Defi nition. Heart failure (HF) is a complex clinical syndrome that can result from any cardiac disorder that impairs the ability of the ventricle to deliver adequate quantities of blood to the metabolizing tissues during normal activity or at rest. Th e condition in the past has been referred to as “congestive heart failure,” owing to the edematous state commonly produced by the fl uid backup resulting in shortness of breath, fatigue, limitation of exercise tolerance, and fl uid retention. Fluid retention may lead to pulmonary and peripheral edema. More recently, because all patients do not necessarily present with fl uid overload at the initial or follow-up evaluations, the term “heart failure” is used to more adequately refl ect the clinical syndrome. B. Mortality rate. Approximately 300,000 patients die as a result of the direct or indirect consequences of HF each year, and the number of deaths owing to HF (primary or secondary causes) has increased steadily, despite treatment advances. Th e risk of death is 5% to 10% annually in patients with mild symptoms and is as high as 30% to 40% in patients with advanced disease manifestations. C. Incidence of HF. HF is a common medical condition that aff ects almost 5 million people in the United States, with more than 500,000 new cases diagnosed each year. Between 1.5% and 2.0% of the population has HF, and the incidence increases to 6% to 10% in patients older than age 65. HF makes up 20% of all hospitalizations in patients older than 65 years of age. HF is the only major cardiovascu- lar disorder that is increasing in incidence and prevalence. During the last 10 years, there has been a dramatic increase in the number of hospitalizations, primarily owing to HF (810,000 in 1990 to more than 1 million, currently). Th e reasons for the increased numbers of hospital admissions include the aging of the population in the United States and improved treatment results obtained for myocardial infarction, coronary artery bypass surgery, and stenting. D. Cost of HF. Th e total costs (direct and indirect) for the treatment of HF in the United States during 2005 were approximately $27.9 billion. Currently in the United States, more than $2.9 billion is spent annually on drugs used in the treatment of HF. E. Causes 1. Although the disease occurs most commonly among the elderly (80% of patients hospitalized with HF are older than 65 years of age), it may appear at any age as a consequence of underlying cardiovascular disease. 2. Th ere currently is no single diagnostic test for HF, and the clinical diagnosis is normally based on patient history and physical examination. 3. HF should not be considered an independent diagnosis because it is superimposed on an under- lying cause. a. Coronary artery disease (CAD) is the cause of HF in about two-thirds of patients with left ventricular systolic dysfunction. b. Th e remaining third of patients have a nonischemic cause of systolic dysfunction owing to other causes of myocardial stress, which include trauma, disease, or other abnormal states (e.g., pulmonary embolism, infection, anemia, pregnancy, drug use or abuse, fl uid overload, arrhythmia, valvular heart disease, cardiomyopathies, congenital heart disease). 4. Th e New York Heart Association (NYHA) developed a classifi cation system still used today to quantify the functional limitations of HF patients. Th e NYHA classes are as follows: a. Class I. Degree of eff ort necessary to elicit HF symptoms equals those that would limit normal individuals.