(Circulation. 2000;102:1093.)
© 2000 American Heart Association, Inc.
Clinical Investigation and Reports |
From the Department of Cardiology, Cleveland Clinic Foundation, Cleveland, Ohio (A.M.L., E.J.T.); Duke Clinical Research Institute, Durham, NC (R.A.H., R.M.C., E.M.O., C.M.P., L.G.B.); St LukesRoosevelt Hospital Center, New York, NY (J.S.H.); St Francis Hospital, Roslyn, NY (A.D.G.); University of Florida, Gainesville (C.J.P.); Mayo Clinic and Foundation, Rochester, Minn (S.L.K.); COR Therapeutics, South San Francisco, Calif (M.M.K.); and Cardialysis, Thoraxcenter, Rotterdam, The Netherlands (M.L.S.).
Correspondence to A. Michael Lincoff, MD, Department of Cardiology, Desk F25, The Cleveland Clinic Foundation, 9500 Euclid Ave, Cleveland, OH 44195.
| Abstract |
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Methods and ResultsPatients presenting with chest pain within the previous 24 hours and ischemic ECG changes or creatine kinaseMB elevation were eligible for enrollment. Of the 10 948 patients randomized worldwide, 4035 were enrolled within the United States. Patients were allocated to placebo or eptifibatide infusion for up to 72 to 96 hours. Other medical therapies and revascularization strategies were at the discretion of the treating physician. Eptifibatide reduced the rate of the primary end point of death or myocardial infarction by 30 days from 15.4% to 11.9% (P=0.003) among patients in the United States. The treatment effect was achieved early and maintained over a period of 6 months (18.9% versus 15.2%; P=0.004). Bleeding events were more common in patients receiving eptifibatide but were predominantly associated with invasive procedures. The magnitude of clinical benefit from eptifibatide was greater among patients in the United States than elsewhere in the world.
ConclusionsPlatelet glycoprotein IIb/IIIa receptor blockade with eptifibatide reduces the incidence of death or myocardial infarction among patients treated for acute ischemic syndromes without ST-segment elevation within the United States.
Key Words: platelets angina myocardial infarction angioplasty glycoproteins
| Introduction |
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Of the 10 948 patients enrolled in PURSUIT, 37% were enrolled in centers in the United States. The current study was therefore carried out to evaluate the efficacy of eptifibatide therapy in the context of management strategies for acute coronary syndromes within the United States, including the more frequent use of heparin and angiographic and revascularization procedures than in other countries. We analyzed outcome among the subset of patients in the PURSUIT trial enrolled in the United States, comparing patient characteristics and outcome in that country with the rest of the world.
| Methods |
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Study Protocol
Details of the trial design have been reported
previously.1 Initially, patients were assigned to 1 of 3
treatment groups: eptifibatide bolus (180 µg/kg) followed by an
infusion of 2.0 µg ·
kg-1 ·
min-1, eptifibatide bolus
(180 µg/kg) followed by an infusion of 1.3 µg ·
kg-1 ·
min-1, or placebo bolus
and infusion. Study drug was to be infused for 72 hours or until
hospital discharge, whichever came first; if
percutaneous coronary
revascularization was performed near the end of
this 72-hour period, the infusion could be continued for an additional
24 hours (total 96 hours). After a protocol-specified interim review of
safety data by an independent committee after 3218 patients had been
enrolled, the low-dose arm was dropped and the trial was completed by
randomization to the placebo and high-dose eptifibatide arms only. Data
for the 1487 patients in the low-dose eptifibatide group were not
included in the final end point or safety analyses.
All patients were to be treated with aspirin or ticlopidine if intolerant to aspirin; a combination of both drugs could be administered after stent implantation. Intravenous or subcutaneous heparin was recommended during study drug infusion, but usage was left to the physicians discretion. Fibrinolytics or open-label GP IIb/IIIa antagonists were not to be administered with the study drug. Use of other medications was at the discretion of the treating physicians, as was the strategy and timing of coronary angiography and revascularization.
Study End Points
The primary efficacy end point of the trial was a composite of
death or nonfatal myocardial (re-) infarction within 30 days of
randomization.1 End point classifications within the first
30 days were made by a clinical events committee, which was blinded to
study group allocation. After 30 days, investigators at individual
sites determined if myocardial infarction had occurred. These events
were confirmed (ie, by discharge summaries) but were not systematically
adjudicated. Safety end points included assessment of bleeding severity
and stroke.1 4 5 Data collection and statistical
analyses were performed as in the overall trial.
| Results |
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Treatment parameters are summarized in Table 2
. Median hospital length of stay was
shorter in the United States (5 days, interquartile range 3 to 8 days)
than outside of the United States (10 days, 7 to 15 days). Patients
enrolled in the United States were more likely to have had the study
drug administered for <72 hours, usually because of hospital discharge
(28% of US patients compared with 2% of non-US patients) or
coronary artery bypass surgery (15% of US patients versus 7%
of non-US patients). US patients more commonly received a heparin
infusion and more frequently underwent cardiac
catheterization and coronary
revascularization. In particular, invasive
diagnostic and revascularization
procedures were carried out earlier in the United States than outside
the United States. The median time from randomization to cardiac
catheterization was 24 hours (13 to 55 hours) in the
United States and 117 hours (64 to 210) outside of the United States;
corresponding times to percutaneous intervention were
38 hours (16 to 75) and 139 hours (69 to 282) and to coronary
bypass surgery were 93 hours (48 to 142) and 256 hours (140 to 407).
Ticlopidine was administered more frequently in the United States; 63%
and 56% of patients in US and non-US sites, respectively, who received
ticlopidine also received stents. Among patients randomized to placebo
or eptifibatide in the United States, treatment parameters
were comparable, although early (before 72 hours) discontinuation of
study drug infusion occurred more frequently in the eptifibatide
treatment group because of bleeding complications (17.5% of patients
in the eptifibatide group versus 2.0% in the placebo group).
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Efficacy End Points
Follow-up of patients in the United States was 100% complete at
30 days and 99.3% complete for 6 months. Event rates for the composite
end point and its individual components at 96 hours, 7 days, 30 days,
and 6 months among patients in the United States are shown in Table 3
and Figure 1
. The primary composite end point of
death or myocardial infarction by 30 days was reduced from 15.4% to
11.9% in the placebo and eptifibatide groups, respectively (3.5%
absolute risk reduction, 23% relative risk reduction,
P=0.0025). This difference was due predominantly to a
decrease in the incidence of myocardial infarction (23% relative risk
reduction), with a lesser effect of eptifibatide on mortality (14%
relative risk reduction). The clinical benefit of eptifibatide was
manifest early (within the first 96 hours) and maintained without
attenuation after discontinuation of study drug; the absolute number of
events (death or myocardial infarction) prevented per 100 patients
treated was 3.2 at 96 hours, 3.0 at 7 days, 3.5 at 30 days, and 3.7 at
6 months. Figure 2
summarizes the odds
ratios for death or myocardial infarction at 30 days for various
patient subgroups. The treatment effect of eptifibatide was highly
consistent, with 7% to 27% relative reductions in the risk of
the composite end point. In particular, men and women in the United
States had a comparable clinical benefit from eptifibatide. The
reduction in ischemic events by eptifibatide was significantly
greater (P=0.024) at every time point among patients
enrolled in the United States than among those in non-US sites (Figure 3
).
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The treatment effect of eptifibatide observed among US patients was
independent of the use of early percutaneous
coronary intervention (PCI) (Figure 4
). By 30 days, the composite end point
of death or myocardial infarction was reduced by 33%
(P=0.017) in patients undergoing PCI within the first 72
hours and by 19% (P=0.036) in patients who did not undergo
early PCI. Patients treated by early PCI tended to have a somewhat
enhanced benefit from eptifibatide therapy, with an absolute 5.5 events
prevented per 100 patients as compared with 2.8 events prevented per
100 patients who did not receive early PCI; the interaction between
eptifibatide therapy and early PCI was not statistically significant
(P=0.32). A stabilization effect before the
performance of early PCI was also apparent, with a 31%
relative reduction in the incidence of preprocedural myocardial
infarction from 9.8% to 6.8%, P=0.052.
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Safety End Points
Bleeding was more common among US patients treated with
eptifibatide than placebo (Table 4
). Most
bleeding occurred at sites of vascular access or in association with
coronary artery bypass surgery, although eptifibatide did not
increase the hemorrhagic risk among bypass surgery patients (major
bleeding in 64% of patients in both the placebo and eptifibatide
groups). Whole blood or packed red blood cell transfusions were
administered during the initial hospitalization to 13.1% and 16.3% of
patients in the placebo and eptifibatide groups, respectively; when
patients undergoing coronary bypass surgery were excluded from
consideration, transfusions were required in 2.3% and 6.7% of
patients, respectively. Rates of hemorrhagic or ischemic stroke
were low and were not influenced by eptifibatide therapy: Hemorrhagic
stroke or transformation occurred in 0.2% and 0.1% of patients in the
placebo and eptifibatide groups, respectively, and ischemic
stroke occurred in 1.0% of patients in both groups.
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Patients in the United States had more bleeding complications than did their non-US counterparts. Excluding patients requiring bypass surgery, major bleeding occurred among 3.3% of US patients and 1.6% of non-US patients. Most of this excess risk for bleeding in the United States appeared to be associated with the use of coronary angiography or percutaneous coronary revascularization; when patients undergoing these invasive catheterization procedures were excluded from consideration, major bleeding rates were 1.5% and 1.0% in the US and non-US sites, respectively.
| Discussion |
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PURSUIT was conducted as a large, relatively simple trial, in which administration of the study drug (eptifibatide or placebo) was superimposed on conventional management of unstable ischemic syndromes. Thus, the trial protocol did not mandate pharmacological therapies aside from the study agent and did not specify the use or timing of coronary angiography and revascularization. The advantage of such a trial design is that the results are representative of outcome which may generally be expected with a diversity of "real life" practice patterns in a variety of medical care systems. Disadvantages of the large, simple trial design, however, include difficulty in extrapolating the overall trial results to relevant specific practice patterns or patient subsets.
Although a significant treatment effect of eptifibatide was demonstrated in the overall patient population enrolled in PURSUIT,1 variability in the magnitude of clinical benefit derived from this therapy was also observed. Among the 4 predefined geographic regions of the world, treatment effect was greatest in North America and less in Western Europe, Eastern Europe, and Latin America. Such variations of outcome among geographic regions have been observed in other international randomized trials.6 Similarly, no impact of eptifibatide on ischemic events was seen among women in the overall trial cohort. An interaction between the efficacy of GP IIb/IIIa blockade and early percutaneous coronary revascularization was suggested by the significant 31% reduction in end points among the 1228 patients in whom early revascularization was performed, in contrast to the 7% reduction in events among the 8233 patients who did not undergo early revascularization (adjusted P=0.63 for the interaction between eptifibatide therapy and early PCI).7 These and other factors that appear to influence outcome among patients treated with eptifibatide are interrelated, as there was substantial geographic variability in patient populations, application of revascularization, use of heparin, and other management strategies.
This current study therefore focused on assessing the treatment effect that would be expected to be achieved with eptifibatide therapy within a single countrys healthcare system. Of the 28 countries participating in the PURSUIT trial, the number of patients enrolled was greatest in the United States, permitting meaningful analyses to be carried out with a sample size of 4035 patients. In fact, the US PURSUIT population itself is the third largest trial population in nonST-elevation acute coronary syndromes, after the overall PURSUIT trial and Global Use of Strategies to Open Occluded Coronary Arteries (GUSTO) IIb trial.8 Prior studies have shown that invasive cardiac procedures, including angiography and coronary revascularization, are used more frequently and earlier in the United States than elsewhere in the world,9 although other national differences in patient populations and management strategies have not been well documented. Variability in medical treatments and clinical outcome have certainly been observed in different regions or hospital types within the United States as well,10 11 but such variability may be less than among countries as a result of clinical practice guidelines, the influence of third-party payers, and the relative ease of communication and transportation within the United States. Moreover, the 282 clinical sites participating in PURSUIT in the United States were representative of the spectrum of medical centers in that country, including a balance of hospitals of various sizes that were academic or nonacademic, tertiary or primary care, and with or without facilities for coronary revascularization. Thus, the findings of this current analysis should be applicable to the general population of patients treated for acute coronary syndromes within the United States.
Within the systems of medical practice in the United States, the treatment effect of eptifibatide was considerable and greater than in non-US patients. Moreover, in contrast to the overall PURSUIT cohort, women in the United States had an equal clinical benefit from eptifibatide as did men. Similarly, although the reduction in ischemic events by eptifibatide appeared to be amplified among patients undergoing early percutaneous coronary revascularization, US patients treated medically without early revascularization also had a significant treatment effect. The efficacy findings in the PURSUIT US patients are consistent with those of other trials of GP IIb/IIIa inhibitors. The absolute 3.5% risk reduction in the PURSUIT US patients compares favorably with the 3.2% risk reduction among the 1915 patients with unstable angina enrolled in the Platelet Receptor Inhibition in Ischemic Syndrome Management in Patients Limited by Unstable Signs (PRISM PLUS) trial testing the nonpeptide GP IIb/IIIa inhibitor tirofiban (Merck).2 In fact, comparison of the PURSUIT and PRISM PLUS trials could be considered more appropriately carried out with the PURSUIT US cohort rather than the overall PURSUIT population; given the protocol specification for revascularization (if possible) during study drug infusion in PRISM PLUS, rates of early percutaneous revascularization were more similar in PRISM PLUS and the PURSUIT US cohort (31% and 26%, respectively) than in the overall PURSUIT trial (13%).
Reasons for the apparent disparity in clinical benefit derived from eptifibatide in the US population relative to non-US patients in PURSUIT have not been defined. Patients enrolled inside and outside the United States had somewhat different demographics and risk factors, yet observed 30-day event rates for the composite end point of death or myocardial infarction in the placebo group was 15.4% for US patients and 15.9% for non-US patients. Thus, differences in treatment effect with eptifibatide do not appear attributable to baseline risk profile. It is more likely that variability in management strategies influenced the clinical benefit of eptifibatide therapy. US patients underwent coronary angiography nearly twice as frequently and early percutaneous revascularization (during study drug infusion) nearly 5 times as frequently as did patients outside of the United States. Diagnostic and revascularization procedures were carried out substantially earlier in the United States than outside of the United States. Rates of heparin and ticlopidine use were higher in the United States as well. The relatively aggressive treatment strategy used in the United States of medical stabilization, prompt angiographic definition of coronary anatomy, and early percutaneous or surgical revascularization may provide a suitable background for optimal clinical effectiveness of GP IIb/IIIa inhibition. This hypothesis is supported by the findings of the Fragmin and Early Revascularization in Unstable Ischemic Syndromes (FRISC II) trial, in which the benefit of therapy with low-molecular-weight heparin for unstable angina was maintained only among patients who underwent coronary revascularization.12
Limitations
This study is subject to the limitations of any post hoc
subgroup analysis. Although evaluation of geographic
variability in PURSUIT was prospectively planned, the cohort of
patients enrolled in the United States was not a prespecified subgroup.
Therefore, observed differences in outcome between patients enrolled
within and outside of the United States may have been due to
statistical chance. Moreover, variability in laboratory techniques for
assessment of creatine kinaseMB levels in different countries may
have contributed to apparent variability in end point myocardial
infarction rates. Importantly, this analysis does not address
differences in clinical outcome or eptifibatide treatment effect among
nations outside of the United States, differences that were clearly
observed in the overall trial analysis, and thus none of the
findings of this study allow estimation of the clinical benefit of
eptifibatide therapy in any single country aside from the United
States. Notwithstanding these limitations, the US cohort of patients is
quite large, with a practice of caring for patients with acute
coronary syndromes that is particularly disparate from the rest
of the international network of countries. The findings provide
strongly supportive evidence for a therapeutic benefit in the US
clinical environment.
| Acknowledgments |
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| Footnotes |
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Received January 26, 2000; revision received March 27, 2000; accepted March 29, 2000.
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