a chronic and progressive condition that can be the final common pathway from a number of structural or functional cardiac disorders that impair the ability of the heart to fill or empty (Arena et al., 2007). Heart failure can occur when the heart muscle is weak (systolic failure) or when it is stiff and unable to relax normally (diastolic failure). Cardiomyopathy, which means “disease of the heart muscle,” is one of many causes of heart failure.

The syndrome of heart failure is often characterized by shortness of breath or fatigue, even during mild exertion. A common feature of heart failure decompensation is retention of excess fluid, which contributes to raise fluid pressures within the heart, lungs, and the rest of the body, which is termed congestion. When congestion occurs on the left side of the heart (left heart failure), it can lead to shortness of breath occurring during modest activity or at rest, particularly while lying down. Elevation of pressures can also occur in the veins draining into the right side of the heart, which can result in peripheral edema and abdominal swelling (ascites). These findings are often termed right heart failure. The type of heart muscle weakness is often described by the pumping strength of the heart, measured by the left ventricular ejection fraction (EF). This is the proportion of blood ejected from the ventricle with each beat, expressed either as a fraction (normally 0.55 to 0.70) or as a percentage of the total volume in the left ventricle (normally 55 to 70 percent).

The primary manifestations of heart failure are fatigue, dyspnea, and peripheral fluid retention, which alone or in combination may limit a patient’s ability to perform activities (Gibbons et al., 2002) and potentially lead to impairment or disability. All three symptoms do not have to manifest for a patient to have heart failure. Although the full-blown chronic syndrome has sometimes been termed “congestive heart failure,” clinical evidence of congestion (as described above) may or may not be present at the time of evaluation (Allen et al., 2008). For example, a patient may experience exercise intolerance from fatigue but have little fluid retention, or may be limited by peripheral swelling without reporting symptoms of fatigue or breathlessness.

EPIDEMIOLOGY

Heart failure is an ongoing public health challenge in the United States. In the adult population over age 20, the prevalence of heart failure is 2.6 percent. It is generally higher in men than in women but highest in black women. The lifetime risk of developing heart failure is one in five at age 40 for both men and women. The prevalence in patients between ages 20 and 39 is less than 0.5 percent of the population. In patients over age 45, the incidence of new cases is estimated at 670,000 annually. From ages 40 to 59, the prevalence is 1.9 per 100 men and 1.4 per 100 women (Lloyd-Jones



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