ENABLE MRI (Magnetic Resonance Imaging)

Key Inclusion Criteria

• Phase I: Subject is indicated per guidelines and will receive a CRT-D or ICD system OR Subject is implanted with a functional and stable CRT-D or ICD system Phase II: Subject is implanted with a functional and stable CRT-D or ICD system
• Subject will receive or is implanted with an ICD or CRT-D pulse generator in the left or right pectoral region
• Subject is able and willing to undergo an MR scan without intravenous sedation (Phase I only)
• Subject is willing and capable of providing informed consent and participating in all testing/ visits associated with this clinical study at an approved clinical study center and at the intervals defined by this protocol
• Subject is age 18 or above, or of legal age to give informed consent specific to state and national law

Key Exclusion Criteria

• Subject implanted with an ICD or CRT-D pulse generator with battery at Explant status
• Subject has other active or abandoned implanted cardiac rhythm devices, components or accessories present such as pulse generators, leads, lead adaptors or extenders
• Presence of metallic objects that represent a contraindication to MR imaging at the discretion of the Radiologist and impacting the ability to conduct the study protocol
• Subject needs or will need a medically necessary MR scan, before completing the 1-month post-MR follow-up visit (Phase I only)
• Subject with:
• A history of syncope related to brady-arrhythmia
• A history of syncope of unknown etiology
• Sinus pauses (Pause > 2 s)
• Permanent or intermittent complete AV (Atrioventricular ) block
• Documentation of progressive AV nodal block over time
• Trifascicular block (alternating bundle branch block or PR > 200 ms (interval between P wave and R-wave) with LBBB ( Left bundle branch block) or other bifascicular block) Note: It is required to run a 12 lead ECG (Electrocardiography) and a 10s rhythm strip to document this exclusion criterion. During ECG acquisition, subjects must be in either their own intrinsic rhythm or, in subjects with an existing device implant, the device must be programmed to VVI (ventricular demand pacing) 40 ppm.
• Subject is not clinically capable of tolerating the absence of pacing or Resynchronization therapy support in a supine position for the duration that the pulse generator is in MRI Protection Mode, per Physician discretion
• Subject is not clinically capable of tolerating the absence of Tachycardia therapy support for the duration that the pulse generator is in MRI Protection Mode, per Physician discretion
• Subjects with a planned RA( right atrium), RV ( right ventricle) or LV (left ventricle) lead revision or extraction within 30 days of enrollment (Phase I only)
• Subjects with an implanted lead that is planned to be extracted during the study implant procedure
• Subjects currently requiring dialysis
• Subject has a mechanical heart valve
• Subject has a known or suspected sensitivity to dexamethasone acetate (DXA)
• Subject is currently on the active heart transplant list
• Subject has documented life expectancy of less than 12 months
• Subject is enrolled in a concurrent study, with the exception of local mandatory governmental registries and observational studies/registries, without the written approval from Boston Scientific
• Women of childbearing potential who are or might be pregnant, and will receive an ICD or CRT-D pulse generator

VF Induction Sub-study Exclusion Criteria:

In addition to meeting all of the inclusion criteria and none of the exclusion criteria of the ENABLE MRI study, subjects enrolled in the VF Induction Sub-study must also not meet any of the following VF Induction Sub-study exclusion criteria:

• Unstable heart failure requiring hospitalization in the last 30 calendar days
• Unable to tolerate sedation (e.g. IV (intravenous sedation )sedation, general anesthesia)
• Planned cardiac revascularization procedure
• Right Ventricular Lead R wave is less than 5 mV(