TheInfoList

An ejection fraction (EF) is the volumetric
fraction A fraction (from Latin ', "broken") represents a part of a whole or, more generally, any number of equal parts. When spoken in everyday English, a fraction describes how many parts of a certain size there are, for example, one-half, eight-fifths ...
(or portion of the total) of fluid (usually
blood Blood is a body fluid in humans and other animals that delivers necessary substances such as nutrients and oxygen to the Cell (biology), cells and transports metabolic waste products away from those same cells. In vertebrates, it is composed ...

) ejected from a chamber (usually the
heart The heart is a cardiac muscle, muscular Organ (biology), organ in most animals, which pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste ...

) with each contraction (or
heartbeat Heartbeat or heartbeats may refer to: Physiology *Cardiac cycle, of the heart *Contraction of the cardiac muscle, muscles of the heart, or a perceived effect of it, such as: **Heart sounds, the noises generated by the beating heart and the resulta ...
). Thus understood, ejection fraction may be used to measure a fluid of any viscosity discharged from a hollow organ to another cavity or outside of the body. Blood, bile and urine are commonly studied under this mathematical platform. For example, it may refer to the cardiac atrium, ventricle, gall bladder, or leg veins, although if unspecified it usually refers to the left ventricle of the heart. EF is widely used as a measure of the pumping efficiency of the heart and is used to classify heart failure types. It is also used as an indicator of the severity of
heart failure Heart failure (HF), also known as congestive heart failure (CHF) and (congestive) cardiac failure (CCF), is a caused by the failure of the 's function as a pump supporting the ; its result from a structural and/or functional abnormality of the ...
, although it has recognized limitations. The EF of the
left heart The heart is a muscular organ in most animals, which pumps blood through the blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cel ...
, known as the left ventricular ejection fraction (LVEF), is calculated by dividing the volume of blood pumped from the
left ventricle A ventricle is one of two large chambers toward the bottom of the heart The heart is a muscle, muscular Organ (anatomy), organ in most animals, which pumps blood through the blood vessels of the circulatory system. The pumped blood carries ...
per beat (
stroke volume In cardiovascular physiologyCardiovascular physiology is the study of the cardiovascular system, specifically addressing the physiology of the heart ("cardio") and blood vessels ("vascular"). These subjects are sometimes addressed separately, unde ...
) by the volume of blood collected in the left ventricle at the end of diastolic filling (
end-diastolic volume In cardiovascular physiologyCardiovascular physiology is the study of the cardiovascular system, specifically addressing the physiology of the heart ("cardio") and blood vessels ("vascular"). These subjects are sometimes addressed separately, unde ...
). LVEF is an indicator of the effectiveness of pumping into the
systemic circulation The circulatory system, also called the cardiovascular system or the vascular system, is an organ system An organ system is a group of organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many o ...
. The EF of the
right heart The heart is a muscular MUSCULAR (DS-200B), located in the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use ...
, or right ventricular ejection fraction (RVEF), is a measure of the efficiency of pumping into the
pulmonary circulation The mammalian heart is divided between the systemic and the pulmonary circulation, generally agreed upon as left and right sided circuits. The right circuit is the portion of the circulatory system The circulatory system, also called the car ...
. A heart which cannot pump sufficient blood to meet the body's requirements (i.e., heart failure) will often, but not invariably, have a reduced ventricular ejection fraction.

Measurement

Modalities applied to measurement of ejection fraction is an emerging field of medical mathematics and subsequent computational applications. Perhaps the first common bedrock measurement method was
echocardiography An echocardiography, echocardiogram, cardiac echo or simply an echo, is an of the . It is a type of of the heart, using standard ultrasound or . Echocardiography has become routinely used in the diagnosis, management, and follow-up of patients ...
, although cardiac magnetic resonance imaging (MRI), cardiac computed tomography, ventriculography and
nuclear medicine Nuclear medicine is a medical specialty A medical specialty is a branch of medical practice that is focused on a defined group of patients, diseases, skills, or philosophy. Examples include children (paediatrics Pediatrics (American and Briti ...
( gated SPECT and radionuclide angiography) scans may also be used. Measurements by different modalities are not easily interchangeable. Historically, the
gold standard A gold standard is a monetary system A monetary system is a system by which a government provides money in a country's economy. Modern monetary systems usually consist of the national treasury, the mint (facility), mint, central bank, the cen ...
for measurement of the ejection fraction was ventriculography, but cardiac MRI is now considered the best method. Prior to these more advanced techniques, the combination of electrocardiography and phonocardiography was used to accurately estimate ejection fraction.

Physiology

Normal values

In a healthy man, the stroke volume is approximately 70 mL, and the left ventricular end-diastolic volume (EDV) is approximately 120 mL, giving an estimated ejection fraction of , or 0.58 (58%). Healthy individuals typically have ejection fractions between 50% and 65%, although the lower limits of normality are difficult to establish with confidence.

Pathophysiology

Heart failure categories

Damage to heart muscle (
myocardium Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism ...

), such as occurring following
myocardial infarction A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow Hemodynamics American and British English spelling differences#ae and oe, or haemodynamics are the Fluid dynamics, dynamics of blood flow. The circulatory sy ...

or
cardiomyopathy Cardiomyopathy is a group of diseases that affect the heart muscle Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate Vertebrates () comprise all species of animal Animals (also called Metaz ...
, compromises the heart's performance as an efficient pump and may reduce ejection fraction. Such reduction in the EF can manifest itself as
heart failure Heart failure (HF), also known as congestive heart failure (CHF) and (congestive) cardiac failure (CCF), is a caused by the failure of the 's function as a pump supporting the ; its result from a structural and/or functional abnormality of the ...
. The 2016
European Society of Cardiology The European Society of Cardiology (ESC) is a non-profit A nonprofit organization (NPO), also known as a non-business entity, not-for-profit organization, or nonprofit institution, is a legal entity organized and operated for a collective, pub ...
guidelines for the diagnosis and treatment of acute and chronic heart failure subdivided heart failure into three categories on the basis of LVEF: # normal or preserved LVEF ‰¥50% (HFpEF) # moderately reduced LVEF n the range of 40â€“49%(HFmrEF) # reduced LVEF (HFrEF)] A chronically low ejection fraction less than 30% is an important threshold in qualification for disability benefits in the US.

Calculation

By definition, the volume of blood within a Ventricle (heart), ventricle at the end of diastole is the
end-diastolic volume In cardiovascular physiologyCardiovascular physiology is the study of the cardiovascular system, specifically addressing the physiology of the heart ("cardio") and blood vessels ("vascular"). These subjects are sometimes addressed separately, unde ...
(EDV). Likewise, the volume of blood left in a ventricle at the end of systole (contraction) is the end-systolic volume (ESV). The difference between EDV and ESV is the
stroke volume In cardiovascular physiologyCardiovascular physiology is the study of the cardiovascular system, specifically addressing the physiology of the heart ("cardio") and blood vessels ("vascular"). These subjects are sometimes addressed separately, unde ...
(SV). The ejection fraction is the fraction of the end-diastolic volume that is ejected with each beat; that is, it is stroke volume (SV) divided by end-diastolic volume (EDV): $EF \left(\%\right) = \frac\times100$ Where the stroke volume is given by: $SV = EDV - ESV$ EF is inherently a relative measurementâ€”as is any fraction,
ratio In mathematics, a ratio indicates how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8âˆ¶6, which is equivalent to ...

, or
percentage In mathematics Mathematics (from Greek: ) includes the study of such topics as numbers (arithmetic and number theory), formulas and related structures (algebra), shapes and spaces in which they are contained (geometry), and quantities a ...

, whereas the stroke volume, end-diastolic volume or end-systolic volume are absolute measurements.

History

After
William Harvey William Harvey (1 April 1578 â€“ 3 June 1657) was an English physician who made influential contributions in anatomy Anatomy (Greek ''anatomÄ“'', 'dissection') is the branch of biology concerned with the study of the structure of organis ...

's description of the basic mechanism of the circulation in 1628, it was initially assumed that the heart emptied completely during systole. However, in 1856 and Faivre observed that some fluid remained in the heart after contraction. This was confirmed by Roy and Adami in 1888. In 1906, Henderson estimated the ratio of the volume discharged in systole to the total volume of the left ventricle to be approximately 2/3. In 1933, Gustav Nylin proposed that the ratio of the heart volume/stroke volume (the reciprocal of ejection fraction) could be used as a measure of cardiac function. in 1952 Bing and colleagues used a minor modification of Nylin's suggestion (EDV/SV) to assess right ventricular function using a dye dilution technique. Exactly when the relationship between end diastolic volume and stroke volume was inverted into its current form is unclear. Holt calculated the ratio SV/EDV and noted that '...The ventricle empties itself in a "fractional" manner, approximately 46 per cent of its end-diastolic volume being ejected with each stroke and 54 per cent remaining in the ventricle at the end of systole'. In 1962, Folse and Braunwald used the ratio of forward stroke volume/EDV and observed that "estimations of the fraction of the left ventricular end-diastolic volume that is ejected into the aorta during each cardiac cycle, as well as of the ventricular end-diastolic and residual volumes, provide information that is fundamental to a hemodynamic analysis of left ventricular function". Elliott, Lane and Gorlin used the term "ejection fraction" in a conference paper abstract published in January 1964. In 1965 Bartle et al. used the term ejected fraction for the ratio SV/EDV, and the term ejection fraction was used in two review articles in 1968 suggesting a wide currency by that time.

References

{{Cardiovascular physiology Cardiovascular physiology