The aim of the study is to compare the efficacy and safety of treating recurrent sustained Ventricular Tachycardia (sVT) after prior Catheter Ablation (CA) in patients with Implanted Cardioverter-Defibrillator (ICD) between re-do of conventional endocardial CA and Stereotactic Arrhythmia Radioablation (STAR).

Study Objectives:

To evaluate the safety and efficacy of Stereotactic Arrhythmia Radioablation (STAR) as a second-line therapy for sustained Ventricular Tachycardia (sVT) in optimally treated patients following endocardial Catheter Ablation (CA).

Study Design:

This study is a single-center randomized, noninferiority, head-to-head control trial comparing the efficacy and safety of two ablation methods for recurrent sVT after failing CA.

Patient Population:

Optimally treated patients aged ≥18 with Implantable Cardioverter-Defibrillators (ICD) in the primary or secondary prevention of sudden cardiac death (SCD), who have undergone endocardial CA and are candidates for re-ablation of recurrent symptomatic ventricular tachycardia (VT) following the 2022 European Society of Cardiology Guidelines for the management of patients with ventricular arrhythmias and the prevention of SCD.

The planned size of the group is 150.

The planned recruitment period is 42 months, and the observation period is 18 months.

Patients will be randomly assigned to experimental and control groups for a 1:1 group size ratio. The block randomized stratification method will be used with a central randomization system. Sex and left ventricular ejection fraction (≤40% vs. >40%) will be stratifying factors.

Intervention:

The intervention under investigation (experimental) will be STAR ablation. The standard intervention will be repeated endocardial radiofrequency CA. The target area for sVT ablation will be the arrhythmogenic substrate, defined by electrophysiological study (EPS) with three-dimensional electroanatomical mapping (obligatory in the standard therapy arm, optional in the STAR arm) and imaging tests (i.e., MSCT/CMR/PET-CT). The following will be integrated using dedicated computer software: 1) anatomical data-locating the arrhythmogenic scar area with channels of heterogeneous tissue-obtained using MSCT, CMR, PET-CT/SPECT, 2) three-dimensional electroanatomical maps-locating electrograms showing low peak-to-peak voltage, local abnormal ventricular activities, the sequence of myocardial activation, and critical isthmus sites for re-entrant VT, and 3) electrocardiograms detected during sinus rhythm and ventricular pacing during EPS. In the experimental arm, the obtained data will become the basis for STAR planning by a team consisting of a diagnostic cardiologist, radiologist, electrophysiologist, and radiotherapist. The obtained data will become the basis for endocardial CA planning in the control arm.

Observation:

Observation will include 1) clinical assessment-with the determination of the New York Heart Association functional class and exercise capacity in the 6-minute walk test (6MWT); 2) echocardiography-with the assessment of global and segmental left ventricular systolic function, mitral valve function, and the presence of fluid in the pleural and pericardial cavities; 3) parameters of pacing, sensing, lead impedance, and ventricular arrhythmic events recorded by the ICD/CRT-D; 4) QoL; and 5) procedure-related adverse events. Evaluation will be performed at 1, 3, 6, 12, and 18 months post-procedure, with endpoints assessed at 6 and 18 months.

The co-primary endpoints will assess 1) treatment efficacy, defined as the number of events of monomorphic sVT over six months following the comparison procedures, and 2) treatment safety, defined as no procedure-related serious adverse events.

The most important clinical parameters evaluating the effectiveness of ablation (i.e., post-procedural reduction in the sVT burden, occurrence/time to the first sVT episode, number of adequate ICD/CRT-D therapies, number of hospitalizations for arrhythmic reasons, QoL improvement) and mortality (death from any cause) were selected as secondary endpoints.

Inclusion Criteria:

1. Age ≥ 18 years at the time of enrollment.
2. Presence of structural heart disease (SHD) of either ischemic or non-ischemic etiology.
3. Implanted ICD or CRT-D device for primary or secondary prevention of sudden cardiac death (SCD).
4. History of at least one endocardial CA procedure targeting a substrate of monomorphic sVT.
5. Recurrence of at least one clinically significant and symptomatic episode of monomorphic sVT.
6. Optimal pharmacological treatment of underlying SHD, including maximally tolerated doses of guideline-recommended heart failure therapies and appropriate antiarrhythmic management.
7. Provision of written informed consent prior to study participation.

Exclusion Criteria:

1. Reversible cause of sVT recurrence, particularly acute coronary syndrome (ACS), acute myocarditis, or lead-related infective endocarditis (LDIE).
2. Myocardial infarction (MI) or cardiac surgery within the last 40 days.
3. Idiopathic sVT unrelated to SHD or sVT associated with genetically determined channelopathies.
4. Ongoing or persistently recurrent hemodynamically unstable sVT until clinical stabilization is achieved.
5. Acute decompensation of heart failure, classified as New York Heart Association (NYHA) Class IV, until clinical stabilization is achieved.
6. Worsening angina, classified as Canadian Cardiovascular Society (CCS) Class III or IV until coronary diagnostic evaluation and clinical stabilization are completed.
7. A mobile thrombus within the left ventricle (LV).
8. Presence of a left ventricular assist device (LVAD).
9. Presence of comorbidities or known risk factors for CA complications that, in the judgment of the electrophysiologist, constitute a contraindication to the procedure for safety reasons.
10. Active, uncontrolled malignancy and/or chemotherapy or immunotherapy administered or planned within 1 month of the scheduled ablation procedure.
11. Features of an active systemic, pulmonary, or pericardial inflammatory process requiring systemic treatment (disease-modifying therapies, corticosteroids, immunosuppressants) within the past 6 months.
12. Presence of comorbidities or known risk factors for radiotherapy complications that, in the judgment of the radiation oncologist, constitute a contraindication to STAR for safety reasons.
13. Pregnancy or breastfeeding.
14. Systemic disease that limits the probability of survival to less than 1 year
15. Other comorbidities, addictions, or social indications that, in the investigator's opinion, would preclude practical cooperation or otherwise disqualify the patient from participation in the clinical study.
16. Refusal to participate or lack of written informed consent for study participation.

Due to General Data Protection Regulation (GDPR) - EU regulation on personal data protection (Regulation (EU) 2016/679).

Due to the distinct nature of the interventional procedures, blinding of the study is not feasible.