1. Patients with primary prevention indications for ischemic or non-ischemic cardiomyopathy with EF≤35%, with existing devices (ICD/CRT-D), regardless of when the device was implanted, who have experienced at least ONE episode of VT/VF appropriately treated with ICD therapy (ATP or shock) or had untreated NSVT lasting at least 10 beats with heart rate of at least 170 bpm, documented by electrogram of their implanted device.