Mapping and Pacing of the His Bundle for Heart Failure Patients With Left Bundle Branch Block

Inclusion Criteria:

1. Patients are undergoing implant of an Abbott pacemaker or CRT device under standardindications
2. An ECG with a wide QRS complex (>130 ms)
3. ECG morphology of typical complete LBBB,
4. Patients have heart failure with NYHA Class II-IV symptoms,
5. LV EF <50%
6. At least 18 years old and not pregnant.
7. Must provide written informed consent prior to any clinical investigation relatedprocedure.
8. Willing to comply with study evaluation requirements
9. Female subjects of child-bearing potential are required to have a negative pregnancytest done within 7 days prior to the implant procedure per site standard test. Femalepatients of childbearing potential should be instructed to use safe contraception (e.g., intrauterine devices, hormonal contraceptives: contraceptive pills, implants,transdermal patches hormonal vaginal devices, injections with prolonged release.)

Exclusion Criteria:

1. Patients have non-specific intraventricular conduction delay or right bundle branchblock
2. Previously implanted cardiac devices with three or more permanent leads
3. History of aortic valve repair or replacement
4. History of tricuspid valve replacement
5. Pregnant or nursing subjects and those who plan pregnancy during the clinicalinvestigation follow-up period.
6. Recent (< 3 months) myocardial infarction, ablation, electrolyte imbalance, or anycondition within the last 90 days that would contraindicate for pacemaker or CRTimplant in the opinion of the investigator
7. Presence of other anatomic or comorbid conditions, or other medical, social, orpsychological conditions that, in the investigator's opinion, could limit thesubject's ability to participate in the clinical investigation or to comply withfollow-up requirements, or impact the scientific soundness of the clinicalinvestigation results.