(Circulation. 1998;98:2017-2023.)
© 1998 American Heart Association, Inc.
Clinical Investigation and Reports |
From the Section of Cardiology, Baylor College of Medicine, Houston, Tex.
Correspondence to John J. Mahmarian, MD, 6550 Fannin St, SM-1246, Houston, TX 77030-2716. E-mail johnj{at}bcm.tmc.edu
| Abstract |
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Methods and ResultsWe performed a prospective, randomized pilot
study comparing intensive medical therapy with coronary
angioplasty (PTCA) for suppression of myocardial ischemia in 44
stable survivors of AMI. Myocardial ischemia was quantified
with adenosine 201Tl tomography (SPECT) performed
4.5±2.9 days after AMI. All patients at baseline had a large total
(
20%) and ischemic (
10%) left ventricular
perfusion defect size (PDS). SPECT was repeated at 43±26 days after
therapy was optimized. The total stress-induced PDS was comparably
reduced with medical therapy (from 38±13% to 26±16%;
P<0.0001) and PTCA (from 35±12% to 20±16%;
P<0.0001). The reduction in ischemic PDS was
also similar (P=NS) in both groups. Cardiac events
occurred in 7 of 44 patients over 12±5 months. Patients who remained
clinically stable had a greater reduction in ischemic PDS
(-13±9%) than those who had a recurrent cardiac event (-5±7%;
P<0.02). Event-free survival was superior in the 24
patients who had a significant (
9%) reduction in PDS (96%) compared
with those who did not (65%; P=0.009).
ConclusionsIn this small pilot study, intensive medical therapy and PTCA were comparable at suppressing ischemia in stable patients after AMI. Sequential imaging with adenosine SPECT can track changes in PDS after anti-ischemic therapies and thereby predict subsequent outcome. Corroboration of these preliminary findings in a larger cardiac-event trial is warranted.
Key Words: myocardial infarction tomography ischemia
| Introduction |
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The purpose of this pilot study was to determine the relative efficacy of intensive anti-ischemic medical therapy versus coronary angioplasty (PTCA) for suppression of ischemia in high-risk but stable survivors of AMI. This study was not designed to determine differences in cardiac event rates between the 2 treatment strategies. Ischemia suppression was assessed with sequential adenosine 201Tl single-photon emission computed tomography (SPECT).
| Methods |
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18 years) were admitted to our coronary care unit with
the diagnosis of AMI based on standard
criteria.7 12 Thirty-four patients with initial
clinical instability (ie, cardiogenic shock [n=5], need for emergent
coronary revascularization [n=10], or
concomitant serious noncardiac illnesses [n=9]), death of
ventricular fibrillation (n=2), or a
contraindication to adenosine (n=8) were excluded. The
remaining 133 patients (80%) had adenosine SPECT performed
4.5±2.9 days after AMI.
Sixty-three (47%) of 133 patients had a large total (
20%) and
ischemic (
10%) left ventricular (LV) perfusion
defect size (PDS) and were considered for study entry pending
coronary angiography. This scintigraphic profile defines a
population at high risk for recurrent cardiac events after
AMI.2 Patients with significant (
50%) left
main stenosis, 3-vessel coronary artery disease (CAD)
and an LV ejection fraction (EF) <35%,13 14 and
CAD not amenable to PTCA were excluded. Forty-five of 63 patients met
all entry criteria; 1 patient randomized to PTCA had CABG and
was excluded. Thus, 44 patients constituted the study population.
Study Design
This was a prospective, randomized pilot study of a larger trial
evaluating the clinical utility of adenosine SPECT early after
AMI. The protocol was approved by the Baylor Institutional Review
Board, and all patients signed informed consent forms.
Patients meeting entry criteria were randomized to either PTCA (n=21)
or intensive anti-ischemic medical therapy (n=23); the latter
combined isosorbide dinitrate (ISDN) with metoprolol (Lopressor) and
diltiazem (Cardizem CD). After therapy was optimized, 22 of 23 patients
randomized to medical therapy and 19 of 21 randomized to PTCA had
repeat adenosine SPECT 43±26 days after their baseline study.
All 44 patients were prospectively followed up for
6 months (mean,
12±5 months).
Medical Therapy Group
Anti-ischemic medications were titrated to maximally
tolerated doses over 4 to 8 weeks. In patients with
asymptomatic bradycardia and/or a systolic blood
pressure <110 mm Hg, medications were not titrated to higher
doses. All patients were to receive ISDN up to the target dose of 120
mg/d. In patients with an LVEF
40%, metoprolol was administered
(maximal dose, 200 mg/d), whereas in those with an LVEF >40%, both
diltiazem (maximal dose, 300 mg/d) and metoprolol were given as
clinically tolerated. Metoprolol was initially chosen for patients with
an LVEF
40% because of the known survival advantage with
ß-blockers in this population.5 15 Diltiazem
was chosen for patients with an LVEF >40% on the basis of trials
demonstrating a significant reduction in early
reinfarction7 and late cardiac
events16 with this medication and no excess risk
of heart failure.17 All patients received
aspirin, and lipid-lowering agents were given to treat
hypercholesterolemia. Patients continued the
same anti-ischemic dosing regimen throughout the study.
Coronary Angioplasty Group
All patients had PTCA of the infarct-related artery and any
other artery with significant (
50%) stenosis that was
supplying an ischemic zone as determined by adenosine
SPECT. Anti-ischemic medications were given to treat residual
angina, and ß-blocker use was empirically encouraged. Aspirin and
lipid-lowering agents were administered as in the medical treatment
group.
Adenosine 201Tl SPECT
Adenosine SPECT was performed as previously reported by
our laboratory.2 Adenosine was
administered intravenously with a standard 6-minute
protocol, with injection of 201Tl at minute 3.
Initial and 4-hour-delayed images were acquired.
SPECT quantification was performed by 1 experienced investigator
(J.J.M.) who was blinded to patient randomization. The initial and
4-hour-delay polar maps were independently computer generated and
normalized with circumferential profile
analysis.2 Raw data polar maps for each
patient were compared statistically with a corresponding normal data
bank to determine total LV PDS and the extent of scarring and
ischemia. Anti-ischemic medications were withheld
12
hours before SPECT 1 was performed but were given on the morning of
SPECT 2.
Cardiac Events
All patients were closely monitored after hospital discharge in
the outpatient clinic: weekly for the first 2 months, monthly for 3
months, and once every 3 months thereafter. Cardiac events were
prospectively defined as (1) cardiac death, (2) nonfatal reinfarction
(ie, rise in creatine kinase-MB in a patient with new ST changes and/or
chest pain), and (3) unstable angina (ie, rest or worsening exertional
chest pain requiring hospital admission, with transient ST changes but
no rise in cardiac enzymes).2
Statistical Analysis
The primary study goal was to determine the extent to
which each treatment strategy reduced the mean total LV PDS. Secondary
goals were to compare reductions in mean ischemic PDS with each
strategy and determine the relationship between changes in PDS and
patient outcome. A
9% reduction in PDS with SPECT defines the 95%
CI for a significant change beyond technique
variability.18 With a sample size of 40 patients,
at an
of .05, this study had 80% power to detect a >4% absolute
difference in total and ischemic PDS between strategies.
Baseline characteristics and changes in SPECT variables between
groups were compared with unpaired t tests. Differences in
medication doses and SPECT variables over time were assessed by
paired t tests.
2 analysis
compared discrete data variables. Kaplan-Meier analysis
compared event rates based on a change in PDS dichotomized at 9%. Data
are presented as mean±SD. A P value <0.05 was
considered significant.
| Results |
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Anti-Ischemic Medical Therapy
Patients randomized to medical therapy had a marked increase in
the number and doses of medications administered during the titration
phase of the study (Figure 1
). The dose
of ISDN increased from 58±14 mg/d in 14 patients to 113±23 mg/d in 21
patients, whereas the dose of metoprolol doubled and that of diltiazem
tripled. After therapy was optimized, all patients in the medical limb
were taking either 2 (73%) or 3 (27%) drugs (Table 2
). Furthermore, 95% and 59% of
patients were taking maximal doses of at least 1 or 2 medications,
respectively.
|
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In the PTCA group, the number and doses of anti-ischemic
medications did not significantly differ between SPECT 1 and 2 (Figure 1
). These patients were ultimately taking
1 (42%) or at most 2
(58%) medications (Table 2
). Only 3 patients (16%) were taking
maximal doses of any medication, and in 2 this was for treatment of
hypertension. Thus, at the time of SPECT 2, patients assigned to
medical therapy were (1) taking significantly higher doses of
metoprolol and ISDN and (2) taking a greater number of
anti-ischemic medications (2.3±0.5 versus 1.5±0.6;
P<0.0001) at maximal dosages (95% versus 16%;
P<0.0001) than those assigned to PTCA. Ten patients in each
treatment strategy were taking lipid-lowering medications
(P=NS).
Coronary Angioplasty
No patient randomized to medical therapy had coronary
revascularization before SPECT 2. Patients
randomized to PTCA had revascularization performed
in either 1 (n=17) or 2 (n=2) arteries: 12 left anterior descending, 4
circumflex, and 5 right coronary arteries. Stents were
deployed in 6 patients. PTCA was successfully performed in 19 (79%) of
24 coronary arteries with >50% stenosis and
scintigraphic ischemia within their vascular territory.
Side Effects With Medical Therapy
In patients randomized to medical therapy, ISDN was discontinued
(n=1) or titrated downward (n=2) in 3 patients owing to headaches, but
19 of 22 were maintained on maximal doses (Table 3
). Metoprolol was
discontinued or titrated downward in 4 of 22 patients because of
intolerable side effects. Nine additional patients did not achieve
maximal doses because of asymptomatic bradycardia or
hypotension or because of fatigue; 6 of these 9 patients were already
taking high-dose diltiazem. Metoprolol was not added in 4 others who
were taking maximal doses of ISDN and diltiazem. Diltiazem was
discontinued in only 1 patient owing to tremor but was not started in 8
patients who had either an LVEF
40% (n=6) or
asymptomatic bradycardia while taking high-dose metoprolol
(n=2). Ten patients were taking maximal doses of diltiazem. Overall, 8
(36%) of 22 patients had 1 of their medications discontinued or
titrated downward owing to side effects (Table 3
).
|
In patients randomized to PTCA, ISDN was discontinued in 1 because of headaches, and metoprolol was titrated downward in another owing to fatigue.
SPECT Results
In the 41 patients studied with sequential SPECT, the total LV PDS
significantly decreased from 37±13% at baseline to 23±16% after
anti-ischemic therapy (P<0.0001). The reduction in
ischemic PDS from 20±10% to 8±9% (P<0.0001)
accounted entirely for the decrease observed in total PDS. The scar
size did not significantly change with therapy.
Total and ischemic PDS were significantly reduced in patients
randomized to either medical therapy or PTCA (Figure 2
). The magnitude of the absolute
reduction in total (-12±11% versus -15±14%) and ischemic
(-12±10% versus -12±9%) PDS was similar (P=NS) in both
groups. A significant (
9%) reduction in total PDS was observed in an
equal number of patients randomized to either strategy (n=12) (Figure 3
).
|
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Cardiac Events
Cardiac events occurred in 7 of 44 patients. In the medical
therapy group, 1 patient died, and 3 developed unstable angina; 2 had
CABG, but this occurred after SPECT 2. In the PTCA group, 1 patient
died, and 2 had nonfatal reinfarction. One patient in each group
continued to have intermittent exertional angina. Cardiac event rates
were similar between patients treated medically (17%) and those who
underwent PTCA (14%; P=NS).
Cardiac Events Based on Changes in Ischemia
Sequential adenosine SPECT assessed the relationship
between ischemia suppression and patient outcome. Baseline
total PDS (35±11% versus 37±13%) and ischemic PDS (18±12%
versus 20±9%) were similar (P=NS) in patients who did
(n=7) or did not (n=34) have a recurrent event. Patients who were
clinically stable at follow-up had a greater reduction in their total
PDS (-15±13% versus -6±7%; P<0.02) and
ischemic PDS (-13±9% versus -5±7%; P<0.02)
than those who had an event, respectively. Only 1 (4%) of 24 patients
who had a significant (
9%) reduction in PDS with
anti-ischemic therapy returned to the hospital with a
subsequent event versus 6 (35%) of 17 patients who had persistent
defects (P=0.009) (Figure 4
).
The sequential SPECT images of a patient randomized to medical therapy
are shown in Figure 5
.
|
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| Discussion |
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The present study is the first randomized, prospective trial to directly compare the anti-ischemic effects of intensive medical therapy and PTCA in clinically stable patients who had "high-risk" scintigraphic ischemia demonstrated early after AMI. By study design, patients with an LVEF <35% were excluded because CABG is preferable in this group of patients who also have ischemia.13 To avoid potential treatment bias, patients were only randomized after they were deemed amenable to PTCA. Our results indicate that intensive medical therapy suppresses myocardial ischemia to a degree comparable to that achieved by a combination of PTCA and low-dose background medical therapy. The sequential SPECT results suggest that ischemia suppression with either strategy results in a favorable event-free survival at 1 year.
Ischemia Suppression With Medical Therapy
Our results with medical therapy in patients surviving AMI are
directionally similar to those reported in trials evaluating patients
with stable CAD.21 22 23 24 25 26 Various nitrate
preparations,23 24 25
ß-blockers,26 and calcium
antagonists25 can effectively reduce
stress-induced scintigraphic ischemia. The
Asymptomatic Cardiac Ischemia Pilot (ACIP) study
likewise demonstrated that ischemia suppression is achievable
with combination medical therapy.27 28 In ACIP,
coronary revascularization was superior to
medical therapy in suppressing ambulatory ECG ischemia, but the
latter was less aggressively administered than in the present
study. In fact, most patients in ACIP were only taking low doses of 1
or, at most, 2 medications.28
The Danish trial in Acute Myocardial Infarction (DANAMI)29 compared the relative efficacy of medical therapy versus coronary revascularization in patients surviving AMI. Although mortality rates were similar over 2.4 years, infarct-free survival was significantly better in patients randomized to revascularization (90.8%) than in those who received medical therapy (85.1%). However, medical therapy was prescribed only according to local practice, with no guidelines for dose titration, so that a minority of patients were taking ß-blockers (40%), calcium antagonists (41%), or long-acting nitrates (25%). No data were reported as to the number or doses of medications that patients received.
To ensure an objective comparison between medical therapy and PTCA, the present study titrated medical therapy over 4 to 8 weeks until protocol-directed dosing end points were achieved. Accordingly, all of our patients randomized to medical therapy were ultimately taking maximally tolerated doses of 2 (73%) or 3 (27%) drugs. These differences in study design may help explain the apparent disparity between our results and those reported by the ACIP and DANAMI investigators.
Tracking Ischemia Suppression With Adenosine SPECT
Exercise SPECT is an accurate and reproducible technique for the
evaluation of ischemia
suppression.23 24 30 The present study and
others26 31 demonstrate that SPECT, when combined
with pharmacological stressors, can also track changes in myocardial
ischemia after medical therapy. The mechanisms underlying these
changes may relate to the effects of medications on resting
coronary flow reserve. Nitrates improve resting myocardial
blood flow in patients with CAD32 through direct
vasodilation of epicardial33 or collateral
vessels.23 The improved detection of tissue
viability in underperfused myocardium after
nitroglycerin-augmented 201Tl
reinjection imaging further supports this
finding.34 ß-Blockers reduce resting myocardial
oxygen demands in normal subjects and thereby increase coronary
blood flow during dipyridamole-induced
hyperemia.35 Anti-ischemic
medications, by improving resting coronary flow reserve, may
allow a more homogeneous increase in myocardial blood flow
during pharmacologically induced hyperemia, thereby reducing
perfusion defects.
Ischemia Suppression and Subsequent Outcome
The presence and extent of residual myocardial ischemia
after AMI predict subsequent risk for cardiac
events.1 2 Mounting evidence supports the concept
that ischemia suppression in patients with CAD may reduce risk
and improve long-term outcome.36 37 38 In both the
ACIP and Atenolol Silent Ischemia Study, suppression of
ambulatory ECG ischemia predicted an improved event-free
survival.36 37 In the Angioplasty Compared to
Medicine study, survival was improved if medical therapy or PTCA
suppressed exercise-induced scintigraphic
ischemia.38 Our results are in agreement
with these findings. Patients who remained clinically stable had a
significantly greater reduction in ischemic PDS after therapy
than those who had a subsequent event. In fact, event-free survival was
96% in patients who had a significant (
9%) reduction in PDS
compared with only 65% in those who did not. These preliminary data
all indicate that ischemia suppression, by whatever means, may
improve patient outcome. Our results support the role of
adenosine SPECT for tracking patient risk on the basis of
changes in the extent of inducible myocardial ischemia.
Study Limitations
The small sample size of this single-center pilot study precludes
direct comparison of cardiac event rates between treatment groups. This
is precisely why SPECT parameters were chosen as a
surrogate end point for events. The high reproducibility of
SPECT18 affords evaluation of
anti-ischemic therapies with relatively small sample
sizes.23 24 30
Although anti-ischemic medications and PTCA were comparable at suppressing ischemia, neither therapy accomplished this in all patients. It is possible that more complete coronary revascularization, as achieved with CABG, might have more effectively reduced ischemia than either medical therapy or PTCA.39
Conclusions
This prospective, randomized study demonstrates that medical
therapy and PTCA are comparable at suppressing myocardial
ischemia in stable but high-risk survivors of AMI. The
sequential imaging results further strengthen the concept that future
outcome is closely linked to the degree of ischemia
suppression. Adequately powered clinical event trials are needed to
better define the independent and combined roles of medical and
revascularization strategies in suppressing
ischemia. Such trials will ultimately have profound
implications for both the management of patients after AMI and the
proper allocation of healthcare resources.
| Acknowledgments |
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| Footnotes |
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Received January 6, 1998; revision received May 4, 1998; accepted July 16, 1998.
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