The purpose of this Post Market Study (PMS) is to evaluate the use of the CardioMEMS HF System in patients with New York Heart Association (NYHA) Class III Heart Failure in a commercial setting.

Inclusion Criteria:

1. Written informed consent obtained from subject
2. ≥ 18 years of age
3. Diagnosis of NYHA Class III Heart Failure
4. At least 1 HF hospitalization within 12 months of Baseline visit
5. Subjects with reduced LVEF heart failure should be receiving a beta blocker for 3 months and an ACE-I or ARB for one month unless in the investigator's opinion, the subject is intolerant to beta blockers, ACE-I or ARB.
6. Subjects with a BMI ≤ 35. Subjects with BMI >35 will require their chest circumference to be measured at the axillary level, if > 65 inches the patient will not be eligible for the study.
7. Subjects with pulmonary artery branch diameter ≥ 7mm - (implant target artery - assessed during the RHC)
8. Subjects willing and able to comply with the follow-up requirements of the study

Exclusion Criteria:

1. Subjects with an active infection
2. Subjects with history of recurrent (> 1) pulmonary embolism or deep vein thrombosis
3. Subjects who, in the Investigator's opinion, are unable to tolerate a right heart catheterization
4. Subjects who have had a major cardiovascular event (e.g., myocardial infarction, open heart surgery, stroke, etc.) within 2 months of Baseline Visit
5. Subjects with Cardiac Resynchronization Device (CRT) implanted < 3 months prior to enrollment
6. Subjects with a Glomerular Filtration Rate (GFR) < 25 ml/min (obtained within 2 weeks of the baseline visit) who are non-responsive to diuretic therapy or who are on chronic renal dialysis
7. Subjects with congenital heart disease or mechanical right heart valve(s)
8. Subjects likely to undergo heart transplantation or VAD within 6 months of baseline visit
9. Subjects with known coagulation disorders
10. Subjects with a hypersensitivity or allergy to aspirin, and/or clopidogrel (not applicable for subjects taking anti-coagulation therapy or other approved anti-platelets therapy).

Adults with New York Heart Association (NYHA) Class III Heart Failure (HF) who have experienced a heart failure hospitalization within the past 12 months.

Patients who underwent a successful implant constitute the Effectiveness Population

2 years

An adverse event (AE) is any untoward medical occurrence, unintended disease or injury, or untoward clinical signs (including abnormal laboratory findings) in subjects, users or other persons, whether or not related to the medical device under investigation.