Inclusion Criteria:

Group 1: HFpEF-CKD-will consist of 30 subjects with:

- Ejection fraction of greater than 55%; and

- Evidence of increased LV filling pressures, including at least 2 of the following:
average septal-lateral E/e' ratio > 15; tricuspid regurgitation (TR) peak velocity >
2:8 m/s;

- Left atrial volume index >34mL/m^2 assessed by echocardiography; and

- Previous diagnosis of HF with New York Heart Association (NYHA) functional class
II-III symptoms on chronic loop diuretic therapy; and

- CKD defined as glomerular filtration rate (eGFR) of 15-60 mL/min/1.73 m^2 as estimated
by the Modification of Diet in Renal Disease equation. Subject needs to be on stable
dose of chronic loop diuretic for at least 4 weeks prior to study and maintained on
the same dose for the duration of the study. In addition to the exclusion criteria
listed below, to ensure a more homogenous group of subjects, we will exclude subjects
with Diabetes or BMI > 35 (because endogenous natriuretic peptide levels are low in
obese subjects).

Group 2: HFpEF-EI-will consist of 30 subjects with:

- Ejection fraction of greater than 55%; and

- Previous invasive determination of normal pulmonary capillary wedge pressure (< 15
mmHg) at rest and ≥ 25 mmHg during exercise12; and

- New York Heart Association (NYHA) functional class II-III symptoms but not on chronic
loop diuretic therapy; and

- Glomerular filtration rate (eGFR) of > 60 mL/min/1.73 m^2 as estimated by the
Modification of Diet in Renal Disease equation. In addition to the exclusion criteria
listed below, to ensure a more homogenous group of subjects, we will exclude subjects
with Diabetes or BMI>35 (because endogenous natriuretic peptide levels are low in
obese subjects).

Exclusion Criteria:

- Body mass index > 35.

- Blood pressure < 100/60 or > 180/100 mmHg.

- Diabetes.

- Myocardial infarction within 6 months of screening.

- Unstable angina within 6 months of screening, or any evidence of myocardial ischemia.

- Significant valvular heart diseases.

- Hypertrophic, restrictive or obstructive cardiomyopathy.

- Constrictive pericarditis.

- Primary pulmonary hypertension.

- Biopsy proven active myocarditis.

- Severe congenital heart diseases.

- Cardiac amyloidosis.

- Fabry disease.

- Sarcoidosis.

- Sustained ventricular tachycardia or ventricular fibrillation within 14 days of
screening.

- Second or third degree heart block without a permanent cardiac pacemaker.

- Stroke within 3 months of screening, or other evidence of significantly compromised
CNS perfusion.

- Hemoglobin < 9 g/dl

- ALT > 2 times the upper limit of normal; serum sodium of < 135 mEq/dL or > 150 mEq/dL.

- Serum potassium of < 3.5 mEq/dL or > 5.7 mEq/dL.

- Bother acute or chronic medical conditions or laboratory abnormality which may
increase the risks associated with study participation or may interfere with
interpretation of the data.

- Received an investigational drug within 1 month prior to dosing.

- Patients with an allergy to iodine; female subject who is pregnant or breastfeeding.

- In the opinion of the investigator, is unlikely to comply with the study protocol or
is unsuitable for any reasons.

Note: Other protocol defined Inclusion/Exclusion criteria may apply.

Eligibility last updated 5/16/23. Questions regarding updates should be directed to the study team contact.