Substrate Targeted Ablation Using the FlexAbility™ Ablation Catheter System for the Reduction of Ventricular Tachycardia

Inclusion Criteria: * Patient is receiving a new St.Jude Medical (SJM) Implantable Cardioverter Defibrillator (ICD) or SJM Cardiac Resynchronization Therapy-Defibrillator (CRT-D) implant, which has study required programing capabilities and is appropriate for remote monitoring. Subjects who have received the ICD / CRT-D up to 90 days prior to enrollment are also eligible. * Patient who has a high risk of ICD shock as shown by at least one documented Monomorphic VT (MMVT)\*\* by one or more of the following: Spontaneous MMVT or Inducible MMVT during electrophysiology (EP) Study or Inducible MMVT during Non-Invasive Programmed Stimulation (NIPS) Study * 18 to 75 years of age * Patient has been informed of the nature of the study and has agreed to its provisions and provided written informed consent approved by the Institutional Review Board. * Note Pleiomorphic ventricular tachycardia (VT) (multiple MMVT morphologies) is acceptable but polymorphic VT or ventricular fibrillation (VF) is not. Exclusion Criteria: * Any history of stroke * S-T elevation myocardial infarction (MI) or previous cardiac surgery within 60 days prior to enrollment * Patient is pregnant or nursing * Patient has New York Heart Association (NYHA) class IV heart failure * Patient has incessant ventricular tachycardia (VT) necessitating immediate treatment (Patients with Incessant VT have continuous sustained VTs that recur promptly despite repeated intervention for termination over several (≥3) hours) * Patient has VT/VF thought to be from channelopathies * Limited life expectancy (less than one year) according to Investigator * Patient has current class IV angina * Recent coronary artery bypass graft (CABG \< 60 days) or percutaneous coronary intervention (PCI \< 30 days) * Patient is currently participating in another investigational drug or device study * Patient is unable or unwilling to cooperate with the study procedures * Known presence of intracardiac thrombi (i.e., positive Transesophageal Echocardiogram (TEE) for LA or LV clot). TEE is required for history of left atrium (LA) or left ventricle (LV) clot and recommended for history of atrial fibrillation (AF) with CHADS \> 1 * Prosthetic mitral or aortic valve * Mitral or aortic valvular heart disease requiring immediate surgical intervention * Major contraindication to anticoagulation therapy or coagulation disorder * Left Ventricular Ejection Fraction \< 15% * Patient has had a previous ablation procedure for ventricular tachycardia (VT), excluding remote (\> 3 months) outflow tract tachycardia * Patient has glomerular filtration rate (GFR) \< 30 mL/min/1.73m2 within the past 3 months * Patient has peripheral vascular disease that precludes LV access * Patient has a premature ventricular contraction (PVC) or VT induced cardiomyopathy that is expected to resolve with ablation and will not require an ICD * Patient has reversible cause of VT * Use of left ventricular assist device (LVAD) or Tandem Heart devices (Impella and Balloon pumps are acceptable) * There is a strong clinical reason to believe that, in the opinion of the investigator, the patient only has septal scar that is deep