Noninvasive Cardiac Radioablation for Ventricular Tachycardia Refractory to Medication and Catheter Ablation

Inclusion Criteria: * Patients must be ≥ 18 years old. * Patients must have documented sustained monomorphic VT by 12-lead ECG or intracardiac ICD interrogation. * Minimum VT burden: 4 or more documented VT episodes (including sustained VT, ICD anti-tachycardia pacing \[ATP\], or ICD shock) in the 5 months preceding enrollment on this trial. Patients must have at least two episodes of electrocardiographically documented symptomatic, recurrent, sustained monomorphic VT in the 3 months prior to enrollment * \*ATP and appropriate ICD shock are acceptable surrogates for VT-associated symptoms * Patients must have an ICD. * Patients must have ischemic or non-ischemic cardiomyopathy previously diagnosed with LVEF ≤ 35%. * Patients must have received at least one antiarrhythmic medication (i.e. amiodarone, sotalol, mexiletine) without control of symptoms or with poor toleration. AND Patients must have undergone at least one catheter-ablation procedure (or have a contraindication to catheter-ablation) or have VT arising from an inaccessible location. * Contra-indications to endocardial catheter ablation procedure include dual aortic and mitral mechanical valves, active left ventricular thrombus, and anesthesia intolerance. * Contra-indications to epicardial catheter ablation include prior cardiac surgery or anesthesia intolerance. * Patients with ischemic cardiomyopathy should have failed at least one endocardial ablation performed at an academic center. * Patients wit…