The purpose of this study is to demonstrate that the safety and efficacy of the Lumax HF-T with optimized interventricular delay biventricular pacing (OPT) is non-inferior to the Lumax HF-T with simultaneous biventricular pacing (SIM) in patients with heart failure requiring cardiac resynchronization therapy.

This study is a randomized, double-blinded, crossover, multi-center, prospective trial. The study will consist of up to 122 subjects who require treatment of advanced heart failure through cardiac resynchronization therapy (CRT) with back-up defibrillation capabilities. Eligible patients will have a successfully implanted BIOTRONIK Lumax HF-T CRT-D system and have received simultaneous biventricular pacing for a minimum of 90 days prior to enrollment. The 90-day period is being required to allow the treatment effect of CRT therapy with SIM to be complete and to ensure the patient is receiving a stable and optimal CHF medical regimen. The patients will have the interventricular delay feature programmed after a standardized optimization procedure. Patients, along with study personnel evaluating the study endpoint measures, will be blinded to the type of CRT therapy delivered during the study follow-up period.

Inclusion Criteria:

• Meet the indications for therapy
• Successfully implanted with a BIOTRONIK Lumax HF-T CRT-D system and have received SIM for a minimum of 30 days prior to enrollment. A successful implantation is defined as having a measured LV pacing threshold which allows for a minimum 1-volt safety margin without any phrenic nerve stimulation at the time of enrollment.
• Treated with stable and optimal CHF medications, which includes an ACE inhibitor (ACE-I) or Angiotensin Receptor Blocker (ARB) at therapeutic dose for 1 month prior to enrollment, if tolerated, and a Beta Blocker that is approved and indicated for HF for 3 months prior to enrollment, if tolerated, with a stable dosage for 1 month prior to enrollment. If the patient is intolerant of ACE-I or beta blockers, documented evidence must be available. Eplerenone requires dosage stability for 1 month prior to enrollment. Diuretics may be used as necessary to keep the patient euvolemic. Therapeutic equivalence for ACE-I substitutions is allowed within the enrollment stability timeliness. Stable is defined as no more than a 100% increase or a 50% decrease in dose.
• Age ≥ 18 years
• Able to understand the nature of the study and give informed consent
• Able to complete all testing required by the clinical protocol, including the 6-minute walk test and QOL questionnaire
• Available for follow-up visits on a regular basis at the investigational site

Exclusion Criteria:

• Meet one or more of the contraindications
• Have a life expectancy of less than 6 months
• Expected to receive heart transplantation within 6 months
• Have had more than 1 CHF-related hospitalization within past 30 days
• Currently receiving IV inotropic medications
• Chronic atrial fibrillation
• Enrolled in another cardiovascular or pharmacological clinical investigation, except for FDA required post-market registries
• Any condition preventing the patient from being able to perform required testing
• Presence of another life-threatening, underlying illness separate from their cardiac disorder