The heart is a muscular pump. In health, the heart circulates blood through the body by contracting vigorously in systole and ejecting blood into the great vessels, then relaxing in diastole and allowing blood to fill the ventricle in preparation for the next systolic contraction. The proper function of the heart depends both on normal contraction in systole and normal relaxation in diastole. Many disease states can weaken the heart muscle and affect its ability to contract normally. Some of these diseases include coronary atherosclerosis, heart attack, valvular heart disease, severe hypertension, thyroid disease, alcoholism, drug abuse, chemotherapy treatment, and viral infection. These disease states vary in mechanism, but all lead to the final common result of a heart that is enlarged and that weakly contracts. This is known as dilated cardiomyopathy, or “enlarged heart,” and is the cause of congestive heart failure. In left-sided congestive heart failure, a weakened left ventricle is unable to pump blood efficiently to the body. As a result, the blood backs up in the lungs, causing symptoms of shortness of breath. In right-sided congestive heart failure, a weakened right ventricle results in blood backing up in the lower extremities and causing leg swelling.

Improper relaxation of the left ventricle in diastole may also lead to left-sided congestive heart failure by not allowing the blood returning from the lungs to easily flow into the left ventricle. This is known as diastolic dysfunction, and results in the lungs becoming congested with blood. Congestive heart failure due to diastolic dysfunction frequently is associated with chronic hypertension but also occurs in the absence of hypertension as the normal heart ages.

Congestive heart failure is treated medically with digitalis, diuretics, ACE inhibitors, nitrates, and beta blockers. If a reversible underlying cause can be identified, more specific treatment is initiated. For example, congestive heart failure due to coronary disease is treated by coronary bypass or angioplasty.

In recent years, the area of congestive heart failure has itself become a subspecialty within cardiology, and congestive heart failure clinics are now open in many parts of the country.