Abstract Background Noise is an important environmental risk factor. Industrial environments are rich in high-intensity infrasound (hi-IFS), which we have found to induce myocardial and coronary perivascular fibrosis in rats. Recently, a significant association between noise exposure and the incidence of atrial fibrillation (AF) was found in large cohort studies but the pathophysiology is unclear. Atrial fibrosis remains the cornerstone of atrial pathology in AF. Purpose: We hypothesized that rats exposed to hi-IFS develop atrial remodeling involving fibrosis and connexin 43, which we sought to evaluate. Material and Methods: Seventy-two Wistar rats, half exposed to hi-IFS (120dB, <20Hz) during a maximum period of 12 weeks and half age-matched controls, were studied. Atrial fibrosis was analyzed by Chromotrope-aniline blue staining. The immunohistochemical evaluation of Cx43 was performed using the polyclonal antibody connexin-43m diluted 1:1000 at 4ºC overnight. Digitized images were obtained with an optical microscope using 400× magnifications. The measurements were performed using image J software. A two-way ANOVA model was used to compare the groups. Results: The mean values of the ratio "atrial fibrosis / cardiomyocytes" increased to a maximum of 0,1095 ± 0,04 and 0,5408 ± 0,01, and of the ratio "CX43 / cardiomyocytes" decreased to 0,0834 ± 0,03 and 0,0966 ± 0,03, respectively in IFS-exposed rats and controls. IFS-exposed rats exhibited a significantly higher ratio of fibrosis (p < 0,001) and lower ratio of Cx43 (p = 0,009). Conclusion: High-intensity infrasound exposure triggers atrial remodeling in rat hearts. Whether this finding correlates to arrhythmogenic substrate in noise induced-AF is not known and reinforces the need for further experimental studies. Table 1 Time of exposure (weeks) Group IFS (n = 36) Group CTL (n = 36) P value Ratio of atrial fibrosis / cardiomyocytesMean ± SD 1 0,0896 ± 0,04 0,0460 ± 0,03 0,007 6 0,0936 ± 0,03 0,0491 ± 0,01 0,001 12 0,1095 ± 0,04 0,0541 ± 0,01 0,001 Ratio of atrial CX43 / cardiomyocytesMean ± SD 1 0,1100 ± 0,03 0,1371 ± 0,03 0,047 6 0,0829 ± 0,04 0,1036 ± 0,03 0,170 12 0,0834 ± 0,03 0,0966 ± 0,03 0,259 Mean ± SD of the two measured outcomes in the two groups. IFS – Infrasound; CTL – Control; SD – standard deviation; Cx43 – Connexin 43 Abstract Figure. Atrial fibrosis and Cx43 /cardiomyocytes