Impact of Anti-Mitochondrial Antibody Positivity on Isolated Cardiac Involvement: A Pilot Study Focusing on the Right Atrial Low Voltage Area and Sick Sinus Syndrome.

Objective Anti-mitochondrial antibodies (AMA) are primarily used as serological markers for primary biliary cholangitis, but they have also been implicated in cardiac dysfunction and arrhythmias. This study aimed to investigate the association between AMA positivity, the right atrial low-voltage area (RA-LVA), and sick sinus syndrome (SSS) in patients with isolated cardiac involvement. Methods We retrospectively analyzed patients who underwent AMA testing at the Ogaki Municipal Hospital between 2008 and 2024. Clinical, electrocardiographic, and echocardiographic data were reviewed at the time of AMA testing. RA-LVA was assessed using data from cardiac implantable electronic device implantation or three-dimensional electroanatomic mapping during catheter ablation. The factors associated with AMA positivity and SSS were evaluated using a univariate logistic regression analysis. Patients Among 5,901 patients who underwent AMA testing, 50 patients with isolated cardiac involvement were included after excluding those with primary biliary cholangitis, mitochondrial myositis, or no cardiac involvement. Five patients were AMA-positive, and 45 were AMA-negative. Results AMA positivity was significantly more frequent in patients with RA-LVA than in those without RA-LVA (100% vs. 4.3%, p <0.001), and similarly in those with SSS (75.0% vs. 4.3%, p = 0.002), indicating a consistent association across RA-LVA and SSS. In the univariate analysis, AMA positivity was strongly associated with SSS (odds ratio 66.0; 95% confidence interval 4.57-953.0; p = 0.002). Conclusion AMA positivity is strongly associated with RA-LVA and SSS in patients with isolated cardiac involvement, suggesting a potential pathogenic role for AMA in right atrial and sinoatrial node dysfunction.