This 2x2 randomized crossover feasibility study will evaluate the therapeutic value of adding pacing from the left ventricular lead to Left Bundle Branch Area Pacing (LBBAP) using a cardiac resynchronization therapy defibrillator (CRT-D). This combined therapy is known as Left Bundle Branch Optimized Cardiac Resynchronization Therapy (LOT-CRT) and will be compared to LBBAP therapy over sequential 6-month periods in CRT-indicated patients with LBBB. Primary and secondary outcomes are echocardiographic changes. Exploratory assessments will include NT-proBNP and subject-reported quality of life (KCCQ). An observational treatment arm will include subjects who have not been randomized due to unsuccessful implant for real-world observational analysis
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 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).