SBRT for Ventricular Arrhythmia

Inclusion Criteria: * Recurrent VTs/VES with significant burden despite guideline-directed therapy * Existing protective ICD (Implantable cardioverter-defibrillator) implantation except in the presence of contraindications * AND lack of response or intolerance to antiarrhythmic medication * AND status post ≥1 catheter ablation due to monomorphic VT(s) and VT early recurrence (\<12 months after the last catheter ablation) OR contraindication for endocardial ablation (mechanical valve prosthesis, LV (left ventricular) thrombus, or lack of vascular access in suspicion of endocardial substrate) * MINIMAL VT BURDEN: The patient must have had at least 3 VT episodes (sustained VT, ICD-ATP, or ICD shock) in the last 3 months prior to study enrollment. * Presence of suitability for radiation therapy with respect to SBRT * Age ≥ 18 years * Existing informed consent Exclusion Criteria: * Acute myocardial infarction or percutaneous coronary intervention or heart surgery (\<3 months before study enrollment) * Status post intra-thoracic pre-radiation * Immediate proximity to radiosensitive structures (e.g., esophagus) making therapy unsafe to administer * Advanced symptomatic heart failure (NYHA Class IV) * Polymorphic VT or ventricular fibrillation (confirmed in 12-lead ECG and/or ICD interrogation) * Extensive myocardial scar substrate that would result in too large of a radiation volume * Life expectancy \< 6 months considering all comorbidities and in the Seattle Heart Failure Model * Presence of a Left Ventricular Assist Device (LVAD) * Use of cytotoxic medications * Pregnancy or lactation - negative pregnancy test within 14 days before study entry required for women of childbearing potential