eli5: how does heart failure cause fluid build up?


My husband just spent 5 days in the hospital getting IV diaretics to remove fluid …lost 10 lbs. He has congestive heart failure. I know that the blood and ergo the oxygen is not flowing freely, by how does this cause fluid buildup and what IS the fluid. How is this different from fluid in lungs from pneumonia?

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4 Answers

Anonymous 0 Comments

This is quite a complex topic

Blood is mostly made up of water. The heart’s job is to pump blood around the body to where it needs to go. In heart failure, the heart is unable to pump blood effectively. The most common type of heart failure is Left Ventricular Heart failure (which is also known as congestive heart failure) and we can characterise that with a percentage score known as the Ejection fraction. When the heart is not pumping blood effectively, there is a backlog of blood waiting to get into the heart to be pumped. In the case of Left ventricular heart failure, that blood is sitting in the lungs waiting to be pumped.

Blood vessels are naturally leaky, they allow some water to leak out into the surrounding tissues. In your husband’s case, the backlog of blood in the lungs meant that the water in the blood started leaking into the lungs making it hard for him to breathe. Fluid in the lungs is called pulmonary odema.

There are two arms of treatment for treating heart failure. The first are medications to help the heart beat harder and stronger. The second is to try and reduce the load on the heart, by removing the amount of water it has to pump around and reducing the pressure in the system (blood pressure) that it has to pump against. To do this, we give medications that stimulate the kidney to make excess urine (we call this diuresis). By making your husband pee, we can make him dehydrated. A dehydrated person has less water to leak out into the surrounding tissue and less blood volume that needs to be pumped. An important part of his ongoing treatment will be limiting the amount of fluid he drinks. He essentially needs to remain in a state of mild dehydration. This can be a tricky balance.

There are also a complex set of hormones involved in fluid regulation, but its a little too complex for ELI5.

The fluid in pneumonia is usually infective as a result of inflammation from infection. But it too also comes from leaky blood vessels.

Anonymous 0 Comments

(firstly sorry about your husband)

1) The heart pushes blood all around the body and sucks it back again.

2) Blood is made up of fluid (plasma) with the blood cells in it making it look red.

3) Heart ‘failure’ is like an engine running on only 2 cylinders so it’s less efficient at pumping it and sucking it back up.

4) So the blood (with fluid) sits around a bit longer (eg in the legs where it’s harder to suck it back from).

5) That stagnant fluid then leaks into the skin hence swelling legs. If it gets so bad it leaks into the lungs and hence interferes with breathing.

Anonymous 0 Comments

When the heart isn’t working well, it can’t pump blood around the body properly. This can cause fluid to build up in different parts of the body, like the lungs or the feet. This is called edema and it can cause swelling, shortness of breath, and other symptoms. There are different ways to treat edema, like taking medicine or making lifestyle changes, depending on what’s causing it.

Anonymous 0 Comments

The right side of the heart is a drain for fluid from the body. It takes fluid from the body as its input, and then pumps this fluid to the lungs as its output.

The left side of the heart is a drain for fluid from the lungs. It takes fluid from the lungs as its input, and then pumps this fluid to the body as its output.

What happens if you clog a drain? The fluid gets backed up.

In right-sided heart failure, fluid gets backed up in the body. This causes swelling of the legs, ankles, feet, or abdomen. Usually lower extremities are more affected than upper extremities because of gravity pulling fluid down.

In left-sided heart failure, fluid gets backed up in the lungs. This causes shortness of breath, coughing (often a productive cough with mucus/phlegm), and difficulty breathing when lying flat.

What is this fluid? The short answer is interstitial fluid. Most cells in the body are bathing in interstitial fluid all the time. This fluid is where cells get their nutrients and oxygen. This fluid is also where cells dump their wastes and carbon dioxide. All day long, this fluid circulates around cells to give them what they need and remove what they do not need. This fluid enters and exits the circulatory system by passing filters called capillaries.

The fluid build-up in heart failure is edema. It is called pulmonary edema when in the lungs, and peripheral edema when in the extremities. At a microscopic level, edema caused by heart failure is mostly interstitial fluid. It can build up in the lungs when it leaks out of microscopic capillaries in the lungs, since the drain is backed up.