Heart failure is a disorder in which the heart pumps blood inadequately, leading to reduced blood flow, back-up (congestion) of blood in the veins and lungs, and other changes that may further weaken the heart.
Many disorders that affect the heart can cause heart failure.
Most people have no symptoms at first, and shortness of breath and fatigue develop gradually over days to months.
Doctors usually suspect heart failure on the basis of symptoms, but procedures, such as echocardiography, are usually done to evaluate heart function.
Treatment focuses on treating the disorder causing heart failure, making lifestyle changes, and treating heart failure with drugs or with surgery or other interventions.
Heart failure can occur in people of any age, even in young children (especially those born with a heart defect). However, it is much more common among older people, because older people are more likely to have disorders that damage the heart muscle or the heart valves. Also, age-related changes in the heart tend to make the heart pump less efficiently. About 5 million people in the US have heart failure and about 500,000 new cases occur each year. Worldwide, about 23 million people are affected. The disorder is likely to become more common because people are living longer and because, in some countries, certain risk factors for heart disease (such as smoking, high blood pressure, and a high-fat diet) are affecting more people.
Heart failure does not mean that the heart has stopped. It means that the heart cannot keep up with the work required to pump adequate blood to all parts of the body (its workload). However, this definition is somewhat simplistic. Heart failure is complex, and no simple definition can encompass its many causes, aspects, forms, and consequences.
The function of the heart is to pump blood (see Biology of the Heart : Function of the Heart). A pump moves fluid out of one place and into another. For example, the right side of the heart pumps blood from the veins into the lungs. The left side of the heart pumps blood from the lungs out through the arteries to the rest of the body. Blood goes out of the heart when the heart muscle contracts (called systole) and comes into the heart when the heart muscle relaxes (called diastole). Heart failure develops when the pumping or the relaxing action of the heart is inadequate, typically because the heart muscle is weak, stiff, or both. As a result, blood may not flow out in adequate amounts. Blood may also build up in the tissues causing congestion. That is why heart failure is sometimes known as congestive heart failure.
Accumulation of blood coming into the left side of the heart causes congestion in the lungs, making breathing difficult. Accumulation of blood coming into the right side of the heart causes congestion and fluid accumulation in other parts of the body, such as the legs and the liver. Heart failure usually affects both the right and left sides of the heart to some degree. However, one side may be affected by disease more than the other. In such cases, heart failure may be described as right-sided heart failure or left-sided heart failure.
In heart failure, the heart may not pump enough blood to meet the body’s need for oxygen and nutrients, which are supplied by the blood. As a result, arm and leg muscles may tire more quickly, and the kidneys may not function normally. The kidneys filter fluid and waste products from the blood into the urine, but when the heart cannot pump adequately, the kidneys malfunction and cannot remove excess fluid from the blood. As a result, the amount of fluid in the bloodstream increases, and the workload of the failing heart increases, creating a vicious circle. Thus, heart failure becomes even worse.