Safety of a high bolus dose of tirofiban in patients undergoing coronary stent placement

Current and Future Roles of Glycoprotein IIb-IIIa Inhibitors in Primary Angioplasty for ST-Segment Elevation Myocardial Infarction

Acute myocardial infarction still represents the major cause of mortality in high-income countries. Therefore, considerable efforts have been focused on the treatment of myocardial infarctions in the acute and long-term phase, with special attention being paid to reperfusion strategies and adjunctive antithrombotic therapies. In fact, despite the successful mechanical recanalization of the epicardial conduit, a substantial percentage of patients still experience poor myocardial reperfusion or acute/subacute in-stent thrombosis. Due the delayed onset of action of currently available oral antiplatelet therapies, glycoprotein (GP) IIb-IIIa inhibitors could be expected to improve clinical outcomes, especially when administrated in the early phase of the infarction, due to the larger platelet composition of fresh thrombi, the dynamic nature of early thrombi, and the larger amount of viable myocardium existing in the early, as compared to a delayed, phase. Considerable evidence has accumulated regarding the benefits from GP IIb-IIIa inhibitors on mortality, especially among high-risk patients and when administered as an upstream strategy. Therefore, based on currently available data, GP IIb-IIIa inhibitors can be considered when the drug can be administered within the first 3 h of symptom onset and among high-risk patients (e.g., those with advanced Killip class or an anterior myocardial infarction). Even though it is not universally accepted, in our opinion, this strategy should be implemented in a pre-hospital setting (in an ambulance) or as soon as possible when arriving at the hospital (at the Emergency Room or Coronary Care Unit, irrespective of whether they are in spoke or hub hospitals). A new, second-generation GP IIb-IIIa inhibitor (zalunfiban) appears to be highly suitable as a pre-hospital pharmacological facilitation strategy at the time of first medical contact due to its favourable features, including its simple subcutaneous administration, rapid onset of action (15 min), and limited time of action (with a half-life of ~1 h), which is likely to minimize the risk of bleeding. The ongoing CELEBRATE trial, including 2499 STEMI patients, may potentially provide compelling data to support the upstream treatment of STEMI patients undergoing mechanical reperfusion. In fact, although the current therapeutic target of increased rates of timely reperfusion has been achieved, the future goal in myocardial infarction treatment should be to achieve the most rapid reperfusion prior to primary percutaneous coronary intervention, thus further minimizing myocardial damage, or, in some cases, even preventing it completely, and improving survival.

The role of Glycoprotein IIb/IIIa inhibitors in acute coronary syndromes and the interference with anemia

The role played by glycoprotein (GP) IIb/IIIa inhibitors (GPI) has continuously evolved until the most recent Guidelines whereby they were stepped down from class I to class II recommendation for treating acute coronary syndromes (ACS). GPI compete with a wider use of ADP inhibitors and novel anticoagulant drugs although GPI use has greatly narrowed. However, GPI may still have a role. Several criteria were proposed to define post-PCI anemia which is strictly related to bleeding and transfusion. In ACS, it should be important to define anemia in comparative terms versus baseline levels: ≥ 15% of red blood cell decrease should be a practical cut-off value. If one wishes to concentrate on hemoglobin (Hb), a≥2g/dl Hb decrease from baseline should be considered. It is important to recognize post-PCI anemia in the setting of ACS. There are sub-populations exposed to short-term hemorrhagic and/or long-term ischemic risks. Ischemic and hemorrhagic risks need to be carefully evaluated along with thrombocytopenia and its prognostic significance in order to put all these blood and rheological parameters into a clinically oriented perspective on which therapeutical decisions should be based. Definition of high risk procedures (complexity, angiographic characteristics and patient's risk profile, regardless whether STEMI or NSTEMI) may help selecting GPI. There are positive elements in GPI use: efficacy, rapid onset and reversibility of action, absence of pharmacogenomic variability, pharmacoeconomic considerations and the possibility of intracoronary administration. All these elements should be evaluated when selecting these agents for therapeutics.

Tirofiban in acute coronary syndromes

Acute coronary syndromes represent a major health problem in terms of incidence and mortality. Intracoronary platelet-rich thrombi may develop in response to plaque rupture, and are involved in the pathogenesis of all acute coronary syndromes. The glycoprotein IIb/IIIa receptor, a platelet surface integrin, plays a key role in platelet aggregation once it has been activated by specific ligands. The development of glycoprotein IIb/IIIa inhibitors has revolutionized the management of acute coronary syndromes. Tirofiban is one of three parenteral glycoprotein IIb/IIIa inhibitors in clinical use, and many trials have demonstrated its clinical efficacy and low rate of adverse effects in patients with non-ST-segment elevation acute coronary syndrome. This article reviews the data concerning its use in the clinical settings of acute coronary syndromes and percutaneous coronary angioplasty, and discusses its benefits in different treatment strategies and in association with other drugs. In particular, the role of early, upstream tirofiban coupled with early aggressive revascularization in the management of high-risk non-ST-segment elevation acute coronary syndromes is emphasized.

Is There Still a Role for Glycoprotein IIb/IIIa Antagonists in Acute Coronary Syndromes?

The role played by glycoprotein (GP) IIb/IIIa inhibitors has continuously evolved from the initial introduction in mid 90 s until the most recent guidelines for treating acute coronary syndromes, and competed with a wider use of ADP inhibitors and novel anticoagulant drugs, to the extent that they stepped down from class I to class II recommendation in the routine setting of acute coronary syndromes. As a consequence, GP IIb/IIIa use was greatly narrowed. The purpose of this review is to define the roles that GP IIb/IIIa inhibitors may still have in acute ischemic settings by explaining why in high risk patients they might be preferable and/or whether they might be added to ADP inhibitors also emphasizing the underlying mechanistic actions. It is concluded that there might be a more extensive use of GP IIb/IIIa inhibitors in patients presenting with acute coronary syndromes, strictly based on the definition for a high risk procedure: complexity, angiographic characteristics and patient's risk profile, regardless whether STEMI or NSTEMI. The positive elements one should appreciate in GP IIb/IIIa inhibitors are: efficacy, rapid onset and reversibility of action, absence of pharmacogenomic variability, pharmacoeconomic considerations and the possibility of intracoronary administration.

Intra-arterial adjuvant tirofiban after unsuccessful intra-arterial thrombolysis of acute ischemic stroke: preliminary experience in 16 patients

INTRODUCTION

Intra-arterial (IA) thrombolysis with plasminogen activator is well-known, but the use of IA tirofiban as an adjuvant for IA thrombolysis is not well-known. We investigated the feasibility of IA tirofiban as an adjuvant after unsuccessful IA recanalization with urokinase (UK) for acute ischemic stroke.

METHODS

We retrospectively analyzed all 16 consecutive patients (11 men and five women; mean age, 61.3 years; range, 36-85 years) who were treated with IA tirofiban after isolated IA thrombolysis with UK or bridging therapy with systemic recombinant tissue plasminogen activator (rt-PA; 0.6 mg/Kg) and IA UK for acute ischemic stroke. Outcome measures included angiographic recanalization (thrombolysis in cerebral infarction, TICI), symptomatic and asymptomatic intracerebral hemorrhage (ICH), mortality, and functional independence at 3 months (modified Rankin Scale, 0-2).

RESULTS

Among the 16 patients treated with IA tirofiban as an adjuvant, 10 patients had conventional dose (<25 ug/kg, bolus) and six patients had high dose (≥25 ug/kg, bolus) of IA tirofiban after unsuccessful IA thrombolysis whether systemic rt-PA used or not. Successful angiographic recanalization (TICI grade 2b or 3) was achieved in 13 patients (13/16) and a functional independence at 3 months in eight patients (8/16). Three months after therapy, three patients had died. There were two patients of symptomatic ICH and four asymptomatic ICH.

CONCLUSION

Conventional dose of IA tirofiban as an adjuvant during IA thrombolysis for acute ischemic stroke seems feasible. However, further dose escalation studies should be performed regarding the IA use of tirofiban for acute ischemic stroke.

Safety of downstream high-dose tirofiban bolus among 1578 patients undergoing percutaneous coronary intervention: the Sant'ANna TIrofiban Safety study

BACKGROUND

The Sant'ANna TIrofiban Safety study (SANTISS) is an open-label investigator-initiated single-centre registry launched to assess the combination of bleeding and access site in-hospital complications (primary end-point) in patients undergoing percutaneous coronary intervention (PCI) by femoral approach only.

METHODS

We compared patients who were on oral single antiaggregating drug (AAD) and received, just prior to PCI, high-dose tirofiban and a second oral antiplatelet agent (triple AAD: group 1, n = 970) with those who were already on an oral double AAD regimen and did not receive tirofiban (double AAD: group 2, n = 608).

RESULTS

Group 2 patients were slightly older, presented less frequently with unstable angina and had chronic renal failure more frequently. They were more than twice as frequently on rescue PCI, being more than three-fold less frequently on primary PCI (all: 0.01>P < 0.001). Overall, there were 87 in-hospital (average 4.7 days of stay) complications: 51 (5.3%) in group 1 and 36 (5.9%) in group 2 (not significant). Haemotransfusions were needed in 34 patients: 21 (2.2%) in group 1 and 13 (2.1%) in group 2 (not significant). Of the 16 hospital deaths, eight (0.8%) were seen in group 1 and eight (1.3%) in group 2 (not significant). Multivariate prediction showed a high predictive accuracy (areas under the curve >0.700) of female sex, rescue PCI and chronic renal failure to index complications, with highly significant odds ratios. The presence of high-dose tirofiban did not increase complication risk.

CONCLUSION

In the real world, high-dose tirofiban is well tolerated by patients on elective, primary or rescue PCI, and the in-hospital complication rate, including major bleeding, is low. This may have pharmacoeconomic consequences.

High-dose tirofiban with enoxaparin and inflammatory markers in high-risk percutaneous intervention

AIM

The study assessed the benefit of high bolus dose tirofiban (HD-tirofiban) with enoxaparin compared with HD-tirofiban with unfractionated heparin (UFH). The study examined markers of platelet activation, thrombin generation and inflammation.

MATERIALS AND METHODS

The study is a prospective single centre open-label trial of patients with high-risk acute coronary syndrome treated with percutaneous intervention (PCI) who were randomized to anticoagulation with UFH or enoxaparin with HD-tirofiban (25 microg kg(-1) bolus). This study measured a panel of platelet activation markers, inflammatory biomarkers and thrombus generation between the two groups.

RESULT

Sixty patients undergoing high-risk PCI were enroled in the study. Platelet inhibition as assessed by whole blood aggregometry following HD-tirofiban infusion was similar in both the UFH and enoxaparin groups. CD40 ligand expression on platelets was significantly reduced following PCI with HD-tirofiban and either UFH or enoxaparin. Following PCI, there were significant reductions measured in other markers of platelet activation including PAC-1, P selectin, factor V/Va, platelet-monocyte aggregates and monocyte expression of Mac-1 as determined by analysis of venous blood samples using flow cytometry. Prothrombin fragment 1+2, D-dimer, von Willebrand factor and high sensitive C-reactive protein levels were significantly less post PCI in the enoxaparin group compared with those patients receiving UFH.

CONCLUSION

The combination of HD tirofiban with enoxaparin resulted in an attenuated inflammatory response when compared with that of the combination of HD tirofiban with UFH.

The in-vitro effect of tirofiban, glycoprotein IIb/IIIa antagonist, on various responses of porcine blood platelets

The present study systematically evaluates the in-vitro effect of tirofiban, glycoprotein IIb/IIIa (integrins alphaIIbbetaIII) antagonist, on porcine blood platelets. It was found that tirofiban at concentrations up to 5,000 ng/ml did not affect the calcium signal produced by thrombin. Tirofiban, in a concentration-dependent manner reduced platelet aggregation evoked by ADP (IC50 approximately 70 ng/ml), collagen (IC50 approximately 200 ng/ml), and thrombin (IC50 approximately 5,000 ng/ml). Substantial thrombin-evoked platelet aggregation still occurred at high (5,000 ng/ml) tirofiban concentrations. The concentrations of tirofiban completely blocking the optical aggregation evoked by ADP or collagen failed to eliminate microaggregate formation totally. Tirofiban strongly inhibited the dense-granule and lysosome secretion induced by ADP (IC50 approximately 70-170 ng/ml), moderately inhibited that induced by collagen (IC50 approximately 420-500 ng/ml) and very poorly inhibited that elicited by thrombin (IC50 approximately 1,500-5,000 ng/ml). The extent of the inhibition of aggregation and secretion rose as concentrations of the stimulus lowered. Tirofiban was a moderate inhibitor (IC50 approximately 200 ng/ml) of adhesion and a poor inhibitor of platelet procoagulant response induced by collagen. Thromboelastography measurements indicate that, in whole blood, tirofiban, up to concentrations of 2,000 ng/ml, did not affect the kinetics of tissue factor induced clot formation. The obtained results reveal that in porcine platelets, the maximal concentrations of tirofiban used in human medicine (250 ng/ml), effectively block platelet responses triggered by ADP, partly block those induced by collagen and very poorly block those evoked by thrombin. The reason for this phenomenon seems to be the inability of tirofiban to reduce platelet secretion completely.

Current strategies with high-dose tirofiban

The glycoprotein (GP) IIb/IIIa receptor is a platelet-specific adhesion receptor that mediates the formation of platelet aggregates. Pharmacologic blockade of the receptor is associated with a reduction in major cardiovascular adverse events after percutaneous coronary interventions and in the setting of acute coronary syndromes. Three intravenous GP IIb/IIIa receptor inhibitors are available: abciximab, tirofiban and eptifibatide. Tirofiban is a small, synthetic non-peptide, competitive GP IIb/IIIa antagonist with high specificity and high affinity for the GP IIb/IIIa receptor. In a head-to-head comparison, tirofiban 10-microg/kg bolus followed by a 0.15-microg/kg/min infusion was found to be inferior to standard dose of abciximab in patients undergoing percutaneous coronary intervention. Insufficient platelet inhibition with low-dose tirofiban may likely explain these results. Subsequently, a high-bolus dose of tirofiban (25 microg/kg bolus) followed by standard infusion was tested and evidence suggest that in this dosing tirofiban may be as effective as abciximab and have a comparable safety profile. Therefore, high-bolus dose tirofiban may be an appealing and cost-effective alternative to abciximab. However, further testing is warranted given the short follow up and limited statistical power of the available data.

Safety and efficacy of low-dose unfractionated heparin during percutaneous coronary revascularisation and the relationship between activated clotting time and haemorrhagic or ischaemic complications: our results

OBJECTIVE

An inverse relation between the degree of heparin anticoagulation and the subsequent risk of postprocedural thrombotic complications was observed in the era of conventional balloon angioplasty, but the optimal dose of heparin during percutaneous coronary intervention (PCI) using newer interventional equipment and glycoprotein IIb/IIIa receptor inhibition has not been clearly defined. Previous studies did not assess the increased risk of adverse cardiac events with an activated clotting time of <200 s using strategies of routine stent placement and glycoprotein IIb/IIIa receptor inhibition. We hypothesised that the efficacy and safety of PCI would be maintained, if not improved, especially when performed in conjunction with glycoprotein IIb/IIIa receptor inhibitors (abciximab, tirofiban or eptifibatide as a bolus plus infusion for 12-18 h) and oral antiplatelet therapy (clopidogrel 75 mg plus aspirin 325 mg/day) associated with low doses (5000-10 000 U) of unfractionated heparin using a target activated clotting time of </=200 s during PCI. In this way, the sheath could be immediately removed at the end of the procedure.

METHODS

We evaluated the outcome at 30 days and at one year of 2552 consecutive patients who underwent PCI and stenting; most of them were treated with PCI and selective administration of glycoprotein IIb/IIIa inhibitors in high-risk cases (61%).

RESULTS

By design, the activated clotting time was 184 +/- 39 s. The incidence of access site complications and of in-hospital major adverse cardiac events during the first 48 h following PCI was 3.7% and 3.3%, respectively. The incidence of major adverse cardiac events was 4.5% at 30 days and 7.6% at one year.

CONCLUSIONS

This study shows the safety and efficacy of this therapeutic strategy in the era of frequent stent implantation and aggressive intravenous and oral platelet inhibition. Additional research is warranted to determine whether these results can be extrapolated routinely to patients with acute myocardial infarction or undergoing PCI without stent implantation.

Thrombus predicts ischemic complications during percutaneous coronary intervention in saphenous vein grafts: Results from TARGET (do tirofiban and reopro give similar efficacy trial?)

BACKGROUND

Saphenous vein graft (SVG) percutaneous coronary intervention (PCI) carries a high risk of ischemic complications. However, there are scant recent data to identify which SVG lesions carry particularly high risk in recent years. We studied demographic and angiographic factors associated with ischemic complications after SVG PCI without distal protection in the TARGET (do tirofiban and reopro give similar efficacy trial?) study.

METHODS

TARGET was a multicenter double-dummy, double-blinded study randomizing 4,809 PCI patients to tirofiban or abciximab. Of these, 254 patients underwent PCI involving an SVG lesion. The primary endpoint of this analysis was major adverse cardiac events (MACEs) at 30 days, including death, nonfatal myocardial infarction (MI), and urgent target vessel revascularization.

RESULTS

No demographic characteristic was associated with 30-day MACE. Lesion length > 20 mm (odds ratio [OR] = 2.7, P = 0.03), thrombus (OR = 3.9, P = 0.003), eccentricity (P = 0.001), thrombolysis in myocardial infarction flow < 3 post-procedure (OR = 5.6, P = 0.037), and >1 target lesion (OR = 2.5, P = 0.035) were univariate variables associated with 30-day MACE. Multivariate analysis associated only thrombus (OR = 3.8, P = 0.015) with 30-day MACE. No difference in outcomes was noted between patients receiving abciximab and tirofiban. SVG patients had lesser angiographic success (95.6% vs. 98%, P = 0.04) and increased 30-day Q-wave MI (2.5% vs. 0.9%, P = 0.039) compared with non-SVG patients, but a similar incidence of death (0% vs. 0.4%), non-Q-MI (5.9% vs. 4.5%), and target vessel revascularization (0.5% vs. 1%).

CONCLUSION

In the era of routine stenting and GpIIb/IIIa inhibitors, thrombus is the angiographic characteristic most closely associated with adverse outcomes of SVG PCI.

Benefit of bolus-only platelet glycoprotein IIb/IIIa inhibition during percutaneous coronary intervention: insights from the very early outcomes in the Evaluation of 7E3 for the Prevention of Ischemic Complications (EPIC) trial

BACKGROUND

Platelet glycoprotein IIb/IIIa inhibitors are administered during percutaneous coronary intervention as a bolus followed by infusion. The need for an infusion was established by the Evaluation of 7E3 for the Prevention of Ischemic Complications (EPIC) trial conducted during the percutaneous transluminal coronary balloon angioplasty (PTCA) era, when the threat of acute thrombotic complications prevailed over concerns regarding bleeding, and stenting was considered an adverse event.

METHODS

The EPIC trial randomized high-risk PTCA patients to 3 arms: placebo, abciximab bolus only, and abciximab bolus plus infusion. The present analysis of the EPIC outcomes was done at 6-hour intervals during the first 24 hours after PTCA to identify any early benefit derived from the abciximab bolus-only arm.

RESULTS

At 6 hours after randomization, the primary composite end point of death, myocardial infarction, or urgent intervention was significantly reduced by 46% with abciximab bolus-only compared with placebo (2.9% vs 5.3%; P = .022), which is mainly due to a reduced rate of urgent intervention. There was also a numerical but not statistically significant reduction in myocardial infarction rate using abciximab bolus-only compared with placebo. A lower bleeding rate in the bolus-only arm compared with bolus plus infusion has been reported.

CONCLUSIONS

As stenting and thienopyridine use have become routine, there has been a decrease in the incidence of acute closure and an increasing concern for bleeding complications after percutaneous coronary intervention, which potentially may be addressed by adopting a bolus-only glycoprotein IIb/IIIa inhibitor strategy. The early protective ischemic effect of abciximab bolus-only observed in the EPIC trial may be relevant in this regard.

Angiographic and clinical outcome in ST-segment elevation myocardial infarction patients receiving an adjunctive double bolus regimen of tirofiban for primary percutaneous coronary intervention

BACKGROUND

Because of different dosages, the efficacy of adjunctive tirofiban therapy for primary percutaneous coronary intervention (PCI) is currently unclear. The hypothesis that a double bolus regimen of tirofiban will improve angiographic and clinical outcomes in patients with ST-segment elevation acute myocardial infarction (STEMI) undergoing PCI was tested in the present study.

METHODS AND RESULTS

Primary PCI was performed in 217 STEMI patients: 80 received standard PCI (control group) and 137 received tirofiban (tirofiban group). Tirofiban was given as a bolus (10 mg/kg) in the emergency room and again upon arrival at the cardiac catheterization laboratory, followed by infusion of 0.15 mg . kg(-1) . min (-1) until the total dose reached 12.5 mg. The primary endpoint was emergency target vessel revascularization, recurrent myocardial infarction, or cardiovascular mortality at 30 days and 1 year. Baseline clinical and angiographic variables of the 2 groups were similar, as were angiographic results after PCI and bleeding complications at 30 days. The primary 30-day and 1-year endpoints were 5.1% and 11.7% in the tirofiban group, respectively, vs 10.0% (p = 0.171) and 18.8% (p = 0.151) in the control group.

CONCLUSION

Although angiographic and clinical benefits were not demonstrated, the results suggest that research into an effective and uniform dosing regimen of adjunctive tirofiban therapy for PCI is warranted.

Comparison of abciximab with “high-dose” tirofiban in patients undergoing percutaneous coronary intervention

BACKGROUND

The TARGET study has been criticised for sub-optimal platelet inhibition with tirofiban. We aimed to compare a high-dose bolus regimen of tirofiban (hd-tirofiban) to standard dose of abciximab for patients undergoing percutaneous coronary intervention (PCI).

METHODS

We assessed consecutive patients who received either hd-tirofiban (25 mcg/kg bolus followed by 0.15 mcg/kg/min infusion for 18 h) or standard dose abciximab. In-hospital and 6-month outcomes were obtained in all cases.

RESULTS

Over an 18-month period, 109 patients who received hd-tirofiban were compared with 110 patients who received abciximab. Both hd-tirofiban and abciximab groups had acute coronary syndromes in 86% and 80% and diabetes in 10% and 13% respectively. Most patients had coronary stent implantation (96% vs. 98%). Thrombocytopenia (platelet count< 100,000) developed in 0.9% of patients receiving hd-tirofiban and 2% of patients receiving abciximab (p = 0.566). Bleeding requiring transfusion occurred in 7.3% and 3% of patients respectively (p = 0.118). Peri-procedural troponin rise was 0.9% in patients receiving hd-tirofiban and 5.5% in patients receiving abciximab (p = 0.07). MACE (Myocardial infarction, Stroke, Revascularisation and Death) at 6 months was 23% in the hd-tirofiban group and 20% in the abciximab group (p = 0.711). The pharmaceutical costs were AUD 322 for hd-tirofiban (one ampoule) and AUD 1,350 for abciximab (3 ampoules).

CONCLUSION

There was a small increase in bleeding requiring transfusion and a lower rate of peri-procedural troponin rise in the hd-tirofiban group however, the overall 6-month MACE rates were similar in both groups. There was a considerable cost-saving with the use of hd-tirofiban. A prospective randomised trial of hd-tirofiban vs. abciximab is warranted.

Variability in extent of platelet function inhibition after administration of optimal dose of glycoprotein IIb/IIIa receptor blockers in patients undergoing a high-risk percutaneous coronary intervention

The Ultegra Rapid Platelet Function Assay was used to measure the inhibition of platelet aggregation at baseline and 10 minutes and 8 hours after starting therapy in 114 patients undergoing high-risk percutaneous coronary intervention with the planned use of a glycoprotein IIb/IIIa inhibitor. The abciximab-treated patients received a 0.25 mg/kg bolus, followed by a 0.125 microg/kg/min infusion for 12 hours; the eptifibatide-treated patients received 2 boluses of 180 microg/kg administered 10 minutes apart, followed by a 2 microg/kg/min infusion for 24 hours; the tirofiban-treated patients received a 25 microg/kg bolus, followed by a 0.15 microg/kg/min infusion for 18 hours. Ten minutes after starting therapy, the mean level of platelet inhibition was 86 +/- 9% for abciximab, 92 +/- 6% for eptifibatide, and 95 +/- 5% for tirofiban (p <0.001); > or =95% platelet inhibition was achieved in 29% of the patients treated with abciximab, 44% of those receiving eptifibatide, and 68% of the those receiving tirofiban (p = 0.02). In conclusion, at the evaluated doses, tirofiban seemed to be the most effective drug in achieving "optimal" platelet inhibition very early after percutaneous coronary intervention.

Downstream administration of a high-dose tirofiban bolus in high-risk patients with unstable angina undergoing early percutaneous coronary intervention

BACKGROUND

The best treatment option for high-risk patients with unstable coronary syndrome is an early invasive strategy accompanied by intensive anti-platelet therapy. We tested the effect on clinical outcome of early coronary angioplasty using a high-dose bolus of tirofiban in patients with non-ST segment elevation acute coronary syndrome.

METHODS

One hundred and forty consecutive patients with unstable coronary syndrome who underwent an immediate percutaneous coronary intervention with the administration of a high (25 microg/kg) dose bolus of tirofiban followed by an 18-h infusion of 0.15 microg kg(-1) min(-1) were compared with a matched control group of 162 patients treated with abciximab. The primary endpoint of the study was the 30-day incidence of major adverse cardiac events; the secondary endpoints were the incidence of major and minor bleeding.

RESULTS

The time from admission to PCI was slightly shorter in the tirofiban group (3.9+/-4.8 vs. 4.5+/-4.4 h; P=0.26). The 30-day rate of major adverse cardiac events was similar in the two groups (6% with tirofiban and 8.6% with abciximab: OR=1.37, 95% CI=0.58-3.29, P=0.52). No major bleeding episodes were observed; the incidence of minor bleeding was 3.6% in the tirofiban group and 2.5% in the abciximab group (OR=0.68, 95% CI=0.18-2.59, P=0.74).

CONCLUSIONS

In this preliminary study, the beneficial effect of the administration of a high-dose tirofiban bolus on 30-day clinical outcomes was similar to that of abciximab in high-risk patients with unstable angina undergoing immediate percutaneous coronary intervention. The results of this therapeutic strategy should be tested in a larger randomised study.

Facilitated percutaneous coronary intervention (PCI) in patients with acute ST-elevation myocardial infarction: Comparison of prehospital tirofiban versus fibrinolysis before direct PCI

AIMS

Early start of treatment including coronary revascularization has been recognized as crucial variable in the outcome of acute ST-segment elevation myocardial infarction (STEMI). The lack of availability and the realisation that an optimum reperfusion strategy will need to incorporate mechanical reperfusion as part of that strategy has led to a great deal of interest in pharmacologic reperfusion combined with mechanical reperfusion or facilitated PCI. It is not clear whether GPIIb/IIIa-blockade or fibrinolysis better facilitates PCI.

METHODS

We identified 138 patients who have been primarily treated by our mobile emergency care mobile from July 2001 until February 2003 with tirofiban or fibrinolysis. Seventy-nine patients had ST-elevation myocardial infarction (STEMI) and available angiograms within 24 h.

RESULTS

Forty-four patients had tirofiban (TIRO; 60.6 S.D. 11.4 years, 64% male) and 35 patients underwent fibrinolysis (FIB; 31.4% tenecteplase, 54.3% reteplase, 11.4% alteplase, 2.9% streptokinase; 58.8 S.D. 12.2 years, 80% male). Data were analyzed with respect to TIMI-flow and corrected frame count (cTFC) before and after PCI, bleeding complications at 30 days and long-term follow up for major adverse events (median 288 days; MACE: Death, hospitalized re-infarction, intracranial hemorrhage). Catheter films were re-analyzed by an investigator blinded to the prehospital therapy. Time from onset of symptoms to first medical contact was 1.98 h in TIRO compared to 0.5 h in FIB (p<0.001) and time from first prehospital medical contact to catheter was 1.46 h in the TIRO compared to 2.85 h in the FIB group (p<0.001). TIMI 3-flow before PCI was observed in 20.5% of TIRO and 62.9% in FIB (p<0.001). After PCI TIMI 3-flow was achieved in 90.5% and 90.0%, respectively (p=n.s.). Final cTFC was 24 in TIRO and 29 in FIB (p=n.s.). Visible thrombi were detected in 30.2% in TIRO and 23.5% in FIB (p=n.s.). Major bleeding occurred in one TIRO patient (fatal lung bleeding after ultima ratio abciximab on top of tirofiban), 2 patients (4.5%) received transfusions. In FIB 2 intracerebral hemorrhages, 5 transfusions (14.3%) and 3 pulmonary bleedings during mandatory ventilation were observed. After 30 days 4.5% in TIRO and 22.9% in FIB had MACE (p=0.015). During long-term follow up the primary endpoint was observed in 4.5% of TIRO and 28.6% (p=0.003) of FIB. Two patients died in TIRO and 9 patients in FIB.

CONCLUSIONS

We conclude that (1) prehospital start of tirofiban for facilitated PCI is safe and effective if administered by experienced emergency physicians; (2) routine fibrinolysis should be limited to areas where catheter based therapy is not available within 90 min and (3) fibrinolysis should be given for facilitated PCI in randomized trials only at the moment.

Pharmacodynamics and pharmacokinetics of the platelet GPIIb/IIIa inhibitor tirofiban in patients undergoing percutaneous coronary intervention: implications for adjustment of tirofiban and clopidogrel dosage

INTRODUCTION

Despite extensive data supporting the use of platelet glycoprotein (GP) IIb/IIIa (GPIIb/IIIa) inhibitors in the therapy of patients with acute coronary syndromes (ACS), there is considerable debate as to the optimal choice of antiplatelet regimen. The objective of this study was to conduct a detailed time-resolved analysis of the effects of the GPIIb/IIIa inhibitor tirofiban with concomitant clopidogrel in ACS patients undergoing percutaneous coronary intervention (PCI) to improve the dosing regimen of these two commonly used antiplatelet drugs.

METHODS

The study was performed in 14 patients with non-ST-segment elevation (NSTE) ACS who underwent PCI while being treated with the current typically utilized regimen of tirofiban (10 microg/kg bolus, 0.15 microg/kg/min infusion) and clopidogrel (300 mg). Platelet function was assessed before, during, and after tirofiban infusion using a panel of agonists for ADP receptors, PAR1 and PAR4 thrombin receptors, and collagen receptors.

RESULTS

Measurements of circulating tirofiban levels demonstrated a trough, which paralleled a reduction in platelet inhibition for all platelet agonists during the time when PCI was being performed. Interestingly, younger ACS patients (<55 years) exhibited less inhibition of platelet function both during the PCI procedure and after termination of the tirofiban infusion. These apparent age differences were primarily attributed to a decreased responsiveness of the younger patients to clopidogrel.

CONCLUSIONS

This study shows that the currently utilized tirofiban dosage is suboptimal and suggests that patients may benefit from a higher dose regimen.

Extracorporeal Elimination of Large Concentrations of Tirofiban by Zero-Balanced Ultrafiltration During Cardiopulmonary Bypass: An In Vitro Investigation

The short-acting platelet glycoprotein IIb/IIIa antagonist tirofiban is beneficial when used in the context of cardiac surgery. Tirofiban has an elimination half-life of 2 h. Renal failure prolongs the half-life and continues inhibition of platelet aggregation refractory to transfusions of platelets. Extracorporeal elimination is necessary to prevent excessive hemorrhage in this condition. We assessed the elimination of tirofiban by hemofiltration in an in vitro model of cardiopulmonary bypass (CPB). Two hemofilters and one plasmapheresis filter were assessed. Three separate filters of each type were tested serially. The CPB circuit was primed with a total volume of 1000 mL. Tirofiban was added to a calculated concentration of 200 ng/mL. Portions of 50 mL of filtrate were retrieved from the dialyzer, and equal amounts of fluid were substituted in the circuit. After each filtration, the tirofiban blood level was analyzed. The procedure was repeated 16 times. Peak tirofiban concentrations ranged from 160 to 260 ng/mL. The elimination of tirofiban followed an exponential decay curve with fast clearance of the large therapeutic concentrations of 250 to 50 ng/mL. The subsidence coefficient b revealed no significant differences in elimination between the filter systems. These data suggest that ultrafiltration is an effective means for extracorporeal elimination of therapeutic levels of tirofiban.