Stress test evaluation of patients with poor left ventricular function before and after coronary artery bypass surgery.

Abstract

Between May 1976 and December 1982 (104 months), 152 patients from a total of 3592 patients who had coronary angiography at the Buffalo Veterans Administration Medical Center had coronary artery disease with left ventricular ejection fractions of 40% or below. Sixty-three patients in this group had coronary bypass surgery. Thirty patients who had graded exercise tests done before and after surgery improved in their peak exercise double product and systolic blood pressure (p value <.05) accompanied by increased work capacity (p value < 0.02). Nineteen patients who had identical exercise protocols also showed increases in exercise time (p value <.05). We believe that coronary artery bypass surgery improves exercise capacity in selected patients with compromised left ventricular function.

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Cardiovascular Medicine and Surgery
StressTestEvaluation ofPatients withPoor LeftVentricular
Function Before andAfter CoronaryArteryBypass Surgery
V. Balu, M.D., L. Szmedra, M.A., D. Dean, M.D., and J. Bhayana, M.D.
Between May 1976 and December 1982 (104 months), 152 patients
from a total of3592 patients who had coronary angiography at the
Buffalo Veterans Administration Medical Center had coronary artery
disease with left ventricular ejection fractions of40% or below.
Sixty-three patients in this group had coronary bypass surgery. Thirty
patients who had graded exercise tests done before and after surgery
improved in their peak exercise double product and systolic blood
pressure (p value < .05) accompanied by increased work capacity
(p value < 0.02). Nineteen patients who had identical exerciseprotocols
also showed increases in exercise time (p value < .05). We believe that
coronary artery bypass surgery improves exercise capacity in selected
patients with compromised left ventricularfunction.
EXERCISE TESTING has been used
extensively in evaluating coronary artery
disease in asymptomatic and symptomatic
patients. It is valuable in assessing the risk of
future cardiac events in patients early after
myocardial infarction.
evaluating coronary bypass surgery by quan-
titating exercise performance, pre- and post-
operatively. Following coronary artery bypass
surgery, most of the previous studies have
shown improvement in exercise parameters in
patients with relatively normal ejection frac-
tion at rest. The improvement bears a signif-
icant relationship to the completeness of
revascularization.' In general, there is little
information regarding the functional perfor-
mance of patients with compromised left ven-
tricular function.
Our study was aimed at identifying such
patients with low ejection fractions of40% or
It is also useful in
below, who were able to perform graded exer-
cise tests before and after surgery, and analyze
their exercise parameters.
MATERIALS AND METHODS
Between May 1974 and December 1982,
3592 patients underwent cardiac catheteriza-
tion at the Buffalo Veterans Medical Center.
During this period, there were 152 patients
with coronary artery disease and ejection
fractions of 40% or below who had exercise
stress testing. Sixty-three patients of this
group had coronary artery bypass surgery.
Thirty patients from the study group had
exercise testing before and after coronary
bypass surgery.
All cardiac catheterizations were performed
by the percutaneous transfemoral route as
From the Cardiology Department, Veterans Administration Medical Center, State University
ofNew York at Buffalo.
Address for reprints: V Balu, M.D., Chief, Noninvasive Laboratory, Cardiology Section,
VeteransAdministration Medical Center, 3495 BaileyAvenue, Buffalo, New York 14215.
Texas Heart Institute Journal
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described by Judkins.2 Left ventricular
angiography was performed in the left anterior
and right anterior oblique projections. End-
diastolic and end-systolic angiographic frames
were used to calculate left ventricular volume
and ejection fraction by area length method.3
Graded exercise protocols were used for
exercise testing and included bicycle ergom-
etry, Bruce treadmill protocol, Modified Bruce
treadmill protocol and Naughtonprotocol. The
exercise parameters analyzed included peak
systolic blood pressure, peak exercise heart
rate, peak exercise double product, work
capacity as measured by Mets and exercise
duration. Nineteen of30 patients had identical
exercise protocol before and after surgery.
RESULTS
Coronary artery bypass surgery was per-
formed in 63 patients with low ejection
fraction of 40% or below. Age range was
between 38 and 64. The general criteria for
operability in poor left ventricular function are
shown in Table I.
The ejection fraction as calculated by
angiocardiography is shown in Table II.
Among the 30 patients, 21 had triple vessel
disease, eight had double vessel disease, and
one had single vessel disease. Seven patients
had four vessels grafted, fourhad three vessels
grafted, 16 had two vessels grafted, and two
patients had one vessel grafted. The average
graft per patient was 2.4. Six patients had left
ventricular aneurysmectomy in addition to
coronary artery bypass grafting, and three had
coronary endarterectomy. The various exer-
cise parameters are shown inTable Ill. Theend
points of stress testing are shown before and
after coronary artery surgery in Table IV. The
stress variables in 19 patients with identical
stress test protocols pre- and postoperatively
are shown in Table V.
DISCUSSION
Exercise performance in patients with
compromised left ventricular function is a
complex subject. It involves many factors,
including the left ventricular ejection fraction
TABLE
1. Criteria for Operability in
Patients with Poor Left
Ventricular Function
1. Age 60 or below.
2. Main symptom angina.
3. Adequate contractility of septum.
4. Good distal runoff.
5. Ten percent or more improvement in
ejection fraction by nitroglycerin.
TABLE II. Preoperative Ejection Fraction
Ejection
Fraction
20-25
26-30
31-35
36-40
No. of
Patients
6
4
5
15
30
Total
TABLE 111. Exercise Data (30 Patients)
Pre-Surgery
Post Surgery
P-Value
Peak Exercise
Heart Rate
126 131
N.S.
Peak Exercise
Systolic B.P.
147 157
< 0.05
Peak Exercise
Double Product
18,885
21,000
< 0.06
METS
6
7.1
<0.03
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110

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itself, changes in the ejection fraction occur-
ring with exercise, the extent and severity of
ischemia, and changes in peripheral vascular
resistance, as well as many others. However,
the two most important variables in the clinical
setting are the severity ofischemia and the left
ventricular ejection fraction at rest and during
exercise. Exercise-induced left ventricular
dysfunction
has
been
documented in patients with coronary artery
disease by using radionuclide angiocardiog-
raphy.5 Such ischemia-induced left ventricular
dysfunction is readily detectable in patients
with normal ejection fraction, as the drop in
ejection fraction can be marked. However, in
a patient who already has compromised left
ventricular function, such changes in ejection
fraction may not be as dramatic, and yet
ischemia may be an important factor affecting
exercise performance. There are many reports
reported
and
TABLE IV. Reasons for Stopping Exercise
(30 Patients)
Pre-Post-
Surgery Surgery
Shortness
of breath
Chest pain
Leg fatigue
ST depression
PVCs
17
8
4
14
1
14
0
1
0
1
in the literature showing improvement of left
ventricular function and exercise performance
following coronary bypass surgery.1"6 Most of
the previous studies dealt with patients who
had fairly normal left ventricular ejection
fractions. In contrast, our study population
consisted of patients with left ventricular
ejection fraction of 40% or below. Of the 30
patients who had coronary artery surgery and
stress testing, six had ejection fractions of25%
or below. There was definite improvement in
the exercise parameters. These patients were
able to achieve a better systolic blood pressure
following surgery and ahigherexercise double
product. This was accompanied by a signifi-
cant improvement in work capacity as shown
in Table Ill. In 19 patients who had identical
protocols, there was also a significant increase
in their exercise time, in addition to improve-
ment in all other exercise parameters (Table
V). We previously reported4 the long-term
survival in a similar group of 63 patients who
had coronary artery surgery at this institution.
The long-term survival in that group was very
rewarding, with a 5-year survival of 93.7%.
LIMITATIONS OF THE STUDY
Our study was a retrospective study, and the
ejection fractions were calculated at rest. We
do not have the radioisotope ejection fraction
with exercise on these patients. However, it is
reasonable to assume that the changes in the
ejection fraction with exercise-induced
TABLE V. Stress Parameters of 19 Patients with Identical Protocols, Before and After
Coronary Artery Bypass Surgery
Peak Exercise
Heart Rate
118
Peak Exercise
Systolic Blood Pressure
144
Peak Exercise
Double Product
17,557
METS
6.3
Exercise Duration
(seconds)
421
133
160
21,919
p <.01
p <.01
p <.001
7.8
p < .001
492
p < .05
TIxas Heart Institute Journal
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ischemia in patients with compromised left
ventricular fraction is probably even more
important. There is a definite selection bias in
the group of patients who had surgery. They
had better coronary anatomy suitable for
grafting and, hence, the improvement in stress
testing may have been related to selection bias.
There has been a tremendous improvement in
the management of patients with medical
treatment, particularly with the advent ofnew
anti-anginal agents, including calcium chan-
nel blockers. A recent report from the Cass
study6 has shown that the 7-year survival of
patients with triple vessel disease and an
ejection fraction higherthan .34 but lowerthan
.50 improved with elective bypass surgery
(P value of 0.0094). We believe that exercise
performance is distinctly and adversely
affected by coronary ischemia, even in
patients with compromised left ventricular
function. Revascularization of selected
patients in this group improves exercise perfor-
mance and prolongs long-term survival.
2. Judkins MP. Selective coronary arteriography: A
percutaneous transfemoral technic. Radiology
1967; 89:815.
3. Dodge HT, Sandler H, Ballew DH. Use of
biplane angiocardiography for measurement of
left ventricular volume in man. Am Heart J 1960;
60:762.
4. Bhayana JN, Balderman SC, Dhar N, Masud M,
Dean D, Balu V, Michalek S, GageA. Improved
long-term survival in patients with reduced
ejection fraction; Noninvasive assessment of the
cardiovascular system. In Diethrich EB (Ed):
Diagnostic Principles and Technics. Boston,
John Wright, Publisher, 1982; pp 205-210.
5. Jengo J, Oren V, Conant R, Brizendine M,
Nelson T, Uszler M, Mena I. Effects ofmaximal
exercise stress on left ventricular function in
patients with coronary artery disease using first
pass radionuclide angiocardiography. Circula-
tion 1979; 59(1):60- 65.
6. Passamani E, Davis K, Gillespie MJ, Killip T,
CASS investigators and associates. A ran-
domized trial of coronary artery bypass surgery:
Survival of patients with a low ejection fraction.
N Engl J Med 1985; 312(26):1665-1671.
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