Pathophysiology of Congestive Heart Failure
I. Description: Congestive Heart Failure is more of a syndrome than a disease. Heart failure may be classified according to the side of the heart affected, (left- or right-sided failure), or by the cardiac cycle involved, (systolic or diastolic dysfunction). (Schilling-McCann p. 176). The word "failure" refers to the heart's inability to pump enough blood to meet the body's metabolic needs. (Schilling-McCann p. 176). When the heart fails to deliver adequate blood supply edema may develop. (Cadwallader p. 1141). Where edema occurs depends on what side of the heart is failing.
Left-sided heart failure results from the inability of the left ventricle to function properly. Blood fails to get out to other parts of the body as quickly as it returns from the lungs. When blood doesn't get back to the heart, it backs up in the lungs blood vessels. Blood is then forced into the intracellular space in the lungs causing pulmonary edema. (Cadwallader pp. 1141 - 1142).
Right-sided heart failure results from the inability of the right ventricle to function properly. Blood isn't pumped to the lungs as quickly as it returns from the other parts of the body. Fluid then begins to back up in the veins and pushes out into the tissues, causing edema, most often in the feet, lower legs, and ankles. (Cadwallader p. 1142).
Sluggish blood flow also deprives organs of oxygen and other nutrients causing fatigue and difficultly with physical exertion. The heart tries to compensate for its lack of pumping ability by becoming hypertrophic. This causes the muscle in the heart's wall to thicken thus improving the hearts pumping ability. (Cadwallader p. 1142). The heart may also increase heart rate to improve output and circulation. The kidneys eventually join in by retaining salt and water to increase volume, but this extra fluid can cause edema and further complicate the situation. (Cadwallader p. 1142). Unfortunately, overtime, compensatory measures are not enough to keep the heart pumping enough blood.
Heart failure is a chronic disease with no real cure. However, heart failure can often be managed and treated over time with medications, exercise, a healthy diet, and lifestyle changes. (Cadwallader p. 1142).
II. Etiology: Heart failure can result from numerous causes. Some common causes of heart failure are: CAD, MI, cardiomyopathy, hypertension, heart valve disease, infection of the heart, congenital structural abnormalities, and substance abuse. (Cadwallader p. 1142).
The most common cause of Congestive Heart Failure is CAD (coronary artery disease). The arteries that supply the heart muscle with blood begin to narrow and eventually they become completely blocked. (Cadwallader p. 1142). When the blood doesn't reach a specific area of the heart, a heart attack occurs. Some heart attacks are so slight that they go unrecognized, while others are lethal. The heart is damaged when the blood supply is greatly reduced or blocked. If the damage significantly impairs the ability of the heart to pump blood heart failure occurs.
Cardiomyopathy is a general term describing disease of the heart-muscle tissue. (Cadwallader p. 1142). This can be caused by a genetic defect, substance abuse, CAD, or an infection, usually viral. Cancer treatments have been associated with the development of cardiomyopathy as well as anthracycline or other cardiotoxic agents. (Cadwallader p. 1142). Regardless of the cause or condition, the heart muscle weakens and eventually fails. (Cadwallader p. 1142).
Sustained and uncontrolled high blood pressure is another common cause of heart failure. (Cadwallader p. 1142). The persistent high pressure exerted on arterial walls makes them thicker and less pliable, and resistant to normal blood flow. As a result, the heart compensates by pumping harder, in an attempt to regain normal flow. (Cadwallader p. 1142). Eventually the heart can't keep up with the...