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Routine vs Selective Invasive Strategies in Patients With Acute Coronary Syndromes:  A Collaborative Meta-analysis of Randomized Trials FREE

Shamir R. Mehta, MD, MSc; Christopher P. Cannon, MD; Keith A. A. Fox, MBCHB; Lars Wallentin, MD; William E. Boden, MD; Rudolf Spacek, MD; Petr Widimsky, MD; Peter A. McCullough, MD, MPH; David Hunt, MD; Eugene Braunwald, MD; Salim Yusuf, MBBS, DPhil
[+] Author Affiliations

Author Affiliations: Department of Medicine, McMaster University, and Population Health Research Institute, Hamilton Health Sciences, Hamilton, Ontario (Drs Mehta and Yusuf); TIMI Study Group and Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Mass (Drs Cannon and Braunwald); Department of Medicine, Royal Infirmary, Edinburgh, Scotland (Dr Fox); Uppsala Clinical Research Center, University Hospital, Uppsala, Sweden (Dr Wallentin); Henry Low Heart Center and Division of Cardiology, Hartford Hospital, Hartford, Conn (Dr Boden); Cardiocenter, University Hospital Kralovske Vinohrady, Third Medical School of Charles University, Prague, Czech Republic (Drs Spacek and Widimsky); William Beaumont Hospital, Royal Oak, Mich (Dr McCullough); and Royal Melbourne Hospital, Melbourne, Australia (Dr Hunt).

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JAMA. 2005;293(23):2908-2917. doi:10.1001/jama.293.23.2908.
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Context Patients with unstable angina or non–ST-segment elevation myocardial infarction (NSTEMI) can be cared for with a routine invasive strategy involving coronary angiography and revascularization or more conservatively with a selective invasive strategy in which only those with recurrent or inducible ischemia are referred for acute intervention.

Objective To conduct a meta-analysis that compares benefits and risks of routine invasive vs selective invasive strategies.

Data Sources Randomized controlled trials identified through search of MEDLINE and the Cochrane databases (1970 through June 2004) and hand searching of cross-references from original articles and reviews.

Study Selection Trials were included that involved patients with unstable angina or NSTEMI who received a routine invasive or a selective invasive strategy.

Data Extraction Major outcomes of death and myocardial infarction (MI) occurring from initial hospitalization to the end of follow-up were extracted from published results of eligible trials.

Data Synthesis A total of 7 trials (N = 9212 patients) were eligible. Overall, death or MI was reduced from 663 (14.4%) of 4604 patients in the selective invasive group to 561 (12.2%) of 4608 patients in the routine invasive group (odds ratio [OR], 0.82; 95% confidence interval [CI], 0.72-0.93; P = .001). There was a nonsignificant trend toward fewer deaths (6.0% vs 5.5%; OR, 0.92; 95% CI, 0.77-1.09; P = .33) and a significant reduction in MI alone (9.4% vs 7.3%; OR, 0.75; 95% CI, 0.65-0.88; P<.001). Higher-risk patients with elevated cardiac biomarker levels at baseline benefited more from routine intervention, with no significant benefit observed in lower-risk patients with negative baseline marker levels. During the initial hospitalization, a routine invasive strategy was associated with a significantly higher early mortality (1.1% vs 1.8% for selective vs routine, respectively; OR, 1.60; 95% CI, 1.14-2.25; P = .007) and the composite of death or MI (3.8% vs 5.2%; OR, 1.36; 95% CI, 1.12-1.66; P = .002). But after discharge, the routine invasive strategy was associated with fewer subsequent deaths (4.9% vs 3.8%; OR, 0.76; 95% CI, 0.62-0.94; P = .01) and the composite of death or MI (11.0% vs 7.4%; OR, 0.64; 95% CI, 0.56-0.75; P<.001). At the end of follow-up, there was a 33% reduction in severe angina (14.0% vs 11.2%; OR, 0.77; 95% CI, 0.68-0.87; P<.001) and a 34% reduction in rehospitalization (41.3% vs 32.5%; OR, 0.66; 95% CI, 0.60-0.72; P<.001) with a routine invasive strategy.

Conclusions A routine invasive strategy exceeded a selective invasive strategy in reducing MI, severe angina, and rehospitalization over a mean follow-up of 17 months. But routine intervention was associated with a higher early mortality hazard and a trend toward a mortality reduction at follow-up. Future strategies should explore ways to minimize the early hazard and enhance later benefits by focusing on higher-risk patients and optimizing timing of intervention and use of proven therapies.

Figures in this Article

Despite advances in invasive coronary procedures over the past decade, their optimal role and timing in patients with unstable angina and non–ST-segment myocardial infarction (NSTEMI) remains a challenge.1 The question of whether to routinely refer patients with unstable angina or NSTEMI for invasive procedures, or whether to treat such patients aggressively with pharmacological interventions followed by selective referral of those with refractory or inducible ischemia, is a decision clinicians commonly face. Uncertainty about the value of a routine invasive strategy is reflected by widespread variations in procedure use among individual clinicians, institutions, and countries.24 Over the past decade, randomized trials and large-scale registries addressing this question have spawned debate, partly because they pit different management philosophies against each other and partly because they have challenged clinical practice in some settings.

We sought to evaluate the early and late effects of a routine invasive strategy compared with a selective invasive strategy on major cardiovascular outcomes in patients with unstable angina and NSTEMI, based on the totality of data from randomized trials. If benefits of a routine intervention emerge early, then it could be argued that strategies for the care of such patients should be geared toward rapid catheterization and early revascularization. If, on the other hand, benefits are delayed, a more selective approach might be clinically preferable. To accomplish this task, we performed a collaborative meta-analysis of the randomized trials, focusing on key outcomes during the initial hospitalization and over the longer term.

Search Strategy

Studies were identified through a computerized literature search of the MEDLINE and Cochrane databases from 1970 through June 2004 and screening of abstracts from major cardiology meetings. In addition, extensive hand searching was performed using cross-references from original articles and reviews.

Definitions

A routine invasive strategy was defined as the referral of all patients with unstable angina or NSTEMI for coronary angiography followed by revascularization in those with suitable coronary anatomy. A selective invasive strategy (also referred to as a conservative or noninvasive strategy) was defined as an approach whereby patients were initially treated with pharmacological therapy, after which cardiac catheterization and revascularization was performed only for those with recurrent symptoms or objective evidence of inducible ischemia on noninvasive testing.

Study Selection Criteria

Trials were included if they enrolled patients with unstable angina or NSTEMI and randomly allocated patients to receive a routine invasive strategy or a selective invasive strategy. Trials were excluded if the majority of patients randomized in the trial had stable angina pectoris or acute ST-segment elevation myocardial infarction (MI). Trials with inadequate concealment of the randomized treatment allocation (eg, allocation by day of the week) were excluded, as were trials in which inclusion was determined after the performance of coronary angiography.

Data Extraction and Statistical Analyses

Data on in-hospital and longer-term death, nonfatal MI, the composite of death or nonfatal MI, Canadian Cardiovascular Society class III or IV angina, and rehospitalization were extracted from each of the published studies independently by 2 investigators. The extracted data were then sent to the principal investigators of the selected studies, who were invited to participate in this collaborative meta-analysis. They were asked to verify the accuracy of the data and, when necessary, to provide additional data. Data were checked and verified by the principal investigators in all of the included trials. Procedure-related and non–procedure-related MI was defined in this analysis according to how it was reported in each of the individual trials.

The statistical methods used to combine the data have been described in detail and used extensively.5 The underlying principle is the comparison of patients allocated to intervention in a given trial only with those allocated to control treatment in the same trial, avoiding direct comparisons of patients across different trials. These are basically the standard methods for the combination of information from multiple 2 × 2 tables, as reviewed by Mantel and Haenszel6 and modified by Yusuf et al.7 This method entailed calculating the observed events (O, number of events in the treatment group) minus the expected events (E, average number of events for treatment and control groups) and determining the variance (V) for each trial. Grand totals were calculated for each and the ratio of the 2 was used to estimate the odds ratio (OR) and its 95% confidence interval (CI) for each trial. The χ2 tests for heterogeneity were approximated by summing the N separate χ2 test statistics (O − E2/V) for each trial and subtracting the overall χ2 value (GT2/SIV, where GT indicates grand total and SIV, the sum of the individual variances) from this, using N − 1 degrees of freedom.7 The data were also analyzed using a random-effects model,8 and the relative risks and 95% CIs for each outcome are presented; however, in no case did the results qualitatively differ from those of the primary analysis. Comprehensive Meta-analysis version 1.0.25 (Biostat Inc, Englewood, NJ) was used for the analysis. P<.05 was set as the level of significance.

We identified 84 articles, of which 14 were reports of the main findings of randomized controlled trials. Of these 14 eligible trials, 7 were excluded922 because patient eligibility was based on results of coronary angiography (n = 4),912 because they were limited mainly to patients with ST-segment elevation MI who were receiving thrombolytic therapy (n = 2),13,14 or because randomization was based on day of the week (n = 1).15

Seven trials involving 9208 patients (4608 routine invasive and 4604 selective invasive) met the inclusion criteria and were included in the analysis (Table 1).1622 Verification of data by the trials’ principal investigators was achieved in 100% of the trials.

Table Graphic Jump LocationTable 1. Entry Criteria, Use of Antithrombotic Medications, Timing of Interventions, and Definitions of Non–Procedure-Related and PCI-Related Myocardial Infarction in Trials of Routine vs Selective Invasive Management of Acute Coronary Syndromes
Baseline Characteristics

Baseline characteristics are shown in Table 2. The weighted mean duration of follow-up of all patients was 17.3 (range, 6-24) months. The mean age of patients was 62.4 (range, 59-66) years. The mean proportion of patients with diabetes was 18.9% (range, 12%-28%), and 32.5% (range, 21%-43%) had a history of MI. A total of 59.0% of patients presented with NSTEMI and 41.0% with unstable angina. Electrocardiographic ST-segment depression was present at baseline in 37.0% of patients, ST-segment elevation (mostly transient) in 9.6%, and T-wave inversion in 49.4%.

Table Graphic Jump LocationTable 2. Baseline Characteristics of Included Studies

In-hospital and follow-up revascularization rates among the studies are shown in Table 1. During the initial hospitalization, 2691 (58.4%) of 4608 patients underwent revascularization in the routine intervention group and 1104 (24.0%) of 4604 patients underwent revascularization in the selective intervention group, for a 34.4% in-hospital contrast in revascularization between the groups. At the end of follow-up, 2934 (63.6%) of 4608 underwent revascularization in the routine invasive group compared with 1909 (41.5%) of 4604 in the selective invasive group, for a 22.1% overall contrast in revascularization between the groups. Percutaneous coronary intervention (PCI) was performed in 1167 (25.3%) of 4608 in the routine invasive group and 454 (9.9%) of 4604 in the selective invasive group. Coronary artery bypass graft surgery was performed in 796 (17.3%) of 4608 in the routine invasive group and in 404 (8.8%) of 4604 in the selective invasive group.

Main Outcomes

Randomization to Hospital Discharge. Main outcomes for this period are shown in Figure 1. During the initial hospitalization, 82 (1.8%) of 4608 patients in the routine invasive group died compared with 51 (1.1%) of 4604 in the selective invasive group (OR, 1.60; 95% CI, 1.14-2.25; P = .007). Myocardial infarction was also increased, with 171 (3.7%) of 4608 having had an MI during the initial hospitalization in the routine invasive group, compared with 139 (3.0%) of 4604 in the selective invasive group (OR, 1.24; 95% CI, 0.99-1.56; P = .07). Overall, 238 (5.2%) of 4608 patients in the routine invasive group had a death or MI during the initial hospitalization compared with 177 (3.8%) of 4607 in the selective invasive group (OR, 1.36; 95% CI, 1.12-1.66; P = .002).

Figure 1. Main Outcomes From Randomization to Hospital Discharge in Trials of Routine vs Selective Invasive Management of Acute Coronary Syndromes
Graphic Jump Location

Sizes of data markers are proportional to the amount of data contributed by each trial. Tests for heterogeneity: mortality, P = .15; nonfatal myocardial infarction (MI), P = .001; composite of death or MI, P = .001. Relative risks and 95% confidence intervals (CIs) from random-effects model: mortality, 1.56 (0.96-2.53); nonfatal MI, 1.20 (0.73-1.97); death or MI, 1.31 (0.85-2.01). OR indicates odds ratio. See Table 1 footnote for trial dates and expansions of trial names.

Hospital Discharge to End of Follow-up. Main outcomes for this period are shown in Figure 2. After hospital discharge the number of events were fewer in the routine intervention group. Overall, 172 (3.8%) of 4526 patients died during this period in the routine invasive group compared with 223 (4.9%) of 4552 in the selective invasive group (OR, 0.76; 95% CI, 0.62-0.94; P = .01). Similarly, there was a 44% relative odds reduction in MI during this period (164/4370 [3.8%] vs 294/4430 [6.6%]; OR, 0.56; 95% CI, 0.46-0.67; P<.001) and a 36% relative odds reduction in the composite of death or MI (323/4370 [7.4%] vs 486/4430 [11.0%]; OR, 0.64; 95% CI, 0.56-0.75; P<.001).

Figure 2. Main Outcomes From Hospital Discharge to End of Follow-up in Trials of Routine vs Selective Invasive Management of Acute Coronary Syndromes
Graphic Jump Location

Sizes of data markers are proportional to the amount of data contributed by each trial. Tests for heterogeneity: mortality, P = .04; nonfatal myocardial infarction (MI), P = .02; composite of death or MI, P = .001. Relative risks and 95% confidence intervals (CIs) from random-effects model: mortality, 0.74 (0.52-1.05); nonfatal MI, 0.57 (0.40-0.80); death or MI, 0.65 (0.46-0.91). See Table 1 footnote for trial dates and expansions of trial names. OR indicates odds ratio.

Randomization to End of Follow-up. Main outcomes for this period are shown in Figure 3. Overall, death occurred in 254 (5.5%) of 4608 patients in the routine invasive group compared with 274 (6.0%) of 4604 in the selective invasive group, a nonsignificant 8% relative odds reduction in mortality (OR, 0.92; 95% CI, 0.77-1.09; P = .33). Myocardial infarction occurred in 335 (7.3%) of 4608 patients in the routine invasive group and 433 (9.4%) of 4604 in the selective invasive group (OR, 0.75; 95% CI, 0.65-0.88; P<.001). The composite of death or MI was also significantly reduced in the routine invasive group: 561 (12.2%) of 4608 compared with 663 (14.4%) of 4604 in the selective invasive group (OR, 0.82; 95% CI, 0.72-0.93; P = .001).

Figure 3. Main Outcomes From Randomization to End of Follow-up in Trials of Routine vs Selective Invasive Management of Acute Coronary Syndromes
Graphic Jump Location

Sizes of data markers are proportional to the amount of data contributed by each trial. Tests for heterogeneity: mortality, P = .04; nonfatal myocardial infarction (MI), P = .51; composite of death or MI, P = .06. Relative risks and 95% confidence intervals (CIs) from random-effects model: mortality, 0.88 (0.66-1.18); nonfatal MI, 0.76 (0.65-0.88); death or MI, 0.82 (0.68-0.99). See Table 1 footnote for trial dates and expansions of trial names. OR indicates odds ratio.

Rehospitalization and Angina

There was a significant reduction in rehospitalizations with a routine invasive strategy (1889/4571 [41.3%] vs 1487/4576 [32.5%] for selective vs routine, respectively; OR, 0.66; 95% CI, 0.60-0.72; P<.001) (Figure 4). There was also a significant reduction in the proportion of patients with Canadian Cardiovascular Society class III or IV angina in the routine invasive strategy group compared with the selective invasive strategy group (633/4507 [14.0%] vs 507/4525 [11.2%]; OR, 0.77; 95% CI, 0.68-0.87; P<.001). A summary of ORs for all major outcomes is shown in Table 3.

Figure 4. Rates of Canadian Cardiovascular Society (CCS) Class III-IV Angina and Rehospitalization at End of Follow-up in Trials of Routine vs Selective Invasive Management of Acute Coronary Syndromes
Graphic Jump Location

Sizes of data markers are proportional to the amount of data contributed by each trial. Tests for heterogeneity: CCS class III-IV angina, P<.001; rehospitalization, P<.001. Relative risks and 95% confidence intervals (CIs) from random-effects model: CCS class III-IV angina, 0.78 (0.58-1.04); rehospitalizations, 0.71 (0.55-0.92). See Table 1 footnote for trial dates and expansions of trial names. OR indicates odds ratio.

Table Graphic Jump LocationTable 3. Summary of Odds Ratios for All Major Outcomes
Exploring Heterogeneity

There was evidence of heterogeneity in the outcome of in-hospital MI (P = .001 for heterogeneity) and the composite of death or MI (P = .001 for heterogeneity). Sensitivity analysis revealed that the source of this heterogeneity was almost entirely due to the TACTICS-TIMI 18 (Treat Angina With Aggrastat and Determine Cost of Therapy With an Invasive or Conservative Therapy–Thrombolysis in Myocardial Infarction 18) trial20 (and to a lesser extent, the much smaller VINO [Value of First Day Angiography/Angioplasty in Evolving ST-Segment Elevation Myocardial Infarction] trial21) relative to the other studies (P = .14 for heterogeneity with TACTICS-TIMI 18 excluded). The possible reasons for the heterogeneity in early MI may have been related to the routine use of a glycoprotein IIb/IIIa antagonist in TACTICS but not in the other trials. Alternatively, it may have been related to the TACTICS differential cardiac marker threshold for an MI outcome after PCI (3 times the upper limit of normal), compared with a non–procedure-related MI (defined as cardiac marker levels above the upper limit of normal) (Table 1). Since procedures were more commonly performed in the routine invasive group, this differential may have biased the results in favor of this group. Although some of the other trials also had a higher threshold for PCI-related MI, the differentials between PCI-related and spontaneous MIs were smaller than in TACTICS (Table 1).

Stratified Analyses

A stratified analysis according to year of publication was performed to assess the impact of advances in overall care, including medical and interventional therapies over the years (Figure 5). Trials published prior to 1999 demonstrated neutral results for death or MI at end of follow-up, whereas trials published after 1999 demonstrated a clear reduction in death or MI with a routine invasive strategy. Troponin data were available in the 3 most recently performed trials. In patients who were troponin-positive at baseline, there was a clear reduction in the composite of death or MI in favor of a routine invasive strategy. However, in those who were troponin-negative, there was no advantage of a routine invasive strategy. Similar results are observed when any biomarker (including creatine kinase, creatine kinase–MB, or troponin) was used. All the trials were included in this latter analysis.

Figure 5. Stratified Analyses of Trials Published Before and After 1999 and According to Baseline Troponin and Cardiac Biomarker Status: Death or Myocardial Infarction From Randomization to Follow-up
Graphic Jump Location

Sizes of data markers are proportional to the amount of data contributed by each trial. Cardiac biomarkers are creatine kinase, creatine kinase–MB fraction, and troponin. In 3 of the 7 trials included in this analysis (VANQWISH, MATE, and VINO), all patients had elevated marker levels at baseline. See Table 1 footnote for trial dates and expansions of trial names.
*TIMI 3B, VANQWISH, and MATE.
†FRISC II, TACTICS, VINO, and RITA 3.
‡FRISC II, TACTICS, and RITA 3.

Our meta-analysis has demonstrated that, in patients with unstable angina and NSTEMI, a routine invasive strategy is superior to a selective invasive (ie, conservative) strategy in reducing long-term major cardiovascular events, as well as severe angina and rehospitalizations. The benefits of a routine invasive strategy emerged mainly after hospital discharge; during the initial hospitalization, this strategy was associated with an increased early hazard. This early hazard, followed by later benefit, suggests that further strategies to favorably enhance the overall benefit-risk ratio associated with a routine invasive strategy need to be considered.

First, appropriate risk stratification of patients with unstable angina and NSTEMI can maximize the benefits of a routine invasive strategy by focusing on those patients who are at higher risk, in whom the absolute benefits of a routine invasive approach are greatest.1 The main benefits of routine intervention over the long term were observed in higher-risk patients with positive baseline cardiac marker levels, with no such benefit observed in patients with negative marker levels (Figure 5), a finding also observed in subgroup analyses from 2 of the trials.23,24 The early hazard associated with routine intervention might be deemed acceptable in the higher-risk patients but unacceptable in most lower-risk patients, in whom there is no evidence of long-term benefit.

Despite these data and the recommendations of expert guideline committees,1 contemporary registry data suggest that higher-risk patients are paradoxically being treated more conservatively, while lower-risk patients are more likely to undergo an invasive strategy.3 The data from our meta-analysis further support the wider adoption of a routine invasive strategy in higher-risk patients and suggest that lower-risk patients, in whom the hazards have a greater likelihood of outweighing the benefits, might be better managed with a more selective approach. In addition to patients with positive baseline cardiac marker levels, the American College of Cardiology/American Heart Association guidelines recommend an invasive strategy in other high-risk groups, such as those with cardiogenic shock or significant heart failure and those with refractory symptoms who are already receiving maximal medical therapies.1

Second, the timing of angiography and revascularization in the routine invasive group may also influence both early and late outcomes. The timing of intervention in patients receiving a routine invasive strategy can involve either very early angiography (for example, within the first 24 hours), or it may involve a more delayed approach (after a period of a few days). Although the TACTICS trial (mean time to angiography, 22 hours) and FRISC II (Fragmin and Fast Revascularization During Instability in Coronary Artery Disease 2) trial (mean time to angiography, 4 days) both demonstrated benefit of a routine invasive strategy on a composite of events, the trial in which intervention was delayed (the FRISC II trial) additionally demonstrated a reduction in mortality. Because the benefits of a routine invasive strategy emerge mainly over the long term (with evidence of early hazard), very early timing of intervention may not enhance the benefits of routine intervention. On the other hand, it may be that there is an immediate hazard with any invasive or surgical procedure that cannot be mitigated by delaying the timing of the procedure. Thus, although a policy of very early intervention has been adopted in some regions, the benefits of this approach on major cardiovascular outcomes remain unclear compared with those of interventions performed after a few days. Clarifying this issue has considerable importance for optimum patient care as well as for the organization of health care services, especially access to rapid cardiac catheterization for all high-risk patients with acute coronary syndromes.

Two randomized studies have addressed the potential benefits of early intervention, with contrasting results. First, a very small, single-center trial demonstrated apparent benefit of an early invasive strategy vs a delayed invasive strategy (12/203 vs 24/207; relative risk, 0.51; 95% CI, 0.26-0.99); however, the CIs of this study were very wide, in keeping with its modest sample size and small number of outcome events.25 Given these important limitations, a much larger number of patients is needed to reliably assess the effects of early vs delayed intervention. Second, a recent Dutch randomized trial of 1201 patients reported no benefit of a routine early invasive strategy, with an overall increase in MI.26 As opposed to most of the trials in this meta-analysis, this trial used the same definition of spontaneous events and MI after PCI. In addition, newer therapies such as clopidogrel and high-dose statins were used in a greater proportion of patients in both groups compared with the older studies. These factors may have narrowed the difference between the 2 groups. Two additional large-registry studies have shown that patients who present to hospitals with catheterization laboratories undergo invasive procedures earlier, yet in these studies mortality was not improved in such centers and there were increases in bleeding and stroke.2,27 Therefore, to reliably address the question of timing of intervention (ie, whether earlier is superior to delayed intervention) among patients undergoing a routine invasive strategy, much larger randomized trials than those currently reported are needed.

Third, greater use of adjunctive pharmacological therapies prior to and after PCI have the potential to reduce periprocedural events and could improve the outcomes associated with the routine invasive approach. Trials of clopidogrel in addition to aspirin have shown that pretreatment with these agents reduces the risk of events that occur prior to, during, and after the revascularization procedure.2831 However, the benefit of clopidogrel is apparent not only in patients treated prior to PCI (at least 6 hours) but also in those treated medically.28 In both these groups, benefit emerges as early as 24 hours, with incremental reductions in death, MI, and stroke with continued long-term therapy.31 Because the trials included in this meta-analysis were designed before the benefits of thienopyridines in patients with unstable angina and NSTEMI were known, these agents were mainly given to patients for 30 days following stent placement, thus creating an imbalance in their use between the groups, which may have impacted on the results of the trials.

Early use of glycoprotein IIb/IIIa inhibitors has also been proven to reduce cardiovascular events, mainly in patients with unstable angina and NSTEMI who are undergoing PCI.32,33 Greater use of these agents in eligible patients would therefore be expected to enhance the benefits of a routine invasive strategy. The TACTICS-TIMI 18 trial used these agents as background therapy in both groups for 48 hours, which may have contributed to the better outcomes in the routine invasive group in that study.

Although antithrombin agents such as enoxaparin are as effective as standard unfractionated heparin in patients with unstable angina and NSTEMI who are undergoing an invasive strategy,34,35 newer agents such as the synthetic penta-saccharide fondaparinux or the direct thrombin inhibitor bivalirudin may potentially provide incremental benefit over unfractionated heparin in this setting and are currently being studied in large-scale randomized trials. Meanwhile, increased long-term use of statins, β-blockers, and angiotensin-converting enzyme inhibitors would improve outcomes in patients with unstable angina and NSTEMI, regardless of management approach.

Combining the data from these trials comparing selective vs routine invasive strategies has several advantages. First, it improves statistical power to detect important differences between the groups. Because these trials involved a pragmatic clinical approach comparing 2 management strategies, revascularization procedures were allowed in both groups. Thus, contrast in revascularization rates between the routine and selective invasive strategies was modest (34% during the initial hospitalization and 22.1% at follow-up), which reduces statistical power in the individual trials. By combining the data in the form of a meta-analysis, as we have done, the power to detect even moderate but clinically important differences between the 2 strategies substantially increases. Second, there has been controversy about the interpretation of individual trial results when they may not intuitively support specific practice philosophies. It is possible that an unexpected result for a single outcome in a particular randomized trial may be real or due to the play of chance. For example, there has been discussion regarding the higher mortality associated with routine intervention in the VANQWISH (Veterans Affairs Non-Q-Wave Infarction Strategies in Hospital) study18 vs the others. However, sensitivity analysis demonstrates that when VANQWISH is removed from the analysis, there is still a consistent early risk in mortality among the other trials (OR, 1.35; 95% CI, 0.92-2.00), with no statistical heterogeneity. The advantage of combining the results of all trials addressing the same broad question is that the results reflect a wider range of practices and technical skills,36 and a more robust estimate of risk is likely to be obtained.35 This also minimizes the play of chance affecting a particular end point in any one trial. Consequently, if a real difference (or lack of a difference) exists, it is likely to be detected.

The largest benefits of a routine invasive strategy in our meta-analysis were in preventing severe angina and rehospitalization, followed by MI prevention and a trend toward a reduction in death. Given the 25% reduction in nonfatal MIs, most of which occurred after hospital discharge, it is plausible that the benefits of a routine invasive strategy on mortality could widen during even longer-term follow-up, as observed in at least 1 trial in this meta-analysis.37,38 In the trials of coronary artery bypass graft surgery vs medical therapy, for example, reductions in mortality became evident only after 1 year, with maximum benefit not observed until 5 to 7 years.39 Thus, longer-term follow-up of the patients included in the current trials would be important to further assess the relative value of the 2 strategies, particularly with respect to mortality.

In patients with unstable angina and NSTEMI, a routine early invasive strategy is superior to a selective invasive strategy in reducing major cardiovascular events as well as severe angina and rehospitalization. However, the main benefit of a routine invasive strategy was in preventing events over the longer term with evidence of early hazard. Therefore, future strategies should explore means of minimizing the early hazard and enhancing the later benefits by focusing on higher-risk patients, optimizing the timing of intervention, and maximizing the use of adjunctive evidence-based therapies.

Corresponding Author: Shamir R. Mehta, MD, MSc, FRCPC, Interventional Cardiology, McMaster University and Hamilton Health Sciences General Division, 237 Barton St E, Room 508, Hamilton, Ontario, Canada L6K 1B8 (smehta@mcmaster.ca).

Author Contributions:Dr Mehta had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Mehta, Cannon, Fox, Wallentin, Boden, McCullough, Hunt, Braunwald, Yusuf.

Acquisition of data: Mehta, Cannon, Fox, Wallentin, Boden, Spacek, Widimsky, McCullough, Braunwald.

Analysis and interpretation of data: Mehta, Cannon, Fox, Wallentin, Boden, Spacek, Widimsky, McCullough, Yusuf.

Drafting of the manuscript: Mehta, Cannon, Fox, Boden, Yusuf.

Critical revision of the manuscript for important intellectual content: Mehta, Cannon, Fox, Wallentin, Boden, Spacek, Widimsky, McCullough, Hunt, Braunwald, Yusuf.

Statistical analysis: Mehta, Boden.

Obtained funding: Cannon, Spacek, Widimsky, Braunwald.

Administrative, technical, or material support: Mehta, Cannon, Wallentin, Boden, Spacek, Widimsky, McCullough, Yusuf.

Study supervision: Mehta, Cannon, Fox, Boden, Hunt, Braunwald, Yusuf.

Financial Disclosures: Dr Cannon receives grant support from Bristol-Myers Squibb, Merck, Sanofi-Aventis, and AstraZeneca; serves on advisory boards of AstraZeneca, Bristol-Myers Squibb, GlaxoSmithKline, Guilford Pharmaceuticals, Merck, Merck/Schering-Plough Partnership, Pfizer, Sanofi-Aventis, Schering Plough, and Vertex; has received lecture fees at continuing medical education conferences with sponsorship from AstraZeneca, Bristol-Myers Squibb, Guilford Pharmaceuticals, Merck, Millenium, Pfizer, Sanofi-Aventis, and Schering Plough; and has received honoraria for preparation of educational materials from BestMed, i3Magnifi, and NCME. None of the other authors report financial disclosures.

Funding/Support: Dr Mehta was supported by a Canadian Institutes of Health Research (CIHR) New Investigator Award. Dr Yusuf was supported by an HSFO endowed chair and a CIHR senior scientist award. Drs Spacek and Widimsky were supported by Charles University Research Project MSM0021620817.

Braunwald E, Antman EM, Beasley JW.  et al. American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on the Management of Patients With Unstable Angina).  ACC/AHA guideline update for the management of patients with unstable angina and non-ST-segment elevation myocardial infarction—2002: summary article: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on the Management of Patients With Unstable Angina).  Circulation. 2002;106:1893-1900
PubMed   |  Link to Article
Yusuf S, Flather M, Pogue J.  et al.  Variations between countries in invasive cardiac procedures and outcomes in patients with suspected unstable angina or myocardial infarction without ST elevation.  Lancet. 1998;352:507-514
PubMed   |  Link to Article
Bhatt DL, Roe MT, Peterson ED.  et al. CRUSADE Investigators.  Utilization of early invasive management strategies for high-risk patients with non-ST-segment elevation acute coronary syndromes: results from the CRUSADE Quality Improvement Initiative.  JAMA. 2004;292:2096-2104
PubMed   |  Link to Article
Fox KA, Goodman SG, Klein W.  et al.  Management of acute coronary syndromes: variations in practice and outcome: findings from the Global Registry of Acute Coronary Events (GRACE).  Eur Heart J. 2002;23:1177-1189
PubMed   |  Link to Article
Antithrombotic Trialists’ Collaboration.  Collaborative meta-analysis of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high-risk patients.  BMJ. 2002;324:71-86
PubMed   |  Link to Article
Mantel N, Haenszel W. Statistical aspects of the analysis of data from retrospective studies of disease.  J Natl Cancer Inst. 1959;22:719-748
PubMed
Yusuf S, Peto R, Lewis J, Collins R, Sleight P. Beta blockade during and after myocardial infarction: an overview of the randomized trials.  Prog Cardiovasc Dis. 1985;27:335-371
PubMed   |  Link to Article
DerSimonian R, Laird N. Meta-analysis in clinical trials.  Control Clin Trials. 1986;7:177-188
PubMed   |  Link to Article
 Unstable angina pectoris: National Cooperative Study Group to Compare Surgical and Medical Therapy.  Am J Cardiol. 1978;42:839-848
PubMed   |  Link to Article
Luchi RJ, Scott SM, Deupree RH. Comparison of medical and surgical treatment for unstable angina pectoris: results of a Veterans Administration Cooperative Study.  N Engl J Med. 1987;316:977-984
PubMed   |  Link to Article
Scott SM, Deupree RH, Sharma GV, Luchie RJ. VA study of unstable angina: 10-year results show duration of surgical advantage for patients with impaired ejection fraction.  Circulation. 1994;90:II120-II123
PubMed   |  Link to Article
Brown CA, Hutter AM, DeSanctis RW.  et al.  Prospective study of medical and urgent surgical therapy in randomizable patients with unstable angina pectoris: results of in-hospital and chronic mortality and morbidity.  Am Heart J. 1981;102:959-964
PubMed   |  Link to Article
Madsen JK, Grande P, Saunamaki K.  et al.  Danish multicenter randomized study of invasive versus conservative treatment in patients with inducible ischemia after thrombolysis in acute myocardial infarction (DANAMI).  Circulation. 1997;96:748-755
PubMed   |  Link to Article
SWIFT (Should We Intervene Following Thrombolysis?) Trial Study Group.  SWIFT trial of delayed elective intervention v conservative treatment after thrombolysis with anistreplase in acute myocardial infarction.  BMJ. 1991;302:555-560
PubMed   |  Link to Article
Michalis LK, Stroumbis CS, Pappas K.  et al.  Treatment of refractory unstable angina in geographically isolated areas without cardiac surgery: invasive vs conservative surgery (TRACS study).  Eur Heart J. 2000;21:1954-1959
PubMed   |  Link to Article
TIMI IIIB Investigators.  Effects of tissue plasminogen activator and a comparison of early invasive and conservative strategies in unstable angina and non-Q-wave myocardial infarction: results of the TIMI IIIB trial.  Circulation. 1994;89:1545-1556
PubMed   |  Link to Article
McCullough PA, O'Neill WW, Graham M.  et al.  A prospective randomized trial of triage angiography in acute coronary syndromes ineligible for thrombolytic therapy.  J Am Coll Cardiol. 1998;32:596-605
PubMed   |  Link to Article
Boden WE, O'Rourke RA, Crawford MH.  et al. Veterans Affairs Non-Q-Wave Infarction Strategies in Hospital (VANQWISH) Trial Investigators.  Outcomes in patients with acute non-Q-wave myocardial infarction randomly assigned to an invasive as compared with a conservative management strategy.  N Engl J Med. 1998;338:1785-1792
PubMed   |  Link to Article
FRagmin and Fast Revascularisation during InStability in Coronary artery disease (FRISC II) Investigators.  Invasive compared with non-invasive treatment in unstable coronary-artery disease: FRISC II prospective randomised multicentre study.  Lancet. 1999;354:708-715
PubMed   |  Link to Article
Cannon CP, Weintraub WS, Demopoulos LA.  et al. TACTICS (Treat Angina with Aggrastat and Determine Cost of Therapy with an Invasive or Conservative Strategy)—Thrombolysis in Myocardial Infarction 18 Investigators.  Comparison of early invasive and conservative strategies in patients with unstable coronary syndromes treated with the glycoprotein IIb/IIIa inhibitor tirofiban.  N Engl J Med. 2001;344:1879-1887
PubMed   |  Link to Article
Spacek R, Widimsky P, Straka Z.  et al.  Value of first day angiography/angioplasty in evolving non-ST segment elevation myocardial infarction: an open multicenter randomized trial.  Eur Heart J. 2002;23:230-238
PubMed   |  Link to Article
Fox KA, Poole-Wilson PA, Henderson RA.  et al. Randomized Intervention Trial of unstable Angina Investigators.  Interventional versus conservative treatment for patients with unstable angina or non-ST-elevation myocardial infarction: the British Heart Foundation RITA 3 randomised trial.  Lancet. 2002;360:743-751
PubMed   |  Link to Article
Diderholm E, Andren B, Frostfeldt G.  et al. Fast Revascularisation during InStability in Coronary artery disease (FRISC II) Investigators.  The prognostic and therapeutic implications of increased troponin T levels and ST depression in unstable coronary artery disease: the FRISC II invasive troponin T electrocardiogram substudy.  Am Heart J. 2002;143:760-767
PubMed   |  Link to Article
Morrow DA, Cannon CP, Rifai N.  et al. TACTICS-TIMI 18 Investigators.  Ability of minor elevations of troponins I and T to predict benefit from an early invasive strategy in patients with unstable angina and non-ST elevation myocardial infarction: results from a randomized trial.  JAMA. 2001;286:2405-2412
PubMed   |  Link to Article
Neumann FJ, Kastrati A, Pogatsa-Murray G.  et al.  Evaluation of prolonged antithrombotic pretreatment (“cooling-off” strategy) before intervention in patients with unstable coronary syndromes: a randomized controlled trial.  JAMA. 2003;290:1593-1599
PubMed   |  Link to Article
de Winter RJ. Invasive versus Conservative Treatment in Unstable coronary Syndromes (ICTUS) Investigators. Presented at: the European Society of Cardiology Congress; August 29, 2004; Munich, Germany
Van de Werf F, Gore JM, Avezum A.  et al.  Access to catheterisation facilities in patients admitted with acute coronary syndrome: multinational registry study.  BMJJanuary 24, 2005. epub ahead of print
CURE Trial Investigators.  Effects of clopidogrel in addition to aspirin in patients with acute coronary syndromes without ST-segment elevation.  N Engl J Med. 2001;345:494-502
PubMed   |  Link to Article
Mehta SR, Yusuf S, Peters RJ.  et al. Clopidogrel in Unstable angina to prevent Recurrent Events trial (CURE) Investigators.  Effects of pretreatment with clopidogrel and aspirin followed by long-term therapy in patients undergoing percutaneous coronary intervention: the PCI-CURE study.  Lancet. 2001;358:527-533
PubMed   |  Link to Article
Steinhubl SR, Berger PB, Mann JT 3rd.  et al. CREDO Investigators.  Early and sustained dual oral antiplatelet therapy following percutaneous coronary intervention: a randomized controlled trial.  JAMA. 2002;288:2411-2420
PubMed   |  Link to Article
Yusuf S, Mehta SR, Zhao F.  et al. Clopidogrel in Unstable angina to prevent Recurrent Events Trial (CURE) Investigators.  Early and late effects of clopidogrel in patients with acute coronary syndromes.  Circulation. 2003;107:966-972
PubMed   |  Link to Article
PURSUIT Trial Investigators.  Inhibition of platelet glycoprotein IIb/IIIa with eptifibatide in patients with acute coronary syndromes.  N Engl J Med. 1998;339:436-443
PubMed   |  Link to Article
Platelet Receptor Inhibition in Ischemic Syndrome Management in Patients Limited by Unstable Signs and Symptoms (PRISM-PLUS) Study Investigators.  Inhibition of the platelet glycoprotein IIb/IIIa receptor with tirofiban in unstable angina and non-Q-wave myocardial infarction.  N Engl J Med. 1998;338:1488-1497
PubMed   |  Link to Article
SYNERGY Trial Investigators.  Enoxaparin vs unfractionated heparin in high-risk patients with non-ST-segment elevation acute coronary syndromes managed with an intended early invasive strategy: primary results of the SYNERGY randomized trial.  JAMA. 2004;292:45-54
PubMed   |  Link to Article
Blazing MA, de Lemos JA, White HD.  et al. A to Z Investigators.  Safety and efficacy of enoxaparin vs unfractionated heparin in patients with non-ST-segment elevation acute coronary syndromes who receive tirofiban and aspirin: a randomized controlled trial.  JAMA. 2004;292:55-64
PubMed   |  Link to Article
Ellis SG, Weintraub W, Holmes D, Shaw R, Block PC, King SB 3rd. Relation of operator volume and experience to procedural outcome of percutaneous coronary revascularization at hospitals with high interventional volumes.  Circulation. 1997;95:2479-2484
PubMed   |  Link to Article
Wallentin L, Lagerqvist B, Husted S.  et al.  Outcome at 1 year after an invasive compared with a non-invasive strategy in unstable coronary-artery disease: the FRISC II invasive randomised trial.  Lancet. 2000;356:9-16
PubMed   |  Link to Article
Lagerqvist B, Husted S, Kontny F.  et al.  A long-term perspective on the protective effects of an early invasive strategy in unstable coronary artery disease—a 2 year follow-up of the FRISC II invasive study.  J Am Coll Cardiol. 2002;40:1902-1914
PubMed   |  Link to Article
Yusuf S, Zucker D, Peduzzi P.  et al.  Effect of coronary artery bypass graft surgery on survival: overview of 10-year results from randomised trials by the Coronary Artery Bypass Graft Surgery Trialists’ Collaboration.  Lancet. 1994;344:563-570
PubMed   |  Link to Article

Figures

Figure 1. Main Outcomes From Randomization to Hospital Discharge in Trials of Routine vs Selective Invasive Management of Acute Coronary Syndromes
Graphic Jump Location

Sizes of data markers are proportional to the amount of data contributed by each trial. Tests for heterogeneity: mortality, P = .15; nonfatal myocardial infarction (MI), P = .001; composite of death or MI, P = .001. Relative risks and 95% confidence intervals (CIs) from random-effects model: mortality, 1.56 (0.96-2.53); nonfatal MI, 1.20 (0.73-1.97); death or MI, 1.31 (0.85-2.01). OR indicates odds ratio. See Table 1 footnote for trial dates and expansions of trial names.

Figure 2. Main Outcomes From Hospital Discharge to End of Follow-up in Trials of Routine vs Selective Invasive Management of Acute Coronary Syndromes
Graphic Jump Location

Sizes of data markers are proportional to the amount of data contributed by each trial. Tests for heterogeneity: mortality, P = .04; nonfatal myocardial infarction (MI), P = .02; composite of death or MI, P = .001. Relative risks and 95% confidence intervals (CIs) from random-effects model: mortality, 0.74 (0.52-1.05); nonfatal MI, 0.57 (0.40-0.80); death or MI, 0.65 (0.46-0.91). See Table 1 footnote for trial dates and expansions of trial names. OR indicates odds ratio.

Figure 3. Main Outcomes From Randomization to End of Follow-up in Trials of Routine vs Selective Invasive Management of Acute Coronary Syndromes
Graphic Jump Location

Sizes of data markers are proportional to the amount of data contributed by each trial. Tests for heterogeneity: mortality, P = .04; nonfatal myocardial infarction (MI), P = .51; composite of death or MI, P = .06. Relative risks and 95% confidence intervals (CIs) from random-effects model: mortality, 0.88 (0.66-1.18); nonfatal MI, 0.76 (0.65-0.88); death or MI, 0.82 (0.68-0.99). See Table 1 footnote for trial dates and expansions of trial names. OR indicates odds ratio.

Figure 4. Rates of Canadian Cardiovascular Society (CCS) Class III-IV Angina and Rehospitalization at End of Follow-up in Trials of Routine vs Selective Invasive Management of Acute Coronary Syndromes
Graphic Jump Location

Sizes of data markers are proportional to the amount of data contributed by each trial. Tests for heterogeneity: CCS class III-IV angina, P<.001; rehospitalization, P<.001. Relative risks and 95% confidence intervals (CIs) from random-effects model: CCS class III-IV angina, 0.78 (0.58-1.04); rehospitalizations, 0.71 (0.55-0.92). See Table 1 footnote for trial dates and expansions of trial names. OR indicates odds ratio.

Figure 5. Stratified Analyses of Trials Published Before and After 1999 and According to Baseline Troponin and Cardiac Biomarker Status: Death or Myocardial Infarction From Randomization to Follow-up
Graphic Jump Location

Sizes of data markers are proportional to the amount of data contributed by each trial. Cardiac biomarkers are creatine kinase, creatine kinase–MB fraction, and troponin. In 3 of the 7 trials included in this analysis (VANQWISH, MATE, and VINO), all patients had elevated marker levels at baseline. See Table 1 footnote for trial dates and expansions of trial names.
*TIMI 3B, VANQWISH, and MATE.
†FRISC II, TACTICS, VINO, and RITA 3.
‡FRISC II, TACTICS, and RITA 3.

Tables

Table Graphic Jump LocationTable 1. Entry Criteria, Use of Antithrombotic Medications, Timing of Interventions, and Definitions of Non–Procedure-Related and PCI-Related Myocardial Infarction in Trials of Routine vs Selective Invasive Management of Acute Coronary Syndromes
Table Graphic Jump LocationTable 2. Baseline Characteristics of Included Studies
Table Graphic Jump LocationTable 3. Summary of Odds Ratios for All Major Outcomes

References

Braunwald E, Antman EM, Beasley JW.  et al. American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on the Management of Patients With Unstable Angina).  ACC/AHA guideline update for the management of patients with unstable angina and non-ST-segment elevation myocardial infarction—2002: summary article: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on the Management of Patients With Unstable Angina).  Circulation. 2002;106:1893-1900
PubMed   |  Link to Article
Yusuf S, Flather M, Pogue J.  et al.  Variations between countries in invasive cardiac procedures and outcomes in patients with suspected unstable angina or myocardial infarction without ST elevation.  Lancet. 1998;352:507-514
PubMed   |  Link to Article
Bhatt DL, Roe MT, Peterson ED.  et al. CRUSADE Investigators.  Utilization of early invasive management strategies for high-risk patients with non-ST-segment elevation acute coronary syndromes: results from the CRUSADE Quality Improvement Initiative.  JAMA. 2004;292:2096-2104
PubMed   |  Link to Article
Fox KA, Goodman SG, Klein W.  et al.  Management of acute coronary syndromes: variations in practice and outcome: findings from the Global Registry of Acute Coronary Events (GRACE).  Eur Heart J. 2002;23:1177-1189
PubMed   |  Link to Article
Antithrombotic Trialists’ Collaboration.  Collaborative meta-analysis of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high-risk patients.  BMJ. 2002;324:71-86
PubMed   |  Link to Article
Mantel N, Haenszel W. Statistical aspects of the analysis of data from retrospective studies of disease.  J Natl Cancer Inst. 1959;22:719-748
PubMed
Yusuf S, Peto R, Lewis J, Collins R, Sleight P. Beta blockade during and after myocardial infarction: an overview of the randomized trials.  Prog Cardiovasc Dis. 1985;27:335-371
PubMed   |  Link to Article
DerSimonian R, Laird N. Meta-analysis in clinical trials.  Control Clin Trials. 1986;7:177-188
PubMed   |  Link to Article
 Unstable angina pectoris: National Cooperative Study Group to Compare Surgical and Medical Therapy.  Am J Cardiol. 1978;42:839-848
PubMed   |  Link to Article
Luchi RJ, Scott SM, Deupree RH. Comparison of medical and surgical treatment for unstable angina pectoris: results of a Veterans Administration Cooperative Study.  N Engl J Med. 1987;316:977-984
PubMed   |  Link to Article
Scott SM, Deupree RH, Sharma GV, Luchie RJ. VA study of unstable angina: 10-year results show duration of surgical advantage for patients with impaired ejection fraction.  Circulation. 1994;90:II120-II123
PubMed   |  Link to Article
Brown CA, Hutter AM, DeSanctis RW.  et al.  Prospective study of medical and urgent surgical therapy in randomizable patients with unstable angina pectoris: results of in-hospital and chronic mortality and morbidity.  Am Heart J. 1981;102:959-964
PubMed   |  Link to Article
Madsen JK, Grande P, Saunamaki K.  et al.  Danish multicenter randomized study of invasive versus conservative treatment in patients with inducible ischemia after thrombolysis in acute myocardial infarction (DANAMI).  Circulation. 1997;96:748-755
PubMed   |  Link to Article
SWIFT (Should We Intervene Following Thrombolysis?) Trial Study Group.  SWIFT trial of delayed elective intervention v conservative treatment after thrombolysis with anistreplase in acute myocardial infarction.  BMJ. 1991;302:555-560
PubMed   |  Link to Article
Michalis LK, Stroumbis CS, Pappas K.  et al.  Treatment of refractory unstable angina in geographically isolated areas without cardiac surgery: invasive vs conservative surgery (TRACS study).  Eur Heart J. 2000;21:1954-1959
PubMed   |  Link to Article
TIMI IIIB Investigators.  Effects of tissue plasminogen activator and a comparison of early invasive and conservative strategies in unstable angina and non-Q-wave myocardial infarction: results of the TIMI IIIB trial.  Circulation. 1994;89:1545-1556
PubMed   |  Link to Article
McCullough PA, O'Neill WW, Graham M.  et al.  A prospective randomized trial of triage angiography in acute coronary syndromes ineligible for thrombolytic therapy.  J Am Coll Cardiol. 1998;32:596-605
PubMed   |  Link to Article
Boden WE, O'Rourke RA, Crawford MH.  et al. Veterans Affairs Non-Q-Wave Infarction Strategies in Hospital (VANQWISH) Trial Investigators.  Outcomes in patients with acute non-Q-wave myocardial infarction randomly assigned to an invasive as compared with a conservative management strategy.  N Engl J Med. 1998;338:1785-1792
PubMed   |  Link to Article
FRagmin and Fast Revascularisation during InStability in Coronary artery disease (FRISC II) Investigators.  Invasive compared with non-invasive treatment in unstable coronary-artery disease: FRISC II prospective randomised multicentre study.  Lancet. 1999;354:708-715
PubMed   |  Link to Article
Cannon CP, Weintraub WS, Demopoulos LA.  et al. TACTICS (Treat Angina with Aggrastat and Determine Cost of Therapy with an Invasive or Conservative Strategy)—Thrombolysis in Myocardial Infarction 18 Investigators.  Comparison of early invasive and conservative strategies in patients with unstable coronary syndromes treated with the glycoprotein IIb/IIIa inhibitor tirofiban.  N Engl J Med. 2001;344:1879-1887
PubMed   |  Link to Article
Spacek R, Widimsky P, Straka Z.  et al.  Value of first day angiography/angioplasty in evolving non-ST segment elevation myocardial infarction: an open multicenter randomized trial.  Eur Heart J. 2002;23:230-238
PubMed   |  Link to Article
Fox KA, Poole-Wilson PA, Henderson RA.  et al. Randomized Intervention Trial of unstable Angina Investigators.  Interventional versus conservative treatment for patients with unstable angina or non-ST-elevation myocardial infarction: the British Heart Foundation RITA 3 randomised trial.  Lancet. 2002;360:743-751
PubMed   |  Link to Article
Diderholm E, Andren B, Frostfeldt G.  et al. Fast Revascularisation during InStability in Coronary artery disease (FRISC II) Investigators.  The prognostic and therapeutic implications of increased troponin T levels and ST depression in unstable coronary artery disease: the FRISC II invasive troponin T electrocardiogram substudy.  Am Heart J. 2002;143:760-767
PubMed   |  Link to Article
Morrow DA, Cannon CP, Rifai N.  et al. TACTICS-TIMI 18 Investigators.  Ability of minor elevations of troponins I and T to predict benefit from an early invasive strategy in patients with unstable angina and non-ST elevation myocardial infarction: results from a randomized trial.  JAMA. 2001;286:2405-2412
PubMed   |  Link to Article
Neumann FJ, Kastrati A, Pogatsa-Murray G.  et al.  Evaluation of prolonged antithrombotic pretreatment (“cooling-off” strategy) before intervention in patients with unstable coronary syndromes: a randomized controlled trial.  JAMA. 2003;290:1593-1599
PubMed   |  Link to Article
de Winter RJ. Invasive versus Conservative Treatment in Unstable coronary Syndromes (ICTUS) Investigators. Presented at: the European Society of Cardiology Congress; August 29, 2004; Munich, Germany
Van de Werf F, Gore JM, Avezum A.  et al.  Access to catheterisation facilities in patients admitted with acute coronary syndrome: multinational registry study.  BMJJanuary 24, 2005. epub ahead of print
CURE Trial Investigators.  Effects of clopidogrel in addition to aspirin in patients with acute coronary syndromes without ST-segment elevation.  N Engl J Med. 2001;345:494-502
PubMed   |  Link to Article
Mehta SR, Yusuf S, Peters RJ.  et al. Clopidogrel in Unstable angina to prevent Recurrent Events trial (CURE) Investigators.  Effects of pretreatment with clopidogrel and aspirin followed by long-term therapy in patients undergoing percutaneous coronary intervention: the PCI-CURE study.  Lancet. 2001;358:527-533
PubMed   |  Link to Article
Steinhubl SR, Berger PB, Mann JT 3rd.  et al. CREDO Investigators.  Early and sustained dual oral antiplatelet therapy following percutaneous coronary intervention: a randomized controlled trial.  JAMA. 2002;288:2411-2420
PubMed   |  Link to Article
Yusuf S, Mehta SR, Zhao F.  et al. Clopidogrel in Unstable angina to prevent Recurrent Events Trial (CURE) Investigators.  Early and late effects of clopidogrel in patients with acute coronary syndromes.  Circulation. 2003;107:966-972
PubMed   |  Link to Article
PURSUIT Trial Investigators.  Inhibition of platelet glycoprotein IIb/IIIa with eptifibatide in patients with acute coronary syndromes.  N Engl J Med. 1998;339:436-443
PubMed   |  Link to Article
Platelet Receptor Inhibition in Ischemic Syndrome Management in Patients Limited by Unstable Signs and Symptoms (PRISM-PLUS) Study Investigators.  Inhibition of the platelet glycoprotein IIb/IIIa receptor with tirofiban in unstable angina and non-Q-wave myocardial infarction.  N Engl J Med. 1998;338:1488-1497
PubMed   |  Link to Article
SYNERGY Trial Investigators.  Enoxaparin vs unfractionated heparin in high-risk patients with non-ST-segment elevation acute coronary syndromes managed with an intended early invasive strategy: primary results of the SYNERGY randomized trial.  JAMA. 2004;292:45-54
PubMed   |  Link to Article
Blazing MA, de Lemos JA, White HD.  et al. A to Z Investigators.  Safety and efficacy of enoxaparin vs unfractionated heparin in patients with non-ST-segment elevation acute coronary syndromes who receive tirofiban and aspirin: a randomized controlled trial.  JAMA. 2004;292:55-64
PubMed   |  Link to Article
Ellis SG, Weintraub W, Holmes D, Shaw R, Block PC, King SB 3rd. Relation of operator volume and experience to procedural outcome of percutaneous coronary revascularization at hospitals with high interventional volumes.  Circulation. 1997;95:2479-2484
PubMed   |  Link to Article
Wallentin L, Lagerqvist B, Husted S.  et al.  Outcome at 1 year after an invasive compared with a non-invasive strategy in unstable coronary-artery disease: the FRISC II invasive randomised trial.  Lancet. 2000;356:9-16
PubMed   |  Link to Article
Lagerqvist B, Husted S, Kontny F.  et al.  A long-term perspective on the protective effects of an early invasive strategy in unstable coronary artery disease—a 2 year follow-up of the FRISC II invasive study.  J Am Coll Cardiol. 2002;40:1902-1914
PubMed   |  Link to Article
Yusuf S, Zucker D, Peduzzi P.  et al.  Effect of coronary artery bypass graft surgery on survival: overview of 10-year results from randomised trials by the Coronary Artery Bypass Graft Surgery Trialists’ Collaboration.  Lancet. 1994;344:563-570
PubMed   |  Link to Article
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