Congestive Heart Failure Explained
CHF is Not a Diagnosis Unto Itself; It is Often a Result
Nov 3, 2008
The human heart is essentially a four-chambered, muscular pump that pushes fluid to all of the organs and tissues in the body. The right side of the heart, consisting of an atrium and a ventricle, pushes blood exclusively to the lungs. The left side of the heart, also consisting of an atrium and a ventricle, supplies blood to the remainder of the body.
The heart and blood vessels normally comprise a “closed” system; that is, what gets pumped OUT of the heart eventually RETURNS to the heart. Thus, balanced fluid movement is essential to maintaining the health and efficiency of the pump.
The Cardiovascular Circuit
It is easier to understand why the heart sometimes fails if one is familiar with the normal flow of blood through the cardiovascular system.
Starting at the right atrium, blood is pumped into the right ventricle. From there it is pushed through the pulmonary arteries to the lungs, where the blood absorbs oxygen.
Once oxygenated, blood leaves the lungs via the pulmonary veins and enters the left atrium of the heart. It is then pumped into the left ventricle, which in turn pushes the blood through the aorta and eventually through all other vessels in the body. After the blood has delivered oxygen and other nutrients to the cells and tissues, it returns through the veins to the right atrium of the heart, thus completing the circuit.
Consequences of Pump Failure
Any time the pumping efficiency of the heart is impaired, fluid “backs up” in the system somewhere. Usually, this fluid is deposited in the lowest-pressure “upstream” reservoir: if the left side of the heart is weakened, fluid builds up in the lungs; if the right side is impaired, fluid may collect in the soft tissues of the lower extremities or in the abdominal organs.
Excessive fluid in the organs or in the tissues interferes with the normal function of these structures. The symptoms that arise from this dysfunction are the clinical hallmarks of congestive heart failure (CHF).
Causes of Congestive Heart Failure
- Hypertension: Since the heart must push against the pressure in the vessels, chronic uncontrolled hypertension leads to pump failure.
- Ischemia: Poor oxygen delivery to the myocardium (heart muscle), usually the result of coronary artery disease, can injure the heart. A myocardial infarction (heart attack) may limit the contractility of portions of the heart wall.
- Toxins: Alcohol, certain medications, and other chemicals are toxic to the cells of the myocardium.
- Infection: Viruses or bacteria can invade the heart muscle or the lining of the heart and impair its ability to contract efficiently.
- Autoimmune disease: The myocardium—or the surrounding pericardium—is sometimes the target of inflammation in these diseases.
- Infiltrative diseases: Myocardial cells are occasionally crowded or replaced by abnormal substances, such as amyloid in multiple myeloma or B-cell lymphoma (Hassan, et al. Tex Heart Inst J. 2005;32(2):178-184)
- Valvular disease: Damage to the heart’s valves may cause backwashing of blood or obstruction to forward flow.
- Lung disease: Increased backpressure from damaged lungs (e.g., emphysema) can lead to right-sided heart failure.
- Metabolic disorders: Thyroid disease, carnitine deficiency, Pompe’s disease and other conditions can adversely affect the myocardium. Indeed, CHF itself is a metabolic disorder that, once established, can become self-perpetuating.
- Arrhythmias: Abnormal rhythms (e.g., atrial fibrillation) can lead to decreased cardiac output and CHF.
CHF can be secondary to a multitude of other disorders. Though diagnosis may be elusive in early stages, once CHF is recognized any underlying cause(s) must be sought out and treated.
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