Abciximab Therapy and Unplanned Coronary Stent Deployment
Favorable Effects on Stent Use, Clinical Outcomes, and Bleeding Complications
Background—The clinical and angiographic demographics of patients requiring unplanned coronary stent deployment and the optimal adjunct pharmacotherapy in this population are not well described. This report details the EPILOG trial experience with unplanned coronary stent deployment and the effect of abciximab platelet glycoprotein IIb/IIIa blockade to improve clinical outcomes during 6 months of follow-up.
Methods and Results—After randomization in the EPILOG double-blind, placebo-controlled trial of abciximab therapy during percutaneous coronary intervention, 326 (12%) of 2792 patients required unplanned coronary stent deployment. Although stented patients were not distinguished by clinical variables, they had greater coronary lesion complexity by American Heart Association/American College of Cardiology criteria (P=.003) and greater incidence of lesion length >10 mm (P=.002), lesion eccentricity (P=.027), irregular lesion contour (P=.001), and bifurcation involvement (P=.019) than nonstented patients. Unplanned stents were required less often in patients treated with abciximab and low-dose, weight-adjusted heparin than in patients receiving placebo and standard-dose heparin (9.0% versus 13.7%; P=.001). Although adverse clinical outcomes including target-vessel revascularization and bleeding events were more frequent in patients requiring unplanned coronary stent deployment, abciximab therapy reduced adverse outcomes in these patients at 30 days and 6 months to a greater extent than was observed in patients not requiring stent placement. Among stented patients, abciximab therapy did not increase bleeding events.
Conclusions—Patients requiring unplanned coronary stent deployment have more complex coronary lesion morphology and a more complicated clinical course after coronary intervention. Abciximab therapy both reduces the need for unplanned stent deployment and confers clinical benefit to patients requiring an unplanned stent, without increasing bleeding complications.
Coronary stent deployment is often unplanned and related to abrupt or threatened coronary closure or a suboptimal angiographic result after balloon angioplasty. Clinical and angiographic demographics of patients with unplanned stent deployment are not well described. In addition, although adjunct antiplatelet therapy with ticlopidine and aspirin appears superior to systemic anticoagulation after planned stent deployment,1 2 3 the adequacy of such therapy in patients with an unplanned stent is not defined. Lastly, the potential for platelet GP IIb/IIIa blockade to improve clinical outcomes in patients with unplanned coronary stent deployment has not been prospectively evaluated in a placebo-controlled, randomized trial. Although planned stent deployment was not allowed in the EPILOG trial study design, approved coronary stent devices could be placed at the discretion of the clinical investigator. This report describes the clinical and angiographic profiles of patients requiring unplanned stent deployment and the ability of abciximab to improve clinical outcomes at 30 days and 6 months.
The EPILOG trial was a randomized, double-blind, placebo-controlled trial conducted in 69 clinical sites in the United States and Canada. Overall trial results have been published previously.4 Planned patient enrollment of 4800 was stopped early after enrollment of 2792 patients on recommendation of the Safety and Efficacy Monitoring Committee because of the efficacy of abciximab. Patients undergoing percutaneous coronary revascularization with a Food and Drug Administration–approved device were considered eligible for enrollment if they were >21 years old and had a target lesion stenosis ≥60% in severity. Patients suffering from acute myocardial infarction or unstable angina with associated ECG changes within 24 hours were excluded. Although planned stent deployment was not allowed by the initial EPILOG protocol, 58 patients randomized to elective stent deployment (EPILOG stent substudy initiated shortly before study termination) and 40 patients who did not undergo percutaneous coronary intervention were excluded from analysis. One patient was excluded for both reasons, resulting in 97 patients removed from analysis. Other exclusion criteria were rotational atherectomy, percutaneous coronary intervention performed within the prior 3 months, and unprotected left main coronary restenosis of >50%; concurrent warfarin therapy or a baseline prothrombin time >1.2× control; cerebral vascular accident within the prior 2 years or with residual neurological deficit; intracranial neoplasm, aneurysm or arterial venous malformation; history of vasculitis; known hemorrhagic diathesis or active internal bleeding; hypertension with systolic blood pressure >180 mm Hg or diastolic blood pressure >100 mm Hg; or major surgery or gastrointestinal or genitourinary bleeding within the previous 6 weeks. The protocol was approved by the institutional review board at each clinical site, and all patients gave informed consent.
The protocol design for this study has been described in detail.4 Briefly, 2792 patients were randomized to receive either placebo with “standard-dose,” weight-adjusted heparin (100 U/kg bolus, maximum 10 000 U, with supplemental heparin administered per nomogram to achieve an ACT ≥300 s); abciximab with standard-dose heparin or abciximab with low-dose, weight-adjusted heparin (70 U/kg bolus, maximum 7000 U, with supplemental heparin to achieve an ACT ≥200 s) during percutaneous transluminal coronary angioplasty. Abciximab was administered as a 0.25 mg/kg bolus initiated at least 10 minutes before coronary revascularization and a 12-hour infusion at 0.125 μg · kg−1 · min−1 (maximum 10 μg/min). All patients received aspirin 325 mg orally at least 2 hours before revascularization and daily thereafter. Discontinuation of heparin after the interventional procedure and early vascular access sheath removal when the ACT was ≤175 s was recommended by protocol. Elective stent deployment was disallowed by protocol, and stent use was reserved to optimize patency after a suboptimal balloon angioplasty result (≥40% residual stenosis, dissection types C through F) or threatened and abrupt closure. Stent deployment was routinely followed by high-pressure (≥16 atm) balloon dilatation within the stented segment. Algorithms were provided for management of uncontrolled bleeding, urgent coronary bypass surgery, or thrombocytopenia, and it was recommended that red blood cell transfusions be administered according to the clinical guidelines of the American College of Physicians.5 Although it occurred infrequently, investigator-directed unblinding of the protocol in the interest of patient safety occurred more commonly in those patients who required unplanned stent deployment (16 [4.9%] of 326) than in those who did not (14 [0.6%]of 2369).
Study End Points
The primary end point of the trial was the clinical composite of death from any cause, myocardial infarction, or urgent revascularization (angioplasty or surgery) within 30 days of randomization. A second efficacy end point was the composite of death, myocardial infarction, or revascularization (urgent or nonurgent) by 6 months of follow-up. An end point of in-hospital myocardial infarction was defined by one of two criteria: (1) new significant Q waves in two or more contiguous ECG leads or (2) elevation of creatine kinase or its MB isoenzyme ≥3× the upper limit of normal in at least two serial samples. Enzyme analyses were conducted on blood obtained before and 2 hours after initiation of study agent, every 6 hours until 24 hours, then every 8 hours until 48 hours or discharge. After hospital discharge, myocardial infarction was defined by the occurrence of new Q waves or creatine kinase–MB isoenzyme elevation to >2× the upper limit of normal. The MB isoenzyme value was used unless unavailable, in which case total creatine kinase was used. Bleeding events were classified as major or minor according to the criteria used by the Thrombolysis In Myocardial Infarction study group. Major bleeding events were defined as intracranial bleeding or bleeding associated with a decrease either in hemoglobin of >5 g/dL or hematocrit ≥15%. Minor bleeding was defined as spontaneous gross hematuria or hematemesis, observed hemorrhage resulting in a decrease in hemoglobin >3 g/dL or hematocrit ≥10%, or a decrease in hemoglobin >4 g/dL or hematocrit ≥12% with no identified bleeding site.
The statistical design and analysis of the full study have been described previously.4 Percentages for demographic characteristics are given as a proportion of nonmissing values. Means are reported ±1 SD. Hospital outcomes (eg, bleeding and procedural outcomes) are reported as percentages. Thirty-day and 6-month outcomes are reported as Kaplan-Meier estimates ±1 SE. Relative risks are based on Cox proportional hazards models. Corresponding Wald χ2 probability values and CIs are also reported.
An unplanned coronary stent was deployed in 326 (12%) of patients enrolled in this trial. Clinical demographics did not differ between patients with and without stent deployment (Table 1⇓). Patients with an unplanned stent were more likely to have been treated with balloon angioplasty than with directional coronary atherectomy. Patients classified as high risk on the basis of recent (≤7 days) myocardial infarction or adverse coronary lesion morphology6 were slightly more likely to have unplanned stenting (225 of 1720 patients or 13.1%) than those patients in the lower-risk stratum (101 of 975 or 10.4%; P=.037). Unplanned stent deployment occurred less frequently in patients who were given abciximab in combination with low-dose, weight-adjusted heparin (Fig 1⇓).
Analysis of angiographic variables (Table 2⇓) demonstrates significant differences between groups, with unplanned stent patients having greater lesion complexity by AHA/ACC criteria7 (81% versus 71% B2 or C criteria; P=.003) and a higher incidence of lesion length >10 mm (56% versus 46%; P=.002), lesion eccentricity (72% versus 66%; P=.027), irregular lesion contour (59% versus 50%; P=.001), and bifurcation involvement (11% versus 8%; P=.019). Patients requiring unplanned stent deployment did not differ with respect to the presence of calcification or thrombus on the control (preintervention) angiogram. The requirement for unplanned stent deployment by lesion subtype and the pharmacological treatment regimen is shown in Fig 2⇓.
The clinical course of patients requiring unplanned stent deployment was more complicated, as outlined in Table 3⇓. The composite primary end point of the trial (death, myocardial infarction, or urgent intervention at 30 days) occurred in 14.4% versus 6.3% of stented and nonstented patients, respectively (P=.001). Although the incidence of death did not differ between groups, myocardial infarction (11.4% versus 4.4%; P=.001) and urgent intervention (specifically emergency coronary bypass surgery; 2.5% versus 0.8%; P=.003) was increased in stented patients. When it was conditioned on having an unplanned stent deployed, the composite primary end point at 30 days was observed more frequently for patients who had been classified in the high- (16.0%) versus low-risk (10.9%; P=.225) stratum at the time of randomization.6
Both major and minor bleeding events were also more common in patients with unplanned stent deployment (P=.001). Within the population of patients having an unplanned stent, bleeding events were not increased by abciximab therapy (Fig 3⇓). In this population, major nonsurgical bleeding was observed less frequently in patients who had received abciximab. Table 4⇓ describes the fraction of patients experiencing major or minor non–coronary artery bypass graft bleeding by randomized treatment group and postprocedural therapy with ticlopidine or coumadin. The proportional occurrence of bleeding events was greater in patients receiving coumadin alone or in combination with ticlopidine.
Clinical Outcomes at 30 Days
Efficacy at 30 days by pharmacological treatment group for patients with and without unplanned stent deployment is shown in Table 5⇓. Significant reductions in the primary end point of the trial (death, myocardial infarction, or urgent revascularization) and the composite end point of death or myocardial infarction by 61% and 68%, respectively, were observed in patients treated with abciximab. Patients receiving low-dose, weight-adjusted heparin assignment faired slightly better in each analysis. The benefit associated with abciximab therapy appeared greater in stented versus nonstented patients for each outcome analyzed. Table 6⇓ describes the fraction of patients with death, myocardial infarction, or urgent revascularization at 30 days by randomized treatment group and concomitant therapy with ticlopidine or coumadin. The consistency of benefit associated with abciximab and low-dose, weight-adjusted heparin therapy is reflected by the smaller proportional occurrence of adverse events in this group regardless of concomitant medication.
Clinical Outcomes at 6 Months
Analysis of outcomes at 6 months by treatment group is shown in Table 7⇓. Reductions in composite negative outcomes, most notably death, myocardial infarction, urgent revascularization, and death or myocardial infarction by 55% and 60%, respectively, were observed in abciximab-treated patients. The composite of death, myocardial infarction, and any revascularization as well as the need for target-vessel revascularization were reduced by 33% and 40%, respectively, in patients receiving abciximab therapy. Those abciximab-treated patients assigned to low-dose heparin fared somewhat better than those receiving standard-dose heparin administration with respect to all end points except target-vessel revascularization. Target-vessel revascularization at 6 months was slightly less frequent in patients receiving standard-dose heparin in addition to abciximab. Again, the relative benefit of abciximab in stented versus unstented patients for each outcome analyzed was observed.
This trial prospectively evaluated clinical and angiographic descriptors, clinical outcomes, and the effect of adjunctive platelet GP IIb/IIIa receptor blockade in patients with unplanned coronary stent deployment. Because elective stents placed in the context of the primary stent substudy were excluded from these analyses, all stents deployed in the present series were by definition unplanned. The decision to deploy a stent was at the discretion of the investigator and was made in large part owing to a clearly suboptimal balloon angioplasty result or threatened coronary closure. In this respect, the overall frequency of stent use in the EPILOG trial (12%) was similar to that in the balloon angioplasty group of the BENESTENT II8 (13.2%) and BOAT9 (14%) trials, in which stents were provisionally deployed for suboptimal results. An important finding of the present study was that the requirement or need for unplanned stent deployment was reduced by abciximab and low-dose, weight-adjusted heparin administration (Fig 1⇑). This observation suggests that the immediate angiographic outcome of balloon angioplasty was improved by abciximab and low-dose heparin and may be consistent with a preferential reduction in adverse outcomes previously observed in those patients having the most complex coronary lesion morphology.10 In this context, although no differences existed in clinical demographics between groups, patients with unplanned stent deployment had more complex coronary lesion morphology (by AHA/ACC classification) and specifically longer lesion length, eccentricity, irregular contour, and bifurcation involvement (Table 2⇑). Thus, provisional stent deployment for a suboptimal balloon result is predictably more frequent in patients having these complex angiographic characteristics and is less often required in those patients receiving abciximab in conjunction with low-dose heparin. The reason for a discrepancy in stent requirement by heparin dosing is not clear; however, this observation is consistent with multiple other subgroup analyses that also suggested enhanced efficacy of abciximab and greater clinical benefit in patients administered the lower dose of weight-adjusted heparin.4
Patients with unplanned coronary stent deployment also experienced a more complex clinical course. Both the occurrence of myocardial infarction and the requirement for urgent coronary intervention (Table 3⇑) were more common in this group. These observations are similar to those reported from a series of patients who did not receive adjunctive platelet GP IIb/IIIa blockade.11 12 In the present study, clinical follow-up at 30 days and 6 months revealed important differences in outcomes between pharmacological treatment groups among stented patients. At both 30 days and 6 months, the composite of death, myocardial infarction, and urgent intervention was significantly reduced in patients treated with abciximab. Likewise, death, myocardial infarction, and any intervention and the need for target-vessel revascularization were reduced by abciximab. Interestingly, although nonsurgical bleeding events were increased in stented versus nonstented patients, abciximab therapy was not associated with increased bleeding. Indeed, among stented patients, major nonsurgical hemorrhage was observed less frequently in those patients receiving abciximab therapy and compared favorably with rates of major bleeding and transfusion observed in prior series of unplanned stent deployment followed by systemic anticoagulation.11 12 13
To date, the optimal adjunct pharmacology for patients with unplanned stent deployment has not been adequately defined. Recent clinical trials1 2 3 have concluded that antiplatelet therapy with a combination of ticlopidine and aspirin is superior to aspirin alone or anticoagulation with coumadin and aspirin for patients with elective stent deployment. Likewise, the regimen of ticlopidine and aspirin was associated with better outcomes than coumadin-aspirin combination in patients stented for evolving acute myocardial infarction14 and in those patients at high risk for stent-vessel occlusion.13 The benefit of adjunctive platelet GP IIb/IIIa blockade in patients having emergency coronary stent deployment for threatened or abrupt coronary closure was reported from the IMPACT II trial of Integrilin, a parenteral competitive antagonist of the RGD binding site on the GP IIb/IIIa receptor.15 In the IMPACT II trial, patients who required emergency stenting and who had received Integrilin on a randomized basis during the interventional procedure had a reduction in the composite of death, infarction, and emergency revascularization (P=.021) and in the occurrence of myocardial infarction (P=.017) by 37% and 50%, respectively, at 30 days.15 The present study confirms and extends this observation and assesses the effect of adjunctive abciximab platelet GP IIb/IIIa blockade on clinical outcomes in long-term follow-up. Because patients randomly assigned to receive placebo in this trial also received therapy with combination ticlopidine and aspirin or coumadin anticoagulation, the relative inadequacy of these pharmacotherapies compared with abciximab is evident. Adverse events were observed commonly in patients treated with placebo.
The observed benefit of abciximab in patients with unplanned coronary stent deployment has increasing importance in light of recent data supporting the practice of provisional stent deployment for suboptimal balloon angioplasty results. Recent trials have observed a “crossover” to unplanned or provisional stent deployment in 12% to 14% of patients treated by intention with balloon angioplasty.8 9 The current experience suggests that these patients will accrue significant benefit by the adjunctive administration of abciximab.
An important consideration in the interpretation and extrapolation of these data into clinical practice is that the benefit observed in the current study was achieved with abciximab administered prospectively and initiated before the performance of coronary intervention. Whether or not unplanned “rescue” abciximab therapy will be associated with similar benefit after unplanned stent deployment is not answered by the current series. Recent reports16 17 have suggested that ad hoc or unplanned abciximab therapy reduces abrupt thrombotic coronary occlusion and the need for urgent revascularization. Unfortunately, bleeding complications are frequent when this strategy of administering abciximab to patients already receiving “full-dose” heparin is followed. In this context, both the ability of abciximab to increase the ACT in heparin-treated patients17 18 19 and the correlation of maximum ACT in the catheterization laboratory with vascular repair and transfusion have been described.20 Although experience is limited, partial reversal of heparin anticoagulation with intravenous protamine in abciximab-treated patients appears to be well tolerated and has successfully reduced in-laboratory ACT values to levels not associated with hemorrhagic risk.21
In conclusion, the present series characterizes the angiographic profile and clinical course of patients with unplanned coronary stent deployment. The need for unplanned stent placement was reduced by prospective therapy with abciximab and low-dose, weight-adjusted heparin. Patients requiring an unplanned coronary stent have more complex preintervention coronary lesion morphology and a more complicated clinical course after the interventional procedure. Abciximab therapy confers substantial clinical benefit in these patients for up to 6 months without increasing bleeding complications. Adjunct pharmacological therapy with abciximab should be considered in patients having unplanned or provisional stent deployment.
Selected Abbreviations and Acronyms
|ACC||=||American College of Cardiology|
|ACT||=||activated clotting time|
|AHA||=||American Heart Association|
|EPILOG||=||Evaluation in PTCA to Improve Long-term Outcome with ABCIXIMAB GP IIb/IIIa blockade|
- Received August 8, 1997.
- Revision received October 29, 1997.
- Accepted November 6, 1997.
- Copyright © 1998 by American Heart Association
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