Download Right Ventricular Ejection Fraction During Exercise in Normal

Right Ventricular Ejection Fraction During Exercise
in Normal Subjects and in Coronary Artery Disease
Patients: Assessment by Multiple-gated
Equilibrium Scintigraphy
JAMSHID MADDAHI, M.D., DANIEL S. BERMAN, M.D., DALE T. MATSUOKA,
ALAN D. WAXMAN, M.D., JAMES S. FORRESTER, M.D., AND H. J. C. SWAN, M.D., PH.D.
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SUMMARY The response of right ventricular ejection fraction (RVEF) during exercise and its relationship
to the location and extent of coronary artery disease are not fully understood. We have recently developed and
validated a new method for scintigraphic evaluation of RVEF using rapid multiple-gated equilibrium scintigraphy and multiple right ventricular regions of interest. The technique has been applied during upright bicycle exercise in 10 normal subjects and 20 patients with coronary artery disease. Resting RVEF was not
significantly different between the groups (0.49 ± 0.04 vs 0.47 ± 0.09, respectively, mean ± SD). In all 10 normal subjects RVEF rose (0.49 ± 0.04 to 0.66 ± 0.08, p < 0.01) at peak exercise. At peak exercise in coronary artery disease patients, the group RVEF remained unchanged (0.47 ± 0.09 to 0.50 + 0.11, p = NS),
but the individual responses varied. In the coronary artery disease patients, the relationship between RVEF
response to exercise and exercise left ventricular function, septal motion and right coronary artery stenosis
were studied. Significant statistical association was found only between exercise RVEF and right coronary
artery stenosis. RVEF rose during exercise in seven of seven patients without right coronary artery stenosis
(0.42 ± 0.06 to 0.58 ± 0.08, p = 0.001) and was unchanged or fell in 12 of 13 patients with right coronary
artery stenosis (0.50 + 0.09 to 0.45 i 0.10, p = NS). We conclude that (1) in normal subjects RVEF increases during upright exercise and (2) although RVEF at rest is not necessarily affected by coronary artery
disease, failure of RVEF to increase during exercise, in the absence of chronic obstructive pulmonary disease
or valvular heart disease, may be related to the presence of significant right coronary artery stenosis. The
possibility that severe left ventricular dysfunction in the absence of proximal right coronary artery obstruction
may cause abnormal RVEF response to stress requires further evaluation in a larger, more varied patient population.
rapid method well-suited to the evaluation of RVEF
during multiple stages of graded exercise.
Using the new approach to multiple-gated equilibrium cardiac blood pool scintigraphy for measurement of RVEF, our results10 supported those reported
by other investigators", 12 that RVEF at rest is not a
sensitive indicator of the presence of coronary artery
disease (CAD) and bears no relationship to the degree
of right coronary artery narrowing.
As with the left ventricle, functional abnormalities
of the right ventricle may be seen under circumstances
of physiologic stress. Therefore, the evaluation of
RVEF during stress may provide a sensitive indicator
for right ventricular myocardial functional reserve.
In the present study we evaluated (1) the normal
response of RVEF to stress, (2) abnormal right ventricular function during exercise as related to the
presence of CAD, and (3) the relationship between
RVEF response to stress and exercise left ventricular
function, septal motion during exercise, and the
presence of right coronary artery stenosis.
THE MEASUREMENT of left ventricular ejection
fraction (LVEF) by equilibrium scintigraphy was
recently validated'-3 and applied to the evaluation of
left ventricular function during stress.46 However,
only preliminary reports have been made of right ventricular ejection fraction (RVEF) during exercise and
its relationship to coronary anatomy.79
We recently developed a new method of analysis
using multiple-gated equilibrium cardiac blood pool
scintigraphy to measure RVEF, using the same scintigrams that are routinely obtained for assessment of
left ventricular function.10 This multiple-gated
equilibrium scintigraphic technique for determination
of RVEF demonstrated a high correlation with estimates of RVEF made by first-pass scintigraphy and
was associated with minimal inter- and intraobserver
variations.10 These findings, therefore, defined a new,
From the Division of Cardiology, Department of Medicine,
and the Department of Nuclear Medicine, Cedars-Sinai Medical
Center, and the Departments of Medicine and Radiology, UCLA
School of Medicine, Los Angeles, California.
Supported in part by SCOR grant HL 17651, NIH, and research
grants from California chapters of the American Heart Association.
Presented in part at the 51st Annual Scientific Sessions of the
American Heart Association, Dallas, Texas, November 14, 1978.
Address for correspondence: Publications Office, Division of Cardiology, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Los
Angeles, California 90048.
Received July 27, 1979; revision accepted January 5, 1980.
Circulation 62, No. 1, 1980.
Materials and Methods
Patients
Multiple-gated cardiac blood pool scintigraphic
studies for evaluation of RVEF were performed on 30
subjects. Of 10 subjects (eight males and two females)
with mean age of 36 years (range 23-66 years), two
had normal coronary arteriograms and the other eight
133
134
CIRCULATION
normal volunteers (normal group). These
volunteers were considered normal by having all of the
following: (1) no symptoms of cardiopulmonary disease; (2) a normal physical examination; (3) a normal
exercise ECG; and (4) no smoking history. Twenty
patients (19 males and one female) with mean age of
56 years (range 39-75 years) had angiographically
proved CAD. The mean interval between coronary
angiography and exercise testing was 19 days (range
1-99 days). A diameter luminal narrowing of > 75%
of the normal portion of the vessel was considered
significant coronary artery stenosis. Of the 20 CAD
patients, five had one-vessel disease, eight had twovessel disease and seven had three-vessel disease. All
20 patients had significant left anterior descending or
left circumflex stenosis or both. Thirteen patients had
significant right coronary artery stenosis and seven
had normal right coronary arteries. The location of
narrowing in all patients with right coronary artery
stenosis was proximal. The stenosis was proximal to
the right ventricular branch in 10 and distal to the
were
VOL
62, No 1, JULY 1980
right ventricular branch but proximal to the acute
marginal branch in the remaining three. The results of
coronary arteriography in each subject are included in
table 1. Patients who were receiving propranolol discontinued its use at least 48 hours before exercise testing. Patients with a history and/or clinical findings of
pulmonary disease or with a documented prior myocardial infarction were not included in the study.
Specifically, no patient had history of more than 10
pack-years of smoking and no patient had a
pathologic Q wave on resting ECG. Only one patient
had segmental akinesis or dyskinesis on left ventricular contrast ventriculography. This patient, who
had apical dyskinesis, unassociated with pathologic Q
waves, had normal apical wall motion after subsequent aortocoronary bypass surgery.
Radionuclide Data Acquisition
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The multiple-gated equilibrium cardiac blood pool
scintigraphic technique involved serial 2-minute
TABLE 1. Response of Heart Rate, Right Ventricular Ejection Fraction, Left Ventricular Ejection Fractzon, and Septal Motion to
Maximum Exercise and Angiographic Findings in Coronary Artery Disease Patients
Abn ex response
Heart rate
RVEF
Angiographic CAD
(beats/min)
Septal
(>75%70 stenosis)
(Abn ex
(%)
Max ex
Rest
Max ex response) LVEF
motion
Rest
LAD
Case
LCX
RCA
1
130
98
0.57
0.46
+
(+)
+
+
+
120
2
66
0.46
+)
0.55
+
+
+
+
+
(+)
3
0.46
69
150
0.27
+
+
+
+
+
(-)
4
140
0.42
60
0.31
+
+
+
+
+
(+)
140
0.64
5*
70
0.60
+
+
+
120
56
0.55
(+)
6
0.58
+
+
+
70
120
0.36
7
0.36
(+)
+
+
+
+
130
0.53
8
62
0.47
(+)
+
+
+
+
+
120
60
0.61
(+)
9
0.56
+
+
+
80
(+)
10
50
0.51
0.45
+
+
+
+
11
120
(+)
61
0.47
0.49
+
+
+
+
12
108
160
0.43
(+)
0.34
+
+
+
+
13
86
(+)
48
0.35
0.53
+
+
+
+
+
(-)
14
120
59
0.45
0.63
+
+
+
+t
(-)
15
68
120
0.51
0.58
+
+
+
(-)
16
140
59
0.46
0.60
+
(-)
17
63
120
0.41
0.49
+
+
-+
(-)
18
61
120
0.31
0.46
+
+
+(- )
19
72
140
0.41
0.64
+
+
+
(-)
20
77
160
0.39
0.67
+
+
p= 0.38
p < 0.001
Mean
66.85
126.80
0.47
0.50
SD
14.33
20.17
0.09
0.11
SEM
3.20
4.51
0.02
0.03
*All subjects were male except for case 5.
tStenosis distal to the first septal perforator branch.
Abbreviations: Max ex = maximal exercise; Abn ex = abnormal exercise; LVEF = left ventricular ejection fraction; RCA
right coronary artery; LAD = left anterior descending coronary artery; LCX = left circumflex artery.
RV FUNCTION DURING EXERCISE/Maddahi et al.
assessments of right ventricular function. Studies were
performed with a portable scintillation camera (Searle
Low Energy Mobile) equipped with a shielded,
parallel-hole, low-energy, all-purpose collimator and a
mobile minicomputer (Medical Data Systems, PAD).
Images were obtained in the 40-50° left anterior
oblique view. In each case, the degree of obliquity used
was that which provided the best separation between
the right and left ventricles. During each 2-minute
acquisition, the computer divided the scintigraphic
data from the first two-thirds of each cardiac cycle
into 14 frames and added the corresponding frames of
the cycles imaged. The average frame contained approximately 100,000 counts. All data were acquired
with a hardware zooming device that expanded the
data 1.7 times and were recorded in a 64 X 64 BYTE
mode matrix.
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Radionuclide Data Processing
RVEF determination from multiple-gated equilibrium scintigrams has been described in detail previously.'0 Briefly, the technique of analysis involved
light-pen assignment of two regions of interest over
the right ventricle, one in the end-systolic and the
other in the end-diastolic phase of the cardiac cycle.
Assignment of the regions of interest involved conventional nine-point smoothing, determination of the enddiastolic and end-systolic frames and display of the
data in an endless-loop movie format. This movie display substantially improved the visual perception of
the borders of the right ventricle throughout the cardiac cycle and was particularly important in defining
the borders between the right ventricle and the
pulmonary artery. With this technique it is important
that separate right ventricular regions of interest for
end-systole and end-diastole be assigned in order to
minimize the contribution of right atrial radioactivity
to counts in the right ventricular region of interest.'0
For background, a light pen assigned end-systolic left
paraventricular region of interest was selected. This
background region was crescent-shaped, separated by
one matrix element from the left ventricular activity
and was three to five matrix elements wide. We have
empirically found that this paraventricular region of
interest best represents the contribution of background activity to right ventricular counts.'0 RVEF
was determined by dividing the background-corrected
stroke counts (end-diastolic counts - end-systolic
counts) by the background-corrected end-diastolic
counts. LVEF measurement was performed with
light-pen assignment of left ventricular end-diastolic
and end-systolic regions of interest, using the same
background subtraction and ejection fraction calculation as for RVEF. Septal motion was assessed semiquantitatively using a five-point scoring system (-1 =
dyskinesis, 0 = akinesis,1 = severe hypokinesis, 2 =
mild hypokinesis, and 3 = normal)." Similar to
RVEF, LVEF response to exercise was considered
normal if the exercise ejection fraction increased by
> 10% of the resting ejection fraction value.6 Septal
motion during exercise was considered abnormal
when the wall motion score during exercise
135
deteriorated by . 1 point compared with the resting
septal motion score.
Exercise Protocol
For this procedure, sitting exercise was the form of
stress using an ergometer (Collins) with electrically
controlled workload. Before exercise, control 2minute multiple gated imaging was performed in the
sitting position. After control imaging, the patient underwent a warmup pedaling at 0 work load and 70 rpm
for 1 minute. Subsequently, beginning at 25 W, the
work load was gradually increased until target heart
rates of 100, 120, 140, 160 and 170 beats/min were
reached. At each stage of exercise, after stabilization
of heart rate at the desired level, imaging was performed for 2 minutes. The exercise protocol was continued to the end point ol maximal predicted heart
rate, severe fatigue or angina pectoris.
Statistical Methods
RVEFs and heart rates during control and maximal
exercise stages were compared in the CAD patients
using the paired t test. RVEFs and heart rates of the
normal subjects were each analyzed by analysis of
variance for repeated measurements in order to compare the mean values obtained at rest, intermediate
and maximal exercise stages. When the analysis of
variance indicated a significant result, the NewmanKeuls test was used to ascertain which of the means
were significantly different from one another. An unpaired t test was used to compare the RVEFs and
heart rates at rest and exercise between the normal
subjects (intermediate exercise) and the CAD patients
(maximal exercise).
Fisher's exact test was used to assess the significance of the relationship between RVEF response
to stress and exercise LVEF, septal motion during
exercise, and the presence of right coronary artery
stenosis. This statistical procedure is used to provide
an exact test of significance when the data are arrayed
in a 2 X 2 contingency table and the smallest expected
value is less than 5. P values < 0.05 were defined as
statistically significant.
Results
Clinical Illustrations
Figures 1, 2 and 3 depict the responses of RVEF
and LVEF to exercise in a normal subject, a patient
with dominant right CAD and a patient with left coronary artery disease and a normal right coronary
arteriogram, respectively.
Figure 1 demonstrates the response of LVEF and
RVEF to exercise in a normal subject (case 1, table 2).
RVEF increased from 0.45 to 0.68 and LVEF increased from 0.63 to 0.83. This improvement in right
and left ventricular function is evident from visual inspection of the ventricular radioactivity in the multiple
gated equilibrium scintigrams.
The patient (case 1 1, table 1) illustrated in figure 2
had a proximal 90% left anterior descending stenosis
CIRCULATION
136
Voi 62, No 1, JULY 1980
CONTROL
RVEF
HR=76
tED
ES
EXERCISE
HR 170
RVEF
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FIGURE 1. Representative example of normal response of right and left ventricular ejection fractions
(R VEF and L VEF) to stress in a normal subject. The end-diastolic (ED) images are on the left and the endsystolic (ES) images are on the right. The top panel represents the control images and the bottom panel the
maximal exercise images. During control, the R VEF was 0.45 and the L VEF was 0.63. During maximal exercise to a heart rate (HR) of 170 beats/min, R VEF rose to 0.68 and L VEF increased to 0.83. The improvement in right and left ventricular function is evident from inspection of ventricular activity in the multiplegated equilibrium cardiac blood pool scintigrams.
and a distal 99% first-diagonal narrowing. The right
coronary system had a combination of a proximal
75% and mid 90% stenoses. During the control phase,
RVEF was normal at 0.47. During maximal exercise
to heart rate 120 beats/min, RVEF remained un-
changed (0.49) while LVEF increased from a resting
value of 0.54 to 0.66. The unchanged RVEF is evident
from inspection of the multiple-gated equilibrium cardiac blood pool scintigraphic images.
The patient illustrated in figure 3 (case 14, table 1)
CONTROL
HR= 61
:;RVEF-A*7
::
E0 :D
V.'
i;: ...:
ES.
:;
_
RVi:f:00:;: tEF~ ::
CONTROL
HR=I2O
FIGURE 2. Representative example of abnormal right ventricular ejection fraction (R VEF) and normal
left ventricular ejection fraction (L VEF) responses to exercise in a coronary artery disease patient with right
coronary artery stenosis. A t rest, the R VEF and L VEF were 0.47 and 0.54, respectively. During maximal
exercise (HR of 120 beats/min), the R VEF did not change (0.49), but L VEF increased to 0.66. This lack of
improvement in right ventricularfunction is evidentfrom inspection of the multiple-gated equilibrium cardiac blood pool scintigrams.
RV FUNCTION DURING EXERCISE/Maddahi et al.
CONTROL
HR:59
137
DXSrr - AFx
n v Lr: . n:
:::
:: :::::
ED:
Sfi
fe;::f;
i::
:t::::
:::
ES
::
::
::::
:::
::
::
EXERCISE
HR
tV _F ,s
_
12:0
,
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FIGURE 3. Representative example of normal right ventricular ejection fraction (RVEF) and abnormal
left ventricular ejection fraction (L VEF) responses to exercise in a coronary artery disease patient without
right coronary stenosis. At rest, the R VEF and L VEF were 0.45 and 0.65 respectively. During maximal
ex-ercise (heart rate IHRJ of 120 beats/min), the R VEF rose to 0.63 but the L VEF did not change. These
findings are evident from inspection of the multiple-gated equilibrium scintigrams.
had a proximal 99% left anterior descending stenosis
and distal 90% left circumflex narrowing. The right
coronary system was normal. RVEF rose from a resting value of 0.45 to a maximal exercise level of 0.63,
while the left ventricle developed apical dyskinesis at
maximal exercise and the resting LVEF of 0.65 was
unchanged (exercise LVEF - 0.66).
Group
Responses
Values for RVEF at rest and during exercise in normal subjects and the coronary artery disease patients
are shown in figure 4 and in tables 1 and 2. For the
CAD patients, rest and maximal exercise values are
shown. Since many of the CAD patients did not
TAB3LE 2. Responses of Heart Rate and RVEP to Intermiediate (Intermed) and MUaximal (Max) Exercise (Ex)
in Normal Subjects
Case
Age
(years)
29
34
30
Rest
76
71
69
69
97
68
75
32
42
66
88
80
1
2
3
28
32
4*
35)
5
6
7
8
9
10
30
68
Mean
76
SD
10(
.3
SEM
Heart rate (beats/nin )
Intermed ex Max ex
170
120
120
130
170
160
140
140
100
120
120
170
170
170
170
160
140
126
13
4
162
12
4
140
140
lRest
RVEF (% )
Intermed ex
0.45
0.55
0.50
0.49
0.48
0.49
0.42
0.48
0.53
0.52
-
0.53
0.55
0.52
0.54
0.71
0.69
0.68
0.67
0.67
0.61
0.69
0.62
0.54
0.60
0.80
0.77
0.60
0.67
0.08
0.07
0.02
0.02
excluding case 4. However, the means
0.49
0.04
0.01
*AIialysis of variance for repeated measuLrem-ienits was performred
atnd standard deviations for this ttable are comnpu-ted inicluding this normal subject.
Abbreviations: Intermed ex =intermediate exercise; -Max ex
0.58
0.65
0.62
Max ex
inaximal exercise.
VOL 62, No 1, JULY 1980
CIRCULATION
138
CORONARY
ARTERY DISEASE
n=20
NORMALS
nf10
80
A
A
80
0
LL
W
0
LiL
60
cn_
/
0~
601
(I)
Lii
LLJ
/s
0Z
0
/
0
/
c)
LiJ
LLJ
x
40
o Intermedite Exercise
AMaximum Exercise
o/
401
.0..fii
/
iout RCA Disease
*With RCA Dismse
/-
x
0
:20
1
40
60
RESTING EF (%)
n
1)
/
20
--
- - -
,20
0U
40
60
RESTING EF (%)
A
80
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FIGURE 4. Graphic representation of the relationship between right ventricular ejection fraction (R VEF)
and during exercise in the normal subjects (left panel) and the coronary artery disease (CAD) patients
(right panel). The solid line is the line of identity, the dashed line represents exercise values 1 0% greater than
the resting R VEF, and the dashed-dotted line represents exercise values 20% greater than the resting L VEF.
The dashed and dashed-dotted lines converge to zero intercept. RCA = right coronary artery.
at rest
achieve a maximal heart rate as high as the normal
subjects, RVEF values at an intermediate level of exercise are included for the normal subjects.
Normal Subjects
The mean RVEF in the normal subjects at rest was
0.49 ± 0.04 (mean ± SD). At the intermediate stage of
exercise, RVEF increased significantly to 0.60 ± 0.07
and during peak exercise, further increased to
0.67 ± 0.08. The mean heart rate at rest was 76 ± 10
beats/min, increased to 126 ± 13 beats/min during
intermediate stage of exercise and further increased to
162 ± 12 beats/min at peak exercise. (All exercise
values were significantly different from resting values
at p < 0.01). In each of the normal subjects, the intermediate exercise RVEF rose by at least 10% and
the maximal RVEF increased by at least 20% of the
resting value (fig. 1).
CAD Patients
In the patients with CAD, mean resting RVEF was
not significantly different from the resting RVEF in
normals (0.47 ± 0.09 vs 0.49 ± 0.04, p = 0.49). During maximal exercise in the CAD patients as a group,
RVEF did not rise significantly (0.47 ± 0.09 vs
0.50 ± 0.11, p 0.38). Mean maximal RVEF in
CAD patients was significantly lower than mean
RVEF of normals at intermediate stage of exercise
(0.50 ± 0.11 vs 0.60 ± 0.07). The individual responses
of RVEF in the CAD patients showed marked variation. RVEF increased by 10% of the resting value in
eight and either remained unchanged (± 10%) or
decreased (> 10% fall) in 12 of the 20 patients with
CAD.
Since right ventricular function during exercise
might be affected by exercise left ventricular function,
septal motion during exercise and the presence of right
=
stenosis, we further analyzed the
relationship between normal and abnormal RVEF
response to stress and each of these parameters.
Although nine of 12 patients with abnormal RVEF
response had abnormal LVEF response to stress, five
of eight patients with normal RVEF during exercise
had abnormal LVEF response to exercise. The difference between these proportions was not statistically
significant.
Abnormal exercise septal motion was observed in
10 of 12 patients with abnormal RVEF response and
in seven of eight patients with normal RVEF response
to exercise. There was no significant difference
between these proportions.
Of 12 patients with abnormal RVEF exercise
response, all had right coronary artery stenosis. In
contrast, of the eight patients with normal exercise
RVEF, one had right coronary artery stenosis. The
difference between these proportions was significant
(p < 0.001).
In patients subgrouped by the presence of right coronary artery stenosis, mean RVEF values at rest and
maximal exercise were compared. In the seven
patients without right coronary artery stenosis, RVEF
rose during exercise (0.42 ± 0.06 to 0.58 ± 0.08,
p = 0.001) similar to the response observed in normal
subjects at comparable heart rates (fig. l). In five of
the seven patients, RVEF increased by more than 20%
of the resting value and in the remaining two patients
the increase was between 10-20%. In contrast, in the
subgroup with right coronary stenosis, mean RVEF
did not change significantly (0.50 ± 0.09 to
0.45 ± 0.10, p = 0.08).
Discussion
The results have demonstrated that our new
technique for evaluating RVEF from standard
multiple-gated scintigraphic gated blood pool images
coronary artery
RV FUNCTION DURING EXERCISE/Maddahi et al.
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can be applied to the assessment of RVEF during exercise.
The RVEF response in normal subjects was
characterized by a significant increase during intermediate exercise and by a marked increase during
maximal exercise.
It is well-recognized that resting RVEF or LVEF
may be normal in the presence of severe disease of any
part of the coronary artery system.10' 12, 13 The results
of the present study corroborate this finding in that the
mean resting RVEF was not statistically different in
the patients with CAD from the resting RVEF of the
normal subjects.
The present study describes the responses of RVEF
to stress in patients with CAD. In the CAD patients,
as a group, RVEF did not rise significantly during exercise, in contrast to the normal subjects. However,
the wide scatter in the individual responses was not
readily explained by the mere absence or presence of
CAD.
Since the right and left ventricles function as pumps
in series, abnormalities of right ventricular function
during stress might be secondary to stress-induced left
ventricular dysfunction. Sharma et al."1 have demonstrated that during supine bicycle exercise in normals
and CAD patients, left ventricular filling pressure increased to a greater extent in CAD patients. This increased left ventricular end-diastolic pressure increased right ventricular afterload. This increase in
right ventricular afterload might reduce RVEF;
however, this was not measured by these investigators.
Since the interventricular septum comprises a major portion of the right ventricular wall, abnormality
of septal motion might produce right ventricular
dysfunction. Brooks et al.'5 demonstrated deterioration of right ventricular function after induced
anteroseptal infarction in the pig.
Since the vascular supply of the free wall of the
right ventricle is largely derived from the right coronary artery,'6 right ventricular dysfunction during
stress might be related to right coronary artery
stenosis with exercise-induced right ventricular
ischemia. Brooks and co-workers'7 evaluated performance of the right ventricle in a canine model during
graded increase in right ventricular afterload and
assessed the relationship between stress right ventricular function and right coronary artery blood flow.
They have demonstrated that with right coronary
artery occlusion, right ventricular dysfunction occurs
at a much lower level of stress.
Therefore, three mechanisms - global left ventricular dysfunction during exercise, abnormal exercise septal motion, or ischemia of the right ventricular
free wall - could explain abnormal RVEF response
to stress. In our study, no significant association
between exercise RVEF response and either left ventricular function during exercise or exercise septal motion was found. However, a significant relationship
was observed between exercise RVEF response and
right coronary artery stenosis. In 19 of the 20 patients
with CAD, concordant results regarding the presence
of right coronary artery stenosis and the RVEF
response were noted. In contrast, with respect to the
139
relationship between left ventricular function and
right ventricular function, discordant results were
observed in eight of the 20 patients, including the abnormal subject illustrated in figure 2. With respect to
the relationship between septal motion during exercise
and RVEF response, discordant responses were
observed in nine of the 20 patients.
These findings suggest a major role of right coronary artery stenosis in the production of abnormal
RVEF fraction during stress. Further elucidation of
the mechanism for abnormal RVEF response in
patients with CAD will require assessment of patients
with severe left ventricular dysfunction in the absence
of proximal right coronary artery stenosis and
patients with isolated right coronary artery stenosis.
These aspects are currently under investigation in our
laboratories. We suspect that all three of the
postulated mechanisms might interact to produce an
abnormal RVEF response to stress.
None of the CAD patients in this study had prior
myocardial infarction. In patients with prior right ventricular myocardial infarction, response of RVEF to
exercise is variable and depends on the extent of functional myocardium and residual ischemia.
Additional information provided by determination
of RVEF during stress may improve the accuracy of
exercise left ventricular wall motion analysis for
assessment of the severity and extent of CAD. Although abnormalities of the septal wall motion imply
the presence of left anterior descending CAD, and abnormalities of posterolateral wall motion imply the
presence of left circumflex CAD, the standard left
anterior oblique scintigrams do not provide direct
visualization of the portion of the left ventricle
supplied by the right coronary artery. Abnormalities
of the inferoapical left ventricular region of the left
anterior oblique scintigrams may be secondary to
obstruction of any of the three major coronary
arteries. If assessment of larger numbers of patients
with CAD supports the high specificity of abnormal
RVEF response to stress for right coronary artery
stenosis, this measurement could provide additional
information for assessment of the extent of CAD.
Since this new method for evaluation of RVEF during stress provides a technique for assessment of right
ventricular functional reserve, the technique may be
applicable in a variety of other clinical settings, including the evaluation of patients with pulmonary disease and valvular heart disease.
Acknowledgment
The authors gratefully acknowledge the research assistance of
Nancy Pantaleo, RN., the technical assistance of Autumn Anderson, Debbie Drake, Lance Laforteza, Terry Collett and Tina Orvis,
and the statistical support of Jo Ann Prause and Emily Kushida.
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Circulation. 1980;62:133-140
doi: 10.1161/01.CIR.62.1.133
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