Prospective Randomized Clinical Trial for Effect of Stellate Ganglion Block in Medically Refractory Ventricular Tachycardia

The investigators will compare the effects of PSGB(percutaneous stellate ganglion block) in patients with recurrent sustained VT/VF in spite of appropriate medical therapy and cardio-version/ defibrillation after correction of underlying correctable factors with those without PSGB by prospective randomized trail. PSGB will be performed every 3 days by anesthesiology specialist after cardiologist's request, until the stabilization of VT/VF. We will compare the frequency and episode number of VT/VF, procedure related complication, acute and long-term mortality.