What Is Heart Failure?

How the normal heart works
What is heart failure?
Left-sided heart failure
Right-sided heart failure
Congestive heart failure

How the normal heart works
The normal heart is a strong, muscular pump a little larger than a fist. It pumps blood continuously through the circulatory system.

The heart has four chambers, two on the right and two on the left:

Two upper chambers called atria (one is an atrium)
Two lower chambers called ventricles

Oxygen-rich blood travels from the lungs to the left atrium, then on to the left ventricle, which pumps it to the rest of the body.

The right atria takes in oxygen-depleted blood from the rest of the body and sends it back out to the lungs throught the right ventricle.

The heart pumps blood to the lungs and to all the body's tissues by a sequence of highly organized contractions of the four chambers. For the heart to function properly, the four chambers must beat in an organized way.

Watch an animation of heart failure compared to the healthy heart

What is heart failure?

Heart failure is a chronic, progressive condition in which the heart muscle is unable to pump enough blood through the heart to meet the body’s needs for blood and oxygen. Basically, the heart can’t keep up with its workload.

At first the heart tries to make up for this by:

Enlarging. When the heart chamber enlarges, it stretches more and can contract more strongly, so it pumps more blood.
Developing more muscle mass. The increase in muscle mass occurs because the contracting cells of the heart get bigger. This lets the heart pump more strongly, at least initially.
Pumping faster. This helps to increase the heart's output.

The body also tries to compensate in other ways:

The blood vessels narrow to keep blood pressure up, trying to make up for the heart's loss of power.
The body diverts blood away from less important tissues and organs to maintain flow to the most vital organs, the heart and brain.

These temporary measures mask the problem of heart failure, but they don't solve it. Heart failure continues and worsens until these substitute processes no longer work.

Eventually the heart and body just can't keep up, and the person experiences the fatigue, breathing problems or other symptoms that usually prompt a trip to the doctor.

The body's compensation mechanisms help explain why some people may not become aware of their condition until years after their heart begins its decline. (It's also a good reason to have a regular checkup with your doctor.)

Heart failure can involve the heart's left side, right side or both sides. However, it usually affects the left side first.

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Left-sided heart failure

The heart's pumping action moves oxygen-rich blood travels from the lungs to the left atrium, then on to the left ventricle, which pumps it to the rest of the body. The left ventricle supplies most of the heart's pumping power, so it's larger than the other chambers and essential for normal function. In left-sided or left ventricular (LV) heart failure, the left side of the heart must work harder to pump the same amount of blood.

There are two types of left-sided heart failure. Drug treatments are different for the two types.

Systolic failure: The left ventricle loses its ability to contract normally. The heart can't pump with enough force to push enough blood into circulation.
Diastolic failure: The left ventricle loses its ability to relax normally (because the muscle has become stiff). The heart can't properly fill with blood during the resting period between each beat.

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Right-sided heart failure

The heart's pumping action moves "used" blood that returns to the heart through the veins through the right atrium into the right ventricle. The right ventricle then pumps the blood back out of the heart into the lungs to be replenished with oxygen.

Right-sided or right ventricular (RV) heart failure usually occurs as a result of left-sided failure. When the left ventricle fails, increased fluid pressure is, in effect, transferred back through the lungs, ultimately damaging the heart's right side. When the right side loses pumping power, blood backs up in the body's veins. This usually causes swelling in the legs and ankles.

Congestive heart failure is a type of heart failure which requires seeking timely medical attention, although sometimes the two terms are used interchangeably.

As blood flow out of the heart slows, blood returning to the heart through the veins backs up, causing congestion in the body's tissues. Often swelling (edema) results. Most often there's swelling in the legs and ankles, but it can happen in other parts of the body, too.

Sometimes fluid collects in the lungs and interferes with breathing, causing shortness of breath, especially when a person is lying down. This is called pulmonary edema and if left untreated can cause respiratory distress.

Heart failure also affects the kidneys' ability to dispose of sodium and water. This retained water also increases swelling in the body's tissues (edema).