Mechanisms of Diuretic Resistance in Heart Failure, Aim 3

This study examines why some patients with heart failure become resistant to diuretics (water pills used to remove excess fluid), and whether certain kidney or cardiovascular tests can predict or explain this. Participants will have measurements taken to understand the mechanisms behind diuretic resistance. **You may be eligible if...** - You have a clinical diagnosis of heart failure - You have shown resistance to diuretics (your kidneys do not excrete enough sodium in response to a standard dose) - Your heart failure medications are stable and you have not been hospitalized urgently in the last 2 months - Your blood potassium, sodium, and hemoglobin levels are within acceptable ranges **You may NOT be eligible if...** - Your heart failure medications are being changed during the study period - You have had a recent emergency hospitalization related to heart failure - Your lab values are outside the safe range for participation Talk to your doctor to see if this trial is right for you.