This document provides an overview of current problems and trends in the catheter ablation of atrial fibrillation, summarizes the opinions of specialists, obtained during a web-based electronic  survey, on aspects and parameters of radiofrequency ablation. The  approaches on improving the efficacy and safety of radiofrequency  catheter ablation of atrial fibrillation are provided. 

Purpose. To design a mathematical model, that can predict a positive response to cardiac resynchronization therapy (CRT) in patients with congestive heart failure (CHF) and sinus rhythm, according to complex analysis of neurohumoral and immune activation biomarkers, fibrosis, renal dysfunction, echocardiography.
Methods. Parameters of echocardiography, plasma levels of NT-proBNP, interleukins-1β, 6, 10, tumor necrosis factor α, С-reactive protein (СRP), matrix metalloproteinase-9 (ММР-9), tissue inhibitors of metalloproteinase 1 and 4, cystatin С (CYSTATIN) were studied in 40 CHF patients with sinus rhythm (65% coronary artery disease patients, 75% males, mean age 54.8±10.6 years old) during the period of maximum decrease of left ventricular end-systolic volume (LVESV) (mean duration 27.5 [11.1; 46.3] months). Responders (decrease in LVESV ≥15%) and non-responders (decrease in LVESV <15%) were identified.
Results. The number of responders was 26 (65%). The initial set of variables included: age, left ventricular ejection fraction (EF), pulmonary artery systolic pressure, right ventricle size and NT-proBNP, СRP, ММР-9, CYSTATIN. According to logistic regression analysis, a prediction model of positive CRT response was created. The specificity of the model was 92.9%, sensitivity - 83.3%, AUC=0.952 (р˂0.001).
Conclusion. The proposed model, based on the assessment of left ventricle EF and circulating biomarkers of inflammation, fibrosis, and renal function, strongly suggests a higher possibility of response to CRT.

Purpose. The study aimed at the comparison of computed tomography (СT) contrast enhancement (CE) protocols for optimal visualization of cardiac chambers, evaluation of their impact on results of non-invasive superficial cardiac mapping.
Methods. The study included 93 patients with heart rhythm disorders in whom catheter ablation of arrhythmia was planned. Noninvasive cardiac mapping for arrhythmia localization was performed and included multichannel ECG-registration and CT with intravenous СE (1st group - monophasic (50 patients), 2nd group - split-bolus (18 patients), 3^rd group - with pre-bolus (25 patients). Qualitative and quantitative (measurement of mean blood attenuation in four chambers, calculation of ventricular-myocardial [VM] contrast-to-noise ratio VM-LV и VM-RV for the left ventricle [LV] and right ventricle [RV], respectively) parameters were compared between the groups. Fusion of ECG and CT data was carried out a semi-automatic mode with a non-invasive imaging complex.
Results. Regardless of CE technique, sufficient and homogeneous contrast attenuation was obtained for the left atrium (LA) and LV (mean blood attenuation in LA more than 278 HU, LV 250 HU, VM-LV 0,582). In most cases, the enhancement of the right heart was insufficient with the monophasic protocol; the average CT density was lower than 200 HU, VM-RV 0,256. The split-bolus protocol improved visualization of the right atrium (RA) and RV (blood density in RA 258HU, RV 227HU, VMRV 0,541); however, there was a heterogeneity of the RA cavity due to artifacts from the superior vena cava (VC) and unenhanced blood from the inferior VC. Pre-bolus administration increased the contrast ratio between RA myocardium and blood due to the improvement of blood CT density in the inferior VC (blood density 294 HU). The quality of RV CE was similar to 2nd group (blood density 264 HU, VM-RV 0,565).
Conclusion. The split-bolus and with pre-bolus CE protocols improve visualization of the RV, supporting the high-level enhancement of the left heart. The protocol with a pre-bolus is preferable for exact differentiation of the right atrial endocardial contour.

Aim. To study the relationship between growth differentiation factor 15 (GDF-15) level in blood serum and patient clinical and functional status parameters, and to determine predictors of GDF-15 level in pts with non-valvular atrial fibrillation (AF).
Material and methods. Eighty-seven pts (with the mean age of 56.9±9.2 years) with non-valvular AF were studied. A general clinical examination, as well as echocardiography and laboratory tests were performed. These included fasting serum glucose (mmol/l), highly sensitive C-reactive protein (h/s CRP) (mg/l), creatinine level (μmol/l) and subsequent calculation of glomerular filtration rate (ml/min/1.73m2), and N-terminal pro-B-type natriuretic peptide (NT-proBNP) (pg/ml). The level of GDF-15 (pg/ml) in blood serum was determined using an enzyme immunoassay with a human ELISA analytical kit.
Results. An increase in GDF-15 level was associated with age, ischemic heart disease, severity of hypertension, and heart failure, resulting in a higher risk of stroke, according to the CHA2DS2 -VASc score, carbohydrate metabolism disorders and obesity, increased h/s CRP and NT-proBNP levels, enlargement of the right and left atria, signs of diastolic left ventricular dysfunction and structural remodeling in the form of eccentric hypertrophy. Multiple linear regression analysis revealed 2 independent predictors of GDF-15 levels: age and fasting glucose.
Conclusion. GDF-15 is an integral biomarker of age-related metabolic disorders and structural and functional changes in the heart, which opens up prospects for further study of its prognostic significance in pts with non-valvular AF.

Aim. To study the incidence and possible risk factors for atrial fibrillation (AF) in the early postoperative period after transapical implantation of the first Russian aortic valve (TAP-AVI).
Methods. The study included 118 patients after successful TAP-AVI. Patients with open aortic valve replacement due to dislocation of the prosthesis were excluded, as well as subjects with permanent AF and who died in the early postoperative period. The mean age of the patients was 71.1±4.9 years, body mass index 31.1±5.9 kg/m2 , males - 39.8%, hypertension was present in 93.2%, diabetes mellitus (DM) - in 27.9%, paroxysmal AF - in 12.7%, coronary artery disease (CAD) was in 56.7%, 8.4% were smokers. The median follow-up time corresponded to the hospital stay - 9.5 days. To identify cardiac arrhythmias, regular daily ECG recording in 12 leads was initiated from the first day after TAP-AVI. In the presence of palpitations, 24-hour ECG monitoring was performed. Indicators such as age, male gender, DM, history of AF, interatrial block before surgery, CAD, and echocardiographic parameters were studied as possible predictors of AF development in the early postoperative period after TAP-AVI. There were no significant differences in the baseline parameters in patients with AF paroxysms and sinus rhythm.
Results. In the early postoperative period, AF was encountered in 46 (39%) of patients. New-onset AF occurred in 38 (32.2%) patients. No cerebrovascular event occurred in patients with post-surgery AF. The only statistically significant risk factor for AF in the postoperative period was CAD (OR 5.756; 95% CI 1.009-8.132; p = 0.048).
Conclusion. In the early postoperative period, the only significant predictor of AF was the presence of documented CAD.

Purpose. The experimental study aimed to study the effects of stereotaxic radioablation of various doses on the myocardium of the atria, ventricles and atrioventricular (AV) node in the long term (up to 6 months); as well as assessment of collateral damage during radioablation.
Methods. The study comprised 4 domestic pigs. The animals were 10-12 weeks old, the average weight was 30±2.7 kg. A linear accelerator was used for the experiment. Each animal underwent radiation exposure in different areas: 1st animal - AV node (dose 35 Gy), 2nd animal - AV node and the apex of the left ventricle (LV) (dose 40/35 Gy, respectively), 3rd animal - pulmonary veins (PV) and left atrium (dose 30 Gy), 4th - AV node and LV free wall (dose 45/40 Gy). Under intravenous sedation with hemodynamic monitoring, contrast-based CT of the heart was performed to assess the degree of displacement of the heart chambers in one respiratory and cardiac cycle and to assess the anatomy of the chambers of the heart and adjacent organs. The allocation and the contouring of the target zones were carried out in three projections: axial, frontal and sagittal. For electrocardiographic control, a loop recorder was implanted in each animal. The average exposure time was 11±7 minutes. After a follow-up period, morphological examination of the autopsy material was performed.
Results. The average follow-up period after ablation was 134.75±77.34 days. The electrophysiological effect of the ablation was achieved in cases of complete AV-block development. This effect was developed in 2 out of 3 animals, where AV-node was exposed: 2nd animal - 40 Gy on 108th day of observation and 4th animal - 45 Gy on 21st day of observation. No cardiac tachyarrhythmia was recorded in the animals. The results of myocardium macro- and microscopic examination showed significant changes in the target zones. These areas had precise but uneven damage boundaries, which were within the planned ones (conformal exposure with a high degree of precision). The transmural nature of the changes was noted as well. Massive fields of fibrous tissue of various degrees of maturity (with a predominance of subepicardial localization) with focal hemorrhages of various ages and granulations were detected, which were surrounded by cardiomyocytes with coagulated and vacuolated cytoplasm.
Conclusion. The use of non-invasive stereotactic treatment of tachyarrhythmias has high prospects in modern electrophysiology as an alternative ablation method.

 A case report of cryoballoon ablation for atrial fibrillation in a patient after atrial septal defect closure is presented. 

 A case of successful endocardial lead implantation into the His bundle position is presented. Procedure technique and transient atrioventricular block during implantation are described.