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.

Short QT syndrome (SQTS) is a rare inherited cardiac channelopathy disease resulting from mutations in potassium channels. It has been associated with several dysrhythmias, including ventricular tachycardia, ventricular fibrillation, atrial fibrillation, and atrial flutter. We report, for the first time, a case of a 19-year-old man presenting with recurrent syncope due to SQTS concomitant with sick sinus syndrome, who underwent implantation of an implantable cardioverter-defibrillator.

Intestinal tuberculosis (TB) typically presents with gastrointestinal symptoms, and cardiac conduction abnormalities associated with isolated intestinal TB have rarely been reported. We describe a 37-year-old male presenting with abdominal pain, constipation, and significant weight loss, with epidemiological exposure to cattle and raw milk. During hospitalization, he developed sinus bradycardia with a lowest corrected heart rate of approximately 46 beats per minute. The bradycardia persisted despite treatment with propantheline and atropine. Colonoscopy revealed terminal ileitis, and histopathology demonstrated nonspecific chronic ileitis without granuloma formation. Cardiac evaluation including echocardiography, troponin levels, electrolytes, and serum cortisol was unremarkable. Hydrocortisone administration was temporally associated with improvement in heart rate within 48 hours. Empirical anti-tuberculosis therapy was subsequently initiated, and the patient demonstrated sustained clinical improvement. Although causality cannot be definitively established, this case illustrates a rare temporal association between presumptive intestinal tuberculosis and steroid-responsive bradycardia. The report highlights the importance of considering systemic inflammatory processes in unexplained bradycardia, particularly in tuberculosis-endemic settings.

The heme oxygenase/carbon monoxide system is well-established as a critical regulator of contractile cardiomyocyte development. Although the heme oxygenase/carbon monoxide system is known to have protective effects against arrhythmias by reducing oxidative stress and preserving mitochondrial function in general myocardium, its specific impact on components of the cardiac conduction system, such as the sinoatrial and atrioventricular nodes, is unclear. On the one hand, the antioxidant and anti-inflammatory properties of the heme oxygenase/carbon monoxide system are believed to help maintain normal electrical conduction and prevent arrhythmias. On the other hand, pathological conditions such as age-related sick sinus syndrome have been linked to dysfunction of the heme oxygenase/carbon monoxide system, even though carbon monoxide is detrimental at toxic levels. This review synthesizes the current evidence on the dual nature of the heme oxygenase/carbon monoxide system in the cardiac conduction system. This review highlights the critical need for further investigation of the heme oxygenase/carbon monoxide system's physiological roles and therapeutic potential for conduction pathologies. JOURNAL/mgres/04.03/01612956-990000000-00091/figure1/v/2026-04-13T130436Z/r/image-tiff.