Atrial fibrillation (AF) is a progressive condition with significant health implications, where fibrosis plays a central role. This study aimed to evaluate the impact of adding mineralocorticoid receptor blockade to standard therapy in patients with AF after restoration of sinus rhythm, focusing on arrhythmia recurrence, hospitalizations, and changes in Galectin-3 levels as a fibrosis marker. We prospectively enrolled 101 consecutive patients (56 females; mean age 68.2 ± 7 years) with AF who had achieved sinus rhythm. Participants were randomized to receive spironolactone in addition to standard therapy or standard therapy alone (“usual care”) and were followed for arrhythmia recurrence, hospitalizations, and mortality. The Safety of spironolactone was also assessed. AF recurrence occurred in 64% of patients in the non-spironolactone group versus 57% in the spironolactone group (p = 0.44). Spironolactone was associated with fewer AF-related hospitalizations, though this reduction was not statistically significant (p = 0.14). Cox regression analysis indicated a protective trend of spironolactone against AF hospitalizations (HR = 0.48; 95% CI = 0.2–1.15; p = 0.098). For all-cause hospitalizations, spironolactone significantly reduced events (HR = 0.44; 95% CI = 0.2–0.94; p = 0.035). There was no significant difference in the composite endpoint of recurrence, all-cause hospitalizations, and death. Treatment with spironolactone did not alter Galectin-3 levels or significantly affect serum potassium or creatinine. Spironolactone appears to reduce all-cause hospitalizations and shows a protective trend against AF-related hospitalizations, but it does not affect fibrosis marker Galectin-3 over one year. Spironolactone is safe in patients with AF, though regular monitoring is recommended, and further research is needed to clarify its potential to improve AF outcomes.
