Cohort Study - SBRT for VT Radioablation

Inclusion Criteria: * Structural heart disease: ischemic or non-ischemic cardiomyopathy diagnosed with cardiac imaging demonstrating either segmental myocardial dysfunction, or presence of scar, AND * One of the following monomorphic VT events despite prior attempted catheter ablation (or contraindication for ablation), AND despite treatment with a class III antiarrhythmic drug (contraindicated, ineffective or not tolerated): A: Documented sustained monomorphic VT terminated by pharmacologic means, DC cardioversion or manual ICD Therapy. B: ≥3 episodes of monomorphic VT treated with antitachycardia pacing (ATP), at least one of which was symptomatic C: ≥ 5 episodes of monomorphic VT treated with antitachycardia pacing (ATP) regardless of symptoms D: ≥1 appropriate ICD shocks, E: ≥3 monomorphic VT episodes within 24 hours \*\* VT events must be confirmed by ECG/monitor or ICD download. Exclusion Criteria: * Unable or unwilling to provide informed consent * Have received prior radiotherapy to the likely treatment field * Inotrope-dependent heart failure or an anticipated life-expectancy of \< 1 year in the absence of VT * Presenting arrhythmia: polymorphic VT or ventricular fibrillation (VF) * Pregnancy * Active ischemia (acute thrombus diagnosed by coronary angiography, or dynamic ST segment changes demonstrated on ECG) or another reversible cause of VT (e.g. drug-induced arrhythmia), had recent acute coronary syndrome within 30 days thought to be due to acute coronary arterial thrombosis, or have CCS functional class IV angina. Note that biomarker level elevation alone after ventricular arrhythmias does not denote acute coronary syndrome or active ischemia.