What is heart failure?

As early as the 4th century BC, humans have been fixated on the heart and what is represents. Although our knowledge of the heart and its functions has greatly advanced since then, whenever a patient is diagnosed with a heart condition, they immediately assume the worst. This is an understandable reaction as the heart is a central component of the body and essential for life to exist. However, unlike what people commonly think, heart failure (also known as cardiac failure) is not a pathological condition in which the heart "fails" as in stops working. So what exactly is heart failure?
According to Harrison's Principles of Internal Medicine, heart failure is defined as "a clinical syndrome in which an abnormality of cardiac structure or function is responsible for the inability of the heart to eject/fill with blood at a rate commensurate with the requirement of the metabolizing tissues." In simple words, it is a condition where the heart is unable to pump enough blood. Heart failure may occur as a consequence of most forms of heart disease but it is more frequently first seen when an acute disturbance places an additional load on an already excessively burdened heart. In developed nations, almost all heart failure is due to either ischemic heart disease, hypertension, valvular disease or congenital heart disease. However, childhood rheumatic fever causing heart failure secondary to mitral stenosis is still a major problem in poorer communities. The exact cause of the heart failure will naturally determine exactly what form of heart failure it is and subsequently, the signs and symptoms experienced by the patient.

While there are numerous ways of classifying heart failure including low-output vs. high-output, acute vs. chronic and backward vs. forward, the most common division is right-sided and left-sided heart failure, which refers to failure of the right and left ventricles respectively. After a ventricle is initially affected and fails to pump properly, there is a build-up of fluid in the veins upstream to it. Many of the clinical manifestations of heart failure are a result from this fluid accumulation and thus, indicate which side of the heart is affected.

In left-sided heart failure, fluid accumulates in the pulmonary veins in the lungs. This causes some of the excess fluid to leak into the lung alveoli (air sacs), causing difficulty in breathing. As a result, patients often experience shortness of breath during light exertion and in severe cases, even at rest. In addition, when the patient lies down, fluid from the periphery flows back to the chest region, further complicating the matter. This results in the condition of orthopnea, which is shortness of breath when lying down. Right-sided heart failure, on the other hand, has fluid accumulation in the systemic veins throughout the body. Thus, fluid leakage would occur in the lower limbs around the ankles. The exertion that gravity has on the fluid means that ankle swelling is most prominent at the end of the day. Furthermore, build-up of fluid in the inferior vena cava would travel back to the portal veil in the liver, causing portal hypertension and in the long term, hepatomegaly (enlarged liver). While the distinction between right and left heart failure is useful, it is important to note that over time, both ventricles would become affected and the patient will suffer from all of the symptoms above.
The diminished cardiac output would result in inadequate blood supply around the body as well as a falling blood pressure. The body has several compensatory mechanisms to deal with this problem, not all of which are beneficial in the long run. Firstly, the heart would try to beat faster (tachycardia) to compensate for the fall in cardiac output. This in the long run would aid in the hypertrophy (abnormal enlargement) of the ventricles, deteriorating the condition of the heart. Secondly, total peripheral resistance and vascular tone would increase in an attempt to maintain a normal blood pressure. Thirdly, the rennin-angiotensin system would be activated to retain sodium and water via the kidneys in the hope that the increase in extra-cellular fluid would help sustain a normal blood pressure. While this does help improve the blood pressure, the increase in volume exacerbates the edema (fluid build-up leading to swelling) as well as the heart problem as the heart can't cope with the increase load.

Treatments for heart failure focus on alleviating the clinical symptoms and progression of the disease. If the underlying cause of the heart failure is reversible (e.g. infection, alcohol etc.), then the appropriate steps would be taken. Diuretics are administered to not only remove excess fluids but also prevent the kidneys from retaining more fluids. The patient would also be on a low sodium and water lifestyle to further control their extra-cellular volume. Beta-blockers, although previously contra-indicated for heart failure, is now recommended for acute heart failure as it has been shown to improve ventricular function and thus, cardiac output. If all else fails, heart transplantation should be considered.

In conclusion, heart failure is not a condition where the heart stops functioning but a clinical syndrome in which the heart fails to pump properly. After all, any heart conditions could be critical to one's health. If you suffer from any of the symptoms mentioned above, it is vital for you to seek medical attention as soon as possible. It's better to be safe than sorry.

Reference:

Harrison, T. et al. (2005) Harrison's Principles of Internal Medicine, 16th Edition. USA: McGraw-Hill Companies, Inc.