Atrial fibrillation(AF) is the most common disorder of cardiac rhythm. It has a high morbidity, mortality and disability, and serious impact on quality of life of patients. It is demonstrated that atrial remodeling which includes atrial electrical remodeling and structural remodeling,are the central contributors to the development and selfperpetuating of AF. However, The mechanisms that underlie the atrial remodeling process in AF have not yet been completely elucidated. New strategies for the prevention and termination of AF should build on our knowledge of the mechanisms of atrial remodeling. Medication for the reversal of atrial remodeling may be the new target for the treatment of AF. At present, drugs that target atrial remodeling have already obtained fruitful results in the experimental and clinical investigations. Now some recent advancements of this area is reviewed in this article.
Abstract： Objectives To determine the atrial expression of the collagen Ⅰ, collagen Ⅲ and the transforming growth factorbeta 1 (TGF-β1) in patients with rheumatic heart disease (RHD) and permanent atrial fibrillation(PAF) and to investigate the relationship between the extent of atrial fibrosis and the effectiveness of radiofrequency maze procedure in patients with RHD and PAF. Methods A total of 40 patients with RHD and PAF (≥6 months) who underwent a radiofrequency maze procedure with concomitant valvular surgery were collected for the experimental group. We acquired 100 mg of the left auricle tissue in each patient and followed up these patients after 3, 6 months of [CM(158mm]surgery. Then we assigned these patients to nonAF group and persistent AF group according to the results of the 6month followup. Another 10 patients with RHD and sinus rhythm(SR) who underwent valvular surgery alone were assigned to SR group and their left auricle tissue was also obtained. In order to determine the extent of atrial fibrosis, we observed the amount of collagen volume fraction Ⅰ，Ⅲ(CVF-Ⅰ,CVF-Ⅲ) by semiquantitative analysis with picrosirius red staining method. Using the β actin protein as the endogenous reference gene, we detected the expressions of TGF-β1 mRNA by semiquantitative reverse transcriptionpolymerase chain reaction(RT-PCR) technique. Results Each group has the same clinical baseline. At 6month follow-up, 28 among the 40 patients were categorized into the nonAF group and 12 into the AF group. (1) Patients in the nonAF group and the AF group had higher mRNA expressions of TGF-β1, CVF-Ⅰ and CVF-Ⅰ/CVF-Ⅲ compared with the SR group (F=6.487, P=0.003; F=3.711, P=0.032; F=3.697, P=0.032). The AF group had higher mRNA expressions of TGF-β1, CVF-Ⅰ and CVF-Ⅰ/CVF-Ⅲ than the nonAF group (t=4.372, P=0.043; t=4.603, P=0.038; t=4.776, P=0.035). But the CVFⅢ had no significant differences among the three groups (P＞0.05). (2) The patients whose left atrial function recovered after Maze procedure had lower mRNA expression than those patients whose left atrial function did not recover in the nonAF group (t=5.570, P=0.027). (3) The TGF-β1 mRNA expression has a positive correlation with both the contents of CVF-Ⅰ and left atrial diameter (r=0.786, Plt;0.05; r=0.858, Plt;0.05). Multiple logistic regression analysis revealed that the mRNA expression levels of TGF-β1, CVF-Ⅰ and left atrial diameter were independently associated with the postoperative persistence of atrial fibrillation. Conclusion The extent of atrial fibrosis in patients with RHD and PAF may be related to the sinus rhythm restoration and maintenance after AF surgical radiofrequency ablation and the resumption of atrial function.