enhanced vagal activity.