Advancing Clinical Heart Failure Outcomes Leveraging Defibrillation Lead Implant System for Left Bundle Branch Area Pacing

• LBBAP Therapy (Device): CRT-D programmed for LBBAP (LV lead OFF)
• LOT-CRT (Device): CRT-D programmed for LOT-CRT (LBBAP + LV lead ON)
• ICD (Device): ICD programmed for LBBAP
• LOT-CRT (Device): CRT-D programmed for LOT-CRT (LBBAP + LV lead ON)

Primary outcomes

• Left ventricular ejection fraction (LVEF) [Baseline, 6 months, 12 months]: Change in LVEF assessed by echocardiography during each therapy period (baseline to 6 months, 6 months to 12 months).
• Left ventricular end-systolic volume (LVESV) [Baseline, 6 months, 12 months]: Change in LVESV assessed by echocardiography during each therapy period (baseline to 6 months, 6 months to 12 months).

Secondary outcomes

• Left ventricular ejection fraction (LVEF) [Baseline, 6 months]: Change in LVEF assessed by echocardiography from baseline to 6 months
• Left ventricular end-systolic volume (LVESV) [Baseline, 6 months]: Change in LVESV assessed by echocardiography from baseline to 6 months.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Subject meets current ACC/AHA/HRS guidelines for implantation of a CRT-D device.
* Subject has documented LVEF ≤ 35% within 60 days of enrollment.
* Subject meets the criteria for presence of Strauss-defined LBBB.
* Subject meets NYHA classification II or III.
* Subject is willing and able to provide written consent.
* Subject is at least 18 years of age at the time of consent.
* Subject is geographically stable and willing and able to complete study procedures, including follow-up visits.
* The subject's medical records must be accessible by the enrolling site over the follow-up period.

Exclusion Criteria:

* Subject has documented myocardial infarction before enrollment.
* Subject has non-LBBB conduction patterns such as Right Bundle Branch Block (RBBB) or non-specific IVCD.
* Subject has 2nd or 3rd degree AV block.
* Subject has persistent or permanent atrial fibrillation (AF) or atrial flutter (AFL).
* Subject has intrinsic (non-paced) QRS duration ≤ 120ms.
* Subject with previous or existing pacemaker (including transvenous and transcatheter pacing system), Implantable Cardioverter Defibrillator (ICD, transvenous) or CRT-D (transvenous) device or leads.
* Subject has contraindications for screw-in transvenous lead placement (e.g., mechanical right heart valve).
* Subject underwent valve surgery within 90 days prior to enrollment.
* Subject is unable or unwilling to undergo baseline CMR imaging, if previously collected CMR images are unavailable or do not meet minimum acceptable criteria.
* Subject is post-heart transplantation or is actively listed on the transplantation list.
* Subject is implanted with a left ventricular assist device (LVAD).
* Subject has severe renal disease.
* Subject is on continuous or uninterrupted infusion (inotropic) therapy for heart failure.
* Subject has complex and uncorrected congenital heart disease.
* Subject has life expectancy of less than 12 months.
* Subject is pregnant or breastfeeding.
* Subject is enrolled or planning to enroll in a concurrent clinical study that may confound the results of this study, without documented pre-approval from a Medtronic study manager.