Effects of sterile pericarditis on connexins 40 and 43 in the atria: correlation with abnormal conduction and atrial arrhythmias.

The canine sterile pericarditis model is characterized by impaired conduction and atrial arrhythmia vulnerability. Electrical and structural remodeling processes caused by the inflammatory response likely promote these abnormalities. In the present study, we tested the hypothesis that altered distribution of atrial connexins is associated with markedly abnormal atrial conduction, thereby contributing to vulnerability to atrial flutter (AFL) and atrial fibrillation (AF) induction and maintenance. During rapid pacing and induced, sustained AFL or AF in five sterile pericarditis (SP) and five normal (NL) dogs, epicardial atrial electrograms were recorded simultaneously from both atria (380 electrodes) or from the right atrium (RA) and Bachmann's bundle (212 electrodes). Tissues from RA sites were subjected to immunostaining and immunoblotting to assess connexin (Cx) 40 and Cx43 distribution and expression. Transmural myocyte (alpha-actinin) and fibroblast (vimentin) volume were also assessed by immunostaining. RA pacing maps showed markedly abnormal conduction in SP, with uniform conduction in NL. Total RA activation time was significantly prolonged in SP vs. NL at 300-ms and 200-ms pacing-cycle lengths. Sustained arrhythmias were only inducible in SP [total: 4/5 (AFL: 3/5; AF: 1/5)]. In NL, Cx40, Cx43, alpha-actinin, and vimentin were homogeneously distributed transmurally. In SP, Cx40, Cx43, and alpha-actinin were absent epicardially, decreased midmyocardially, and normal endocardially. SP increased epicardial vimentin expression, suggesting fibroblast proliferation. Immunoblot analysis confirmed reduced expression of Cx40 and Cx43 in SP. The transmural gradient in the volume fraction of Cx40 and Cx43 in SP is associated with markedly abnormal atrial conduction and is likely an important factor in the vulnerability to induction and maintenance of AFL/AF in SP.