Congestive heart failure is the inability of the heart to pump an adequate amount of blood throughout the body. The heart has two pumps: a right ventricle and a left ventricle. The right ventricle pumps non-oxygenated blood to the lungs to become oxygenated. This oxygenated blood is sent from the lungs to the left ventricle, which pumps it to the entire body. When either of these pumps fails, tissues and organs do not receive enough vital nutrients and oxygen.
Left Sided Heart Failure
Donna D. Ignatavicius, MS RN, and M. Linda Workman, Ph.D, discuss congestive heart failure in the 2006 edition of "Medical-Surgical Nursing: Critical Thinking for Collaborative Care" textbook. There are two phases in the pumping action of the heart. The active pumping phase is called systole. This is when the heart muscle contracts to force the blood out of the ventricle. The other phase, diastole, is when the heart rests so that the ventricle can fill with blood. Left-sided heart failure can be caused by diastolic or systolic heart failure.
In systolic heart failure, the left ventricle cannot effectively overcome the systemic vascular resistance. This means the left ventricle is not strong enough to pump the blood through the aorta to the rest of the body because of very high pressures in the systemic circulation. High blood pressure or narrowing of the aorta can cause this.
The result of not being able to fully "empty" the left ventricle is an increase in left-sided heart pressures and not enough blood reaching the tissues and organs. Initially, the left ventricle attempts to compensate by becoming thicker and larger. This is called hypertrophy. The American Heart Association explains that over time, the enlarged ventricle fails and fluid backs up in the heart, causing congestion in the lungs and low systemic blood pressure.
With diastolic heart failure, the heart does not properly relax after contracting, and this prevents proper filling of the ventricles. This means there is less blood in the left ventricle to pump out.
Right Sided Heart Failure
Left-sided heart failure, if left untreated or poorly controlled, often leads to right-sided heart failure. After the left pump fails, blood backs up into the pulmonary system. This increases the pressure in the lungs. The right side of the heart has to work harder to pump the non-oxygenated blood that it receives from the systemic circulation into the lungs. Over time, the right ventricle becomes hypertrophied, and is unable to pump effectively. Blood backs up throughout the venous system. As the AHA "Signs and Symptoms of CHF" outline, this produces the classic signs of swelling in the lower extremities, fatigue and shortness of breath.
High Output Failure
In this situation, the heart is pumping fine for normal conditions. However, the body is experiencing a hyper-metabolic state. This means an illness or disease process is causing the body to need more nutrient- and oxygen-rich blood than the heart can pump out. Conditions such as septicemia (systemic infection), anemia or hyperthyroidism can lead to this type of heart failure.
References
- "Medical-Surgical Nursing - Critical Thinking for Collaborative Care"; Donna D. Ignatavicius MS RN, & M. Linda Workman Ph.D; 2006
- American Heart Association: "What is Heart Failure"
- American Heart Association: "Signs and Symptoms of CHF"
