MIRACLE EF Clinical Study

* Patient has diagnosis of chronic heart failure > 90 days in duration

* Has left ventricular ejection fraction (LVEF) between 36% and 50%, inclusive, as documented at baseline or within 30 days prior to enrollment

* Is either: (a) NYHA Class III at enrollment or at baseline OR (b) NYHA Class II at enrollment or at baseline, with a documented hospitalization for HF in the 12 months prior to enrollment OR (c) NYHA Class II at enrollment or at baseline, without a documented hospitalization for HF in the prior 12 months, but with BNP ≥250 pg/ml or NT-proBNP ≥1000 pg/ml

* Has documented left bundle branch block (LBBB) with QRS ≥130ms at baseline or within 30 days prior to enrollment.

* Is in sinus rhythm at time of enrollment or at the baseline visit.

* Has had no additions to or subtractions from non-diuretic heart failure medical therapy within 30 days prior to enrollment

* Is on maximum tolerated (guideline) dosages of medications in ACC/AHA guidelines for HF, Ischemic Heart Disease, Hypertension and AF as appropriate.

* Has signed and dated the study informed consent.

* Is able to receive a pectoral CRT-P implant.

* Is expected to remain available for follow-up visits.

* Is willing and able to comply with the Clinical Investigation Plan.

* Requires permanent cardiac pacing.

* Indicated for implantable cardioverter defibrillator (ICD), such as for secondary prevention of prior sudden cardiac arrest, related to prior history of ventricular tachycardia and/or ventricular fibrillation.

* Less than 18 years of age, or under a higher minimum age requirement as defined by local law.

* Unstable angina or an acute MI within 40 days prior to enrollment.

* Coronary artery bypass graft (CABG) or percutaneous coronary intervention (PCI) within the 90 days prior to enrollment.

* Chronic (permanent) atrial arrhythmias. Chronic (permanent) atrial arrhythmias are defined as cases of long-standing atrial fibrillation (e.g., greater than 1 year) in which cardioversion has not been indicated or attempted.

* Cardioversion for atrial fibrillation within 30 days prior to enrollment.

* Treatable pericardial constraint within 30 days prior to enrollment.

* Restrictive (infiltrative) cardiomyopathies, such as amyloidosis, sarcoidosis, or hemochromatosis.

* Enrolled in a concurrent study, with the exception of a study-manager approved study that is strictly observational in nature and does not confound the results of this study (e.g. registries).

* Life expectancy of less than 24 months due to non-cardiac conditions.

* Pregnant, or of childbearing potential and not on a reliable form of birth control.

* CRT-P, pacemaker, ICD or CRT-D device implanted previously, or currently.

* Restrictive, hypertrophic, or reversible cardiomyopathy.

* Mechanical right heart valve.

* Primary valvular disease and is indicated for valve repair or replacement.

* Heart transplant, or is currently on a heart transplant list.

* Significant renal dysfunction, as manifested by serum creatinine level >2.5 mg/dl or ≥275 μmol/L or estimated glomerular filtration rate (GFR) ≤30 mL/min/1.73 m2, which is documented within the 30 days prior to enrollment or at baseline.

* Significant hepatic dysfunction, as evidenced by a hepatic function panel (serum) > 3 times upper limit of normal, which is documented within the 30 days prior to enrollment or at baseline.

* Chronic or treatment-resistant severe anemia (hemoglobin <10.0 g/dL), which is documented within the 30 days prior to enrollment or at baseline.

* On intravenous inotropic drug therapy.