Primary Objectives Phase I:
-Assess acute toxicity and efficacy with SABR in treating refractory structural cardiac ventricular tachyarrhythmias (VT). Ensure safety and treatment efficacy.
Primary Objectives Phase II:
* Investigate overall toxicity with SABR compared to next best management practices (standard of care) in treating refractory structural cardiac ventricular tachyarrhythmias (VT).
* Investigate VT episode reduction with SABR compared to standard of care to evaluate effectiveness and potential superiority of SABR to current day options.
Primary Objectives Phase I:
1\. Assess acute toxicity and efficacy with SABR in treating refractory structural cardiac ventricular tachyarrhythmias (VT). Ensure safety and treatment efficacy.
Primary Objectives Phase II:
1. Investigate overall toxicity with SABR compared to next best management practices (standard of care) in treating refractory structural cardiac ventricular tachyarrhythmias (VT).
2. Investigate VT episode reduction with SABR compared to standard of care to evaluate effectiveness and potential superiority of SABR to current day options.
Secondary Objectives
The following endpoints will be analyzed retrospectively based on prospectively collected (event-free survival endpoints) and at the specified time points (e.g. QOL questionnaire). Participation in QOL assessment and bio specimen collection for secondary endpoints is completely voluntary and not mandated by the trial.
1. 6-month and 1-year overall survival (OS) of SABR compared to standard of care.
2. Quality of life (QOL) with SABR compared to standard of care (baseline and at 6 months after randomization).
3. Hospitalization-free survival with SABR compared to standard of care (evaluated at 1-year).
4. Cost-effectiveness analysis with SABR compared to standard of care (evaluated at 1-year).
5. Freedom-from Antiarrhythmic medications with SABR compared to standard of care (evaluated at 1-year).
6. Freedom-from Electrical Storm with SABR compared to standard of care (evaluated at 1-year).
7. Treatment-free Survival with SABR compared to standard of care (evaluated at 1-year).
8. Event-free Survival with SABR compared to standard of care (evaluated at 1-year).
9. Long term (\>1year) toxicity with SABR compared to standard of care (evaluated at 1-year).
10. Ejection fraction improvement with SABR compared to standard of care (evaluated at 1-year).
11. Transplant/LVAD-free survival with SABR compared to standard of care (evaluated at 1-year).
12. Number, type, and treatment success and cycle length of ICD-treated VTs with SABR compared to standard of care (evaluated at 1-year).
13. Parameters obtained from cardiac imaging, and/or serum markers will be associated with frequency of survival, response to treatment, and toxicity at regular time intervals using cardiac ECHO, MRI, CT imaging, ICD interrogation, and/or serum/blood work studies for prognostic/predictive biomarker and radiomic identification.
