Significance of low-dose dobutamine stress echocardiography for the prediction of the long-term prognosis for patients with acute myocardial infarction.

Abstract

Detection of stunned myocardium using low-dose dobutamine stress echocardiography is a good predictor of improvement of cardiac function in patients with acute myocardial infarction during short hospital stays. The present study evaluated the detection of stunned myocardium as a predictor of the long-term prognosis for patients with acute myocardial infarction.
One hundred and two patients (83 males, 19 females, mean age 61.5 years) with initial myocardial infarction underwent successful reperfusion therapy (direct percutaneous transluminal coronary angioplasty or stent) in the acute stage. Within 7 days, low-dose dobutamine was administered by intravenous drip and improvement of wall motion of the infarct area was evaluated by echocardiography. The patients were divided into two groups, the viable group that showed one grade or more improvement (61 patients), and the non-viable group that showed no improvement (41 patients). These groups were compared to determine the differences in clinical findings such as remodeling of the left ventricle measured by two-dimensional echocardiography, physical work capacity during serial multi-step exercise testing, and the prognosis.
The viable group showed greater improvement in hemodynamics and wall motion of the infarct areas than the non-viable group. After discharge, the physical work capacity was significantly increased and there was no recognizable enlargement of the left ventricle in the viable group. No sudden cardiac death or heart failure occurred in the viable group, in contrast to incidences of 6% and 9%, respectively, in the non-viable group. Unstable angina and nonfatal re-infarction occurred more frequently in the viable group.
The presence of stunned myocardium is a predictor of the prognosis for patients with acute myocardial infarction.

Full text

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109
J Cardiol 2003 Mar; 41 （3） : 109–117
Significance of Low-Dose Dobuta-
mine Stress Echocardiography for
the Prediction of the Long-Term
Prognosis for Patients With Acute
Myocardial Infarction
Hiroyuki
Masaki
Shuhaku
Masami
Hiroaki
Kitaro
Hiromi
Yasushi
Masaichi
Takashi
KAYANO, MD
OZAWA, MD
KOH, MD
SORIMACHI, MD
UEDA, MD
KAWAMURA, MD
ANDOH, MD
AKUTSU, MD
HASEGAWA, MD
KATAGIRI, MD,
─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Objectives. Detection of stunned myocardium using low-dose dobutamine stress echocardiography is a
good predictor of improvement of cardiac function in patients with acute myocardial infarction during
short hospital stays. The present study evaluated the detection of stunned myocardium as a predictor of the
long-term prognosis for patients with acute myocardial infarction.
Methods. One hundred and two patients （83 males, 19 females, mean age 61.5 years） with initial
myocardial infarction underwent successful reperfusion therapy （direct percutaneous transluminal coronary
angioplasty or stent） in the acute stage. Within 7 days, low-dose dobutamine was administered by intra-
venous drip and improvement of wall motion of the infarct area was evaluated by echocardiography. The
patients were divided into two groups, the viable group that showed one grade or more improvement （61
patients） , and the non-viable group that showed no improvement （41 patients） . These groups were com-
pared to determine the differences in clinical findings such as remodeling of the left ventricle measured by
two-dimensional echocardiography, physical work capacity during serial multi-step exercise testing, and
the prognosis.
Results. The viable group showed greater improvement in hemodynamics and wall motion of the infarct
areas than the non-viable group. After discharge, the physical work capacity was significantly increased
and there was no recognizable enlargement of the left ventricle in the viable group. No sudden cardiac
death or heart failure occurred in the viable group, in contrast to incidences of 6% and 9%, respectively, in
the non-viable group. Unstable angina and nonfatal re-infarction occurred more frequently in the viable
group.
Conclusions. The presence of stunned myocardium is a predictor of the prognosis for patients with acute
myocardial infarction.
─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────J Cardiol 2003 Mar; 41 （3） : 109－117
Key Words
Myocardium stunned, viability
Myocardial infarction, treatment acute
─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─
昭和大学医学部 第三内科: 〒142－8666 東京都品川区旗の台1－5－8
The Third Department of Internal Medicine, Showa University School of Medicine, Tokyo
Address for correspondence: KAYANO H, MD, The Third Department of Internal Medicine, Showa University School of Medicine,
Hatanodai 1－5－8, Shinagawa-ku, Tokyo 142－8666
Manuscript received July 3, 2002; revised October 17 and December 20, 2002; accepted December 20, 2002
Stress echocardiography low-dose dobutamine
Prognosis
Abstract

Page 2

INTRODUCTION
Selection of the optimum treatment in the acute
and chronic stages of myocardial infarction
requires accurate assessment of the condition of
individual patients and knowledge of the incidence
of cardiac events such as sudden death, re-infarc-
tion, and heart failure. Low-dose dobutamine stress
echocardiography （LDSE） is effective for identify-
ing and evaluating hibernating myocardium in
patients with acute myocardial infarction, and
LDSE is an independent predictor of the
prognosis1－4）. However, most LDSE studies have
only investigated the infarcted area in the acute and
chronic stages after intra-coronary thrombolysis to
assess the correlation between hibernating
myocardium and the prognosis. Relief of ischemia
is believed to result in the recovery of the hibernat-
ing myocardium and consequently improves the
outcome5－8）. We previously found that LDSE can
identify stunned myocardium after successful
reperfusion in the hyper-acute stage （within 6 hr） of
acute myocardial infarction9）. However, the rela-
tionship between the identification of stunned
myocardium and the long-term prognosis following
myocardial infarction remains unclear10,11）. This
study investigated the relationship between the
detection of stunned myocardium by LDSE and the
prognosis for patients with acute myocardial infarc-
tion.
SUBJECTS AND METHODS
This study included 102 patients, 83 males and
19 females （mean age 61.5 years） with initial
myocardial infarction who successfully underwent
reperfusion therapy in the acute stage. The infarct
area was located in the anterior wall in 45 patients
and in the infero-posterior wall in 47 patients. All
patients showed sinus rhythm during dobutamine
stress. No serious complications occurred early
after infarction such as cardiogenic shock, ventricu-
lar septal perforation, or severe arrhythmias.
After obtaining informed consent, LDSE was
performed within 7 hospital days （mean 4.2 days） in
all patients. The patients were placed in the left lat-
eral or semi-lateral position, and images of the left
ventricle were recorded by setting the long and
short axis in the parasternal and apical approach.
Examination of wall motion evaluated the 16 areas
included in the American Society of Echo-
cardiography Standard12）using five grades, from
normokinesis to akinesis or dyskinesis. The blood
pressure, heart rate, electrocardiography, and
recording echocardiography were all monitored
during dobutamine administration. Dobutamine
was administered by intravenous drip at
5μ g/kg/min for 5min and 10μ g/kg/min for 5min,
and improvement of the wall motion of the infarct
area was evaluated. Two trained operators with 10
years or longer experience of echocardiography
individually analyzed myocardial wall motion to
determine myocardial viability. If their analyses did
not agree, the analysis of another trained operator
was taken into consideration. The patients were
divided into two groups, the viable group（Group
V） with one grade or more improvement of the wall
motion, and the non-viable group （Group NV） with
no improvement. Comparisons between these
groups focused on the hemodynamics, remodeling
of the left atrium and left ventricle, improvement of
the physical work capacity, and outcome after dis-
charge.
Serial multi-step exercise testing （Bruce’s proto-
col） was carried out before discharge （mean 28 hos-
pital days） and after discharge （mean 2 years） . The
target heart rate, ischemic changes by electrocar-
diography, and the appearance of severe arrhyth-
mias and chest symptoms were employed as the
discontinuation criteria. Patients with restenosis
underwent further revascularization before dis-
charge. Follow-up data were obtained from hospital
records, personal communication with the patient’s
physician and follow-up examination such as
echocardiography, coronary angiography and perfu-
sion scintigraphy with exercise testing. After dis-
charge, patients with suspected recurrent myocar-
dial infarction or angina pectoris underwent
myocardial perfusion scintigraphy and exercise
testing for the detection of ischemia. Coronary
angiography followed by revascularization was per-
formed as required. Wall motion of the area in hos-
pitalized and discharged patients was assessed by
only echocardiography unless ischemia （hibernating
myocardium） due to restenosis was identified.
Changes in the wall motion of the area 1 year after
discharge were assessed by echocardiography. The
end-point of this study was the occurrence of car-
diac events such as cardiac sudden death, angina
pectoris or congestive heart failure during the long-
term clinical progression after discharge. The inci-
dence of cardiac events was assessed （mean 2.8
years follow-up） .
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J Cardiol 2003 Mar; 41 （3） : 109–117

Page 3

The unpaired t-test, theχ2test, and the Kaplan-
Meier curve （Logrank, Breslow-Gehan-Wilcoxon）
were used for statistical analysis. A p level of less
than 0.05 was regarded as significant.
RESULTS
Clinical characteristics
The profiles of the 61 patients in Group V and
the 41 patients in Group NV are shown in Table 1.
There were no significant differences between the
two groups in age, sex, infarct area or mean time
until reperfusion. The peak creatine kinase in
Group V was significantly lower than that in Group
NV （2,133± 1,452 vs 2,955± 1,732IU/l, p＜
0.05） . Coronary risk factors are shown in Table 2.
There were no significant differences regarding
hypertension, hyperlipidemia, diabetes mellitus or
smoking. All patients received angiotensin convert-
ing enzyme inhibitor, antiplatelet agent and
nicolandil. Seven patients in Group V and four
patients in Group NV required calcium antagonist
and four patients and three patients, respectively,
requiredβ blocking agent during LDSE, with no
significant difference.
Hemodynamics during dobutamine stress
The systolic blood pressure （118 vs 122mmHg）
and heart rate （62 vs 65beats/min） in the resting
state showed no significant difference between
Group V and Group NV. The blood pressure and
heart rate were increased to 134 and 130mmHg,
and 96 and 97beats/min during LDSE, respectively,
showing no significant differences. Palpitation and
slight shortness of breath were observed during
LDSE, but chest pain was not recognized.
Electrocardiography detected no ischemic changes
in ST requiring discontinuation. Supraventricular or
ventricular extra-systole was observed in 32% and
20% of the patients in Groups V and NV, respec-
tively, but no patients in either group developed
severe arrhythmia requiring discontinuation of
dobutamine stress.
Wall motion in the infarct area
Fig. 1 shows the improvement of wall motion in
the infarct area. Wall motion was improved in 53 of
61 patients （87%） in Group V after 1 month, and in
58 of 61 patients （95%） after 1 year. In contrast,
wall motion was improved in only 9 of 41 patients
（22%） in Group NV after 1 month and 1 year.
Thus, LDSE had a sensitivity of 95% and specifici-
Stress Echocardiography for Myocardial Infarction
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J Cardiol 2003 Mar; 41 （3） : 109–117
Table 1　Clinical characteristics of the patients
Group NV
Number of patients?
Age （yr）?
Sex （male/female）?
Infarct area （anterior, lateral/inferior, posterior）?
Reperfusion time （hr）?
Peak creatine kinase （IU/l）?
41?
62.0?
35/6?
19/22?
4.6?
2,955± 1,732
t-test
NS?
NS?
NS?
NS?
NS?
p＜0.05
Group V
61?
61.2?
48/13?
22/39?
5.0?
2,133± 1,452
There were no significant differences in age, sex, infarct area or reperfusion time, but there was a significant
difference in peak creatine kinase between the two groups.?
Group V （viable group） : Group with one grade or more improvement of the wall motion. Group NV （non-viable
group） : Group with no improvement of the wall motion.
Table 2　Coronary risk factors
Group V?
Group NV
Hypertension
?
26 （43%）?
21 （51%）?
Diabetes mellitus
15 （26%）?
13 （32%）?
Hyperlipidemia
31 （51%）?
24 （59%）?
Smoking
22 （36%）?
17 （41%）?
χ
?
2 test
NS?
NS
There were no significant differences in coronary risk factors such as hypertension, diabetes mellitus,
hyperlipidemia or smoking between the two groups.?
Explanation of the groups as in Table 1.

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Kayano, Ozawa, Koh et al
J Cardiol 2003 Mar; 41 （3） : 109–117
ty of 78% for evaluating the improvement of wall
motion after 1 year.
Cardiac hemodynamics
Fig. 2 compares the cardiac hemodynamics on
admission and after 1 month. The mean pulmonary
arterial pressure and the pulmonary capillary wedge
pressure on the first hospital day in Groups V and
NV were not significantly different （20.9 vs
20.6mmHg and 15.4 vs 15.3mmHg, respectively） .
However, 1 month later, both values were signifi-
cantly improved in Group V （15.3 vs 19.8mmHg
and 9.2 vs 14.2mmHg, respectively, p＜0.05） .
Changes in the left atrial and left ventricular
diameters
Fig. 3 shows intra-group comparisons of the
time-course changes in the left atrial and left ven-
tricular diameters measured by M-mode echocar-
diography. The mean left atrial diameters on the
first hospital day were 3.4cm and 3.6cm in Groups
V and NV, respectively, showing no significant dif-
ference. The mean diameters were 3.7cm and
4.2cm after 1 month and 3.6cm and 4.4cm after 6
months, respectively. The mean left atrial diameter
was significantly increased in Group NV （p＜
0.01） .
The mean left ventricular diameters on the first
hospital day were 4.7cm and 5.0cm in Groups V
and NV, respectively, showing no significant differ-
ence. The mean diameters were 4.9cm and 5.9cm
after 1 month and were 4.8cm and 5.9cm after 6
months, respectively. The mean left ventricular
diameter was also significantly increased in Group
NV （p＜0.01） .
Physical work capacity
Fig. 4 compares the physical work capacity. The
physical work capacity 1 month after onset was
5.2± 2.0METs and 5.1± 2.4METs in Groups V
and NV, respectively （NS） . The physical work
0
100
75
50
25
Wall motion improvement （％）
1month1year 1month1year
Group VGroup NV
NSχ
2＜0.01
87
95
NS
22
22
Fig. 1 Wall motion improvement in the infarct area
during low-dose dobutamine stress echocardiog-
raphy
Wall motion was improved significantly in Group V
compared to Group NV after 1 year （95% vs 22%） .
Explanation of the groups as in Table 1.
30
20
10
0
Mean pulmonary arterial pressure （mmHg）
First day1month
30
20
10
0
Pulmonary capillary wedge pressure （mmHg）
First day 1month
p＜0.05
p＜0.05
p＜0.05
p＜0.05
NS
NS
NS
NS
Group V
Group NV
Fig. 2 Mean pulmonary arterial pressure （left） and pulmonary capillary wedge pressure （right） on
the first hospital day and 1 month later
The mean pulmonary arterial pressure and the pulmonary capillary wedge pressure on the first hospital day
were not significantly different between the two groups, but these values were significantly improved in
Group V 1 month later （15.3 vs 19.8mmHg and 9.2 vs 14.2mmHg） , respectively （p＜0.05） .
Explanation of the groups as in Table 1.

Page 5

capacity after about 2 years had significantly
improved to 6.3 ± 1.9METs in Group V, but
showed significantly less improvement to 5.5±
2.2METs in Group NV （p＜0.05） .
Outcome
Narrowed coronary arteries （＞75% restenosis）
were detected after revascularization in eight hospi-
talized patients in Group V and six patients in
Group NV, showing no significant difference. Figs.
5 and 6 compare the incidence of cardiac events
over about 2.8 years in 83 patients who could be
followed up. None of the 50 patients in Group V
experienced sudden cardiac death or congestive
heart failure. Two of the 33 patients in Group NV
suffered sudden cardiac death and three experi-
enced congestive heart failure. No patient in either
group suffered non-cardiac death during the follow-
up period. The difference between the two groups
was significant （χ2＜0.02） . Unstable angina and
nonfatal re-infarction were both observed in 13
patients （26%） in Group V. In contrast, unstable
angina was observed in only two patients in Group
NV. The Kaplan-Meier method found a significant
difference between the incidences of ischemic
events in the two groups （p＜0.02） .
DISCUSSION
The present study showed that LDSE had a sen-
Stress Echocardiography for Myocardial Infarction
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J Cardiol 2003 Mar; 41 （3） : 109–117
6
6
8
2
0
4
4
2
0
Left atrial diameter （cm）
Left ventricular diameter （cm）
First day1month6months First day1month6months
NS
NS
NS
＊ ＊
＊
＊
NS
NS
NS
＊ ＊
＊
＊
＊ p＜0.01
Group V
Group NV
Fig. 3 Left atrial （left） and left ventricular （right） diameters on the first day, 1 month later, and 6
months later
The left atrial diameter and left ventricular diameter on the first hospital day were not significantly different
between the two groups. Both left atrial and left ventricular diameters were significantly increased in Group
NV after 1 month and 6 months later （p＜0.01） .
Explanation of the groups as in Table 1.
Physical work capacity （METs）
0
2
4
6
8
1month2years
NS
NS
p＜0.05
p＜0.05
Group V
Group NV
Fig. 4 Physical work capacity at 1 month and at 2
years after onset
One month after onset, the physical work capacity was
not significantly different between the two groups. The
physical work capacity in Group V significantly
improved to 6.3± 1.9METs, whereas physical work
capacity in Group NV showed significantly less
improvement （5.5± 2.2METs, p＜0.05） .
Explanation of the groups as in Table 1.

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sitivity of 95% and specificity of 78% for detecting
wall motion improvement in patients with stunned
myocardium successfully treated by reperfusion
therapy during the acute stage of acute myocardial
infarction. LDSE has a sensitivity of 81－87% and
specificity of 84－88% for detecting hibernating
myocardium11,13,14）. The period required for recov-
ery from myocardial stunning varies from within 3
days15）or 3－6 days16）to longer periods of 7－10
days.
In our study, recovery occurred after 1 month or
later in 5 of the 58 patients （8.6%） in Group V. Such
delayed improvement in wall motion until up to 30
days or later was also found in patients with severe-
ly decreased cardiac function who had undergone
bypass surgery several times17）. Our five patients
who showed delayed improvement had the lowest
and mean values of escaped myocardial enzyme
（peak creatine kinase） of 2,638IU/l and 3,328IU/l,
respectively, which were significantly higher than
the overall mean values of the patients in Group V.
Although it is generally considered that myocardi-
um recovers from stunning in about 7 days, our
results show that patients with seriously compro-
mised cardiac function may show delayed recovery.
Careful observation is essential in such patients.
The left atrial and left ventricular diameters were
not increased in Group V but were significantly
increased in Group NV （p＜0.01） . Apparently,
improvement of the intra-cardiac pressure was
good in Group V and the clinical course involved
no remodeling. In contrast, improvement was
delayed in Group NV and the persistent cardiac
load resulted in remodeling. Therefore, myocardial
viability assessment is useful for the prediction of
left atrial or left ventricular remodeling 6 months
after discharge, and also for short-term changes in
cardiac function following myocardial infarction.
Patients with non-viable myocardium should be
treated with angiotensin converting enzyme
inhibitor early in the course of acute myocardial
infarction because remodeling is likely to develop
by 6 months after discharge. The physical work
capacity showed significantly more improvement in
Group V than in Group NV after 2 years. The max-
imal oxygen consumption rate is significantly
improved during exercise in ischemic cardiomyo-
pathic patients with hibernating myocardium18）.
Improvement of the wall motion in patients with
hibernating myocardium through exercise therapy
may be due to structural and functional changes in
the microvascular vessels perfusing the myocardi-
um rather than the main coronary artery18）. The
improvement in physical work capacity is generally
believed to derive from improved cardiac pump
function and adaptation to exercise of the peripher-
al tissues （muscle） . Many studies on healthy adults
conducted more than 20 years ago have confirmed
that appropriate exercise therapy effectively
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Incidence （％） Incidence （％）
50
40
30
20
10
00
40
30
20
10
0
9
6
0
50
χ
2＜0.02
χ
2＜0.02
Group V
Group NV
Group V
Group NV
Fig. 5 Incidences of sudden death （left） and congestive
heart failure （right） over the follow-up period of
mean 2.8 years
None of the 50 patients followed up in Group V experi-
enced sudden cardiac death or congestive heart failure.
Two of the 33 patients in Group NV suffered sudden
cardiac death and three experienced congestive heart
failure. The difference between two groups was signifi-
cant （χ2＜0.02） .
Explanation of the groups as in Table 1.
p＜0.02
Group V
Group NV
Occurrence ratio
1
0.8
0.6
0.4
0.2
0
0400800 1,2001,600
Time （days）
Fig. 6 Incidences of angina pectoris and re-infarction
using the Kaplan-Meier method
Both unstable angina and nonfatal re-infarction were
observed in 13 patients in Group V. In contrast, only
unstable angina was observed in only two patients in
Group NV. The Kaplan-Meier method found a signifi-
cant difference between the incidences of ischemic car-
diac events in the two groups （p＜0.02） .
Explanation of the groups as in Table 1.

Page 7

improves the cardiac function19－21）. Similarly, our
study found that cardiac function significantly
improved in Group V with improved wall motion
of the area compared to Group NV without
improved wall motion and remodeling and no
remodeling. Our study suggests that Group V had a
greater circulating blood volume than Group NV,
contributing to the significantly improved physical
work capacity in Group V.
The incidence of re-infarction at the same site
and unstable angina during the 2.8-year observation
period was 26% in Group V, in contrast to only 6%
in Group NV. Two patients in Group V experienced
recurrence of acute myocardial infarction at the
same site within 6 months after discharge. Eleven
patients in Group V experienced unstable angina
pectoris following acute myocardial infarction,
seven patients within 1 year of discharge who all
had restenosis at the same site, and four after 1 year
of whom two had restenosis at the same site. Two
patients in Group NV experienced unstable angina
pectoris following acute myocardial infarction
within 6 months of discharge, one had restenosis at
the same site, whereas the other had restenosis at a
different site. Such incidents may be due to
ischemia caused by restenosis of the responsible
blood vessel during the clinical course1,22）. The
incidence of re-infarction and unstable angina was
40% in patients with hibernating myocardium, in
contrast to only 7.5% in patients without hibernat-
ing myocardium22）. Patients with non-Q-myocar-
dial infarction have smaller infarct size and better
cardiac function than patients with Q-myocardial
infarction, whereas patients with Q-myocardial
infarction develop re-infarction and angina more
readily because of the greater viability23）.
Heart failure occurred in 9% of Group NV com-
pared to 0% in Group V. Patients in Group NV
showed remodeling of the left atrium and left ven-
tricle, so the cardiac function was reduced and heart
failures were more likely to occur. Patients without
hibernating myocardium had reduced left ventricu-
lar ejection fraction and the incidence of heart fail-
ure was 18%, compared to 10% in patients with
hibernating myocardium22）. In our study, the inci-
dence of sudden death was 0% in Group V versus
6% in Group NV. Sudden death occurred in 4% and
2% of patients with and without hibernating
myocardium, respectively, within a mean of 1.5
years due to new ischemia1）. Our study found poor
left ventricular function with increased infarction
volume in two cases of sudden deaths in Group NV
（peak creatine kinase＝6,225IU/l, 7,003IU/l, left
ventricular end-diastolic dimension 6 months after
discharge＝6.6cm, 7.0cm） . Therefore, our study
suggests that exacerbation of chronic heart failure
or arrhythmia may contribute to sudden death, so
follow-up examination must consider the possibili-
ty of ischemia in patients with stunned myocardi-
um, and heart failure in patients without stunned
myocardium.
LDSE is generally considered to be a safe
method. Ventricular extrasystole, paroxysmal atrial
fibrillation and decreased blood pressure were
observed during LDSE in 13－14%, 3%, and 3% of
patients tested, respectively, but there were no
ischemic changes or serious complications, and
LDSE was discontinued in none of the patients. In
our study, no serious arrhythmia or ischemic
changes were observed during LDSE, and dobuta-
mine stress could be applied at a rate up to
10μ g/kg/min. Therefore, we also concluded that
LDSE is a safe test method. Therefore, LDSE is
clinically useful to detect stunned myocardium and
hibernating myocardium for predicting the long-
term prognosis for patients with myocardial infarc-
tion.
Limitations
Coronary angiography was routinely performed
twice, during the hyper-acute stage of myocardial
infarction and before discharge, in nearly all
patients. Patients underwent revascularization if
significantly narrowed coronary arteries （75%
restenosis） were observed. However, myocardial
perfusion scintigraphy in conjunction with an exer-
cise test was performed if ischemia was suspected
in the patients at post-discharge follow-up exami-
nation. Patients with ischemia underwent coronary
angiography followed by revascularization. The
underlying disease may not have been detected, but
ischemia was relieved if the area could be identi-
fied.
Left atrial and left ventricular remodeling was
assessed by M-mode echocardiography which gen-
erates a one-dimensional view of the heart.
Accurate assessment of remodeling requires shape
analysis of remodeling with the modified Simpson
method in the presence or absence of ventricular
aneurysm using the left ventricular volume as an
index.
No-reflow or slow-flow phenomenon identified
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Page 8

by coronary angiography in the hyper-acute stage
was not examined. If the extent of no-reflow or
slow-flow is assessed, more detailed information on
the prediction of cardiac events can be obtained.
CONCLUSIONS
LDSE is a safe and useful method for detecting
stunned myocardium in the infarct area of acute
myocardial infarction, and the presence of stunned
myocardium is a predictor of the prognosis for
patients with myocardial infarction.
Acknowledgement
I deeply thank Drs. Mikitaka Murakami and Masatoshi
Nagayama, as well as the other members of the medical staff who
helped with this study.
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急性心筋梗塞の長期予後予測における低用量
ドブタミン負荷心エコー図法の有用性
茅野　博行　　小澤　優樹　　江　 修 博　　反町　政巳　　上田　宏昭
川村喜太郎　　安藤　浩巳　　阿久津　靖　　長谷川雅一　　片 桐　 敬
目　的: 冬眠心筋は心筋梗塞患者の長期予後を推測するうえでの独立した規定因子であると報告
されている．これまでに我々は，低用量ドブタミン負荷心エコー図法を用いて心筋梗塞急性期の気
絶心筋を検出し，気絶心筋を有する例は入院後短期間における心機能の改善が良好であると報告し
てきた．本研究は気絶心筋が心筋梗塞の長期予後を推測するうえでの規定因子になりうるかを検討
することである．
方　法: 対象は急性期再灌流療法 （ダイレクト経皮的冠動脈形成術またはステント留置） に成功し
た初回心筋梗塞102例 （男性83例，女性19例，平均年齢61.5歳） である．全例7病日以内に末梢静
脈より低用量のドブタミンを点滴投与し，心エコー図法で梗塞部の壁運動改善を評価した．壁運動
改善の違いから対象を1段階以上壁運動が改善したViable群 （61例） と改善しなかったNon-viable群
（41例） の2群に分けそれぞれ，心エコー図法から求めた左房と左室径の経時的変化，連続的多段階
運動負荷試験から得られた運動耐容能の改善などや退院後の長期予後について比較検討した．
結　果: Viable群はNon-viable群に比べて入院後短期間における梗塞部の壁運動の改善が有意に
大きかった．Viable群は退院後の運動耐容能の改善がNon-viable群に比べて有意に大きかった．
Viable群では退院半年後の左房および左室拡大は認められなかったのに対して，Non-viable群では
有意に拡大した．経過観察中，Viable群では突然死や心不全がまったく認められなかったのに対し
て，Non-viable群では突然死が6%，心不全が9%に認められた．不安定狭心症や非致死性の再梗塞
が認められる率において，Viable群はNon-viable群に比べて有意に高かった．Viable群はNon-viable
群に比べて心機能の改善が大きいため，突然死や心不全は認められないが，梗塞部がviableである
ために新たな虚血が生じるものと考えられた．
結　語: 気絶心筋は急性心筋梗塞患者の予後を推測するうえでの規定因子になると考えられた．
J Cardiol 2003 Mar; 41 （3） : 109－117
要　　　約
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