(Circulation. 2001;103:954.)
© 2001 American Heart Association, Inc.
Clinical Investigation and Reports |
From Tel Aviv Sourasky Medical Center and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel (G.I.B.); Rabin Medical Center, Belinson Campus, Petah Tiqva, Israel (Y.B.); the Biostatistical Centre (K.B., E.L.) and the Department of Cardiology (K.H., K.M., F.V.d.W.), Catholic University, Leuven, Belgium; Duke Clinical Research Institute, Durham, NC (M.H., C.B.G., K.P., R.M.C.); Division of Cardiology, Alberta University, Alberta, Canada (Y.F.); the Canadian Heart Research Centre, University of Toronto, Toronto, Canada (S.G.); and the Cleveland Clinic Foundation, Cleveland, Ohio (E.J.T.).
Correspondence to Gabriel I. Barbash, MD, MPH, Tel Aviv Sourasky Medical Center, 6 Weizman St, Tel Aviv, Israel 64239. E-mail gabi{at}tasmc.health.gov.il
| Abstract |
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Methods and ResultsData from the 4% of patients (n=2301) who experienced reinfarction after thrombolytic therapy were studied. Baseline characteristics, 30-day mortality, and incidence of total and hemorrhagic strokes were compared among the 3 treatment groups. The 30-day mortality did not differ between the repeat thrombolysis and revascularization groups (P=0.72), and it was significantly lower among patients treated by these 2 strategies than in those treated conservatively (11% and 11% versus 28%, respectively; P<0.001). Stroke rates did not differ significantly between the 3 treatment strategies (P=0.49). From 1992 to 1998, the percentage of reinfarction patients treated with repeat thrombolysis decreased from 29.3% to 18.5% in US centers and from 51.4% to 41.9% in all other centers (P<0.001). In contrast, use of revascularization procedures increased from 33.5% to 47.9% in US centers and from 8.1% to 23.0% in all other centers (P<0.001).
ConclusionsRepeat thrombolysis and revascularization are associated with significantly lower mortality among reinfarction patients. Randomized trials are necessary to assess the exact risks and benefits of rethrombolysis versus interventional revascularization in this subset of high-risk patients presenting with reinfarction after thrombolytic therapy.
Key Words: myocardial infarction trials thrombolysis revascularization reinfarction
| Introduction |
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Reinfarction may be treated in 1 of the following 3 ways: (1) conservatively with antithrombotic and vasodilating medications, (2) repeat administration of thrombolytic therapy,12 15 16 or (3) with urgent interventional revascularization by coronary angioplasty3 or bypass operation.2
Although many studies have reported on treatment strategies to prevent reinfarction, few studies2 4 have addressed the use and effectiveness of the different treatment strategies for early reinfarction after thrombolysis. We do not know whether intravenous thrombolytic therapy is as effective for reinfarction as for index infarction. Moreover, it is unclear whether the readministration of thrombolytic therapy is associated with the same or a greater risk of bleeding as it is with the first administration. This retrospective comparative analysis used the databases of 2 large-scale, multicenter trials of thrombolytic therapy in acute myocardial infarction and documented the change in the treatment of reinfarction from 1992 to 1998 in the US and non-US centers.
| Methods |
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Definitions
Reinfarction was defined in the GUSTO I trial by at
least 2 of the following 4 criteria: (1) recurrent ischemic symptoms
lasting >15 minutes after resolution of symptoms of the index
myocardial infarction, (2) occurrence of new ST-T wave changes or new Q
waves, (3) a second elevation in cardiac enzymes to over the normal
upper limit (or by a further 20% if already over the normal upper
limit), and (4) angiographic reocclusion of a documented previously
patent infarct-related artery.
In the ASSENT 2 trial, reinfarction was defined in the first
18 hours after the start of drug administration by recurrent signs and
symptoms of ischemia at rest accompanied by new or recurrent ST-segment
elevations of 0.1 mV in at least 2 contiguous leads that persisted for
at least 30 minutes. After 18 hours, reinfarction was defined by the
appearance of new Q waves (by Minnesota Code Criteria) in
2 leads,
new left bundle branch block, and/or enzyme evidence of reinfarction,
which was defined as re-elevation of creatine kinase-MB (CK-MB) to
above the upper limit of normal and increased by
50% over the
previous value. If CK-MB was not available, the total CK was evaluated;
this measurement had to be either re-elevated to at least twice the
upper limit of normal and increased by at least 25%, or re-elevated to
200 U/mL over the previous value; if it was re-elevated to less than
twice the upper limit of normal, the total CK had to exceed the upper
limit of normal by at least 50% and exceed the previous value by
2-fold or to be re-elevated to
200 U/mL. Reinfarction after
percutaneous transluminal coronary angioplasty (PTCA; with or without
stenting) was defined as a CK-MB (or CK, if MB was not available) more
than twice the upper limit of normal and at least 50% greater than the
previous value and/or new Q waves (Minnesota Code) in
2 contiguous
leads. Reinfarction after coronary artery bypass grafting (CABG) was
defined as a CK-MB (or CK, if MB is not available) >5 times the upper
limit of normal and at least 50% greater than the previous value
and/or new Q waves (Minnesota Code) in
2 contiguous
leads.
Bleeding complications in the ASSENT 2 study were documented by the investigators in the case record forms and included all bleeding events that occurred after reinfarction.
Electrocardiographic characterization of the reinfarction
event was made in the GUSTO I study by the investigators, who
documented the symptoms and signs on which the recurrent infarction was
defined. Among these were ECG changes at the time of reinfarction,
including ST-segment elevation
1 mm, ST-segment depression, T-wave
changes, and development of a new Q wave.
In the ASSENT 2 study, experienced readers blinded to
clinical outcome at the ECG core laboratory analyzed the reinfarction
ECGs. ST-segment deviation (of at least 0.1 mV, with at least 0.1 mV
depth and 40 ms duration) in at least 2 contiguous leads was recorded
based on an analysis of the reinfarction ECGs. Modified Selvester QRS
Criteria17 were used for
defining Q-wave (or Q-wave equivalent) infarction, as follows: (1) Q
wave of at least 40 ms in leads I, AVL, and V4V6; (2) Q waves of 20
to 39 ms in leads II, II, and AVF; (3) Q wave of any duration in lead
V2; (4) R wave of at least 40 ms in V1 or 50 ms in V2; and (5) R wave
0.1 mV and 10 ms in lead V2.
Treatment of reinfarction was at the discretion of the treating physicians and was not randomized or specified by the protocol of either trial. For this analysis, patients with reinfarction during the index hospitalization were divided into the following 3 groups: those who received repeated thrombolytic therapy (repeat thrombolysis group), those who underwent interventional coronary revascularization (coronary angioplasty and/or coronary bypass surgery) the same or next day after reinfarction and did not receive repeat thrombolytic therapy (revascularization group), and those who did not receive repeated thrombolysis, PTCA, or CABG the same or next day after reinfarction (conservative group). Stroke was defined as a complication of the reinfarction or its treatment only when it occurred after the reinfarction. The outcome of the 3 treatment strategies was evaluated in the separated and combined GUSTO I and ASSENT 2 populations using a multivariate analysis accounting for treatments and all known baseline characteristics, including treatment in US versus Non-US centers.
Statistical Analysis
Clinical and historical data are presented by numbers
and percentages for categorical variables and by mean, standard
deviation, and 25th, 50th (median), and 75th percentiles for continuous
variables. Differences between patients with and without reinfarction
and between reinfarction treatment groups were evaluated with an exact
2 test, a
t test, or a Kruskal-Wallis
test, whichever was appropriate.
A multiple logistic regression analysis was performed in the subset of patients experiencing reinfarction to check for treatment differences in 30-day mortality and stroke after adjustment for all known baseline characteristics. These baseline characteristics included study, study medication, medical center (US versus non-US), sex, diabetes, hypertension, infarct location, Killip class at entry, previous myocardial infarction (before randomization in the study), current smoker, age, height, weight, systolic and diastolic blood pressures, race, heart rate, previous PTCA, previous CABG, and ST-segment elevation reinfarction.18
| Results |
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Treatment Strategies
Figures 1
and 2
show the proportional use of the 3
reinfarction treatment strategies in medical centers in the United
States and elsewhere. Centers outside the United States used repeated
thrombolytic therapy almost twice as often as US centers in both the
GUSTO I and ASSENT 2 studies. Non-US centers referred significantly
fewer patients to interventional coronary revascularization. The
differences in treatment strategies between the 2 geographic areas were
highly significant (P<0.001
for each of the studies).
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From 1992 (GUSTO I) to 1998 (ASSENT 2), fewer patients with
reinfarction were treated with repeated thrombolytic therapy (from
29.3% to 18.5% in US centers and from 51.4% to 41.9% in all other
centers;
Figures 1
and 2
). This change was balanced by a significant
increase in the use of urgent coronary angioplasty or bypass surgery
(from 33.5% to 47.9% in US centers and from 8.1% to 23.0% in all
other centers). As a result, the proportion of patients treated
conservatively decreased by 3.6% in the US centers and by 5.5% in all
other centers.
Baseline Characteristics by Treatment
Groups
Table 2
summarizes the baseline characteristics of the
patients in the 3 treatment groups in the combined GUSTO I and ASSENT 2
populations. Patients treated conservatively tended to be women, older,
and less often current smokers and to have a higher rate of previous
myocardial infarction and a higher incidence of Killip classification
>1 on admission. Among patients treated conservatively, the timing of
reinfarction was, on average, 1 day later. The proportion of
reinfarction patients developing recurrent ST-segment elevation
infarction was significantly higher among patients in the
rethrombolysis treatment group compared with the revascularization and
conservative treatment groups (97.4% versus 89.7% and 85.7%,
respectively;
P<0.001).
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Clinical Outcome by Treatment Groups
Tables 3
and 4
summarize indices of myocardial damage after
reinfarction and mortality and safety outcomes of the 3 treatment
groups for the GUSTO I and ASSENT 2 populations. In the GUSTO I study,
fewer patients in the rethrombolysis group developed a new Q wave after
the reinfarction (6.3% compared with 11.7% and 10.1% in the
revascularization and conservative groups, respectively;
P=0.006). Conversely, in the
ASSENT 2 study, new Q waves developed in only 15.7% of the patients in
the conservative group but in 18.1% and 27.5% of those in the
rethrombolysis and revascularization groups, respectively
(P=0.04). The overall stroke
rate was not significantly different among the treatment groups in the
combined trials. However, the rate of intracranial hemorrhage was
significantly different
(P=0.046) among treatment
groups in the GUSTO I study.
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Mortality, both in-hospital and 30-day, was
significantly higher for the conservative group
(P<0.0001), even after
adjusting for all known baseline characteristics, including an ST or
nonST-segment elevation myocardial infarction
(Table 5
). The 30-day mortality was significantly
higher in the conservative group compared with the rethrombolysis group
(odds ratio, 2.2; 95% confidence interval, 1.5 to 3.1;
P<0.001) and the
revascularization group (odds ratio, 2.2; 95% confidence interval, 1.4
to 3.3; P<0.0001), but it did
not differ significantly between the revascularization and repeat
thrombolysis groups in the combined population of the GUSTO I and
ASSENT 2 trials (odds ratio, 1.0; 95% confidence interval, 0.6 to 1.6;
P=0.99). After adjustment for
all other factors, the 30-day mortality rate was not statistically
different in US versus non-US centers
(P=0.53). Results were similar
when the analysis was restricted to only the population with
ST-elevation myocardial infarction.
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In the ASSENT 2 population, detailed bleeding event data were collected. In this study, bleeding complications occurred significantly more often in the patients treated with repeated thrombolytic therapy (29%) and interventional revascularization (31%) than in those treated conservatively (18%; P=0.005).
| Discussion |
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It is interesting to note that although not commonly advocated and despite concerns about bleeding complications, a significant proportion of patients with reinfarction were treated with a repeat dose of thrombolytic agent: 30% to 20% in US centers and almost half of the patients in all other centers. Over time, the increase in interventional revascularization procedures was associated with a decrease in the use of repeat thrombolytic therapy, but it only minimally affected the proportion of patients who were treated conservatively. This retrospective analysis has 3 major conclusions. First, patients with reinfarction are at a high risk for increased in-hospital and 30-day mortality. Second, as previously demonstrated,4 patients with reinfarction who are treated with either pharmacological or interventional reperfusion therapies have significantly lower mortality. It should be noted, however, that although known baseline variables were accounted for, other unaccounted baseline characteristics might have biased the group of patients treated conservatively.
A third and debatable conclusion is that repeat administration of thrombolytic therapy and urgent revascularization strategies for reinfarction are generally safe and have comparable and acceptable bleeding risks. Although the ASSENT 2 results demonstrate significantly higher rates of bleeding events, the incidence of intracranial hemorrhage or life-threatening bleeding after re-exposure to thrombolytic agent or revascularization procedures was not significantly affected.
Our results are not conclusive, and they certainly do not negate all safety concerns. Thrombolytic therapy is usually not readministered to patients who have a bleeding complication after the first thrombolytic dose; hence, selection bias may cause less bleeding in the patients treated with repeat thrombolytic therapy. It is interesting to note that reinfarction occurred 1 day later in the patients treated conservatively. Earlier treatment of reinfarction with repeat thrombolysis or coronary intervention may involve a higher risk for a bleeding complication. In addition, patients in the GUSTO I study who were treated with repeat thrombolytic therapy suffered a higher rate of intracranial hemorrhage than the patients treated in the interventional and conservative groups (1.3% compared with 0.0% and 0.5%, respectively; P=0.046). In the ASSENT 2 study, there was no difference in the rate of intracranial hemorrhage among the 3 treatment groups (0.4%, 1.0%, and 0.0% in the rethrombolysis, revascularization, and conservative groups, respectively; P=0.28). However, in this study, only a few patients (3 of 672) suffered an intracranial hemorrhage; thus, no comfort can be gleaned from these data.
Despite a large overall sample size and excellent data recording, our analysis has a number of important limitations. Neither GUSTO I nor ASSENT 2 were specifically designed to assess treatment strategies for early reinfarction. Criteria for diagnosing reinfarction likely failed to identify some episodes of myocardial necrosis, because study protocols did not mandate standardized ECG monitoring or cardiac enzyme collection after recurrent ischemic symptoms and revascularization procedures. Also, treatment assignment after reinfarction to the conservative, readministration of thrombolytic agent, or early revascularization groups was not randomly assigned. Selection bias of younger, healthier, more hemodynamically stable patients in the more aggressive treatment strategies might therefore greatly affect mortality and bleeding outcomes. Finally, low event rates, particularly for overall stroke and intracranial hemorrhage, leave our analysis underpowered to make strong comparative conclusions between treatment strategies for these important safety outcomes.
Despite these limitations, a more aggressive approach toward patients presenting with reinfarction after thrombolytic therapy is associated with improved prognosis. Repeat thrombolytic therapy should be considered, especially where and when timely cardiac catheterization and interventional capabilities are not readily available.4 However, the risk of repeat thrombolysis is to be weighed carefully with the improved mortality gained at likely risk of increased bleeding, as shown in ASSENT 2.
Finally, it is important to note that although the percentage of patients in whom no attempt was made to reopen the occluded coronary artery slightly decreased from 1992 to 1998, these patients still amounted to more than a third of the reinfarction patients in the ASSENT 2 trial. The results of this analysis clearly decree that more aggressive therapy might benefit these high-risk patients. A randomized trial comparing coronary intervention versus repeat thrombolytics is necessary to evaluate the exact risks and benefits of the two reperfusion strategies.
Received September 1, 2000; revision received October 17, 2000; accepted October 18, 2000.
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