The objective of this study is to demonstrate that higher radiation doses are necessary to induce transmural scar formation which is currently assumed to be the underlying mechanism of successful long-term efficacy of VT treatment and therefore dose-escalation will lead to a significantly reduced long-term VT recurrence rate compared to the currently applied single dose of 25 Gy.

Inclusion Criteria:

Patients with structural heart disease, in particular ischemic and non-ischemic cardiomyopathy: Implanted ICD and/or CRT-D. Prior ≥1 failed catheter ablation (with endocardial ± epicardial approach based on the substrate location and the ECG morphology of clinical VTs) procedure to control sustained monomorphic VT using currently recommended mapping and ablation techniques,2 or patients in whom ablation is not feasible. Reasons for lack of epicardial ablation and non-feasibility of catheter ablation must be specified. Sustained VT recurrence after catheter ablation on optimised antiarrhythmic medication.

Age ≥18 years. IRB-approved, written informed consent must be provided

Exclusion Criteria:

Patients with only premature ventricular contractions.

Patients with sustained VT/VF who demonstrate:

Acute myocardial infarction; Primary electrical disease (channelopathy); Reversible and treatable cause (e.g., drug-induced or intoxication) of VT that can be adequately addressed otherwise; A target that cannot be safely and precisely defined based on stereotactic radiotherapy accuracy requirements (e.g., anatomical interference from OARs, overlapping prior radiation therapy to the thoracic region); Pregnancy or breastfeeding; Inability to provide informed consent.