Remodeling of atrial collagens in patients with atrial fibrillation

Objective To determine whether the expression of atrial collagens is altered in patients with atrial fibrillation (AF) and to investigate their effects on the initiation and maintenance of AF.Methods Right atrial tissue samples were taken from 73 patients with rheumatic heart disease who underwent heart valve replacement surgery.Thirty-four patients had no history of AF,9 patients had paroxysmal AF,and 30 patients had chronic AF.Picrosirius red staining was used for quantitative analysis of collagen accumulation.The mRNA content of collagens type Ⅰand Ⅲ was measured by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR).Results (1) Atrial fibrosis tissue content significantly increased in both the paroxysmal AF and persistent AF groups,compared with that in the sinus rhythm group (all,P0.001);the significant difference was also observed between the persistent AF and paroxysmal AF groups (P0.01).Collagen volume fraction(CVF) significantly correlated with left atria(LA) dimension and AF duration(all,P0.01).(2) The mRNA of collagen type Ⅰ increased significantly in the chronic AF group (P0.001),followed by the paroxysmal AF group (P0.05),compared with the sinus rhythm group.The mRNA of collagen type Ⅲ was slightly higher in both AF groups than that in the sinus rhythm group,but the differences were not statistically significant (P0.05).The mRNA of collagen type Ⅰ was significantly correlated with left atrial dimension (r=0.336,P=0.004) and AF duration (r=0.339,P=0.003).Conclutions The increased level of collagen type Ⅰ in atrium might be one of the molecular mechanisms of atrial fibrosis during atrial fibrillation,which correlates with the initiation and maintenance of AF.