What happens during congestive heart failure?

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Joan Haizlip, MSN
Cardiology (Cardiovascular Disease)
There are a lot of things that happen in congestive heart failure (CHF).  The heart is a pump. If the pump fails or weakens, blood cannot be pumped out as well as before.  As a result many symptoms appear:
 
  • Fluid builds up in the lungs making it hard to breathe (dyspnea)
  • Difficulty breathing while laying flat (orthopnea),
  • Swelling (edema) in dependent parts of the body, like the feet or legs. 
  • Confusion
Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
In congestive heart failure, the heart cannot pump enough blood to meet the body’s needs, so it beats faster and the heart muscle gets bigger, eventually causing the heart to wear out. In addition, your body retains water and salt; the extra fluid build-up is called congestion. This animation explains congestive heart failure in more detail.



Discovery Health
Administration

When the heart begins to fail, first the sympathetic nervous system is activated. This increases the heart rate and the force of heart contractions, and the body's veins are constricted. These factors work together in order to increase cardiac output. But this also constricts arteries, and that increases blood pressure. The heart works harder and uses more oxygen; this may cause further deterioration of the heart over time.

Blood flow to the kidneys is then decreased. This activates the renin-angiotensin-aldosterone system. The kidney releases an enzyme called renin when blood flow is decreased.. Renin converts angiotensinogen, which is an inactive plasma protein, into an active hormone called angiotensin II. This is a powerful constrictor of both arteries and veins which stimulates the adrenal gland to secrete the hormone aldosterone. However, Aldosterone causes the kidneys to retain water and salt and this increases blood volume. The increased blood volume does help to maintain cardiac output - it increases the filling of the heart. But the increased blood volume and the vasoconstriction also increase blood pressure. This becomes a vicious cycle - the increased pressure causes edema, which makes for an increased workload, and which may further weaken the heart.

At the same time, the body increases the secretion of ADH, a hormone in the pituitary gland (anti-diuretic hormone), which causes the kidney to retain more fluid. This may increase blood volume and help cardiac output, but it also increases blood pressure, and the weakened heart has to work even harder.

The heart muscle itself also experiences changes. The thickness of the muscle layer increases (hypertrophy), which enables the heart to contract with greater force and to maintain cardiac output. But this increases the need for oxygen, and eventually leads to further deterioration. Dilation occurs, which is the heart enlarging by stretching and thinning its walls. Initially output may be increased because of the increase of the amount of blood that the heart can hold, however the dilation eventually fails and the disease worsens.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.