Heart failure is a common, costly, and potentially fatal condition. In 2015 it affected about 40 million people globally. Overall around 2% of adults have heart failure and in those over the age of 65, this increases to 6–10%. Rates are predicted to increase. The risk of death is about 35% the first year after diagnosis; while by the second year the risk of death is less than 10% for those who remain alive. This degree of risk of death is similar to some cancers. In the United Kingdom, the disease is the reason for 5% of emergency hospital admissions. Heart failure has been known since ancient times with the Ebers papyrus commenting on it around 1550 BCE.
The term "acute" is used to mean rapid onset, and "chronic" refers to long duration. Chronic heart failure is a long-term condition, usually kept stable by the treatment of symptoms. Acute decompensated heart failure is a worsening of chronic heart failure symptoms which can result in acute respiratory distress.High-output heart failure can occur when there is an increased cardiac output. The circulatory overload caused, can result in an increased left ventricular diastolic pressure which can develop into pulmonary congestion (pulmonary edema).
Heart failure is divided into two types based on ejection fraction, which is the proportion of blood pumped out of the heart during a single contraction. Ejection fraction is given as a percentage with the normal range being between 50 and 75%. The two types are:
1) Heart failure due to reduced ejection fraction (HFrEF). Synonyms no longer recommended are "heart failure due to left ventricular systolic dysfunction" and "systolic heart failure". HFrEFe is associated with an ejection fraction of less than 40%.
2) Heart failure with preserved ejection fraction (HFpEF). Synonyms no longer recommended include "diastolic heart failure" and "heart failure with normal ejection fraction". HFpEF occurs when the left ventricle contracts normally during systole, but the ventricle is stiff and does not relax normally during diastole, which impairs filling.