Heart Failure
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.
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 and because age-related changes in the heart tend to make the heart pump less efficiently. Heart failure develops in about 1 of 100 people. 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, as some people mistakenly believe; it means that the heart cannot keep up with the work required of it (its workload). However, this definition is remarkably simplified. Heart failure is extremely complex, and no simple definition can encompass its many causes, aspects, forms, and consequences.
The function of the heart is to pump blood. Pumping has two aspects: to move a fluid into something (the heart pumps blood into the arteries) and to move a fluid out of something (the heart moves blood out of the veins, as a sump pump moves water out of a basement). Heart failure develops when the pumping action of the heart is inadequate. As a result, blood flow to body tissues is reduced and blood returning to the heart accumulates, causing congestion in the veins. That is why heart failure is also known as congestive heart failure.
Accumulation of blood coming into the left side of the heart (from the lungs (see Section 3, Chapter 20)) causes congestion in the lungs, impairing lung function and making breathing difficult. Accumulation of blood coming into the right side of the heart (from the rest of the body) causes congestion in other parts of the body, including fluid accumulation (edema) in the legs and enlargement of organs such as the liver. Heart failure usually affects both the right and left sides of the heart to some degree. However, one side may be affected more than the other. In such cases, heart failure may be described as right-sided heart failure or left-sided heart failure.
 See the figure Heart Failure: Pumping and Filling Problems.
In heart failure, the heart cannot 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. Blood pressure in the arteries normally enables the kidneys to filter fluid and waste products from the blood into the urine. When the heart cannot pump adequately, blood pressure falls and the kidneys malfunction: The kidneys 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.
Heart failure has two main forms: systolic dysfunction (which is more common) and diastolic dysfunction. In systolic dysfunction, the heart contracts less forcefully and cannot pump out as much of the blood that is returned to it as it normally does. As a result, more blood remains in the lower chambers of the heart (ventricles). Blood then accumulates in the veins. In diastolic dysfunction, the heart is stiff and does not relax normally after contracting. Even though it may be able to pump a normal amount of blood out of the ventricles, the stiff heart does not allow as much blood to enter its chambers from the veins. As in systolic dysfunction, the blood returning to the heart then accumulates in the veins. Often, both forms of heart failure occur together.
Causes
Any disorder that directly affects the heart can lead to heart failure, as can some disorders that indirectly affect the heart. Some disorders cause heart failure quickly; others do so only after many years. Some disorders cause systolic dysfunction, impairing the heart's ability to pump out blood, and others cause diastolic dysfunction, impairing the heart's ability to fill with blood. Some disorders, such as high blood pressure and heart valve disorders, can cause both types of dysfunction.
Systolic Dysfunction: Disorders that cause systolic dysfunction may impair the entire heart or one area of the heart. As a result, the heart does not contract normally.
Coronary artery disease is a common cause of systolic dysfunction. It can impair large areas of heart muscle because it reduces the flow of oxygen-rich blood to the heart muscle, which needs oxygen for normal contraction. Blockage of a coronary artery can cause a heart attack, which destroys an area of heart muscle. As a result, that area can no longer contract normally.
Myocarditis (inflammation of heart muscle) caused by a bacterial, viral, or other infection can damage all or part of the heart muscle, impairing its pumping ability.
Heart valve disorders--narrowing (stenosis) of a valve, which hinders blood flow through the heart, or leakage of blood backward (regurgitation) through a valve--can cause heart failure. Both stenosis and regurgitation of a valve can severely stress the heart, so that over time, the heart enlarges and cannot pump adequately. An abnormal connection (septal defects (see Section 23, Chapter 265 and Section 23, Chapter 265)) between the heart chambers can allow blood to recirculate within the heart, increasing the workload of the heart, and thus can cause heart failure.
Disorders that affect the heart's electrical conduction system, producing changes in heart rhythms, (especially if heartbeats are fast or irregular), can cause heart failure. When the heart beats abnormally, it cannot pump blood adequately.
Some lung disorders, such as pulmonary hypertension (see Section 4, Chapter 54), may alter or damage blood vessels in the lungs. As a result, the heart has to work harder to pump blood into the arteries that supply the lungs (pulmonary arteries). Pulmonary hypertension may lead to cor pulmonale (see Section 4, Chapter 54). In this disorder, the right ventricle, which pumps blood to the lungs, becomes enlarged, eventually resulting in right-sided heart failure.
Sudden, usually complete blockage of a pulmonary artery by several small blood clots or one very large clot (pulmonary embolism) also makes pumping blood into the pulmonary arteries difficult. A very large clot can be immediately life threatening. The increased effort required to pump blood into the blocked pulmonary arteries can cause the right side of the heart to enlarge and may cause the walls of the right ventricle to thicken, resulting in right-sided heart failure.
Disorders that indirectly affect the heart's pumping ability include a deficiency of red blood cells or hemoglobin (anemia), an overactive thyroid gland (hyperthyroidism), an underactive thyroid gland (hypothyroidism), and kidney failure. Red blood cells contain hemoglobin, which enables them to carry oxygen from the lungs and deliver it to body tissues. Anemia reduces the amount of oxygen the blood carries, so that the heart must work harder to provide the same amount of oxygen to tissues. (Anemia has many causes, including chronic bleeding due to a stomach ulcer). An overactive thyroid gland overstimulates the heart, so that it pumps too rapidly and does not empty normally during each heartbeat. When the thyroid gland is underactive, levels of thyroid hormones are low. As a result, all muscles, including the heart, become weak because muscles depend on thyroid hormones to function normally. Kidney failure strains the heart because the kidneys cannot remove excess fluid from the bloodstream, so the heart has to pump more blood. Eventually, the heart cannot keep up, and heart failure develops.
Diastolic Dysfunction: Inadequately treated high blood pressure is the most common cause of diastolic dysfunction. High blood pressure stresses the heart because the heart must pump blood more forcefully than normal to force blood into the arteries against the higher pressure. Eventually, the heart's walls thicken (hypertrophy), then stiffen. The stiff heart does not fill quickly or adequately, so that with each contraction, the heart pumps less blood than it normally does.
As people age, the heart's walls also tend to stiffen. The combination of high blood pressure, which is common among older people, and age-related stiffening makes heart failure particularly common among older people.
Heart failure may result from disorders that cause the heart's walls to stiffen, such as infiltrations and infections. For example, in amyloidosis, amyloid, an unusual protein not normally present in the body, infiltrates many tissues in the body. If amyloid infiltrates the heart's walls, they stiffen, and heart failure results. In tropical countries, infiltration by certain parasites into heart muscle can cause heart failure, even in young people. Some heart valve disorders, such as aortic valve stenosis, hinder blood flow out of the heart. As a result, the heart muscle has to work harder and thickens, and diastolic dysfunction develops initially. Eventually, systolic dysfunction also develops.
In constrictive pericarditis, the sac that envelops the heart (pericardium) stiffens, preventing even a healthy heart from pumping and filling normally.
Compensatory Mechanisms
The body has several mechanisms to compensate for heart failure. The body's first response to stress, including that due to heart failure, is to release the fight-or-flight hormones, epinephrine (adrenaline) and norepinephrine (noradrenaline). For example, these hormones may be released immediately after a heart attack damages the heart. Epinephrine and norepinephrine cause the heart to pump faster and more forcefully. They help the heart increase the amount of blood pumped out (cardiac output), sometimes to a normal amount, and thus help compensate partially and temporarily for the heart's impaired pumping ability.
People who do not have heart disease usually benefit from release of these hormones when more work is temporarily required of the heart. However, for people who have chronic heart failure, this response results in increased demands on an already damaged heart. Over time, the increased demands lead to further deterioration of heart function.
Another of the body's main compensatory mechanisms for heart failure is to decrease the amount of salt and water excreted by the kidneys. Retaining salt and water instead of excreting it into urine increases the volume of blood in the bloodstream and helps maintain blood pressure. The larger volume of blood also stretches the heart muscle, enlarging the heart chambers, particularly the ventricles, which pump blood out of the heart. The more the heart muscle is stretched, the more forcefully it contracts. At first, this mechanism improves heart function, but after a point, stretching no longer helps but instead weakens the heart's contractions (as when a rubber band is overstretched). Consequently, heart failure worsens.
Another important compensatory mechanism is enlargement of the muscular walls of the ventricles (ventricular hypertrophy). When the heart must work harder, the heart's walls enlarge and thicken, as biceps muscles enlarge after months of weight training. At first, the thickened heart walls can contract more forcefully. However, the thickened heart walls eventually become stiff, worsening diastolic dysfunction. Eventually, the contractions become weaker, causing systolic dysfunction.
Symptoms
Symptoms of heart failure may begin suddenly, especially if the cause is a heart attack. However, in most people, symptoms develop over days to months. The disorder may stabilize for periods of time but often progresses slowly and insidiously.
People with heart failure feel tired and weak when performing physical activities, because their muscles are not receiving enough blood. In older people, heart failure sometimes causes vague symptoms such as sleepiness, confusion, and disorientation, as well as weakness and fatigue.
Right-sided heart failure and left-sided heart failure produce different symptoms. Although both types of heart failure may be present, the symptoms of failure of one side often predominate. The main symptoms of right-sided heart failure are fluid accumulation and swelling (edema) in the feet, ankles, legs, liver, and abdomen. Where the fluid accumulates depends on the amount of excess fluid and the effects of gravity. If a person is standing, fluid accumulates in the legs and feet. If a person is lying down, fluid usually accumulates in the lower back. If the amount of fluid is large, fluid also accumulates in the abdomen. Fluid accumulation in the liver or stomach can cause nausea and loss of appetite. Eventually, food is not absorbed well, resulting in loss of weight and muscle. This condition is called cardiac cachexia.
Left-sided heart failure leads to fluid accumulation in the lungs, which causes shortness of breath. At first, shortness of breath occurs only during exertion, but as heart failure progresses, it occurs with less and less exertion and eventually occurs even at rest. People with severe left-sided heart failure may be short of breath when lying down (a condition called orthopnea (see Section 4, Chapter 39)), because gravity causes more fluid to move into the lungs. Such people often wake up, gasping for breath or wheezing (a condition called paroxysmal nocturnal dyspnea). Sitting up causes some of the fluid to drain to the bottom of the lungs, making breathing easier. Eventually, left-sided heart failure causes right-sided heart failure.
A sudden accumulation of a large amount of fluid in the lungs (acute pulmonary edema) causes extreme difficulty breathing, rapid breathing, bluish skin, and feelings of restlessness, anxiety, and suffocation. Some people have severe spasms of the airways (bronchospasms) and wheezing; this condition is called cardiac asthma, which resembles asthma but has a different cause. Acute pulmonary edema is a life-threatening emergency.
When heart failure is advanced, Cheyne-Stokes respiration (periodic breathing) may develop. In this unusual pattern of breathing, a person breathes rapidly and deeply, then more slowly, then not at all for several seconds. Cheyne-Stokes respiration develops because blood flow to the brain is reduced and the areas of the brain that control breathing therefore do not receive enough oxygen.
When the heart cannot pump a normal amount of blood out of its chambers, blood clots can form because blood flow within the chambers is sluggish. Clots may break loose (becoming emboli), travel through the bloodstream, and partially or completely block an artery elsewhere in the body. If a clot blocks an artery to the brain, a stroke may result.
Diagnosis
Doctors usually suspect heart failure on the basis of symptoms alone. The diagnosis is supported by the results of a physical examination, including a weak, often rapid pulse, reduced blood pressure, abnormal heart sounds and fluid accumulation in the lungs (both heard through a stethoscope), an enlarged heart, swollen neck veins, an enlarged liver, and swelling in the abdomen or legs. A chest x-ray can show an enlarged heart and fluid accumulation in the lungs.
Procedures to evaluate heart function are usually performed. Electrocardiography (ECG) (see Section 3, Chapter 21) is almost always performed to determine whether the heart rhythm is normal, whether the walls of the ventricles are thickened, and whether the person has had a heart attack.
Echocardiography (see Section 3, Chapter 21), which uses sound waves to produce an image of the heart, is one of the best procedures for evaluating heart function, including the pumping ability of the heart and the functioning of heart valves. It can show whether the heart walls are thickened, whether the valves are functioning normally, whether contractions are normal, and whether any area of the heart is contracting abnormally. Echocardiography may help determine whether heart failure is due to systolic or diastolic dysfunction by enabling doctors to estimate the thickness of the heart walls and the ejection fraction. The ejection fraction, an important measure of heart function, is the percentage of blood pumped out by the heart with each beat. A normal left ventricle ejects about 60% of the blood in it. If the ejection fraction is low, systolic dysfunction is likely; if it is normal or high, diastolic dysfunction is likely.
Other procedures, such as radionuclide imaging and cardiac catheterization with angiography (see Section 3, Chapter 21), may be performed to identify the cause of heart failure. Rarely, a biopsy is needed, usually when doctors suspect infiltration of the heart (as occurs in amyloidosis) or myocarditis due to a bacterial, viral, or other infection.
Prevention and Treatment
Some disorders that cause heart failure, such as high blood pressure, severe anemia, and an overactive or underactive thyroid gland, can be treated before they lead to heart failure. Preventing heart attacks by treating coronary artery disease can also prevent heart failure.
Although heart failure is a chronic disorder for most people, much can be done to make physical activity more comfortable, improve the quality of life, and prolong life. Treatment focuses on treating the disorder causing heart failure, controlling factors that can worsen heart failure (contributing factors), and treating heart failure itself.
Treatment of the Cause: If the cause of heart failure is a narrowed or leaking heart valve or an abnormal connection between heart chambers, surgery can often correct the problem. Blockage of a coronary artery may require treatment with drugs, surgery, or angioplasty (see Section 3, Chapter 33). Antihypertensive drugs can reduce and control high blood pressure. Antibiotics can eliminate some infections. Treatment of a stomach ulcer or use of an iron supplement may correct anemia. Drugs, surgery, or radiation therapy can be used to manage an overactive thyroid gland, and thyroid hormones can be given to manage an underactive thyroid gland.
Control of Contributing Factors: Several factors that contribute to heart failure can be minimized or eliminated by changes in lifestyle. People who have heart failure should stay as physically fit as possible, even if they cannot exercise vigorously. People who have mild heart failure should follow an exercise program as described by a doctor. Those with more severe heart failure may need to exercise in a cardiovascular rehabilitation facility under the supervision of a trained attendant.
In people who have heart failure and are overweight, the heart must work harder during activity, worsening heart failure. Such people should follow a weight loss diet (see Section 12, Chapter 152).
Smoking damages blood vessels, increasing the risk of a heart attack. Large amounts of alcohol can act as a direct toxin to the heart. Thus, smoking and drinking alcohol can worsen heart failure and should be stopped.
Exercise, weight loss, and stopping smoking help reduce the risk of coronary artery disease, as do good control of diabetes and lowering of cholesterol levels.
Excess salt (sodium) in the diet can cause fluid retention, which counteracts drugs given to increase the excretion of water (such as diuretics) and relieve fluid accumulation. Thus, consuming excess salt worsens symptoms. Almost everyone with heart failure should limit their intake of table salt and salty foods and their use of salt in cooking. The sodium content of packaged foods can be determined by reading the label. People with severe heart failure are usually given detailed information about how to limit salt intake. People who limit their salt intake can usually consume a normal amount of water unless fluid retention is severe. Drinking extra amounts of water is not recommended.
A simple, reliable way to check whether the body is retaining fluid is to check body weight daily. Doctors often ask people with heart failure to weigh themselves as accurately as possible every day, typically once in the morning, after they arise and urinate and before they eat breakfast. Trends are easier to spot when people weigh themselves at the same time every day, use the same scale, wear a similar amount of clothing, and keep a written record of their daily weight. Increases of more than 2 pounds (about 1 kilogram) per day are early warning signs of fluid retention. A consistent, rapid weight gain (such as 2 pounds per day) is a clue that heart failure is worsening.
Many people who limit their salt intake still have swelling. Swollen legs should be kept elevated on a stool when sitting. This position helps the body reabsorb and eliminate the excess fluid. Some people also need to wear full-length supportive stockings that help prevent accumulation of fluid. If fluid accumulates in the lungs, sleeping with several pillows or elevating the head of the bed makes sleeping easier.
Treatment of Heart Failure: Heart failure can be treated with several different types of drugs. Regular communication with and examinations by doctors and other health care practitioners who are trained in the treatment of heart failure are critical, because heart failure can worsen suddenly. For example, nurses often call a person who has heart failure regularly to ask about changes in weight and in symptoms. Thus, they can gauge whether the person needs to see a doctor.
When salt restriction alone does not reduce fluid retention, doctors often prescribe diuretics (see Section 3, Chapter 22). These drugs help the kidneys eliminate salt and water by increasing urine formation and thus decrease fluid volume throughout the body. The diuretics most commonly used for heart failure are furosemide and bumetanide, which are loop diuretics. These diuretics are most commonly taken by mouth on a long-term basis, but in an emergency, they are very effective when given intravenously. Loop diuretics are preferred for moderate to severe heart failure; thiazide diuretics, which have milder effects, may be prescribed for mild heart failure. Because loop and thiazide diuretics can cause potassium to be lost in the urine, a potassium supplement or a diuretic that does not cause potassium loss or that causes potassium levels to increase (a potassium-sparing diuretic) may be given as well. For people with severe heart failure due to systolic dysfunction, spironolactone is the preferred potassium-sparing diuretic to be added. It can prolong life in people with heart failure. Taking diuretics can worsen urinary incontinence. However, a dose of a diuretic can usually be timed so that episodes of incontinence do not occur when a bathroom is unavailable or when access to one is inconvenient.
The mainstay of heart failure treatment is a group of drugs called angiotensin-converting enzyme (ACE) inhibitors (see Section 3, Chapter 22). These drugs not only reduce symptoms and the need for hospitalization but also prolong life. ACE inhibitors reduce the blood levels of the hormones angiotensin II and aldosterone (which normally help increase blood pressure (see Section 3, Chapter 22)). By doing so, ACE inhibitors cause arteries and veins to widen (dilate) and help the kidneys excrete excess water, thus decreasing the amount of work the heart has to perform. These drugs also may have direct beneficial effects on the heart and blood vessel walls.
Angiotensin II receptor blockers (see Section 3, Chapter 22) have effects similar to those of ACE inhibitors. Angiotensin II receptor blockers are used with ACE inhibitors in some people or are used alone in people who cannot tolerate ACE inhibitors because of cough, a side effect of ACE inhibitors. However, the role of angiotensin II receptor blockers is still being evaluated in the treatment of heart failure.
Other drugs that dilate blood vessels (vasodilators) are not used as often as ACE inhibitors, which are more effective. Nonetheless, people who do not respond to or cannot take ACE inhibitors can benefit from vasodilators, such as hydralazine, isosorbide dinitrate, and nitroglycerin patches or spray.
Beta-blockers, a group of drugs that used to be avoided in the treatment of heart failure, are now being used with ACE inhibitors to treat heart failure. Because these drugs slow the heart rate and reduce the force of the heart's contractions, they may initially worsen symptoms. However, by blocking the action of the hormone norepinephrine (which causes the heart to pump faster and more forcefully), these drugs produce long-term improvement in heart function and survival.
Digoxin, one of the oldest treatments for heart failure, increases the force of each heartbeat and slows a heart rate that is too rapid. Digoxin helps relieve symptoms for some people with systolic dysfunction, especially if atrial fibrillation is present, but it does not prolong life.
Anticoagulants, such as warfarin, may be given to prevent clots from forming in the heart chambers. If the heart rhythm is abnormal, antiarrhythmic drugs (see Section 3, Chapter 27) may be given, or an implantable defibrillator (see Section 3, Chapter 27) may be recommended.
Heart transplantation may be an option for a few otherwise healthy people who have very severe, worsening heart failure and who have not responded to drug therapy. Temporary partial or complete mechanical hearts are still largely experimental. Problems of effectiveness, infection, and blood clots are still being worked out.
Several experimental operations are under study; their benefits are doubtful and they are performed only at some research centers. One operation consists of surgically removing the flabby, nonfunctioning heart muscle. In another operation, tiny pumps that boost the pumping action of the heart are inserted in the body, often in the abdomen near the heart. These pumps can help prolong the life of people who are waiting for a heart transplantation. Other experimental procedures include implantation of a pacemaker in each ventricle and delivery of room air or oxygen that is under pressure through a face mask (continuous positive airway pressure).
 See the drug table Some Drugs Used to Treat Heart Failure.
Treatment of Acute Heart Failure: Heart failure that develops or worsens quickly requires emergency treatment in a hospital.
If acute pulmonary edema develops (see Section 3, Chapter 25), oxygen is given through a face mask. Diuretics given intravenously and other drugs such as nitroglycerin given intravenously or under the tongue can produce rapid, dramatic improvement. Morphine relieves the anxiety that usually accompanies acute pulmonary edema. It also decreases the rate of breathing, slows the heart rate, dilates blood vessels, and thereby reduces the amount of work the heart has to do. If these measures do not adequately improve breathing, a tube may be inserted into the person's airway so that a mechanical ventilator can assist breathing.
For people who have severe symptoms and have not responded well to treatments, drugs that are similar to epinephrine and norepinephrine (such as dopamine or dobutamine) or other drugs that make muscle contract more forcefully (such as milrinone or amrinone) are sometimes used for a short time to stimulate heart contractions. These drugs are not useful for long-term treatment.
End-of-Life Issues: Although many people with heart failure live for many years, up to 70% of people die of the disorder within 10 years. Life expectancy depends on how severe the heart failure is, whether its cause can be corrected, and which treatment is used. About half of people who have mild heart failure live at least 10 years, and about half of those who have severe heart failure live at least 2 years. Eventually, for a person with chronic heart failure, quality of life may deteriorate and the possibilities for further treatment may become limited, especially for an older person for whom heart transplantation may not be feasible. Keeping the person comfortable may eventually become more important than trying to prolong life. The person and the family members should be involved in these decisions. Much can be done to provide compassionate care, relieve symptoms, and maintain the person's dignity (see Section 1, Chapter 8).
Heart failure can cause death suddenly and unexpectedly, without symptoms worsening. Consequently, when possible, people who have heart failure should prepare advance directives about the type of care desired in case they are no longer able to make decisions about their care (see Section 1, Chapter 9). Also, making or updating a will is important.
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