His Bundle Pacing Versus Coronary Sinus Pacing for Cardiac Resynchronization Therapy

This is a randomized, single-blinded study of 40 patients to a strategy of HB pacing versus CS pacing, and remain blinded to their treatment allocation. Both treatment options use standard-of-care, FDA-approved devices. The distinction is only in the allocation toward HB pacing and CS pacing. Treating physicians will be aware of assignment in order to facilitate routine device follow-up. Echocardiographic and electrocardiographic evaluation will also be performed in a blinded manner. Cross-over is permitted between treatment group allocation if: * CS lead cannot be placed due to difficult cannulation of the CS, limited branches at the posterolateral or lateral wall, or phrenic nerve capture. These subjects may then cross-over to HB pacing. * HB pacing subjects may cross-over if HB lead cannot be positioned with adequate stability and reasonable pacing output, or if QRS width does not narrow by at least 20% or to a QRS width of ≤ 130 msec. Implant procedure will be per routine percutaneous access, as is standard for pacemaker and ICDs. All subjects will receive an FDA-approved cardiac resynchronization therapy pacemaker or defibrillator device, as per standard of care outlined for the subject. In order to facilitate optimal lead placement, arterial access for levo-phase CS angiography and/or LV septal mapping to characterize site of bundle-branch block may also be performed, at the discretion of the implanting physician per his/her standard practice. Follow-up will be performed at 2 weeks post-implant for incision check and device interrogation as is standard of care. In addition, routine device and clinical follow-up will be scheduled at 1, 3, 6, and 12 months. Electrocardiography (ECG) will be performed pre-implant, prior to hospital discharge, at 3 months, 6 months, and 12 months. Echocardiography will be performed pre-implant and 6 months to evaluate for change in LVEF, chamber dimension, and wall motion with strain imaging as is standard of care in the treatment of patients with advanced heart failure. NYHA functional class and quality of life (utilizing the Kansas City Cardiomyopathy Questionnaire) will be assessed pre-implant and at 6 months.