Inclusion Criteria:

1. Age 18 years or older.
2. NYHA Class III HF.
3. Patient has undergone implantation of CardioMEMS HF System (St. Jude Medical).
4. Patient is characterized by at least one of the following:
   • CardioMEMS implanted within the previous 90 days
   • Received treatment with intravenous diuretics within the previous 30 days
   • Received dose escalation of oral diuretics at least twice within the previous 30 days
5. Patient is able to sit upright for BIS measurements.
6. Patient provides written informed consent and authorization to use and disclose health information.

Exclusion Criteria:

1. Patient is enrolled in a concurrent interventional study of an experimental treatment that may confound the results of this study, in the investigator's opinion.
2. Patient has a clinical condition that would not allow them to complete the study.
3. Patient is pregnant or lactating.
4. Patient has nephrotic syndrome or nephrosis.
5. Patient has estimated glomerular filtration rate (eGFR) < 20 ml/min/1.73m2 or end-stage renal disease requiring chronic dialysis.
6. Patient has been diagnosed with lymphedema.
7. Patient has chronic liver failure or cirrhosis.
8. Patient has a moderate or large pleural effusion as seen on chest X-ray.
9. Patient has been diagnosed with thrombophlebitis or deep vein thrombosis in arms or legs in the past 90 days.
10. Patient has an implanted cardiac rhythm management device (pacemaker or implantable cardioverter defibrillator).
11. Patient has an amputation of a limb.