Cohort Study - SBRT for VT Radioablation

Ventricular tachycardia (VT) contributes to over 350,000 sudden deaths each year in the US. Malignant VTs involve an electrical "short circuit" in the heart, formed by narrow channels of surviving tissue inside myocardial scar. Current treatment for VT consists of either implantable defibrillators (ICDs), suppressive drug therapy, catheter ablation or a combination of all 3. Implantable Defibrillators (ICDs) reduce sudden death and can terminate some ventricular tachycardia (VT) without shocks, but they don't prevent VT. The occurrence of ≥1 ICD shock is associated with reductions in mental well-being and physical functioning, and increases in anxiety and sometimes depression. Further, ICD shocks have been consistently associated with adverse outcomes, including heart failure and death. Furthermore, the most important predictor of ICD shocks is a history of prior ICD shocks. Therapies to suppress VT include antiarrhythmic drug therapy and catheter ablation, neither however is universally effective. When VT recurs despite antiarrhythmic drug therapy and catheter ablation, novel yet invasive, approaches may be required. Such invasive procedures carry consequent risks of cardiac and extra-cardiac injury. Stereotactic body radiotherapy (SBRT) is a non-invasive technique that delivers high doses of radiation precisely to specified regions in the body, while minimizing exposure to adjacent tissue. This technique is currently, and commonly used in the treatment of cancer. Conventional application of SBRT has made use of its ability to spare non-target tissue, including for treatment of tumors near the heart. More recently, clinicians have changed the paradigm, by focusing radioablative energy on ventricular scar responsible for ventricular tachycardia. Pre-clinical studies have supported the concept and were followed by first-in-human VT therapeutic experience in 2017. Subsequent studies have had encouraging results for patients who failed or were unable to tolerate conventional treatment.