Heart failure means that your heart muscle doesn't pump as much blood as your body needs. Because your heart can't pump well, your heart and your body try to make up for it. This is called compensation.
Your body has a remarkable ability to compensate for heart failure. The body may do such a good job that many people don't feel symptoms in the earlier stages of heart failure. It is only when your body isn't able to compensate enough that you will start to have symptoms.
Compensation may help your body adjust to the effects of heart failure in the short term. But over time it can make heart failure worse by further enlarging the heart and reducing how well the heart can pump.
With heart failure, the heart doesn't pump as well as it should. So your body doesn't get enough blood and oxygen. When this occurs, the body believes that there isn't enough fluid inside its vessels. The body's hormone and nervous systems try to make up for this. They increase blood pressure, hold on to salt (sodium) and water in the body, and increase the heart rate. These responses are the body's attempt to compensate for the poor blood circulation and the backup of blood.
If your body senses that the brain and vital organs aren't getting enough blood, the sympathetic nervous system starts working to get more blood to your brain and organs. This system releases substances called catecholamines into the bloodstream. These substances cause the blood vessels to constrict and speed up the heart rate. At the same time, the arteries that supply the brain and vital organs widen to carry the increased blood flow.
When the body thinks it needs more fluid in its blood vessels, it releases specific chemicals (renin, angiotensin, and aldosterone) that cause the blood vessels to constrict. These hormones also cause the body to hold on to more sodium and water. This adds fluid to your circulatory system. This fluid becomes part of the blood circulating throughout your system.
Your heart's goal in compensating for heart failure is to maintain your cardiac output. Cardiac output is the amount of blood your heart is able to pump in 1 minute. The problem in heart failure is that the heart isn't pumping out enough blood each time it beats. This is called low stroke volume. To maintain your cardiac output, your heart can try to beat faster (increase your heart rate) or pump more blood with each beat (increase your stroke volume).
Your brain signals your heart to beat faster by sending messages to your heart's electrical system, which controls the timing of your heartbeat. When your cardiac output is low, your adrenal glands also release more norepinephrine (adrenaline). It travels in the bloodstream and stimulates your heart to beat faster. Beating faster helps to maintain cardiac output as the stroke volume falls. But a faster heart rate can be counterproductive because it allows less time for the ventricle to fill with blood after each heartbeat. Also, a very fast heart rate can weaken the heart muscle over time.
To increase its stroke volume, your heart can try to:
If your body can no longer compensate for heart failure, you will start to have symptoms. There are two major types.
Your body can compensate for heart failure for a long time, often for many years. But how long compensation lasts can vary quite a bit. It depends on the cause of your heart failure and whether you have other medical problems.
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