Congestive Heart Failure (CHF) Overview

Congestive heart failure (CHF) is a condition in which the heart cannot pump enough blood to meet the needs of the body. The term “heart failure” should not be confused with “heart attack.” Heart failure occurs after the heart muscle has been damaged or weakened by another primary cause, such as high blood pressure , coronary artery disease , or certain kinds of infections. Depending on the cause, heart failure can occur gradually, over many years, while the heart tries to compensate for its loss of function, or it may occur more quickly if a lot of the heart muscle is damaged at once.

Blood Flow Through the Heart © 2009 Nucleus Medical Media, Inc.

It is estimated that 5 million Americans are currently living with CHF. As the US population ages, and baby boomers are getting older, that number is expected to climb.

Types of CHF

CHF occurs when the heart muscle cannot pump adequate amounts of blood to meet the body’s needs. When the heart fails to keep up with demand, fluid can accumulate behind the failing heart chambers. In order to understand the types of CHF, you should first understand how the heart—the center of the circulatory systems—works.

The heart has two sides (right and left), and each side has two chambers. The four chambers of the heart have specific functions:

Two upper chambers (atria / atrium)—Receive blood from the body and empty the blood to the lower chambers

Two lower chambers (ventricles)—Receive blood from the upper chambers and pump blood back out to the body

The right atrium receives blood from the body and empties it into the right ventricle. The right ventricle pumps the blood out to the lungs where carbon dioxide is exchanged for needed oxygen. The left atrium receives blood rich in oxygen from the lungs and empties that blood into the left ventricle. The left ventricle is the strongest muscle/chamber in the heart and is responsible for pumping the blood back out to the body.

Heart failure can occur on either side of the heart and is classified as:

• Left-sided failure:There are two main ways that the left ventricle can fail to keep up with the demands of the body. When the left ventricular muscle is damaged, it fails to contract/pump with sufficient force. That is called systolic failure. If the muscle is damaged in such a way that it becomes stiff and cannot accept all the blood it needs from the left atrium, then it is called diastolic failure. The difference between these two types of failure is important because the treatment approach for each type may be different. In either type, when the left ventricle fails to circulate the blood, the blood can “back up” into the lungs. Accumulation of fluid in the lungs causes one of the main symptoms of CHF, shortness of breath. Doctors use the term pulmonary edema to describe severe fluid build-up in the lungs.
• Right-sided failure:This occurs when the right ventricle fails to pump out enough blood to meet the body’s demand. In this case, the right ventricle and atrium cannot accept all the blood returning to the heart, and the blood “backs-up” into the veins and capillaries. The “overflow” of this fluid leaks out of the capillaries to the tissue, causing edema. Edema, or fluid accumulation, usually shows up as swelling, particularly in the legs. Right-sided failure usually occurs as a secondary result of left-sided failure, but it may also be caused by primary conditions that increase the pressure in the lungs.

Pulmonary Edema © 2009 Nucleus Medical Media, Inc.

Causes of CHF

There are several conditions that can cause CHF. It is important to accurately diagnose the underlying cause, as it will guide the course of treatment.

The two most common causes of CHF are:

• Hypertension (high blood pressure):If your arteries have become narrowed from fatty deposits or are less flexible due to aging or other causes, then your heart will have to pump much harder to get the blood through the arteries. This pumping effort is reflected in your “blood pressure.” If your heart muscle has to continually pump much harder than normal, then eventually, this may lead to heart muscle damage, and finally may cause heart failure.
• Coronary artery disease (CAD): Cholesterol and fat can build up in the arteries that supply the heart with blood. This build-up narrows the blood vessels, causing reduced blood flow (ischemia) to the heart muscle, and an inability to meet increased blood flow demands (like from exercise). If the blood flow is completely cut off, a heart attack can occur. Heart attack means that an area of heart muscle has been deprived of blood and nutrients long enough that the area of heart muscle dies. If enough heart muscle is damaged in this way and the muscle cannot pump enough blood to meet the body’s needs, then heart failure occurs.

Other conditions that cause CHF include:

• Valvular heart disease:The four valves of the heart keep blood flowing efficiently and in the correct direction. If these valves become damaged or infected ( endocarditis ), the heart is forced to work harder. Over time, this can weaken the heart muscle.
• Cardiomyopathy:The heart may become damaged due to infection, chronic alcohol abuse, use of certain chemotherapy drugs, cocaine, or scarring from diseases. The damage results in inadequate contraction of the heart muscle, which can lead to CHF.
• Congenital heart defects:When there is a malformation of the heart muscle or valves at birth, the heart is forced to work harder to produce the same output. Over time, this may cause CHF.
• Diabetes :People who have diabetes are at increased risk of developing heart disease. They often have other conditions that increase their risk of heart disease, like high cholesterol and increased weight.
• Abnormal heart rhythms (arrhythmia):If a heart beats too slowly (bradycardia), the heart may not be able to pump out an adequate supply of blood. If the heart beats too quickly (tachycardia), there may not be enough time for the heart to fill with blood. Both of these conditions produce strain and may lead to CHF.
• Hyperthyroidism :This condition, caused by an overactive thyroid gland, increases the metabolic rate in the body. The increased levels of thyroid hormone signal the heart to pump faster and harder to supply the body with blood, causing strain, which (if uncorrected) may lead to CHF.
• Anemia :Red blood cells carry oxygen throughout the body. When the number of red blood cells is reduced ( anemia ), the heart must circulate blood more frequently to supply enough oxygen to the tissues. This is another type of strain that may lead to CHF.

What are the risk factors for congestive heart failure?

What are the symptoms of congestive heart failure?

How is congestive heart failure diagnosed?

What are the treatments for congestive heart failure?

Are there screening tests for congestive heart failure?

How can I reduce my risk of congestive heart failure?

What questions should I ask my doctor?

Where can I get more information about congestive heart failure?

References:

American Heart Association website. Available at: http://www.americanheart.org/presenter.jhtml?identifier=1200000 .

Felker CM, Thompson RE, Hare JM, et al. Underlying causes and long-term survival in patients with initially unexplained cardiomyopathy. N Engl J Med.2000;342:1077.

He, J, Ogden, LG, Bazzano, LA, et al. Risk factors for congestive heart failure in US men and women: NHANES I epidemiologic follow-up study. Arch Intern Med.2001;161:996.

National Heart, Lung, and Blood Institute website. Available at: http://www.nhlbi.nih.gov/ .

Mayo Clinic Heart Center http://www.mayoclinic.com/health/heart-failure/HB00061 Last accessed at January 30, 2007