This study aims to establish the degree to which change in the ratio of ECF to TBW measured using the SOZO BIS device correlates with change in end-expiratory end-diastolic PAP measured using the CardioMEMS HF System (St. Jude Medical).

This is a prospective, single-arm, observational, non-randomized clinical study that will enroll patients with heart failure who have had a CardioMEMS™ device implanted to monitor their diastolic pulmonary artery pressure. The study will recruit and enroll thirty participants. Participants will be monitored daily at home for a period of 30 days. Each day, the patient's diastolic pulmonary artery pressure will be measured by CardioMEMS™ and the ImpediMed's BIS technology. Participant's weight will also be taken each day.

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.

Heart failure patients who have a cardioMEMS device

This is a pilot study, no individual participant data will be made available.