The standard of care to treat congestive heart failure is with a class of medication called diuretics, which remove the extra fluid from the body through urination. Another way to remove extra fluid in patients with heart failure is called ultrafiltration. Ultrafiltration may result in more rapid removal of excess fluid and more rapid improvement in your symptoms compared to standard diuretic treatment. Currently, it is unknown what effects these therapies (diuretics or ultrafiltration) have on the small blood vessels in your heart. These small blood vessels are important to supply blood and oxygen to your failing heart. Thus, the purpose of this research study is to compare the effects (good and bad) of ultrafiltration treatment with standard intravenous (in your vein) diuretic therapy on your heart function and blood flow.