Ejection fraction explained

An ejection fraction (EF) is the volumetric fraction (or portion of the total) of fluid (usually blood) ejected from a chamber (usually the heart) with each contraction (or heartbeat). It can refer to the cardiac atrium,[1] ventricle,[2] gall bladder,[3] or leg veins,[4] 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, although it has recognized limitations.[5]

The EF of the left heart, known as the left ventricular ejection fraction (LVEF), is calculated by dividing the volume of blood pumped from the left ventricle per beat (stroke volume) by the volume of blood present in the left ventricle at the end of diastolic filling (end-diastolic volume). LVEF is an indicator of the effectiveness of pumping into the systemic circulation. The EF of the right heart, or right ventricular ejection fraction (RVEF), is a measure of the efficiency of pumping into the pulmonary circulation. 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.[6]

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),[9] cardiac computed tomography, ventriculography and nuclear medicine (gated SPECT and radionuclide angiography)[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 70kg (150lb) 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%,[15] although the lower limits of normality are difficult to establish with confidence.[16]

Pathophysiology

Heart failure categories

Damage to heart muscle (myocardium), such as occurring following myocardial infarction or cardiomyopathy, compromises the heart's performance as an efficient pump and may reduce ejection fraction. This broadly understood distinction marks an important determinant between ischemic vs. nonischemic heart failure. Such reduction in the EF can manifest itself as heart failure. The 2021 European Society of Cardiology guidelines for the diagnosis and treatment of acute and chronic heart failure subdivided heart failure into three categories on the basis of LVEF:[17]

  1. normal or preserved LVEF [≥50%] (HFpEF)
  2. moderately reduced LVEF [in the range of 41–49%] (HFmrEF)
  3. reduced LVEF [≤40%] (HFrEF)]

A chronically low ejection fraction less than 30% is an important threshold in qualification for disability benefits in the US.[18]

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):[19]

EF(\%)=

SV
EDV

x 100

Where the stroke volume is given by:

SV=EDV-ESV

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.

History

William Harvey described the basic mechanism of the systemic circulation in his 1628 De motu cordis. It was initially assumed that the heart emptied completely during systole.[20] However, in 1856 Chauveau and Faivre[21] observed that some fluid remained in the heart after contraction. This was confirmed by Roy and Adami in 1888.[22] In 1906, Henderson[23] 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.[24] 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.[25] 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'.[26]

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".[27] Elliott, Lane and Gorlin used the term "ejection fraction" in a conference paper abstract published in January 1964.[28] In 1965, Bartle et al. used the term ejected fraction for the ratio SV/EDV,[29] and the term ejection fraction was used in two review articles in 1968 suggesting a wide currency by that time.[30]

Notes and References

  1. Appleton CP, Galloway JM, Gonzalez MS, Gaballa M, Basnight MA . Estimation of left ventricular filling pressures using two-dimensional and Doppler echocardiography in adult patients with cardiac disease. Additional value of analyzing left atrial size, left atrial ejection fraction and the difference in duration of pulmonary venous and mitral flow velocity at atrial contraction . Journal of the American College of Cardiology . 22 . 7 . 1972–82 . December 1993 . 8245357 . 10.1016/0735-1097(93)90787-2 . free .
  2. Sonnenblick EH . Correlation of myocardial ultrastructure and function . Circulation . 38 . 1 . 29–44 . July 1968 . 11712290 . 10.1161/01.cir.38.1.29 . free .
  3. Krishnamurthy GT, Bobba VR, Kingston E . Radionuclide ejection fraction: a technique for quantitative analysis of motor function of the human gallbladder . Gastroenterology . 80 . 3 . 482–90 . March 1981 . 7450441 . 10.1016/0016-5085(81)90009-3 .
  4. Christopoulos DG, Nicolaides AN, Szendro G, Irvine AT, Bull ML, Eastcott HH . Air-plethysmography and the effect of elastic compression on venous hemodynamics of the leg . Journal of Vascular Surgery . 5 . 1 . 148–59 . January 1987 . 3795381 . 10.1016/0741-5214(87)90205-9 . free .
  5. Cikes M, Solomon SD . Beyond ejection fraction: an integrative approach for assessment of cardiac structure and function in heart failure . European Heart Journal . 37 . 21 . 1642–50 . June 2016 . 26417058 . 10.1093/eurheartj/ehv510 . free .
  6. Ponikowski P, Voors AA, Anker SD, Bueno H, Cleland JG, Coats AJ, Falk V, González-Juanatey JR, Harjola VP, Jankowska EA, Jessup M, Linde C, Nihoyannopoulos P, Parissis JT, Pieske B, Riley JP, Rosano GM, Ruilope LM, Ruschitzka F, Rutten FH, van der Meer P . 6 . 2016 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure: The Task Force for the diagnosis and treatment of acute and chronic heart failure of the European Society of Cardiology (ESC) Developed with the special contribution of the Heart Failure Association (HFA) of the ESC . European Heart Journal . 37 . 27 . 2129–2200 . July 2016 . 27206819 . 10.1093/eurheartj/ehw128 . free .
  7. Book: William F. . Armstrong . Thomas . Ryan . Harvey . Feigenbaum . vanc . Feigenbaum's Echocardiography. 2010. Lippincott Williams & Wilkins. 978-0-7817-9557-9.
  8. Wood PW, Choy JB, Nanda NC, Becher H . Left ventricular ejection fraction and volumes: it depends on the imaging method . Echocardiography . 31 . 1 . 87–100 . 2014 . 24786629 . 4231568 . 10.1111/echo.12331 .
  9. Asferg C, Usinger L, Kristensen TS, Abdulla J . Accuracy of multi-slice computed tomography for measurement of left ventricular ejection fraction compared with cardiac magnetic resonance imaging and two-dimensional transthoracic echocardiography: a systematic review and meta-analysis . European Journal of Radiology . 81 . 5 . e757-62 . May 2012 . 22381439 . 10.1016/j.ejrad.2012.02.002 .
  10. Motwani M, Berman DS, Germano G, Slomka P . Automated Quantitative Nuclear Cardiology Methods . Cardiology Clinics . 34 . 1 . 47–57 . February 2016 . 26590779 . 4877137 . 10.1016/j.ccl.2015.08.003 .
  11. Van der Wall EE, Bax JJ . Different imaging approaches in the assessment of left ventricular dysfunction: all things equal? . European Heart Journal . 21 . 16 . 1295–7 . August 2000 . 10952821 . 10.1053/euhj.2000.2195 . free .
  12. Wackers FJ, Berger HJ, Johnstone DE, Goldman L, Reduto LA, Langou RA, Gottschalk A, Zaret BL . Multiple gated cardiac blood pool imaging for left ventricular ejection fraction: validation of the technique and assessment of variability . The American Journal of Cardiology . 43 . 6 . 1159–66 . June 1979 . 443176 . 10.1016/0002-9149(79)90148-6 .
  13. Marcu CB, Beek AM, van Rossum AC . Clinical applications of cardiovascular magnetic resonance imaging . Canadian Medical Association Journal . 175 . 8 . 911–7 . October 2006 . 17030942 . 1586078 . 10.1503/cmaj.060566 .
  14. Kenny . JE . Dec 2018. Systolic Time Intervals. . Pulmccm.org. .
  15. Book: Kumar . Vinay . Abbas . Abul K . Aster . Jon . vanc . Robbins and Cotran pathologic basis of disease . 8th . Elsevier Saunders . St. Louis, Mo . 2009 . 574 . 978-1-4160-3121-5 .
  16. Mahadevan G, Davis RC, Frenneaux MP, Hobbs FD, Lip GY, Sanderson JE, Davies MK . Left ventricular ejection fraction: are the revised cut-off points for defining systolic dysfunction sufficiently evidence based? . Heart . 94 . 4 . 426–8 . April 2008 . 18347374 . 10.1136/hrt.2007.123877 . 45337388 .
  17. McDonagh . Theresa A . Metra . Marco . Adamo . Marianna . Gardner . Roy S . Baumbach . Andreas . Böhm . Michael . Burri . Haran . Butler . Javed . Čelutkienė . Jelena . Chioncel . Ovidiu . Cleland . John G F . Coats . Andrew J S . Crespo-Leiro . Maria G . Farmakis . Dimitrios . Gilard . Martine . 2021-09-21 . 2021 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure . European Heart Journal . en . 42 . 36 . 3599–3726 . 10.1093/eurheartj/ehab368 . 34447992 . 0195-668X. free .
  18. Web site: 4.00-Cardiovascular-Adult.
  19. Book: Feigenbaum's Echocardiography. Armstrong. William F.. Ryan. Thomas . vanc . 2012-02-03. Lippincott Williams & Wilkins. 9781451147834. 126 .
  20. Bruce TA, Chapman CB . Left ventricular residual volume in the intact and denervated dog heart . Circulation Research . 17 . 5 . 379–85 . November 1965 . 5843876 . 10.1161/01.res.17.5.379 . free .
  21. Chauveau. Jean-Baptiste Auguste. Faivre. Jean . vanc . 1856 . Nouvelles recherches expérimentales sur les mouveménts et les bruits normaux du coeur envisages au point de vue la physiologie medicale . Caz. Med. De Par. . 365. 406 .
  22. Adami JG . Remarks on Failure of the Heart from Overstrain . British Medical Journal . 2 . 1459 . 1321–6 . December 1888 . 20752520 . 2198364 . 10.1136/bmj.2.1459.1321 .
  23. Henderson . Yandell . vanc . 1906. The volume curve of the ventricles of the mammalian heart, and the significance of this curve in respect to the mechanics of the heart-beat and the filling of the ventricles. . Am J Physiol. 16 . 3. 325–67. 10.1152/ajplegacy.1906.16.3.325 .
  24. Nylin. Gustav . vanc . The relation between heart volume and cardiac output per beat as a measure of cardiac activity . 1933 . Svenska Läkartidningen . 10 . 1 .
  25. Bing RJ, Heimbecker R, Falholt W . An estimation of the residual volume of blood in the right ventricle of normal and diseased human hearts in vivo . American Heart Journal . 42 . 4 . 483–502 . October 1951 . 14877744 . 10.1016/0002-8703(51)90146-9 .
  26. Holt JP . Estimation of the residual volume of the ventricle of the dog's heart by two indicator dilution technics . Circulation Research . 4 . 2 . 187–95 . March 1956 . 13293819 . 10.1161/01.res.4.2.187 . free .
  27. Folse R, Braunwald E . Determination of fraction of left ventricular volume ejected per beat and of ventricular end-diastolic and residual volumes. Experimental and clinical observations with a precordial dilution technic . Circulation . 25 . 674–85 . April 1962 . 13893859 . 10.1161/01.cir.25.4.674 . free .
  28. Elliott . William C. . Lane . Francis J. . Gorlin . Richard . January 1964 . Measurement of left ventricular volume in man by thermodilution . The American Journal of Cardiology . 13 . 1 . 106 . 10.1016/0002-9149(64)90274-7.
  29. Bartle. Stuart H.. Sanmarco. Miguel E.. Dammann . J.Francis . vanc . 5. Ejected fraction: An index of myocardial function. The American Journal of Cardiology. 15. 1. 125. 10.1016/0002-9149(65)90615-6. 1965.
  30. Krayenbühl HP, Bussmann WD, Turina M, Lüthy E . Is the ejection fraction an index of myocardial contractility? . Cardiologia . 53 . 1 . 1–10 . 1968 . 5733881 . 10.1159/000166167.

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