Download Right Ventricular Ejection Fraction Angiography

Right Ventricular Ejection Fraction
in Patients with Acute Anterior and Inferior
Myocardial Infarction Assessed by Radionuclide
Angiography
EDWARD TOBINICK, M.D., HEINRICH R. SCHELBERT, M.D., HARTMUT HENNING, M.D.,
MARTIN LEWINTER, M.D., ANDREW TAYLOR, M.D.,
WILLIAM L. ASHBURN, M.D., AND JOEL S. KARLINER, M.D.
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SUMMARY We measured right and left ventricular ejection fraction (EF) from high frequency time-activity curves obtained during
the initial passage of an intravenous bolus of 99mTc (Sn)
pyrophosphate. In 22 normal controls right ventricular EF averaged
0.52 ± 0.04 (SD). In 24 acute anterior or lateral infarction patients
right ventricular EF was normal (0.56 ± 0.10), while left ventricular
EF was reduced (0.45 ± 0.10, P < 0.001 vs controls). In 19 acute inferior infarction patients left ventricular EF also was depressed
(0.51 ± 0.09, P < 0.001 vs controls). Among 7 of 19 inferior infarc-
tion patients with right ventricular infarction by scintigraphy, right
ventricular EF was reduced (0.39 ± 0.05; P < 0.001 vs normals;
P < 0.01 vs inferior infarction patients without right ventricular involvement). In the latter group right ventricular EF averaged
0.51 ± 0.10 (NS vs normals). We conclude 1) a single injection of
19mTc (Sn) pyrophosphate can identify right and left ventricular dysfunction and infarct location in acute myocardial infarction, 2) right
ventricular EF is well-preserved except when inferior infarction involves the right ventricle.
ALTHOUGH LEFT ventricular performance has been extensively studied after acute myocardial infarction,1 there is
little information concerning right ventricular function under these circumstances.2 3 The ejection fraction is a well
accepted measure of ventricular function, but right ventricular performance has been difficult to quantitate by conventional means. This is in large part due to the complex
geometry of the right ventricle which makes calculation of
the right ventricular ejection fraction by the standard
angiographic methods extremely difficult. Therefore, we
developed a radionuclide technique for determination of
right ventricular ejection fraction that is free of assumptions regarding the three-dimensional geometry of the right
ventricular chamber. It was the purpose of this investigation
to assess the usefulness and limitations of this virtually noninvasive technique in patients with acute myocardial infarction.
Methods
at least two of the following three criteria: 1) A history of
typical prolonged chest pain; 2) electrocardiographic
changes indicative of acute myocardial infarction; and 3)
characteristic elevations of serum enzymes (CK, SGOT,
LDH).
Twenty-two patients, 11 men and 11 women, with an
average age of 45 years (range 17 to 73 years), served as a
control group to establish normal values for right ventricular
ejection fraction (table 1). All 22 patients were referred to
the Division of Nuclear Medicine for routine diagnostic
bone scans using 15 mCi of 99mTc (Sn) pyrophosphate. None
of the patients had evidence of cardiopulmonary disease as
determined by history, review of prior medical records,
physical examination, resting electrocardiogram and chest
X-ray. Informed written consent was obtained from all 65
patients participating in this study.
Infarct Localization
Radionuclide scintigraphy using 99mTc (Sn) pyrophosphate was performed in all 43 patients with acute myocardial infarction 1 to 8 days (mean 2.6 days) after the onset of
acute symptoms. The location of the acute myocardial infarction was determined from both the electrocardiogram
and the '9mTc (Sn) pyrophosphate images. Imaging was performed using a gamma scintillation camera* equipped with
a low energy, high resolution parallel hole collimator two
hours after the injection of 15 mCi of 99mTc (Sn)
pyrophosphate. Images were obtained in the anterior, 450
left anterior oblique and left lateral projections. All images
were interpreted independently by two observers without
knowledge of the clinical findings. Images were considered
positive if there was discrete myocardial uptake of 99mTc
(Sn) pyrophosphate in intensity equal to or greater than the
activity of the ribs (i.e., 2+ or greater) and if the uptake was
seen in at least two of the three projections.4
Patient Population
Forty-three patients with an acute myocardial infarction
studied. Thirty-two patients were male and 11 female,
with an average age of 63 years (range 34 to 89 years). All
patients were admitted to the Ischemic Heart Disease
SCOR Unit at the University of California Medical Center,
San Diego, with a diagnosis of acute myocardial infarction.
The diagnosis of acute myocardial infarction was based on
were
From the Divisions of Nuclear Medicine and Cardiology, University of
California, San Diego, School of Medicine and the Veterans Administration
Hospital, San Diego, California.
Supported by Specialized Center of Research on Ischemic Heart Disease,
NIH Research Grant HL-17682 awarded by the National Heart, Lung, and
Blood Institute.
The present address of Drs. Tobinick and Schelbert is UCLA School of
Medicine, Los Angeles, California; Dr. Henning's address is University of
British Columbia, Vancouver, B.C.
Address for reprints: Joel S. Karliner, M.D., University of California San
Diego Medical Center, 225 W. Dickinson Street, San Diego, California
92103.
Received June 30, 1977; revision accepted December 26, 1977.
*Pho-Gamma HP, Searle Radiographics, Inc., or Dyna Mo, Picker Corporation.
1078
1 079
RV EF IN MI/Tobinick et al.
TABLE 1. Control Group: Patients without Cardiopulmonary
Disease
Pt/Age/Sex
(yr)
1/44/M
2/28/F
3/67/F
4/72/M
5/63/F
6/35/M
7/35/F
8/43/F
9/54/M
10/17/M
11/45/M
12/56/F
13/22/F
14/45/F
15/73/M
16/51/M
17/38/F
18/25/M
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19/57/F
20/32/M
21/66/F
22/21/M
Mean 45
SD
LVEF
RVEF
LVEF/RVEF
0.69
0.53
0.63
0.56
0.56
0.49
0.70
0.55
0.60
0.56
0.68
0.52
0.54
0.53
0.62
0.58
0.58
0.51
0.58
0.48
0.56
0.56
0.56
0.46
0.53
0.52
0.64
0.60
0.56
0.53
0.56
0.44
0.68
0.55
0.52
0.44
0.73
0.53
0.56
0.46
0.62
0.52
0.58
0.48
0.60
0.52*
0.06
0.04
for difference between LVEF and RVEF.
1.30
1.13
1.14
1.27
1.07
1.31
1.02
1.07
1.14
1.21
1.00
1.22
1.02
1.17
1.06
1.27
1.24
1.18
1.38
1.22
1.19
1.21
1.17
0.10
*P <0.0001
Abbreviations: M male, F female; LVEF left ventricular ejection
fraction; RVEF = right ventricular ejection fraction; SD - standard
deviation.
=
=
Left Ventricular Ejection Fraction
Left ventricular ejection fraction was calculated from the
initial passage of `9mTc (Sn) pyrophosphate injected rapidly
as a bolus through a large median antecubital vein or
through the jugular vein. The volume of the bolus usually
was less than 1 ml but did not exceed 2 ml. The first transit
of the radioactive bolus through the central circulation was
recorded in the 300 right anterior oblique projection using
the previously described gamma scintillation cameras and
stored in an event-by-event mode (one word list mode) on a
small dedicated digital computer (Med II, General Electric
Co.). Left ventricular ejection fraction was calculated as
described previously from our laboratory.5 In brief, the im-
data were replayed, a region-of-interest assigned to the
left ventricular blood pool and a high frequency left ventricular time-activity curve was generated. After correcting
this curve for background activity, left ventricular ejection
fraction was derived from the early downslope of the left
ventricular time-activity curve using the root mean square
age
technique
as
previously described.5
Right Ventricular Ejection Fraction
Right ventricular ejection fraction was obtained from the
time-activity curves derived from the right ventricular blood
pool in a manner similar to the calculation of the left ventricular ejection fraction. The image data recorded during
the initial bolus passage through the central circulation were
replayed and the time segment during which the bolus
passed through the right ventricle was integrated to a
64 X 64 matrix point digital image (fig. 1). A region-ofinterest was precisely assigned with the light pen to the right
ventricular blood pool. Care was taken to exclude the right
atrium and the pulmonary artery from this region-ofinterest. The 300 right anterior oblique projection was found
to be most suitable because it permitted good separation
between the right ventricle, the right atrium, and the
pulmonary artery. To correct for activity originating from
noncardiac background structures a second semi-anular
region-of-interest was then assigned two matrix points away
from the anterior, apical and inferior portions of the right
ventricular wall (fig. 1). The width of this background
region-of-interest was two matrix points. High frequency
time-activity curves (25 curve points/sec) then were
generated from both the right ventricular and the background regions-of-interest. In order to correct for the
difference in size for both regions-of-interest, the
background time-activity curve was multiplied by the
following ratio: number of matrix points in the right ventricular region-of-interest/number of matrix points in the
background region-of-interest. The resulting curve was then
subtracted from the right ventricular time-activity curve and
a weighted 5 point curve-smoothing routine was applied.
This routine was employed for all right ventricular ejection fraction calculations. A typical background corrected
FIGURE 1. A) Right heart radionuclide
angiogram, obtained after integration of the image data recorded during the transit of the bolus
Of 990"Tc (Sn) pyrophosphate through the right
heart.
S
VC
=
superior
atrium; RV= right
vena
cava;
ventricle; PA
RA
right
pulmonary
artery. The two small arrows indicate the position
of the tricuspid and pulmonic valves, respectively.
B) Assignment ofregions-of-interest with the light
pen to the right ventricular cavity (R V-ROI) and
the surrounding noncardiac background (BKGR Ol).
CIRCULATION
1080
ED
260
240
EF: 0. 63
A
ED
A
180-.
.. 160
140
- 120i,>100 -
A*
A A
A
A
.
6040
28
0
A
AA*
Aft
A)
ES
A
1
A
ED
A%
e
i
ES
ES
3
2
time (sec)
A
A%
m
4
FIGURE 2. Typical right ventricular time activity curve after correction for background activity. Each curve point represents the activity during 40 msec intervals (= 25 curve-points/sec). The peaks
on the curve correspond to end diastole (ED), the valleys to end
systole (ES). In this patient, ejection fraction was derivedfrom three
beats.
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and smoothed right ventricular time-activity curve is shown
in figure 2. Each point on the curve represents the number of
counts during a 40 msec period (25 curve points/sec). The
curve is characterized by cyclic fluctuations with each peak
corresponding to end diastole and each valley to end systole.
Right ventricular ejection fraction was then calculated by
dividing the difference in counts between end diastole and
end systole (a value proportional to stroke volume) by the
number of counts at end diastole (a value proportional to
end-diastolic volume). For the calculation only beats from
the early downslope of the right ventricular time-activity
curve were used. Beats with low activity or contaminated by
activity arising from the lung were excluded from analysis.
In general, three or four cardiac cycles were used for deriving the ejection fraction. In five patients, ejection fraction
was calculated from only two beats. In each patient, the
values obtained from the beats analyzed were then averaged.
To determine the effects of activity originating from other
cardiac structures on the right ventricular time-activity
curve and to establish the most easily reproducible background region-of-interest, additional regions-of-interest
were assigned to the right atrium, the tricuspid valve plane,
the pulmonary artery and the area surrounding the entire
right ventricle in six patients. The curves obtained from
these additional regions-of-interest were normalized with
respect to the size of the right ventricular region-of-interest.
However, the activity of these normalized curves exceeded
that obtained from the right ventricle and indicated that the
activity sampled from these regions-of-interest did not
represent background counts. Therefore, the background
region-of-interest found to be most suitable was the
semi-anular ring, described above, that surrounds the free
portion of the right ventricular chamber..
Unlike recordings obtained with multicrystal cameras,
peak end-diastolic right ventricular count rates averaged
only 250 counts/40 msec curve point. These relatively low
count rates raise concern about the statistical reliability of
ejection fraction calculations obtained from first pass timeactivity curves recorded with the standard single crystal
gamma camera. In a previous report from our laboratory
the statistical uncertainty of left ventricular ejection fraction calculations was considerably improved by employing
the root mean square technique.5 This approach determines
the root mean square of the deviations of the raw data curve
VOL 57, No 6, JUNE 1978
points from an "average" curve obtained by applying a 14
point weighted curve-smoothing procedure to the raw data
curve. However, because of the very rapid upstroke and
sharp peak of the right ventricular time-activity curve, the
14 point curve-smoothing procedure did not provide
satisfactory average curves and the root mean square approach often resulted in erroneous right ventricular ejection
fractions (e.g., values > 1.00).
For this reason, and in view of higher right ventricular
count rates, right ventricular ejection fraction was calculated
from the end-diastolic and end-systolic curve points only. As
mentioned earlier, peak right ventricular count rates
averaged 250 counts/40 msec curve point. As shown in the
appendix, the standard deviation for an ejection fraction of
0.52 calculated from a typical right ventricular time-activity
curve is equal to approximately 0.036. The standard deviation of the calculation was reduced further to approximately
0.02 by applying a weighted 5 point-smoothing to the right
ventricular time-activity curve. The relatively high degree of
statistical certainty appears substantiated by the
reproducibility of the technique in the patients with repeat
studies.
While the curve-smoothing procedure improves the
statistical reliability of the calculation, it consistently
reduces right ventricular ejection fraction. Thus, in 14
patients with heart rates ranging from 56 to 89 beats/min,
ejection fractions derived from smoothed time activity
curves were 8.9% ± 1.7 (SE) lower than those obtained
directly from the raw data curves. This raises the question as
to whether right ventricular ejection fraction can be compared to left ventricular ejection fraction. Therefore, left
ventricular ejection fractions were determined in the same
14 patients by three different approaches: the root mean
square technique; directly from the end-diastolic and endsystolic curve points of the unmodified, raw data timeactivity curve; and lastly, from the smoothed time-activity
curve. Compared to ejection fraction values obtained from
the raw data curves, left ventricular fraction values derived
by the root mean square technique were 14.3% ± 1.9 (SE)
lower and ejection fractions derived from the smoothed
curves were 11.3% ± 2.0 (SE) lower. Ejection fractions
derived from the smoothed curves did not differ significantly
from those calculated by the root mean square technique.
Because the reduction in the values of left ventricular ejection fraction introduced by the root mean square technique
is similar in magnitude to that resulting from smoothing the
right ventricular time-activity curve, the ratio between left
and right ventricular ejection fraction remains unaffected.
Moreover, the consistently lower values for right compared
with left ventricular ejection fraction observed in this study
agree well with the findings by Berger et al.6 in 20 normal
subjects in whom left ventricular ejection fraction averaged
0.70 ± 0.01 (SE) and right ventricular ejection fraction
0.54 ± 0.02.
All data were analyzed using Student's t-test for paired
and unpaired data.
Results
Control Group
In the 22 patients without evidence of cardiopulmonary
disease right ventricular ejection fraction ranged from 0.44
1081
RV EF IN MI/Tobinick et al.
to 0.60 with a mean of 0.52 ± 0.04 (SD) (table 1). Left ventricular ejection fraction in these 22 patients ranged from
0.52 to 0.73 with a mean of 0.60 ± 0.06. Thus right ventricular ejection fraction was moderately but significantly
lower (P < 0.001). The mean ratio of left-to-right ventricular ejection fraction was 1.17 + 0.10 (range 1.00 to
1.38). None of these 22 patients showed abnormal myocardial activity on the subsequently recorded '9mTc (Sn) pyrophosphate images.
Reproducibility of the Method
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To evaluate the reproducibility of our method, six patients
with ischemic heart disease who had normal right ventricular ejection fractions were injected twice with 8 mCi of
99mTc DTPA* within a 30 min time interval without changing position. Because of the smaller amount of activity
injected the gamma camera was equipped with a high
sensitivity low energy parallel hole collimator. Right ventricular ejection fraction averaged 0.55 ± 0.05 for the first
measurement; the average value for the second measurement was identical. The variation between the first and second study was small and averaged only 3.4%. It should be
emphasized, however, that the close agreement between two
subsequent studies in the same patient was heavily dependent on the correction of the right ventricular time-activity
curves for activity originating from noncardiac background
structures. For the first measurement the effect of
background correction on the right ventricular ejection fraction was small, i.e., correcting for background activity
resulted in values for ejection fraction that were higher by an
average of 4.8% (range 1.9 to 9.3%). However, analysis of
sequential studies revealed that ejection fractions were lower
by an average of 10.7% (range 2.3 to 22.6%) in the second
study when no background correction was employed.
To evaluate interobserver variation, studies from nine of
the patients were processed independently by two investigators. Calculated right ventricular ejection fraction
displayed close agreement with a mean difference of 2.7%.
Acute Anterior or Anterolateral Wall Myocardial Infarction
In the 24 patients with anterior or lateral myocardial infarctions, left ventricular ejection fraction averaged
0.45 ± 0.10 (range 0.31 to 0.66) and was lower than in the
normal control group (P < 0.001, [table 2]). The average
right ventricular ejection fraction was 0.56 ± 0.10 (range
0.32 to 0.80) and did not differ significantly from that found
in the control group. The ratio of left-to-right ventricular
ejection fraction was 0.83 ± 0.17, a value that was decreased
when compared to control values (P < 0.001).
Acute Inferior Myocardial Infarction
Nineteen patients had an acute inferior myocardial infarction. Left ventricular ejection fraction in these patients
averaged 0.51 ± 0.09 and was reduced compared with control values (P < 0.001) (table 3). Right ventricular ejection
fraction averaged 0.47 ± 0.10 and was lower than in the normal group (P < 0.03), and in the group with anterior or
anterolateral infarction (P < 0.005). This difference was due
*Diethylene triamine penta
acetate
TABLE 2. Patients with Acute Anterior or Lateral Myocardial
Infarction
Pt/Age/Sex
(yr)
Time*
(Days)
LVEF
RVEF
LVEF/RVEF
1/69/F
2/52/F
3/81/M
4/58/M
5/68/M
6/55/M
7/78/M
3
2
3
2
1
2
3
2
3
2
2
8
1
2
1
2
8
4
2
5
4
2
3
5
3
0.61
0.33
0.52
0.44
0.44
0.34
0.37
0.37
0.50
0.43
0.46
0.59
0.38
0.31
0.66
0.53
0.45
0.66
0.42
0.60
0.62
0.64
0.80
0.54
0.41
0.68
0.62
0.92
8/65/M
9/76/M
10/64/M
11/70/F
12/48/M
13/46/M
14/56/M
15/53/F
16/59/F
17/75/M
18/64/M
19/60/M
20/58/M
21/64/M
22/63/M
23/85/M
24/41/M
Mean 63
SD
0.55
0.40
0.56
0.44
0.45
0.31
0.45
0.45
0.10
(P <0.001)
0.47
0.58
0.46
0.32
0.56
0.54
0.46
0.56
0.58
0.64
0.50
0.56
0.60
0.53
0.56
0.79
0.87
0.71
0.69
0.42
0.69
0.90
0.74
0.69
0.98
1.02
0.83
0.97
0.10
1.18
0.98
0.98
0.98
0.69
0.88
0.88
0.80
0.52
0.85
0.83
0.17
(NS)
(P <0.001)
*Time from onset of acute symptoms.
For abbreviations see table 1.
The P values indicate the difference from the control group (table 1).
NS = not significant.
SD = standard deviation.
largely to the patients with right ventricular involvement
(see below). The ratio of left-to-right ventricular ejection
fraction averaged 1.12 + 0.23, a value that was not
significantly different from the normal group.
Right Ventricular Infarction
Utilizing the 99mTc (Sn) pyrophosphate images, patients
with inferior wall myocardial infarction were divided into
two groups with respect to right ventricular involvement: ten
patients exhibited no right ventricular involvement on the
99mTc (Sn) pyrophosphate images (group 1), but in seven
patients an additional region of increased ssmTc (Sn)
pyrophosphate uptake was noted indicating right ventricular
involvement (group 2). As shown in figure 3, this additional
region of abnormal 99mTc (Sn) pyrophosphate uptake was
usually noted best in the 450 left anterior oblique projection
and appeared as an area of activity anterior and to the right
of the left ventricular uptake and adjacent to and in line with
the inferior wall of the left ventricle.7 One of the 19 patients
with acute inferior myocardial infarction by electrocardiography had a negative 99mTc (Sn) pyrophosphate image and in
a second patient with an inferior myocardial infarction by
electrocardiogram the inferior wall pyrophosphate activity
could not be localized to either ventricular chamber.
Mean left ventricular ejection fraction was 0.50 + 0.10 in
group 1 and 0.50 + 0.06 in group 2. These values were
depressed compared to the normal group (P < 0.001). Right
ventricular ejection fraction averaged 0.51 ± 0.10 (NS vs
normals) in group 1 but was only 0.39 ± 0.05 in group 2
(P < 0.001 vs normals; P < 0.01 vs group 1).
CIRCULATION
1082
TABLE 3. Patients with Acute Inferior Myocardial Infarction
Pt/Age/Sex
(yr)
Time*
(Days)
RVEF
LVEF
Group I. Left Ventricular Infarction
1
0.52
1/75/F
1
0.39
2/56/M
1
0.54
3/89/F
2
0.67
4/53/F
2
0.38
5/53/F
3
0.57
6/69/M
1
0.53
7/34/M
1
0.46
8/65/M
5
0.57
9/48/M
5
0.33
10/76/F
2.2
0.50
Mean 62
0.10
SD
(P <0.001)
LVEF/RVEF
Only by Scintigraphy
0.58
0.90
0.45
0.87
0.56
0.64
0.32
0.52
0.58
0.40
0.54
0.48
0.51
0.10
0.96
1.05
1.19
1.10
0.91
1.15
1.06
0.69
0.99
0.15
(NS)
(P <0.001)
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Group 2. Left and Right Ventricular Infarction by Scintigraphy
2
0.41
0.46
1/60/M
0.89
1
0.41
2/57/M
0.52
1.27
2
1.41
0.34
3/74/M
0.48
2
0.45
1.18
4/73/M
0.53
3
1.37
0.38
5/53/M
0.52
2
0.34
1.70
6/80/M
0.58
3
0.43
0.36
1.19
7/73/M
Mean 67
2.1
1.29
0.50
0.39
SD
0.06
0.05
0.25
(NS)
(P <0.001) (P <0.001)
Scintigraphy Negative or Ventricular Localization Not Possible
1
1/42/M
0.62
0.59
1.05
2
1.32
2/59/F
0.58
0.44
All Patients (N 19)
Mean 63
SD
2.1
0.47
0.10
0.23
(P <0.03)
(NS)
0.51
0.09
(P <0.001)
1.12
*Time from onset of acute symptoms.
The P values indicate the difference from the normal control patients
(table 1).
Abbreviations same as table 1.
Discussion
Technical and Statistical Considerations
Left ventricular ejection fraction determined from high
frequency time-activity curves recorded during the initial
transit of a radioactive bolus through the heart has been
shown to correlate closely with the left ventricular ejection
fraction determined from single or biplane cineventriculograms using the area-length method." 89 9
First pass radionuclide angiocardiography has an important advantage over other methods for measuring ejection
fraction: it does not require approximation of the ventricular
chamber by a three-dimensional geometrical model, as is
necessary when ejection fraction is derived from single or
biplane contrast angiography, ECG gated cardiac blood
pool images, or echocardiography. Thus, first pass
radionuclide angiography is more accurate than echocardiography in measuring left ventricular ejection fraction in
patients with wall motion abnormalities, in whom the
geometrical model does not closely approximate the shape
of the left ventricular cavity.10
Because first pass radionuclide angiocardiography does
not depend on variations in ventricular geometry, it is particularly suitable for measuring right ventricular ejection
VOL 57, No 6, JUNE 1978
fraction. Moreover, count rates obtained from the right ventricle are two to three times higher than those obtained from
the left ventricle because the radioactive bolus is still rather
well confined during its passage through the right ventricle
and because of the greater proximity between the right ventricle and the collimator in the right anterior oblique projection.
Correction of the right ventricular time-activity curves for
background activity affected right ventricular ejection fraction by less than 5% because little activity has reached the
lungs when count rates are highest in the right ventricle.
Therefore, right ventricular ejection fraction could be determined without background correction. However, for serial
measurements of ejection fraction, e.g., to evaluate the
effects of interventions on right ventricular performance,
residual activity may cause an upward shift of the right ventricular time-activity curve and result in lower ejection fraction values. In this study, almost identical values for ejection
fraction measurements performed within less than 30
minutes were obtained only after correcting the right ventricular time-activity curves for background activity.
Calculation of right and left ventricular ejection fraction
from a recording of the initial bolus passage through the
central circulation is based on temporal separation of the
right from the left ventricular activity. Due to superimposition of the left and right ventricle in the right anterior
oblique projection, delayed clearance of activity from the
right ventricle, such as may occur when right ventricular
function is depressed, may interfere with accurate measurement of left ventricular fraction. However, even in the seven
patients with evidence of right ventricular infarction, right
and left ventricular activity were sufficiently separated in
time to permit assessment of left ventricular ejection fraction.
Right Ventricular Volumes and Ejection Fraction in Normal
Subjects
There are few studies of right ventricular volumes in normal subjects. Calculation of right ventricular volumes and
ejection fraction from biplane cineangiograms in these
studies was based on approximating the shape of the right
ventricular cavity by various geometric models, e.g., elliptical or rectangular cross-sections or a prism with triangular
base."-"3 Mean right ventricular ejection fraction reported in
these studies ranged from 0.51 to 0.66. This wide range may
be largely due to differences in determining right ventricular
volumes and patient selection.
Steele and co-workers'4 initially introduced first pass
radionuclide angiocardiography to determine right ventricular function. In 14 patients without coronary artery disease, they observed a mean right ventricular ejection fraction of 0.57, with a range of 0.51 to 0.64. The lower average
value for right ventricular ejection fraction for the 22 patients without evidence of cardiopulmonary disease in our
study may be related to differences in data analysis although
it is very similar to the value of 0.54 recently reported by
Berger et al.6 The same authors reported the ejection fraction to be higher for the left than for the right ventricle (leftto-right ratio of 1.30) which is consistent with our findings
(average ratio of left-to-right ventricular ejection fraction of
1.17).
1083
RV EF IN MI/Tobinick et alt
FIGURE 3. Typical "tmTc (Sn) pyrophosphate
images in two patients with acute inferior myocardial infarction. The patient shown in the upper
panel displays involvement of the left ventricle
only, whereas the patient shown in the lower panel
shows involvement of the inferior wall of the left
ventricle and the right ventricular free wall, as indicated by the arrows.
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Right and Left Ventricular Ejection Fraction in Acute
Myocardial Infarction
There are no previously published studies of right ventricular ejection fraction in acute myocardial infarction.
Although isolated right ventricular infarction has been
reported to occur in only 2.5 to 4.6% of patients,'5 1" the incidence of concurrent right and left ventricular infarction
has been reported to be as high as 43%.17
As expected, the average left ventricular ejection fraction
in our patients with acute myocardial infarction was
reduced. Right ventricular ejection fraction, however, was
relatively well preserved in patients with anterior or lateral
infarction, as reflected by both a normal mean right ventricular ejection fraction and a significantly decreased ratio
of left-to-right ventricular ejection fraction. The absence of
right ventricular functional depression in the presence of
anterior or lateral left ventricular functional impairment is
supported by the data of Rigo et al.,'8 who reported a mean
right to left ventricular area of 0.75 in 13 patients with acute
anterior infarction. However, it should be pointed out that
three patients with acute anterior or lateral myocardial infarction had a reduced value for both right and left ventricular ejection fraction (table 2). All three patients had
clinical evidence for congestive cardiac failure during the
course of their acute myocardial infarction and required
digitalis and diuretics as part of their management. Two of
these patients have subsequently died of an ischemic cardiomyopathy.
Right ventricular ejection fraction was not well preserved
in our patients with inferior infarction and right ventricular
free wall involvement, however. In contrast to the patients
with anterior or lateral infarcts, none of whom had involvement of the right ventricular free wall, seven of 19 patients
(37%) with inferior infarction had evidence of right ventricular free wall involvement as visualized by 9smTc (Sn)
pyrophosphate imaging. Identification of right ventricular
infarction by "9mTc (Sn) pyrophosphate has been previously
reported by Sharpe et al.,7 who also found a 35% incidence
of right ventricular infarction in 14 consecutive patients with
acute inferior myocardial infarction. Separation of patients
with acute myocardial infarction confined only to the inferior wall of the left ventricle from those with additional involvement of the right ventricle was supported further by
measurements of reduced right ventricular performance.
Thus, right ventricular ejection fraction was significantly
depressed in patients with right ventricular infarction when
compared with the normal group. In contrast, right ventricular ejection fraction was normal in patients with inferior
infarction not involving the right ventricle.
In our patients a reduction in preload due to volume
depletion cannot be ruled out entirely as a possible reason
for the biventricular reduction in ejection fraction in the
patients with both left and right ventricular infarctions.
Nevertheless, it is of interest that two of the seven patients
with a depressed right ventricular ejection fraction exhibited
clinical signs consistent with right ventricular dysfunction;
both patients had an elevated jugular venous pressure on
physical examination and in one patient direct measurement
of the right atrial pressure revealed a mean value of 10 mm
Hg. Our observations and those of others7' 17 indicate that
right ventricular infarction is more common than previously
suspected, but the resulting depression in right ventricular
performance only rarely leads to clinical signs of right ventricular failure.
Acknowledgments
We are grateful to Ms. Sue Swanson for technical assistance, to Mrs.
Elizabeth Gilpin for statistical advice, and to Mrs. Marianne Lindley, Mrs.
Sandra Edmonds, and Mrs. Rosemary Montoya for secretarial assistance.
The authors also wish to thank Henry Hluang, Ph.D., for his assistance in
preparing the appendix.
Appendix
The statistical uncertainty of the right ventricular ejection fraction
calculated directly from the end-diastolic and end-systolic curve points can be
estimated by the following equations:
SD(EF)2 t ES2 [SD(ED)2
ED2
Where SD
=
ED
+
SD(ES']
ES2
standard deviation; ED
=
(1)
J
counts at end-diastole; ES
=
counts
end-systole; EF = ejection fraction. Assuming the statistics follow
Poisson's distribution, equation (1) becomes:
at
CIRCULATION
1084
I
ES2 (
)
(2)
SD(EF)I
Using several cardiac beats for calculating the ejection fraction SD(EF)
becomes:
SD(EF) = .V/SD(EF) I+ SD(EF)1 ..... SD(EF)2
(3)
Employing a weighted five point curve smoothing,* the SD(EF) is estimated
to be further reduced by-~1/2; for example:
SD(EF)
SD (EF,)
(4)
The statistical uncertainty of the calculated ejection fraction from a typical
right ventricular ejection fraction and using three cardiac cycles is derived:
End-diastolic and end-systolic counts for the first beat are 250 and 120, for
the second beat 185 and 89; and for the third beat 150 and 72. The average
ejection fraction is 0.52. Using equation (2), the standard deviation of the
calculation for the first beat is 0.05, for the second beat is 0.06 and for the
third beat is 0.07. The standard deviation for the ejection fraction averaged
for all three beats is 0.036 (equation 3). According to equation (4) the
weighted five point curve smoothing reduces the standard deviation further to
about 0.02.
*Howell PG: Introduction to Mathematical Statistics. John Wiley and
Sons, Inc. New York, 1977.
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Right ventricular ejection fraction in patients with acute anterior and inferior myocardial
infarction assessed by radionuclide angiography.
E Tobinick, H R Schelbert, H Henning, M LeWinter, A Taylor, W L Ashburn and J S Karliner
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Circulation. 1978;57:1078-1084
doi: 10.1161/01.CIR.57.6.1078
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