Left Ventricular Ejection Fraction
Calculated from Volumes and Areas:
Underestimation by Area Method
JUDITH A. WISNESKI, M.D., CATHERINE N. PFEIL, M.S., D. GEORGE WYSE, PH.D., M.D.,
RICHARD MITCHELL, PH.D., SHAHBUDIN H. RAHIMTOOLA, M.D.,
AND EDWARD W. GERTZ, M.D.
SUMMARY The ejection fraction is one of the most widely used measurements of left ventricular systolic
function. Angiographic measurement of ejection fraction is based on determination of roentgenographic
magnification and calculation of end-diastolic and end-systolic volumes, assuming a prolated ellipse. Because it
is simple and radiographic magnification may not have been determined, some laboratories have obtained an
"ejection fraction" by comparison of end-diastolic and end-systolic areas. A comparison of the two methods
was made using ventriculograms of 538 patients from three cardiac catheterization laboratories. The area
method of ejection fraction calculation consistently underestimates ejection fraction from left ventricular
volumes. A regression equation was derived that allows adjustment of the ejection fraction obtained from areas
to that from volumes.
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LEFT VENTRICULAR FUNCTION has been
assessed by many methods.'-5 In the clinical setting,
ejection fraction has been shown to be one of the most
useful.6'- For example, it is related to prognosis as well
as operative risk in patients with coronary artery disease and in those with other forms of heart disease.' 1-5
The angiographic technique for determination of
left ventricular ejection fraction is based on the actual
calculation of end-diastolic and end-systolic volumes,
using the area-length method of Dodge and associates.'6' 17 These calculations require precise measurements of the distances between the left ventricle, the
x-ray tube and image intensifier, and then filming a
calibration grid at the level of the left ventricle.'8
Some laboratories omit this measurement of the
roentgenographic magnification and report an "ejection fraction" based solely on comparison of enddiastolic and end-systolic silhouette areas. Studies
have appeared without a description of the method for
the determination of ejection fraction.'121 We compared the two techniques of calculating ejection fraction and present a regression curve that allows an accurate and simple determination of ejection fraction
without having to take roentgenographic magnification and volume calculation into account.
Methods
Thirty-degree right anterior oblique (RAO) left
ventriculograms of 538 cases from three cardiac
catheterization laboratories were reviewed. Patients
with coronary artery disease, valvular disease, cardiomyopathies and congenital heart disease were included. The end-diastolic and end-systolic silhouettes
were hand-traced.
Volume Method
Assuming the ventricle to be ellipsoid, the volume
of each silhouette was derived using the formulas of
Dodge and associates.'6-8 Long-axis length (L) was
measured from the mid-aortic root to the apex. Area
(A) was measured by planimetry and minor axis (D)
was calculated as
4A
irL
The volumes (V) were then calculated by
V = 66 (D)2 (L) .
A grid calibration was used to correct for magnification in the measurements. These volumes were then
corrected using the regression equation for RAO
cineangiogram of Kennedy and associates22:
V, = 0.81 V + 1.9
Using the final corrected volumes for end-diastole and
end-systole, the ejection fraction was calculated as
end-diastolic volume - end-systolic volume 100
end-diastolic volume
From the Departments of Medicine, University of California,
San Francisco, and the Veterans Administration Medical Center,
San Francisco, California, and the University of Oregon Health
Sciences Center, Portland, Oregon.
This work was performed during Dr. Wisneski's tenure as a
Research Fellow of the San Francisco Bay Area Heart Association
(Clarence G. Smith Fellowship) and Dr. Wyse's tenure as a Fellow
of the Canadian Heart Foundation.
Supported in part by the Medical Research Service of the
Veterans Administration.
Address for correspondence: Judith A. Wisneski, M.D., Veterans
Administration Medical Center (11 lCl), 4150 Clement Street, San
Francisco, California 94121.
Received March 7, 1980; revision accepted May 23, 1980.
Circulation 63, No. 1, 1981.
Area Method
The areas of the end-diastolic and end-systolic
silhouettes measured by planimetry were used to
calculate an ejection fraction as
end-diastolic area - end-systolic area X 100
149
end-diastolic area
CIRCULATION
150
Statistical Analysis
A nonlinear least-squares regression analysis was
performed on the ejection fractions derived from the
corrected volumes and the ejection fractions
calculated by areas.
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Results
Among the 538 left ventriculograms, the enddiastolic volumes were 68-660 ml. The ejection fractions determined by the actual volumes using the arealength method of Dodge et al."6, 17 ranged from 8-94%.
The correlation between ejection fraction determined
by volumes and the ejection fraction by the area
method is shown in figure 1. The correlation
coefficient by linear regression analysis was 0.98
(p < 0.005). The relationship between the two
methods is best represented by a curvilinear regression
line (fig. 1). This line is represented by the equation
EFv = -0.006 (EFa)2 + 1.656 EFa + 1.351.
The area method consistently underestimates the
ejection fraction as determined by volumes by approximately 15%. For example, if the ejection fraction
calculated by comparing the areas of the end-diastolic
and end-systolic silhouettes is 30%, the ejection fraction by the volume method is 45% (fig. 2).
Having determined the areas of the end-diastolic
and end-systolic silhouettes, an ejection fraction can
be calculated. Using the nomogram in figure 2, this
ejection fraction can be quickly and accurately converted to that obtained from volumes.
VOL 63, No 1, JANUARY 1981
100
Zc
HrI
80'
01
B0'
1->z:
z
Z
_
40
C) >
W0>-
lLiim
LctJ
20'
.30.0
0
20
40
i
60
80
i.
100
EJECTION FRACTION
BY AREA METHOD
2.
FIGURE
Curvilinear regression line as shown in figure 1
without data points.
Discussion
Left ventricular function is an important prognostic
factor in the natural history of cardiac disease and the
assessment of operative risks.10-15 Many measurements, such as Vmax, dP/dt, and Vce, have been used
to quantitate the systolic function of the left ventricle.2''3Clinically, ejection fraction has been shown to
be one of the most useful indexes of left ventricular
function.6'-5
Exact measurements of the image intensifier and
x-ray tube in relation to the left ventricle are required
to determine true volumes.'8 This step is exacting,
time-consuming and often only left ventriculograms
without grid calibration are available. This has led
some laboratories to simply use end-diastolic and endsystolic silhouette areas for calculation of ejection
fraction.
In addition to the method presented in this paper,
an ejection fraction can be determined from the equa-
Z Cx
0
E1
ow
tion
01_
H0
EF
-
WL>m
0
0
_________________________________
20
40
80
80
100
EJECTION FRACTION
BY AREA METHOD
FIGURE 1. Correlation of ejection fraction by volume
method of E)odge et al.6"18 and the ejection fraction by area
method. n = 538, Y = -0.006 X' + 1.656 X + 1.351.
Estimates ojf standard errors of the coefficients are 0.0004,
0.037 and 0. .719, respectively,
=
-_ (end-systolic area2
(diastolic length)
(end-diastolic area2) (systolic length) '
which can be derived from the area-length method of
Dodge. This ejection fraction is equivalent to that obtained by actual volumes and a magnification factor is
not required. The advantage of the method presented
in our paper is that an ejection fraction can be obtained quickly from the end-diastolic and end-systolic
areas alone using the nomogram in figure 2.
This study illustrates that the area technique
provides misleading information if it is compared to
standard values in the literature. In addition, the
relationship of ejection fractions determined by areas
of end-diastole and end-systole to those determined by
actual "true" volumes is demonstrated. We have
shown that ejection fractions determined by areas
EF BY VOLUME AND AREA METHODS/Wisneski et al.
alone are consistently lower than those calculated
using volumes. Calculation of the ejection fraction by
areas alone could lead to serious underestimation of
left ventricular systolic function, particularly in
patients with reduced ejection fraction; e.g., if the ejection fraction by the area method is 20% the ejection
fraction by the volume method would be 33%.
A reasonably good linear correlation (r = 0.98) exists between the ejection fraction by volume method
and that by the area method over the 20-60% range.
This can be improved by using the curvilinear regression line (fig. 2). Having determined the areas of the
end-diastolic and end-systolic silhouettes, the ejection
fraction by "true" volumes can be accurately and
quickly determined using the nomogram in figure 2.
Thus, comparison to prognostic data in the literature
dealing with left ventricular systolic function can be
easily made without determining roentgenographic
magnification for volume calculations.
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Acknowledgment
appreciation to Gunnard Modin, B.S., for his
analysis and to Helen Smeeton for her
secretarial assistance.
We
express our
assistance in the statistical
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-
Left ventricular ejection fraction calculated from volumes and areas: underestimation by
area method.
J A Wisneski, C N Pfeil, D G Wyse, R Mitchell, S H Rahimtoola and E W Gertz
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Circulation. 1981;63:149-151
doi: 10.1161/01.CIR.63.1.149
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