Heart failure is a heart condition characterized by an inability to circulate as much blood as the body needs. In right side heart failure, the heart is not pumping enough blood into the lungs, while left side heart failure involves an inability to circulate blood to the rest of the body. It is not uncommon for both sides of the heart to be involved. This condition can also be classified as systolic, indicating a problem with pumping, or diastolic, where the heart has trouble filling with blood.

This condition can be chronic or acute. There are a number of causes including high blood pressure, coronary artery disease, cardiomyopathy, and myocardial infarction. Patients usually notice a gradual onset of symptoms including fluid retention, shortness of breath, difficulty exercising, and irregular heart rate. A medical examination can reveal problems with the heart and a doctor can recommend diagnostic tests to learn more about what is happening inside the patient's body.

One of the hallmarks of heart failure is fluid retention. When the heart is not pumping enough blood to meet the body's needs, signals are sent to the kidneys to increase blood volume by retaining fluid. This leads to swelling of the extremities, known as edema, and can also result in the formation of ascites, pockets of fluid in the abdomen. People with heart failure may notice that their fingers and toes become clubbed and swollen. Fluid retention is not necessarily caused by heart failure, but it is a strong diagnostic sign.
A cardiologist is usually consulted when a patient has heart failure. Diagnostic tests including blood tests, medical imaging, and stress tests can be used to assess heart function and to learn more about the patient's general level of health. This information will be discussed with the patient to develop a treatment plan. Some people can live for decades with heart failure, while others may need immediate medical intervention.

Treatments can include lifestyle changes such as diet and exercise modifications along with medications designed to reduce the load on the heart. Surgery may be recommended for some patients. Surgical treatments can include steps like cardiac transplants, where a failing heart is replaced with a healthy heart from a donor. Because surgery is highly invasive, other means are usually pursued first, and patients may need to demonstrate that they are ready to make permanent lifestyle changes after surgery before a surgeon will proceed.