Efficiency of cardioversion in persistent atrial fibrillation and maintenance of sinus rhythm in the long-term period in patients with myocarditis

Aim . To compare the immediate and long-term efficacy of cardioversion in patients with persistent atrial fibrillation (AF) in the setting of active myocarditis versus those without myocardial inflammation. Methods . The study included 80 patients with persistent atrial AF (mean age 58.39±14.3 years; 56.2% male), of whom 40 had biopsy- or magnetic resonance imaging-confirmed myocarditis, elevated antimyocardial antibody titers, and ≥3 points on a non-invasive myocarditis diagnostic algorithm (main group). The control group (n=40) consisted of patients with non-inflammatory cardiovascular diseases (coronary artery disease, hypertension). All patients with myocarditis received standard anti-inflammatory therapy. Following pre-treatment with amiodarone for 10-12 days, electrical cardioversion (ECV) was performed. The efficacy of ECV, the need for radiofrequency ablation (RFA), the incidence of persistent AF, and adverse outcomes were evaluated. Differences were considered statistically significant at p < 0.05. Results : Patients in the myocarditis group were characterized by a higher proportion of males (80.0% vs. 32.5%), younger age (49.1±12.0 vs. 67.7±9.5 years), lower left ventricular ejection fraction (LVEF) (37% [30;41] vs. 56% [52;59]), and larger left ventricular end-diastolic volume (152 ml [119;184] vs. 89 ml [76;106]), all with p < 0.001. The duration of AF history and left atrial size did not differ significantly between groups. Only in the myocarditis group did spontaneous sinus rhythm (SR) restoration occur during amiodarone loading, observed in 17.5% of cases. ECV was successful on the first attempt in all patients of the control group and in 57.5% of patients with myocarditis; an additional 15% achieved SR with a second ECV attempt (p < 0.001). Reversible recurrences of AF, terminated by intravenous amiodarone, were observed in 20% of myocarditis patients versus 5% in the control group (p=0.012). By the end of the one-week observation period, irreversible recurrences were recorded in two patients in each group. LVEF improved more significantly in the myocarditis group (to 42% [33;49], p < 0.001). At six months post-ECV, SR was maintained in 50% of patients with myocarditis and 66.5% in the control group (p=0.530). Rhythm control was discontinued in 15% of patients with myocarditis and in 5% of the control group (p=0.547), and radiofrequency ablation was performed in 10% and 5% of patients, respectively (p=0.509). All-cause mortality was documented in 12.5% (n=5) of myocarditis patients. No thromboembolic events or heart transplantations were reported in either group. Conclusion : AF in the context of myocarditis more commonly affects individuals of working age and worsens LV systolic dysfunction. The immediate and long-term efficacy of ECV was non-significantly lower in patients with myocarditis; however, successful restoration and maintenance of SR were associated with a more pronounced improvement in LVEF, supporting the rationale for a rhythm control strategy. Further research is planned to identify predictors of sustained SR in this population.