Ejection fraction
An ejection fraction (EF) is the volumetric
The EF of the
In heart failure, the difference between heart failure with a reduced ejection fraction, and heart failure with a preserved ejection fraction, is significant, because the two types are treated differently.
Measurement
Modalities applied to measurement of ejection fraction is an emerging field of medical mathematics and subsequent computational applications. The first common measurement method is echocardiography,[7][8] although cardiac magnetic resonance imaging (MRI),[8][9] cardiac computed tomography,[8][9] ventriculography and nuclear medicine (gated SPECT and radionuclide angiography)[8][10] scans may also be used. Measurements by different modalities are not easily interchangeable.[11] Historically, the gold standard for measurement of the ejection fraction was ventriculography,[12] but cardiac MRI is now considered the best method.[13] Prior to these more advanced techniques, the combination of electrocardiography and phonocardiography was used to accurately estimate ejection fraction.[14]
Physiology
Normal values
In a healthy 70-kilogram (150 lb) 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 70⁄120, or 0.58 (58%). Healthy individuals typically have ejection fractions between 50% and 65%,[15] although the lower limits of normality are difficult to establish with confidence.[16]
Ventricular volumes | ||
---|---|---|
Measure | Right ventricle | Left ventricle |
End-diastolic volume | 144 mL (± 23 mL)[17] | 142 mL (± 21 mL)[18] |
End-diastolic volume / body surface area (mL/m2) | 78 mL/m2 (± 11 mL/m2)[17] | 78 mL/m2 (± 8.8 mL/m2)[18] |
End-systolic volume | 50 mL (± 14 mL)[17] | 47 mL (± 10 mL)[18] |
End-systolic volume / body surface area (mL/m2) | 27 mL/m2 (± 7 mL/m2)[17] | 26 mL/m2 (± 5.1 mL/m2)[18] |
Stroke volume | 94 mL (± 15 mL)[17] | 95 mL (± 14 mL)[18] |
Stroke volume / body surface area (mL/m2) | 51 mL/m2 (± 7 mL/m2)[17] | 52 mL/m2 (± 6.2 mL/m2)[18] |
Ejection fraction | 66% (± 6%)[17] | 67% (± 4.6%)[18] |
Heart rate | 60–100 bpm[19]
|
60–100 bpm[19]
|
Cardiac output | 4.0–8.0 L/minute[20]
|
4.0–8.0 L/minute[20]
|
Pathophysiology
Heart failure categories
Damage to heart muscle (
- normal or preserved LVEF [≥50%] (HFpEF)
- moderately reduced LVEF [in the range of 41–49%] (HFmrEF)
- reduced LVEF [≤40%] (HFrEF)]
A chronically low ejection fraction less than 30% is an important threshold in qualification for disability benefits in the US.[22]
Calculation
By definition, the volume of blood within a ventricle at the end of diastole is the end-diastolic volume (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 (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):[23]
Where the stroke volume is given by:
EF is inherently a relative measurement—as is any fraction, ratio, or percentage, whereas the stroke volume, end-diastolic volume or end-systolic volume are absolute measurements.[citation needed]
History
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".[31] Elliott, Lane and Gorlin used the term "ejection fraction" in a conference paper abstract published in January 1964.[32] In 1965, Bartle et al. used the term ejected fraction for the ratio SV/EDV,[33] and the term ejection fraction was used in two review articles in 1968 suggesting a wide currency by that time.[2][34]
References
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- ^ a b Normal ranges for heart rate are among the narrowest limits between bradycardia and tachycardia. See the Bradycardia and Tachycardia articles for more detailed limits.
- ^ a b "Normal Hemodynamic Parameters – Adult" (PDF). Edwards Lifesciences LLC. 2009.
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- ^ Nylin G (1933). "The relation between heart volume and cardiac output per beat as a measure of cardiac activity". Svenska Läkartidningen. 10: 1.
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