Platelet-Derived Growth Factor-A Overexpression Correlates with Atrial Fibrosis in the Patients with Atrial Fibrillation Secondary to Rheumatic Valvular Disease

Objective: To investigate the relationship between platelet-derived growth factor-A (PDGF-A) and atrial fibrosis in patients who have developed atrial fibrillation (AF) secondary to rheumatic valvular disease. Methods: 84 selected patients participated in the current study who have developed rheumatic heart disease and were going to have a cardiac surgical operation. In the current study, whole subjects were divided into two group, they were atrial fibrillation (AF) group (the quantity is thirty-nine) and sinus rhythm (SR) group (the quantity is forty-five). Before the operation, complete clinical data was available for the whole patients. During the operation, the right atrial tissue (0.3 - 0.5 mm3) was disserted from every patient. Right atrial fibrosis was observed by Masson staining and the distribution of PDGF-A in right atrium specimen was observed by immunohistochemistry. RT-PCR techniques were applied to admeasure the mRNA expressions of PDGF-A in patients’ atrial tissue. At the same time, western-Blot techniques were employed to admeasure the protein expressions of PDGF-A. Results: In baseline clinical characteristics, in both AF group and SR group, there was no apparently difference between them (P > 0.05);compared with SR group, the diameters of left atrium and right atrium in AF group were apparently increased (P Conclusion: Atrial remodeling plays an important role in patients with valvular atrial fibrillation;PDGF-A in patients with AF was highly expressed in the right atrial, and was closely related with atrial fibrosis.

Eplerenone inhibits atrial fibrosis in mutant TGF-β1 transgenic mices..

The purpose of the present study was to study the impacts of eplerenone （EPL）, an antagonist of mineralocorticoid receptors （MR）, on atrial fibrosis in a mouse model with selective fibrosis in the atrium, and to explore the possible mechanisms. Using mutant TGF-β1 transgenic （Tx） mice, we first demonstrated that EPL inhibited atrial fibrosis specifically and decreased mac- rophage accumulation in the atria of these mice. Results from immunohistochemistry and western blotting showed that EPL attenuated protein expression of fibrosis-related molecules such as connective tissue growth factor （CTGF） and fibronectin in the atria of Tx mice. In culture, EPL inhibited gene expression of fibrosis-related molecules such as fibronectin, ct-SMA, and CTGF in TGF-β1-stimulated atrial fibroblasts, Finally, using a co-culture system, we showed that TGF-β1 stimulated atrial fi- broblasts induced migration of macrophages and this was blocked by EPL. EPL also blocked TGF-β1 induced gene expression of intedeukin-6 （IL-6） in atrial fibroblasts. Therefore, we conclude that EPL attenuated atrial fibrosis and macrophage infiltra- tion in Tx mice. TGF-I31 and IL-6 were involved in the impacts of EPL on activation of atrial fibroblasts and interactions be- tween fibroblasts and macrophages.

Predisposing factors for atrial fibrillation in the elderly

Atrial fibrillation （AF） in the elderly occurs as a consequence of cardiovascular aging and an age related increase of comorbidity. Several predisposing factors for AF have been identified for the overall AF population. Most of them, cardiovascular disease in particular, play a role in younger and older patients. The longer time period during which these risk factors can cause structural changes that ultimately lead to AF may, at least in part, explain the association between age and AF. In addition, less well defined age-related changes in cellular electrophysi- ologic properties and structure predispose to AF in the elderly.

Diagnosis of interatrial block

In the 70＇s, we classified for the first time the blocks at the atrial level into interatrial blocks （IAB）, partial and advanced, and other types of atrial blocks including the concept of atrial aberrancy, and atrial dissociation.

Atrial fibrillation in the elderly： predisposing factors and management

In the last twenty years, new imaging techniques to assess atrial function and to predict the risk of recurrence of atrial fibrillation after treatment have been developed. The present review deals with the role of these techniques in the detection of structural and functional changes of the atrium and diagnosis of atrial remodeling, particularly atrial fibrosis. Echocardiography allows the detection of anatomical, functional changes and deformation of the atrial wall during the phases of the cardiac cycle. For this, adequate acquisition of atrial images is necessary using speckle tracking imaging and interpretation of the resulting strain and strain rate curves. This allows to predict new-onset atrial fibrillation and recurrences. Its main limitations are inter-observer variability, the existence of different software manufacturers, and the fact that the software used were originally developed for the evaluation of the ventricular function and are now applied to the atria. Cardiac magnetic resonance, using contrast enhancement with gadolinium, plays a key role in the visualization and quantification of atrial fibrosis. This is the established method for in vivo visualization of myocardial fibrotic tissue. The non-invasive evaluation of atrial fibrosis is associ- ated with the risk of recurrence of atrial fibrillation and with electro-anatomical endocardial mapping. We discuss the limitations of these techniques, derived from the difficulty of demonstrating the correlation between fibrosis imaging and histology, and poor intra- and inter- observer reproducibility. The sources of discordance are described, mainly due to image acquisition and processing, and the challenges ahead in an attempt to eliminate differences between operators.

Current progress of computational modeling for guiding clinical atrial fibrillation ablation

Atrial fibrillation(AF)is one of the most common arrhythmias,associated with high morbidity,mortality,and healthcare costs,and it places a significant burden on both individuals and society.Anti-arrhythmic drugs are the most commonly used strategy for treating AF.However,drug therapy faces challenges because of its limited efficacy and potential side effects.Catheter ablation is widely used as an alternative treatment for AF.Nevertheless,because the mechanism of AF is not fully understood,the recurrence rate after ablation remains high.In addition,the outcomes of ablation can vary significantly between medical institutions and patients,especially for persistent AF.Therefore,the issue of which ablation strategy is optimal is still far from settled.Computational modeling has the advantages of repeatable operation,low cost,freedom from risk,and complete control,and is a useful tool for not only predicting the results of different ablation strategies on the same model but also finding optimal personalized ablation targets for clinical reference and even guidance.This review summarizes three-dimensional computational modeling simulations of catheter ablation for AF,from the early-stage attempts such as Maze III or circumferential pulmonary vein isolation to the latest advances based on personalized substrate-guided ablation.Finally,we summarize current developments and challenges and provide our perspectives and suggestions for future directions.