LV Endocardial CRT for Patients With Intermediate QRS Width

Inclusion Criteria: * Patients with NYHA Class II-IV ambulatory HF symptoms * Optimal HF Medical Therapy of at least 3 months (2009 ACCF/AHA, ESC 2012) * LVEF less than or equal to 35% * Sinus rhythm (can have paroxysmal atrial fibrillation) * QRS morphology is non-RBBB * QRS duration 120-149 ms * Patients with pacemaker or ICD that meet the above criteria may be upgraded to CRT-D or CRT-P * Patients are able to receive oral anticoagulation Exclusion Criteria: * Patients with atrial septal defect closure * Planned atrial fibrillation ablation within 12 months * Patients with mitral prosthetic valve that precludes the placement of an LV lead trans-septally * Patients with RBBB * Patients with intra-cardiac thrombi * Patients with permanent atrial fibrillation * Patients with contraindications to oral anti-coagulation * In-hospital patients with acute cardiac or non-cardiac illness that requires intensive care * Acute coronary syndrome (including MI) \< 4 weeks * Coronary revascularization (CABG or PCI) \< 3 months * Uncorrected or uncorrectable primary valvular disease * Restrictive, hypertrophic or reversible form of cardiomyopathy * Severe primary pulmonary disease such as cor pulmonale * Patients with a life expectancy of less than one year from non-cardiac cause. * Patients included in other clinical trials that will affect the objectives of this study * Those unable or unwilling to provide informed consent * Those with a history of noncompliance to medical therapy