The study was stopped due to participation in a multi-center randomized controlled trial with competing enrollment criteria.

The purpose of this study is to evaluate the clinical efficacy and safety of stereotactic ablative radiotherapy (SAbR), also known as stereotactic body radiation therapy (SBRT), for treatment of ventricular tachycardia (VT) requiring implantable cardioverter defibrillator (ICD) treatments in patients with VT refractory to standard invasive ablation techniques. We hypothesized that SAbR is effective in suppressing sustained VT and reducing ICD treatments in this group of patients and is associated with acceptably low risk of serious complications.

Inclusion Criteria:

• Age ≥ 18 years
• Have an ICD implanted > 6 months and all VT episodes in the past 6 months are available in device memory.
• Within the past 3 months, the patient has at least one episode of symptomatic monomorphic VT that requires ICD treatment (anti-tachycardia pacing and/or ICD shock) or was sustained/incessant but falls under ICD treatment zone. These VT episodes must occur after at least one standard invasive VT ablation or occur in a patient that is clinically deemed not eligible to the standard VT ablation procedure.
• Two independent cardiac electrophysiologists reviewed the case and agreed that the patient would benefit from suppression of these VT episodes but there is no optimal invasive VT ablation or antiarrhythmic drug options.

Exclusion Criteria:

• Has contraindication to receive SAbR or VT clinically deemed not suitable for SAbR.
• Is pregnant
• Has severe co-morbid medical condition or terminal illness and is unlikely to survive more than 6 months regardless of VT status based on clinical judgement by treating or enrolling physicians.
• On potent immunosuppressive therapy (e.g., post organ transplant)
• Has severe collagen vascular disorder with organ involvement
• Not willing or not able to consent to participate in the study