Model 20066 Left Ventricular (LV) Lead Study

Inclusion Criteria: * Patient meets CRT inclusion criteria as determined by local regulatory and/or hospital policy * Patient has signed and dated the study-specific informed consent form * Patient is 18 years of age or older * Patient is expected to remain available for follow-ups at the investigational center * Patient is willing and able to comply with protocol Exclusion Criteria: * Patient has a previous complete atrial based biventricular CRT system * Patient has a previous LV lead implanted or previous implant attempt within 30 days of implant or ongoing Adverse Events from previous unsuccessful attempt * Patient has known coronary venous vasculature that is inadequate for lead placement * Patient has unstable angina pectoris or has had an acute myocardial infarction (MI) within the past month * Patient has had a coronary artery bypass graft (CABG) or percutaneous transluminal coronary angioplasty (PTCA) within the past three months * Patient has chronic (permanent) atrial arrhythmias * Patient has contraindications for standard transvenous cardiac pacing (e.g., mechanical right heart valve) * Patient has had a heart transplant (patients waiting for heart transplants are allowed in the study) * Patient is enrolled in any concurrent drug and/or device study that may confound the results of this study * Patient has a terminal illness and is not expected to survive more than three months * Patient meets exclusion criteria required by local law (e.g. age, incompetence, pregnancy, breast feeding, etc). * Patient is unable to tolerate an urgent thoracotomy