Features of radiofrequency catheter ablation in patients with atrial fi brillation and secondary atrial septal defect

Objective . To study the peculiarities of radiofrequency catheter ablation in patients with atrial fibrillation and secondary atrial septal defect . Materials and methods. During 2008-2022, 54 (4.8%) patients underwent catheter ablation for atrial fibrillation at the Amosov National Institute of Cardiovascular Surgery of the National Academy of Medical Sciences of Ukraine. The type, early and long-term results of surgical interventions were analyzed. Results. Pulmonary vein isolation was performed in all 54 (100%) patients; linear ablation of the left atrium - in 2 (3.7%), ablation of the cavotricuspid isthmus - in 28 (52.0%). The average duration of the procedure was (204.3 ± 60.5) minutes. Complications occurred in 9 (16.7%) patients. Atrial fibrillation was not detected in 44 (81.5%) patients with a secondary atrial septal defect 3 months after the procedure. Conclusions . Radiofrequency catheter ablation in patients with atrial fibrillation and secondary atrial septal defect is an effective and safe procedure with minimal complications. However, patients should be carefully selected for this procedure in the presence of an occluder and appropriate preoperative preparation should be performed.

Atrial fibrillation (AF) is one of the most common pathologies in middle-aged and elderly patients with atrial septal defect (ASD).AF is detected at a younger age in patients with ASD than in the general population, and its prevalence reaches 50% after 60 years of age [1].
Correction of the defect significantly improves the survival of patients with VSD, but opinions remain controversial regarding its effect on the incidence of AF [2].According to a meta-analysis [3], VSD correction, regardless of the method (surgical or transcatheter), was associated with a reduction in the incidence of atrial tachyarrhythmia, but when considering only AF, this difference was not statistically significant.On the other hand, there is evidence of no effect of malformation correction on the incidence of AF in the long term [4,5], as well as similar AF rates after surgical and non-surgical treatment [6].The presence of AF in patients with VSD significantly worsens the quality and duration of their lives and often leads to the development of heart failure, disability, sudden death, and requires special attention [7].
According to the latest guidelines [8], catheter ablation (CA), or pulmonary vein isolation, is appropriate for persistent and paroxysmal AF in the case of ineffective treatment with class I or III antiarrhythmic drugs.The achievement of stable electrical isolation of the pulmonary veins is now the cornerstone of AF catheter-based treatment.A meta-analysis [9] demonstrated that the effectiveness of catheter-based treatment of AF is approximately 70-80% in the long-term period.However, little is known about its effectiveness in patients with congenital heart disease, including VSD.
The aim of the study was to investigate the features of radiofrequency CA in patients with AF and secondary VSD.

Materials and methods of the study
The results of a comprehensive examination and treatment of 54 patients with AF at the Amosov National Institute of Cardiovascular Surgery of the National Academy of Medical Sciences of Ukraine from 2008 to 2022 were analysed.The study included patients with AF who underwent radiofrequency ablation for paroxysmal or persistent AF insensitive to drug therapy, a combination of AF and atrial flutter, and patients with newly diagnosed AF during the correction of a defect.
In 17 patients, AF was first detected during an attempted transcatheter correction of the defect after the lead was inserted into the pulmonary veins.In these patients, the procedure was postponed and pulmonary vein isolation was performed after their consent to the procedure staging.Two (11.8%) patients refused the proposed treatment sequence.Fifteen (27.8%) patients agreed to undergo CABG before the correction of the defect.In 39 (72.2%) patients, AF was documented by electrocardiography (ECG) and Holter monitoring, 4 (7.4%) had persistent AF, and 35 (64.8%) had paroxysmal AF.
In 1 (1.9%) patient with persistent AF and 9 (16.7%)patients with paroxysmal AF, DMP was first detected after an additional examination for cardiac rhythm disorders.
The basic demographic and clinical characteristics of the patients were analysed, and the history of antiarrhythmic and anticoagulant medication was noted.All patients UJCS.2023 July/August; 90 (4) The Ukrainian Journal of Clinical Surgery underwent general clinical examinations, transthoracic and transesophageal echocardiography (Table 1).
Preoperative preparation.In the preoperative period, all patients received anticoagulant therapy (warfarin until 2011 and new oral anticoagulants since 2011) before CABG.Warfarin was discontinued 2 days before the procedure and replaced with low-molecular-weight heparin.In patients receiving new oral anticoagulants, warfarin was not replaced with lowmolecular-weight heparin, but the drugs were discontinued 1 day before the procedure.
In 32 (59.3%) patients, pulmonary vein isolation was performed through the internal jugular vein, followed by insertion of 6 F or 7 F hemostatic introducers into its lumen and cannulation of the coronary sinus with a 10-pole diagnostic catheter (Response™, Abbott, USA).In 22 (40.7%)patients, the left femoral vein was used for coronary sinus cannulation.After that, two transseptal introducers were inserted into the right atrium via the right femoral vein.Heparinisation was then performed at a rate of 120 U/kg until the target ac-tivated clotting time of at least 250 s was achieved and the preparatory stage of catheter insertion into the left atrial cavity was started.
Mapping stage.After connecting the cooling line, the catheters were inserted into the left atrial cavity.In order to reduce the duration of the procedure, a 20-pole Lasso diagnostic catheter and an ablation catheter were inserted into one introducer to build a 3D anatomical model of the left atrium (Fig. 1).
After the catheters were inserted, the respiratory optimisation phase was performed with the catheter positioned in the coronary sinus.If the position of the catheter in the coronary sinus was found to be unstable, the type of catheter was changed from an uncontrolled 5 F to a controlled 6 F. After the respiratory optimisation stage, the construction of a 3D anatomical model of the left atrium was started using the En-Site NavX mapping system.A Lasso catheter was used to perform 3D anatomical reconstruction of the structures of the left atrium and pulmonary vein mouths.
In our work, we adhered to the concept of achieving electrical and anatomical isolation of the pulmonary veins.Methodologically, we adopted the technique of wide circular ablation of the pulmonary vein mouths.
The ablation points were applied in the appropriate ways: around the upper left and right pulmonary veins, around the lower left and right pulmonary veins and the interatrial septum.
The diameter of the ablation point corresponded to the actual size of the diameter of the destruction zone in the heart (Fig. 2).
Procedural complications of CABG, such as stroke or transient ischaemic attack, pericardial effusion, cardiac tam- The Ukrainian Journal of Clinical Surgery ponade, esophageal injury, diaphragmatic nerve palsy, pericarditis, pulmonary vein stenosis, and vascular complications (puncture site haematoma, vessel dissection or rupture) were studied.
The treatment results were assessed 1, 2 and 3 months after the procedure based on ECG and Holter monitoring.
All patients received anticoagulation therapy for at least one month after the procedure.Its further prescription was based on the results of a follow-up examination and the presence of AF.If AF was not observed, anticoagulant therapy was stopped.In case of early recurrence of AF, patients received antiarrhythmic and anticoagulant drugs.
Statistical analysis.We used descriptive statistics methods.Data are presented as mean ± standard deviation.Statistical analysis was performed using SPSS v. 24 software (SPSS Inc., USA).

Results
Electrical isolation of the pulmonary veins was achieved in all 54 (100%) patients with AF and VF, as evidenced by blocking the pulse entry and exit after stimulation of the pulmonary vein mouths and the disappearance of potentials on the diagnostic catheter.The average duration of the procedure was (204.3 ± 60.5) min (Table 2).
In 2 (3.7%) patients, CABG was performed after correction of the defect by puncturing the occluder to close the DME (Fig. 3).
In 40 (74.1%)patients, the following parameters of radiofrequency CA were used during isolation of the left superior pulmonary vein: 30 to 40 W -anterior wall and the ridge zone between the vein and the left atrial auricle, 25 to 35 W -posterior wall.In 14 (25.9%)patients, the concept of reducing the application duration by increasing the energy power and the following parameters of radiofrequency CA were used: energy power 70 W, application duration 7 s resulted in a resistive tissue heating temperature of 71 °C, which is equivalent to the tissue heating temperature in the previous variant of lower energy power and longer application duration.

The Ukrainian Journal of Clinical Surgery
In 2 (3.7%) patients, at the final stage of the procedure, persistent atypical left atrial "roof-dependent" atrial flutter was noted, and the left atrial roof was isolated between the upper left and right pulmonary veins to eliminate it.
Complications of CABG occurred in 9 (16.7%)patients with AF and MVD, but they did not lead to disability and mortality.In 44 (81.5%) patients with DFM, AF was not detected 3 months after the CABG procedure according to the anamnesis, ECG, and Holter monitoring.

Discussion
Patients with VSD are prone to developing various atrial arrhythmias: atrial flutter, atrial tachycardia, and, most often, AF.As in the general population, the incidence of AF in patients with VSD increases with age.Since VSD is usually asymptomatic at first, many patients may develop AF even before the defect is corrected.
CABG remains one of the main strategies for treating patients with AF and MVD.Several studies have been devoted to different approaches to this procedure, their effectiveness and complications.J.G. Nie and colleagues [10] described CA in patients before VSD correction using direct access through the defect.The effectiveness of the procedure was comparable to that of the procedure in patients without DMD.CA can also be performed in patients after correction of DMD [11,12], which was noted in our study.The authors indicate that when the transseptal access is performed through the actual interatrial septum, the total duration of the procedure and fluoroscopy does not differ in patients with VSD after correction and in patients without VSD [11].However, when the left atrium is accessed through the occluder, it takes longer to puncture it and expand the device to pass the transseptal membrane, and therefore the total duration of the procedure and fluoroscopy increases significantly [12].In our study, we did not find an increase in the duration of the procedure and fluoroscopy in patients with an occluder.D. Lakkireddy and colleagues [11] raised the issue of occluder displacement after puncture due to its insufficient mechanical support by the tissues of the interatrial septum and recommended the presence of an interatrial septal margin of more than 5 mm for safe access through the occluder.In our observations, due to the large size of the occluder, it was decided to perform its puncture, which was effective and did not lead to occluder migration.
The effectiveness of the procedure is similar in patients with and without MVSD, as well as in patients with access through the atrial septum and through the occluder, and ranges from 56 to 77% [10-12].In our study, the effectiveness of CABG was 81.5%, which is probably due to subsequent re-modelling of the heart after correction of the defect.
The literature reports side effects of CA in patients with MVD, including mild pericardial effusion, local haematoma, acute heart failure, and transient ischaemic attack [10][11][12].
All the described complications did not have severe consequences, as in our study.
We also found that the use of CA in accordance with the concept of shortening the application time due to increased energy output in patients with MVD significantly improves catheter stability during the procedure, taking into account the lack of mechanical support of the transseptal introducer by the atrial septal tissue.

Conclusions
Radiofrequency CA for AF and MVP is an effective and safe procedure with minimal complications.However, patients with AF and MVD should be carefully selected for PCI in the presence of an occluder and appropriate preoperative preparation should be performed.
Funding.The work was performed within the framework of the applied research work "To develop and impr ove the treatment of atrial reentry tachycardias by catheter ablation " Funding is budgetary.
Conflict of interest.None.

Fig. 2 .
Fig. 2. Model of the left atrium with ablation points.