heart failure

Definition

Heart failure is a condition in which the heart has lost the ability to pump enough blood to the body's tissues. With too little blood being delivered, the organs and other tissues do not receive enough oxygen and nutrients to function properly.

Description

According to the American Heart Association, about4.9 million Americans are living with congestive heart failure. Of these, 2.5 million are males and 2.4 million are females. Ten people out of every 1,000 people over age 65 have this condition. There are about 400,000 new cases each year.

Heart failure happens when a disease affects the heart's ability to deliver enough blood to the body's tissues. Often, a person with heart failure may have a buildup of fluid in the tissues, called edema. Heart failure with this kind of fluid buildup is called congestive heart failure. Where edema occurs in the body depends on the part of the heart that is affected by heart failure. Heart failure caused by abnormality of the lower left chamber of the heart (left ventricle) means that the left ventricle cannot pump blood out to the body as fast as it returns from the lungs. Because blood cannot get back to the heart, it begins to back up in the blood vessels of the lungs. Some of the fluid in the blood is forced into the breathing space of the lungs, causing pulmonary edema. A person with pulmonary edema has shortness of breath, which may be acute and severe and life threatening. A person with congestive heart failure feels tired because not enough blood circulates to supply the body's tissues with the oxygen and nutrients they need. Abnormalities of the heart structure and rhythm can also be responsible for left ventricular congestive heart failure.

In right-sided heart failure, the lower right chamber of the heart (right ventricle) cannot pump blood to the lungs as fast as it returns from the body through the veins. Blood then engorges the right side of the heart and the veins. Fluid backed up in the veins is forced out into the tissues, causing swelling (edema), usually in the feet and legs. Congestive heart failure of the right ventricle is often caused by abnormalities of the heart valves and lung disorders.

When the heart cannot pump enough blood, it tries to make up for this by becoming larger. By becoming enlarged (hypertrophic) the ventricle can contract more strongly and pump more blood. When this happens, the heart chamber becomes larger and the muscle in the heart wall becomes thicker. The heart also compensates by pumping more often to improve blood output and circulation. The kidneys try to compensate for a failing heart by retaining more salt and water to increase the volume of blood. This extra fluid can also cause edema. Eventually, as the condition worsens over time these measures are not enough to keep the heart pumping enough blood needed by the body. Kidneys often weaken under these circumstances, further aggravating the situation and making therapy more difficult.

For most people, heart failure is a chronic disease with no cure. However, it can be managed and treated with medicines and changes in diet, exercise, and lifestyle habits. Heart transplantation is considered in some cases.

— Toni Rizzo

1. Cessation of normal heart function.
2. The inability of the heart to pump blood at an adequate rate, resulting in congestion in the lungs, shortness of breath, edema in the lower extremities, and enlargement of the liver.

The characteristic symptoms of heart failure are recognizable in writings at least as far back as the twelfth century, when the health problems of Alexius I (Comnenus), the Byzantine emperor, were documented by his physician. The ‘failure’ is manifest in the heart not providing sufficient output of blood to meet the ‘demands’ of the body. A useful term here is ‘exercise intolerance’. A typical heart failure patient will have become accustomed to an inexorable decline in physical vigour. Activities such as climbing stairs, carrying a heavy load (perhaps a suitcase), even walking, far less running, and other such ‘exercises’ usually considered to be within the normal range become increasingly difficult or impossible. One key associated symptom is breathlessness, another is oedema (the accumulation of fluid in the tissues) for example in the ankles. Both symptoms reflect raised pressure in the veins ultimately caused by the insufficient pumping action of the heart. The seriousness of heart failure is such that, at the time of writing, about half of the patients affected die within five years of the initial diagnosis. Of these fatalities, about half will suffer a major heart attack, the remainder will suffer a steady decline of heart function until pump failure itself proves fatal. Against this gloomy scenario, new discoveries about the underlying causes, the development of new drugs to slow down, halt, and ultimately reverse the harmful aspects, and an increasing awareness of the value of lifestyle and dietary change promise to improve the prospects for the heart failure patient in the twenty-first century — even if too late for the Emperor Alexius.

The most common single cause in modern Western society, accounting for about half of the cases, is a heart attack. By killing one region, the attack leaves heart function compromised. Until the later decades of the twentieth century a very major cause was undiagnosed and untreated high blood pressure — the heart in this instance must work harder and harder to force blood into the arteries where the pressure is too high, and eventually ‘tires’. Although long-term high blood pressure is still a contributor to heart failure, modern drugs have helped to reduce its significance. A range of other causes include the various heart valve malfunctions, certain infections, congenital structural abnormalities, genetically-determined disorders, and drug abuse. There is clear evidence that the factors that increase the likelihood of heart attack also contribute to the severity of the ensuing heart failure. These factors include high blood cholesterol, atheromatous vascular disease, sedentary lifestyle, and smoking. In third-World countries, infections such as the insect-transmitted trypanosomal Chagas' disease are among the main causes of heart failure. Even amongst economically advanced nations there are wide differences in the incidence of heart failure between, say, Japan (very low) and Western Europe and the US (high) ; nation-specific combinations of dietary and genetic factors are thus the target of much research into underlying causes. There is widespread agreement that taking regular exercise not only strengthens the heart and improves its own circulation (particularly by improving collateral blood supplies) but also that exercise is a very useful part of any rehabilitation regime designed to prevent the development of heart failure after a heart attack.

Heart failure refers to a characteristic pattern of features caused by an abnormality of the heart. It is a complex clinical syndrome resulting from the entanglement of cause and effect, of symptoms and compensatory changes. Several body systems and organs are involved, especially the lungs, kidneys, and blood vessels, their associated hormonal systems, as well as the heart itself. It is increasingly clear that many and varied patterns of disturbance to each of these systems can result in convergence into the full repertoire of malfunctions which together are termed heart failure.

In normal circumstances, the ‘challenge’ to the heart posed by ‘demand’ for increased blood supply is most obvious during exercise, however mild. The physiological challenge is similar when the heart is unable, by virtue of disease, to meet even normal requirements. In either case, homeostatic mechanisms operate which promote the maintenance of two parameters of heart function: blood pressure and blood flow. An example of these compensatory processes is one promoting retention of water and salts by hormonal influences on the kidneys. This will increase blood volume and tend to keep up both blood pressure and cardiac output (the volume pumped). Unfortunately, in heart failure, the compensatory mechanisms prove clearly ineffective; they actually contribute to the symptoms observed (e.g. breathlessness and ankle swelling) and become important factors in the gradual worsening of the condition. The use of diuretic drugs (which stimulate kidney function and reverse fluid retention) is widespread in the treatment of heart failure. The heart itself generally responds to an abnormal workload by increased growth (hypertrophy), but the nature of the growth is abnormal in subtle ways, unlike the hypertrophy associated with general physical fitness which is positively beneficial. It is now known, for example, that a hypertrophied failing heart both contracts and relaxes more slowly, and is more prone to life-threatening electrical abnormalities.

— David J. Miller, Niall G. MacFarlane

See also heart; heart attack.

A sudden, sometimes fatal, cessation of the heart’s action.

For more information on heart failure, visit Britannica.com.

A condition in which the pumping action of the heart is insufficient to meet the demands of the body. Heart failure may result from overload, damage, or disease of the heart. The sufferer experiences breathlessness.

Inability of the heart to maintain a circulation sufficient to meet the body's needs; most often applied to myocardial failure affecting the right or left ventricle.

• acute h. f. — sudden cardiac arrest such as occurs in anesthetic death and cardiac myopathy of various kinds. It causes death by acute anoxia of tissues especially brain. The clinical syndrome varies between a brief convulsion and the development of pulmonary edema.
• backward h. f. — a concept of heart failure emphasizing the contribution of passive engorgement of the systemic venous system as a cause.
• congestive h. f. (CHF) — that which occurs as a result of impaired pumping capability of the heart and is associated with abnormal retention of water and sodium. The condition ranges from mild congestion with few symptoms to life-threatening fluid overload and total heart failure.
— CHF results in an inadequate supply of blood and oxygen to the body's cells. The decreased cardiac output causes an increase in the blood volume within the vascular system. Congestion within the blood vessels interferes with the movement of body fluids in and out of the various fluid compartments, and they accumulate in the tissue spaces, causing edema. — There are three general kinds of pathological conditions that can bring about CHF: (1) ventricular failure, in which the contractions of the ventricles become weak and ineffective, as in myocardial ischemia from coronary artery disease; (2) mechanical failure of the ventricles to fill with blood during the diastole phase of the cardiac cycle, which can occur when the mitral valve is narrowed or when there is an accumulation of fluid within the pericardial sac (cardiac tamponade) pressing against the ventricles, preventing them from accepting a full load of blood; and (3) an overload of blood in the ventricles during the systole phase of the cycle. High blood pressure, aortic stenosis and aortic valvular regurgitation are some of the conditions that can cause ventricular overload.
• decompensated h. f. — see congestive heart failure (above).
• forward h. f. — a concept of heart failure emphasizing the inadequacy of cardiac output as the primary cause and considering venous distention to be secondary.
• high output h. f. — that in which cardiac output remains high, associated with anemia, emphysema, etc.
• left-sided h. f., left ventricular h. f. — failure of the left ventricle to maintain a normal output of blood. Since the left ventricle does not empty completely, it cannot accept blood returning from the lungs via the pulmonary veins. The pulmonary veins become engorged and fluid seeps out through the veins and collects in the pleural cavity. Pulmonary edema and pleural effusion result. In many cases heart failure begins on the left side and eventually involves both sides of the heart.
• low-output h. f. — that in which cardiac output is diminished, associated with cardiovascular diseases.
• right-sided h. f., right ventricular h. f. — failure of proper functioning of the right ventricle, with subsequent engorgement of the systemic veins, producing pitting edema, enlargement of the liver, and ascites.