There is a group of patients with so-called idiopathic atrial fibrillation (AF) without the causes of arrhythmia established by a standard examination.Aim. To study the effect of histological changes in the myocardium in patients with idiopathic AF on the effectiveness of ablation.Material and methods. The study included 101 patients with idiopathic AF All patients underwent ablation, during which a myocardial biopsy was performed. Depending on the results of intervention, 3 groups were formed: 1 — no AF within 12 months, 2 — recurrent arrhythmia within first 3 months of follow-up, 3 — recurrent arrhythmia after first 3 months of follow-up. To assess inflammatory changes and the severity of fibrosis, histological and immunohistochemical tests of myocardial biopsies were performed.Results. Histological criteria for lymphocytic myocarditis in group 1 observed in 47,5% of patients, in groups 2 and 3 in 27,3% and 25%, respectively. Infiltration of less than 7 cells per 1 mm2 by CD3+ lymphocytes prevailed in group 3. The activity of inflammation in the studied groups did not significantly differ. The minimum severity of fibrosis was significantly less frequently recorded in group 1 than in group 2 and 3. Nonexpression of viral antigens in the first group was significantly less common than in the second and third groups. Moreover, the combination of expression of enterovirus VP1 and human herpesvirus 6 antigens was significantly more often recorded in the first group. Positive correlation was found between the expression of viral antigens and markers of endo- and myocardial fibrosis.Conclusion. The primary risk factor for recurrent arrhythmia was the initial stage of fibrosis, while inflammatory changes and viral infection were not risk factors. The presence of viral antigens in the myocardium had an indirect effect on the clinical outcome.

Background. Atrial fibrillation (AF) is combined with an inflammatory process that occurs in the myocardium. Diagnosis of histological changes, including inflammatory changes, in the myocardium is a complex task in the field of modern medicine. The only reliable way of determining the inflammatory changes in the myocardium is endomyocardial biopsy (EMB). As per our literature review, there are no data on the effect of histological changes in the myocardium on the efficacy of interventional treatment for AF. Moreover, assessing the dynamics of EMB results allows us to approach the treatment of patients in greater detail, thereby lowering the risk of the development and progression of serious cardiac pathologies, particularly AF.Aim. To study the effectiveness of catheter treatment for ‘idiopathic’ AF, depending on the dynamics of histological changes in the myocardium.Methods. We enrolled 48 patients with an ‘idiopathic’ form of AF; the median patient age was 39.0 y (33.5–48.0 y). Of these, 42 (87.5 %) were men and 6 (12.5 %) were women. The median duration of arrhythmic history was 4.0 y (2.0–7.0 y). All the patients underwent radiofrequency isolation of the pulmonary veins (Rcil) and EMB from the right ventricle. Histological tests, using the criteria of Cristina Basso, and immunohistochemical (IHC) tests were performed to determine the antigens of the following viruses: herpes simplex virus (HSV) types 1, 2 and 6, enterovirus (EV), Epstein-Barr, adenovirus and parvovirus (PV). After 6 mon, EMB, histological and IHC studies were repeated. Depending on the clinical form of AF, the patients are divided into the following three groups: group 1—paroxysmal form [21 (43.7 %) patients], group 2—persistent [13 (27.1 %) patients], group 3—long-term persistent [14 (29.2 %) patients]. Based on the results of the observation and evaluation of effectiveness, all the groups were divided into the following three subgroups: a—absence of AF during 12 mon of observation, b—early arrhythmia recurrences were registered during the first 3 mon of observation, c—presence of late arrhythmia recurrence after 3 mon of observation.Results. According to the histological criteria for active lymphocytic myocarditis identified in the subgroups, there were 5 patients (35.7 %) in 1a, 2 (50 %) in 1b, 6 (75 %) in 2a, 2 (66,7 %) in 2b, 7 (70 %) in 3a, 2 (66.7 %) in 3b, and 1 (100 %) in 3c. The rest of the patients showed signs of lymphocytic infiltration. After 6 mon, only in group 2a, there was a significant reduction in the number of patients with active lymphocytic myocarditis (p < 0.05). All the patients showed fibrotic changes and expression of HSV 6 and EV antigens of varying severity; this persisted till after 6 mon. The overall effectiveness of the surgical treatment was 66.7 % for paroxysmal, 61.5 % for persistent and 71.4 % for long-term persistent forms of AF during 12 mon of follow-up.Conclusion. Patients with ‘idiopathic’ AF show inflammatory changes in the myocardium, and 48.7 % met the criteria for myocarditis. All the patients showed the expression of viral antigens and the development of fibrosis that met the criteria for post-inflammatory changes. A repeat study that was conducted after 6 mon showed no significant dynamics of inflammatory and fibrotic changes. Despite the presence of inflammatory changes in the myocardium, the effectiveness of catheter treatment was 66.7 % for paroxysmal, 61.5 % for persistent and 71.4 % for long-term persistent forms of AF. Received 29 April 2020. Revised 1 June 2020. Accepted 3 June 2020. Funding: The study did not have sponsorship. Conflict of interest: Authors declare no conflict of interest. Author contributionsConception and design: A.E. Shelemekhov, R.E. BatalovData collection and analysis: A.E. Shelemekhov, Yu.V. Rogovskaya, S.Yu. Usenkov, E.A. Archakov, M.S. Rebenkova Drafting the article: A.E. ShelemekhovStatistical analysis: A.E. Shelemekhov, A.M. GusakovaCritical revision of the article: R.E. Batalov, Yu.V. Rogovskaya, A.M. GusakovaFinal approval of the version to be published: A.E. Shelemehov, R.E. Batalov, Yu.V. Rogovskaya, S.Yu. Usenkov, E.A. Archakov, A.M. Gusakova, M.S. Rebenkova

The review presents current data on atrial fibrillation, therapeutic approaches, and possibilities of interventional treatment and addresses inflammatory heart damage and its interrelation with arrhythmia.The review presents current data on atrial fibrillation, therapeutic approaches, and possibilities of interventional treatment and addresses inflammatory heart damage and its interrelation with arrhythmia.