Sub Chronic Evaluation for ATP With an Extravascular Placed ICD Lead (STEP ICD) Study

Inclusion Criteria: At least 18 years old Indicated for de novo or replacement ICD procedure Exclusion Criteria: BMI ≥ 35 kg/m2 Subjects who require continual ventricular pacing Presence or planned use of a subcutaneous ICD lead, subcutaneous coils/arrays, epicardial patches or epicardial pace/sense leads within the study period Planned MRI within the study period Subjects on anticoagulation or antiplatelet therapy that cannot be temporarily discontinued for the procedure Circumstances that may prevent data collection or follow-up Participation in any concurrent clinical study without prior written approval from the Sponsor Inability or unwillingness to provide informed consent to participate in the Study Known prior history for any of the following: NYHA IV functional class in past 90 days Inotropic therapy in past 180 days Structural abnormalities of the heart that may increase risk of the study procedure or an obstructed/restricted pathway into the mediastinum Uncontrolled paroxysmal, persistent or permanent atrial fibrillation Median or partial sternotomy Surgery with disruption of the lung, pericardium or connective tissue between the sternum and pericardium Significant anatomic derangement of or within the thorax (e.g., pectus excavatum, significant scoliosis) Thoracic radiation therapy, pneumothorax, pneumomediastinum or other medical treatments which may complicate the AtaCor EV-ICD Lead System implant procedure Any conditions which may complicate the AtaCor EV-ICD Lead System implant procedure Pericardial disease, pericarditis and mediastinitis Medical treatments, surgeries or conditions that increase the potential for adhesions in the thorax FEV1 < 1.0 Liter Surgically corrected congenital heart disease (not including catheter-based procedures) Allergies to the device materials as listed in the Instructions for Use (IFU)