Every year in the United States, there are approximately 550,000 newly diagnosed heart failure patients. Five million patients suffer from chronic heart failure. Acute heart failure exacerbation is the leading cause for hospitalization in Medicare patients over the age of 65. A fundamental understanding in the definition, etiology, pathophysiology and hemodynamics has led to advances in treatments. The complete definition of heart failure is not confined solely to the heart, but involves a complex interplay between the heart and other organs. Definitions in heart failure have mainly focused on impaired pump function and clinical manifestations of venous congestion. Katz (2009) states “heart failure is a clinical syndrome in which heart disease reduces cardiac output, increases venous pressures, and is accompanied by molecular and other abnormalities that cause progressive deterioration of the failing heart” (Katz, Heart failure: pathophysiology, molecular biology, and clinical management, 2nd edn. Lippincott Williams & Wilkins, Philadelphia, 2009).