Controversies surrounding platelet glycoprotein IIb/IIIa inhibitors in percutaneous coronary intervention and acute coronary syndromes

Platelet-dependent thrombosis is an important part of the pathophysiology of both percutaneous coronary interventions (PCI) and acute coronary syndrome (ACS). Data support the use of acute therapies that interfere with platelets to provide clinical benefit to patients presenting with acute cardiovascular disease. The discovery of platelet glycoprotein (GP) IIb/IIIa receptor antagonists has been a major advance in the pharmacotherapy for patients undergoing PCI and those presenting with ACS without ST-segment elevation. This article will cover the role of platelets in acute cardiovascular disease, as well as the discovery and development of the platelet GPIIb/IIIa inhibitors. The major focus of this article will be on examining key lessons from the trials in each of these areas as well as presenting a series of questions that still require answers from either ongoing or future research.     

Glycoprotein IIb/IIIa inhibitors and bivalirudin in patients undergoing percutaneous coronary intervention

Percutaneous coronary intervention (PCI) is currently the standard of care for patients presenting with acute coronary syndrome (ACS), as well those patients with "stable" angina who have failed medical therapy in whom PCI is an acceptable alternative to surgical revascularization. The aim of adjunctive antiplatelet and antithrombotic therapy during PCI is to alleviate the risks associated with platelet activation and aggregation, iatrogenic plaque rupture, and thrombus formation during. The aim of this review is to summarize the evidence that has emerged from the randomized studies comparing a strategy combining heparin and a glycoprotein IIb/IIIa inhibitor (GPI) with that of bivalirudin in patients undergoing elective and urgent PCI.     

GP IIb/IIIa inhibitors during primary percutaneous coronary intervention for STEMI: New trial and registry data

Primary percutaneous coronary intervention (PCI) with adjunctive glycoprotein (GP) IIb/IIIa receptor inhibitor therapy administered in the cardiac catheterization laboratory is the optimal reperfusion strategy for patients with ST-elevation myocardial infarction. Most available data regarding these agents are from trials comparing abciximab to placebo alone. Noninferiority trials comparing small-molecule GP IIb/IIIa receptor inhibitors, such as tirofiban and eptifibatide with abciximab, have used markers for myocardial reperfusion as primary end points but are underpowered to detect significant differences in hard clinical outcomes. Such a trial would need to enroll a very large number of patients and thus make it practically impossible to perform. Registry data reveal that most patients undergoing primary PCI are treated with small-molecule GP IIb/IIIa receptor inhibitors in clinical practice, and no observed difference is observed in safety and efficacy when compared with patients treated with abciximab therapy.     

Planned versus provisional use of glycoprotein IIb/IIIa inhibitors in smokers undergoing percutaneous coronary intervention

Postmortem and angiographic studies have demonstrated that thrombosis is the primary cause of coronary artery occlusion in smokers. Further, smokers have high levels of fibrinogen, increased platelet aggregation, and more platelet-dependent thrombin generation than do nonsmokers, suggesting that glycoprotein (GP) IIb/IIIa inhibitor use during percutaneous coronary intervention (PCI) may be especially useful among smokers. We evaluated a subpopulation of active smokers in the REPLACE-2 trial to assess the effect of treating smokers with bivalirudin and provisional GP IIb/IIIa blockade compared with heparin and planned GP IIb/IIIa blockade. The REPLACE-2 trial enrolled 1,558 smokers and 4,305 nonsmokers. Smokers who were treated with bivalirudin had an absolute 3.2% increase in the composite end point of death and myocardial infarction at 48 hours compared with smokers who were treated with heparin and GP IIb/IIIa inhibitors (7.7% vs 4.5%, p=0.008, interaction p=0.016). This difference was ameliorated when GP IIb/IIIa inhibitors were used consistently in a previous trial that compared bivalirudin with heparin during PCI (4.6% vs 6.7%, p=0.322). In conclusion, these results suggest that smokers may derive particular benefit with GP IIb/IIIa inhibitors for decreasing myocardial infarction and death after PCI. These findings require further validation from other large, randomized trials.     

TARGET versus GUSTO-IV: appropriate use of glycoprotein IIb/IIIa inhibitors in acute coronary syndromes and percutaneous coronary intervention

Until recently, the selection of which glycoprotein IIb/IIIa inhibitor to use for patients with acute coronary syndromes or those undergoing percutaneous coronary intervention largely reflected physician preference, costs, and any evidence supporting the clinical indication. Clinicians often assumed a class effect for these agents: a benefit observed for one agent in one clinical setting (such as percutaneous coronary intervention) would confer benefit in another (such as non-ST-elevation acute coronary syndromes). The need for evidence to guide treatment selection motivated the design of the Do Tirofiban and ReoPro Give Similar Efficacy Trial (TARGET) and the Global Use of Strategies to Open occluded arteries (GUSTO-IV) trials with abciximab. This review examines the results from these and other recent trials of glycoprotein IIb/IIIa inhibition in acute coronary syndromes and percutaneous coronary intervention, presents a rationale for the lack of a consistent benefit with abciximab, and describes future directions for clinical investigation.     

Glycoprotein IIb/IIIa inhibitors in patients with renal insufficiency undergoing percutaneous coronary intervention

Glycoprotein IIb/IIIa receptor antagonists (GPRAs) are agents that block the final common pathway in platelet aggregation by inhibiting the binding of fibrinogen to the GPR on the surface of activated platelets, which then decreases crosslinking of platelets and thus platelet aggregation. Treatment guidelines recommend that patients undergoing percutaneous coronary intervention (PCI) be treated with a regimen of antithrombotic therapy that includes a GPRA to decrease the risk of ischemic events. Three GPRAs are currently available for use in the United States: abciximab (ReoPro), tirofiban (Aggrastat), and eptifibatide (Integrilin). Tirofiban and eptifibatide are renally cleared and thus must have dosage adjustment if used in patients with renal insufficiency (RI). Abciximab is not renally eliminated and does not require dosage adjustment in RI. Bleeding has been associated with worse outcomes after PCI and is the major risk associated with the use of GPRAs. Approximately 30% of PCI patients have RI, and RI increases the risk of bleeding. Unfortunately, clinical trials of GPRAs in PCI have excluded patients with moderate to severe RI. Several subgroup analyses and single center cohort analyses have analyzed the safety of GPRAs in patients with RI. These analyses have confirmed that bleeding is increased in patients with RI and in patients receiving GPRAs; however, the risk does not seem to be magnified by the combination of RI and GPRA therapy. These results are limited by the small study sample sizes and the varying definitions of RI and bleeding. An important finding of recent studies is that doses of eptifibatide and tirofiban are not always adjusted for RI, resulting in an increased risk of bleeding. The presence of RI in patients undergoing PCI should not preclude the use of GPRAs; however, the dose should be adjusted (eptifibatide and tirofiban) if pertinent and bleeding should be closely monitored.     

Use of platelet glycoprotein IIb/IIIa inhibitors in saphenous vein graft percutaneous coronary intervention and clinical outcomes

Platelet glycoprotein (GP) IIb/IIIa inhibitors are widely used in percutaneous coronary intervention (PCI). Previous studies have suggested that they do not offer benefit in saphenous vein graft PCI. Nonetheless, their use remains widespread during vein graft angioplasty. We retrospectively analyzed 1,537 patients who underwent saphenous vein graft PCI. Patients who received a GP IIb/IIIa inhibitor (n = 941) were compared with those who did not receive any GP IIb/IIIa inhibitor (n = 596). The primary end point was myonecrosis after PCI (creatine kinase-MB level >3 times the upper reference limit). The incidence of myonecrosis after PCI was similar between the group that received GP IIb/IIIa and the group that did not (odds ratio for GP IIb/IIIa use 1.39, 95% confidence interval 0.97 to 2.00, p = 0.07). Propensity-adjusted analysis demonstrated no significant difference in myonecrosis after PCI, in-hospital mortality, Q-wave myocardial infarction, or bleeding (blood transfusion, retroperitoneal bleed, or hematoma) between the 2 groups. In an analysis restricted to patients who were treated with an emboli protection device, GP IIb/IIIa use was not associated with decreased myonecrosis after PCI (this was also the case for patients who were not treated with an emboli protection device). Unadjusted survival (mean follow-up 5.5 +/- 0.1 years) was similar between the group that received GP IIb/IIIa and the group that did not (log-rank test, p = 0.89). There was no difference in survival after adjusting for the propensity to receive a GP IIb/IIIa inhibitor (adjusted odds ratio for GP IIb/IIIa use 0.92, 95% confidence interval 0.69 to 1.23, p = 0.59). In conclusion, adjunctive use of platelet GP IIb/IIIa inhibitors in saphenous vein graft PCI does not appear to be associated with less myonecrosis or improved survival.     

Bleeding complications associated with glycoprotein IIb/IIIa inhibitors in patients 80 years of age and older undergoing percutaneous coronary intervention

BACKGROUND:

Treatment of symptomatic coronary artery disease with percutaneous intervention requires antithrombotic therapy. Patients with elevated thromboembolic risk benefit from therapy with glycoprotein IIb/IIIa inhibitors. The safety and effectiveness of glycoprotein IIb/IIIa inhibition have been well documented in clinical trials. Drug-induced bleeding complications in elderly patients have not been specifically addressed.

METHODS:

Between 2006 and 2009, a total of 439 unselected patients 80 years of age and older undergoing percutaneous intervention for symptomatic coronary artery disease were included in the present nonrandomized retrospective study. In one-half of the patients, glycoprotein IIb/IIIa inhibitors were administered peri-interventionally. The in-hospital occurrence of bleeding complications (access site, gastrointestinal and cerebral) were analyzed in the groups with and without glycoprotein IIb/IIIa inhibitors.

RESULTS:

The mean age of the patients was 84 years. Nearly all patients (95%) received dual antiplatelet therapy. Patients treated with glycoprotein IIb/IIIa inhibitors had more complex coronary lesions and bypass graft interventions, and a tendency toward more access site bleeding complications than patients without inhibitors, which included femoral hematomas (4.6% versus 2.3%, respectively; P not significant) and femoral pseudoaneurysms (6% versus 3.2%, respectively; P not significant). The rate of blood transfusion was equal in both groups (0.9%). Major hemorrhagic events did not occur. Vessel closure devices were used more often in patients without glycoprotein inhibition.

CONCLUSIONS:

An increase in minor bleedings must be expected when using glycoprotein IIb/IIIa inhibitors in patients 80 years of age and older. However, this issue must not prevent this treatment option from being offered to elderly patients. There appears to be no elevated risk for major bleeding complications. Broadened use of vascular closure devices in this specific patient population may lower the rate of access site complications.     

Combined thrombectomy and intracoronary administration of glycoprotein IIb/IIIa inhibitors improves myocardial reperfusion in patients undergoing primary percutaneous coronary intervention: a meta-analysis

Background Suboptimal myocardial reperfusion is common in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI). Furthermore, it results in increased infarct size and mortality rates. We performed a meta-analysis to evaluate the role of aspiration thrombectomy (AT) combined with intracoronary administration of glycoprotein IIb/IIIa inhibitors (GPI) in the improvement of myocardial reperfusion and clinical outcomes. Methods PubMed, Embase, Web of Science, and CENTRAL databases were searched for randomized controlled trials (RCTs) investigating combined AT and intracoronary GPI treatment versus AT alone. Outcomes of interest were thrombolysis in myocardial infarction myocardial perfusion grade (TMPG), infarct size (IS) assessed by cardiac magnetic resonance imaging, left ventricular ejection fraction (LVEF), major adverse cardiac events (MACE) at short-term (≤ 1 month) and long-term (6?12 months) follow-up, and bleeding complications during the hospital stay. Results Eight trials involving 923 patients were included. Compared with AT alone, combined AT and intracoronary GPI significantly increased TMPG 3 flow (RR: 1.15, 95% CI: 1.04 to 1.26), reduced IS [mean difference (MD): ?3.46, 95% CI ?5.18 to ?1.73], and improved LVEF (MD: 1.44, 95% CI: 0.54 to 2.33). Furthermore, GPI use decreased the risk of MACE at long-term follow-up (RR: 0.60, 95% CI: 0.37 to 0.98). There was no significant difference between the two groups in the incidence of minor and major bleeding complications. Conclusions Our findings showed that compared with AT alone, combined AT and intracoronary GPI treatment resulted in improved myocardial reperfusion, better cardiac function, and MACE-free survival benefits at the long-term follow-up for patients with STEMI undergoing PPCI.