Reviewed by Brian R. Robinson, MD
Heart failure occurs when one or both sides of the heart become damaged and start to work improperly. Congestive heart failure is when both sides fail at once. It is called congestive heart failure because fluid and blood backs up in the lungs and in other organs.
Copyright 2007 David DiAngelis
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Heart failure is not an immediate cessation of the heart function, like a heart attack; rather, it means that the heart is working, but it is not working properly. It can affect one or both sides of the heart. It occurs when the heart has been weakened by disease or defect, or when high blood pressure forces it to work overtime.
Heart failure is divided into four levels:
- Class I: The least severe class. The patient exhibits no unusual fatigue, shortness of breath, or decrease in physical activity.
- Class II: The patient may experience some fatigue, palpitations, shortness of breath, and mild limitations on activities.
- Class III: Activities are dramatically limited. The patient experiences fatigue, shortness of breath, and pain during activities.
- Class IV: The patient feels uncomfortable at rest, with discomfort increasing with activity.
The heart has four chambers, a left and right atrium on top and a left and right ventricle on the bottom. Blood flows in a cycle through the body. Blood becomes enriched with oxygen in the lungs, and then flows to the left atrium. The left atrium relaxes to fill with the oxygenated blood. The blood is then passed to the left ventricle. The ventricles are much stronger than the atria, because it is their job to pump the blood out of the heart and into the body. The left ventricle contracts and pumps the blood to feed all of the organs except for the lungs. The blood passes through the other organs, leaving behind oxygen and nutrients and picking up waste and carbon dioxide. The waste finally is dumped in the kidney and liver; the carbon dioxide returns with the blood to the right atrium. The right atrium passes the blood to the right ventricle, which contracts to pump the blood through the lungs, where the carbon dioxide is released and more oxygen is picked up.
There are two types of heart failure. Systolic failure occurs when there is a problem in the left side. The heart cannot adequately fill with blood from the lungs and pump it into the body. Diastolic failure occurs when the there is problem in the right side of the heart. The heart cannot adequately fill with blood from the body and pump it back into the lungs. Systolic failure is more common than diastolic; often, however, both sides fail. This malfunctioning of the entire heart is known as congestive heart failure. Sometimes congestive heart failure is used to refer to any type of heart failure, since both types can cause a build-up of fluid, but this is technically incorrect.
Different parts of the heart can cause it to fail. The ventricular wall can become thin or weak, and unable to pump out the blood delivered by the atria. The atrial walls can become stiff, and unable to relax enough to properly fill with blood. In that case, there is a build-up of blood outside the heart. There also may be abnormalities in the valves through which blood leaves the body. If valves become narrowed, then not enough blood can travel from the ventricle into the body, and blood backs up in the heart. If the valves do not close properly after emptying the blood into the body, blood can leak back up into the heart. This means that blood is not getting to the organs, the organs are not getting oxygen and nutrients, and wastes are building up in the body.
Causes and risk factors
Heart failure can be caused my many of the same things as heart disease. Smoking, lack of exercise, stress, obesity, excessive salt intake, alcohol abuse, high cholesterol and high blood pressure can all contribute to deterioration of heart function. In general men are at higher risk than women, but African American women are at very high risk. African Americans are two and a half times as likely as white Americans to die from the disease before age 65. This is partly because African Americans are high risk for diabetes and high blood pressure; differences in care received also account for some of the difference. Cancer survivors also have an increased risk of developing heart failure.
The heart muscle can be damaged in many other ways. During a heart attack, the heart muscle is deprived of oxygen, which can lead to permanent damage. Coronary artery disease can cause heart attack, or heart failure even in the absence of a heart attack. Heart valve disease can also impair heart functioning, as can diabetes. Hyperthyroidism, emphysema, thiamine deficiency, pneumonia, high fever, and liver or kidney failure are all known causes.
The heart’s corrective mechanism can also lead to heart failure. In response to high blood pressure, the heart will often pump faster and enlarge to accommodate more blood. While this is helpful in the short term, in the long term it can cause permanent damage to the ventricles (ventricular remodeling).
Another condition that can cause heart failure is cardiomyopathy. Cardiomyopathy is a genetic disease that causes a heart deformity to develop. In some cases, the ventricle enlarges and its walls become thinner, causing reduced blood pressure. In another type of cardiomyopathy, the muscles become thick and cannot easily contract.
Last updated: Aug-21-07