- katherineLv 51 0 年前最佳解答
http://health.yahoo.com/centers/heart/What Is Heart Failure?Provided by ehealthMD.com
Blood backs up in the veins, and fluid seeps from the veins into the surrounding tissues. That causes swelling (edema). This is most common in the legs and ankles, but may affect other parts of the body as well. Blood also backs up in the blood vessels within the lungs. The inside of the lungs becomes swollen and stiff with the extra fluid, which is why you may feel short of breath and may have a dry cough. There is another problem: extra fluid in the blood. When the blood flow around the body slows down, as occurs in heart failure, the brain gets a signal that there is not enough blood to go around. To make up for the decreased blood flow, the brain signals to the kidneys to retain fluid in the blood. This has further effects:In the daytime, this extra fluid in the blood adds to the swelling in legs and ankles. When you are lying down, the fluid may flow to other parts of your body. Some of it gets into the tissue around your lungs, making it especially hard to breathe at night. The kidneys try to get rid of this extra water, which is why you may have to go to the bathroom more often.
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