The objective of this study is to demonstrate that frequent atrio-ventricular (AV/PV) and inter-ventricular (V-V) delay optimization using QuickOpt in patients with cardiac resynchronization therapy device results in improved clinical response over standard of care (i.e. empiric programming or one-time optimization using any non-intracardiac electrogram optimization methods).

• This is a prospective, double-blinded, multicenter, randomized study
• Patient could be enrolled up to 2 weeks post CRT-D implant and are followed for 12 months post implant with follow-up visits at 3, 6, 9 and 12 months
• Patients will be randomized at enrollment to either Group 1 ("QuickOpt Group") or Group 2 ("Control Group").
• Group 1 - The patient's device is programmed to sequential biventricular pacing mode with AV/PV and VV delays optimized using QuickOpt. For Group 1 patients, optimization using QuickOpt is performed at enrollment, 3 month, 6 month, 9 month, 12 month and at any unscheduled follow-up visits.
• Group 2 - The patient's device is programmed to either simultaneous or sequential BiV pacing mode as per physician's discretion. The AV/PV and inter-ventricular (VV) delays could be programmed empirically or optimized using any non-IEGM based method as per sites standard of care. However, the Group 2 patients can be optimized only once within the first 4 weeks post implant. Any AV/PV and VV delay optimizations performed after 4 weeks post implant in Group 2 patients will be considered protocol deviations.

Inclusion Criteria:

• Patient meets current CRT-D indications and be implanted with a St. Jude Medical (SJM) CRT¬D device with VV timing and a compatible lead system.
• Patient has the ability to complete a 6-minute hall walk with the only limiting factor to be fatigue or shortness of breath.
• Patient has the ability to independently comprehend and complete a QOL questionnaire.

Exclusion Criteria:

• Patient has an epicardial ventricular lead system.
• Patient has the ability to walk ≥ 450 meters in 6 minutes
• Patient has limited intrinsic atrial activity (≤ 40 bpm).
• Patient has persistent or permanent atrial fibrillation (AF).
• Patient has a 2° or 3° heart block.
• Patient's life expectancy is less than 1 year.
• Patient is pregnant.
• Patient is on IV inotropic agents.

Date of birth missing for 1 treatment patient and 1 control patient.