Heart failure is the inability of the heart to pump out the required amount of blood per minute in response to oxygen demands in the body. Heart failure rarely refers to the complete lack of heart contraction; in most cases, the heart still contracts, but it does so ineffectively. Heart failure results in the reduction or lack of effective blood flow to the organs including the kidneys. Low blood flow to the kidneys results in sodium retention.
Oxygen Demand and Heart Function
The heart is part of the circulatory system, which ensures adequate delivery of oxygen-rich blood to the organs; compensatory changes in the circulatory system often involve the modulation of heart rate and strength of cardiac, or heart, contractions. The heart rate is controlled directly by pacemakers and indirectly by the influence of the nervous system on the pacemakers; the autonomic nervous system is the branch of the nervous system, which acts on the pacemakers of the heart without voluntary control by the individual. When oxygen levels drop in the blood and oxygen demand increases, the autonomic nervous system adjusts cardiac function to meet up with oxygen demands.
Sodium Retention
As the amount of blood pumped out by the heart per minute decreases, so does the rate of blood flow to organs of the body. Sodium retention occurs as the result of decreased blood flow to the kidneys; as blood flow in the kidney decreases, the kidneys in turn release a special enzyme which eventually results in the release of aldosterone from the adrenal glands. Aldosterone is a steroid hormone, which acts in the kidneys to increase sodium re-absorption and increase potassium excretion. Increased aldosterone secretion in congestive heart failure, results in increased sodium levels in the blood.
Symptoms Associated with Congestive Heart Failure
When the heart fails, there is increased back flow of blood due to reduction in forward flow. As heart failure progresses, the lungs become congested with excess fluid, thereby preventing adequate oxygenation of blood. A person with congestive heart failure, experiences shortness of breath due to lack of oxygen. Shortness of breath typically worsens with a change in position; shortness of breath commonly occurs at night when a person is in a reclining position. Oxygen is needed to make energy; therefore, a person with congestive heart failure also experiences fatigue. Other symptoms of congestive heart failure include decreased urine formation, swelling of ankles and sometimes, weight loss.
Management of Congestive Heart Failure
A person with congestive heart failure should sit up to reduce lung congestion. Since heart failure reduces the oxygenation of the blood, supplemental oxygen is beneficial in congestive heart failure. Oxygen is typically given via a tight-fitting face mask, which non-invasively provides positive oxygen pressure to the airways. Nitrates -- a class of drugs that widen blood vessels -- are used to reduce symptoms associated with congestion. In congestive heart failure, there is fluid overload as a result of decreased blood flow to kidneys and increased sodium retention; loop diuretics -- a class of drugs that increase urination by causing increased sodium loss -- can remove excessive fluid in the body.
References
- "Davidson's Principles & Practice of Medicine; Nicholas A. Boon; 2006
- "Harrison's Principles of Internal Medicine"; Dennis L. Kasper M.D., et al.; 2005
- Medline Plus; Heart Failure; June 22, 2010
