Platelet glycoprotein IIb/IIIa receptor blockade and low-dose heparin during percutaneous coronary revascularization

Synergistic effect of thrombus aspiration and abciximab in primary percutaneous coronary intervention

BACKGROUND

Previous studies failed to assess the individual prognostic role of thrombus aspiration (TA) or abciximab in primary percutaneous coronary intervention (pPCI), due their prevalent combined use.

METHODS AND RESULTS

A total of 644 consecutive ST-segment elevation myocardial infarction patients treated with pPCI were included in this retrospective registry from January 2006 to December 2008. Patients were divided in: (a) Group 1, with conventional pPCI; (b) Group 2, with pPCI and abciximab; (c) Group 3, with pPCI and TA; (d) Group 4, with pPCI and abciximab plus TA. Primary end point was the composite of major adverse cardiovascular events (MACEs, defined as overall mortality, myocardial infarction, target vessel revascularization, and major bleedings) at 1 year. Baseline clinical and angiographic characteristics were not different among the groups, with the exception of a younger age in group 4. The two groups of patients treated with TA (group 3 and 4) received more frequently direct stenting (P < 0.001 vs. group 1 for both), presented higher rate of end-procedural TIMI flow grade 3 (P < 0.001 vs. group 1 for both), and lower rate of no-reflow (P = 0.016 and P < 0.001 vs. group 1, respectively). Patients of group 2 presented a borderline nonsignificant trend toward higher rate of end-procedural TIMI flow grade 3 (P = 0.083 vs. group 1). MACEs at 1 year were 43 (29%) in group 1 versus 25 (22%) in group 2 versus 24 (19%) in group 3 versus 32 (13%) in group 4 (log-rank P = 0.001). At the multivariate Cox regression analysis, combined TA plus abciximab in group 4 [hazard ratio (HR): 0.48, confidence interval (CI) 95% 0.28-0.84, P = 0.01] and a higher left ventricular ejection fraction (HR: 0.97, CI 95% 0.95-0.98, P < 0.001) were significantly associated with lower MACE rate.

CONCLUSIONS

The combination of pharmacologic and mechanic antithrombotic treatment during pPCI was associated with better 1-year clinical outcome.

Basics of Antithrombotic Therapy for Cardiovascular Disease: Pharmacologic Targets of Platelet Inhibitors and Anticoagulants

Arterial thrombus formation is the common pathophysiologic process of cardiovascular disease manifestations, requiring interplay between platelets and coagulation factors. Current platelet inhibitors block the formation of thromboxane A₂ and interfer with adenosine diphosphate stimulation mediated by the P2Y₁₂ receptor. Novel antiplatelet agents blocking these and other pathways are under clinical development. Thrombin represents a bridge between platelets and coagulation. Indirect and direct thrombin inhibitors are pivotal in clinical settings. Other key coagulation factors include factors IX and X which are therapeutic targets of current and novel anticoagulants. This article reviews the pathophysiology of arterial thrombosis and current and novel antiplatelet and anticoagulant agents.

Monitoring and Reversal of Anticoagulation and Antiplatelets

Since percutaneous transluminal coronary angioplasty was first described and the breakthrough studies of the role of stents were reported, the evolution in anticoagulation and antiplatelet therapy used during percutaneous coronary intervention (PCI) has reduced periprocedural ischemic events and stent thrombosis. Although greater combinations and doses of anticoagulation with antiplatelets seem to provide the best protection against thrombogenic and embolic events, there is a significant trade-off with a higher risk of major and minor bleeding episodes. This review article expands on each of the commonly used antiplatelet and anticoagulants used at time of PCI, focusing on drug monitoring and reversal.

Role of Parenteral Agents in Percutaneous Coronary Intervention for Stable Patients

Numerous agents are available for anticoagulation during percutaneous coronary intervention (PCI), and various antiplatelet agents are also used. With all of the medications available, an assessment must be made regarding the ischemic risk and risk of bleeding for an individual patient during elective PCI when selecting the optimal medical strategy to support PCI. Whether new antiplatelet medications will enhance or reduce complications when paired with various newer anticoagulant agents requires further investigation. This article summarizes existing data examining the benefits and limitations of the various anticoagulant and antiplatelet medications, and summarizes guidelines for their use.

Update on platelet glycoprotein IIb/IIIa inhibitors: recommendations for clinical practice

Antiplatelet therapy is the cornerstone of treatment for patients with acute coronary syndrome (ACS) and undergoing percutaneous coronary intervention (PCI). Glycoprotein IIb/IIIa receptors mediate platelet aggregation, representing the final common pathway of platelet-mediated thrombosis. Therefore, agents blocking this pathway may be desirable for the treatment of patients with ACS and PCI. Glycoprotein IIb/IIIa receptor inhibitors have been widely investigated and have been key to the pharmacological advancements in the field. However, although GPIs have been important to reduce ischemic complications, their elevated risk of bleeding complications remains a major limitation. The poor prognostic implications, including increased mortality, associated with bleeding complication underscores the need for alternative treatment options. Over the past years there have been several advancements in antithrombotic pharmacology which have led to changes in recommendations for GPI usage in clinical practice. This is an overview of the most recent clinical trial data on GPIs, and provides practical insight on their modern day use in ACS therapy.

Antiplatelet medications and evolving antithrombotic medication

In treatment and prevention of thromboembolic events, the two major classes of anticoagulants are the antiplatelet agents and the antithrombotic agents. The antithrombotic agents have traditionally been heparin and warfarin, both of which were isolated in the 1930s, and have been used effectively since becoming commercially available in treatment and thromboprophylaxis of venous thromboembolic events (VTE). Though effective, they have a narrow therapeutic window and the antithrombotic response is variable, depending on the patient, and requires regular monitoring and adjustment to maintain the necessary therapeutic range. Recently developed novel anticoagulants in the prevention and treatment of VTE are now available and are increasingly encountered in day-to-day practice. A general understanding of these agents is essential in the planning of any interventional procedure in order to optimally balance the risk of hemorrhage, during or after a procedure, with the risk of periprocedural thrombosis.

Abciximab bolus with optional infusion in intervention for ST-elevation myocardial infarction

OBJECTIVES

The standard abciximab regimen is a bolus dose followed by a 12-h infusion. Whether the bolus dose alone is sufficient for ST-elevation myocardial infarction patients receiving a high loading dose of clopidogrel is unknown.

DESIGN

In an observational study, 693 consecutive patients were treated with abciximab during percutaneous coronary intervention for ST-elevation myocardial infarction. Totally 354 patients received standard strategy of abciximab bolus and infusion followed by 339 patients that recieved abciximab bolus only (271 patients) or bolus and infusion if suboptimal result (68 patients) in combination with a higher loading dose of clopidogrel (600 mg) - the modified strategy.

RESULTS

The two groups were similar regarding baseline characteristics and in hospital bleeding events. At 30 days, the composite of death, re-infarction or target vessel revascularization was 9.1% in the standard and 7.5% in the modified strategy (p = 0.45). The rate of stent thrombosis was lower in the modified strategy group with 0% and 2.3% in the standard group (p < 0.001) and the mean total medical cost was lower in the modified strategy group with €8032 and €8665 in the standard group (p < 0.001).

CONCLUSIONS

In primary percutaneous coronary intervention with a loading dose of 600 mg clopidogrel, it seems safe and cost-saving to give abciximab bolus with optional infusion.

Antiplatelet and anticoagulant strategies in acute coronary syndrome: where we are in 2013

Multiple antiplatelet and anticoagulant therapies are available for the treatment of acute coronary syndromes. The combination of agents should be tailored to the individual patient carefully considering the balance between ischemic and bleeding risk, as well as the planned revascularization strategy. Despite multiple large-scale, rigorously designed and conducted randomized controlled trials, it can be difficult to select the correct pharmacotherapy for each patient and many unanswered questions remain, such as the safety and optimal doses of differing combinations of antiplatelet/anticoagulant therapy, as well as the timing and duration of therapies. In addition, the headline results of many trials report improved efficacy outcomes at the cost of increased bleeding risk; however, very few show a clear mortality benefit. It is therefore difficult to weigh up the risk–benefit profile of emerging therapies.

Pharmacotherapy During Saphenous Vein Graft Intervention

Coronary revascularization using saphenous vein grafts is an important treatment modality for patients with severe coronary artery disease. Percutaneous intervention of these grafts is often the best option for patients who develop severe stenosis of the vein grafts. Use of adjunctive glycoprotein IIb/IIIa inhibitors does not confer added benefit with ischemic endpoints as compared with heparin alone, but it increases the risk of bleeding. Bivalirudin used as the primary anticoagulant lowers the risk of bleeding. No-reflow frequently complicates vein graft interventions but can be treated with vasoactive agents such as calcium channel blockers, adenosine, and nitroprusside.

Glycoprotein IIb/IIIa Receptor Antagonists and Risk of Bleeding: A Single-Center Experience in 1020 Patients

The safety of glycoprotein (GP) IIb/IIIa inhibitors has been well documented in clinical trials. Although these trials have included a broad patient population, the strict enrollment criteria may have resulted in exclusion of patients at a higher risk of bleeding complications. The authors conducted a retrospective chart review of 1020 consecutive patients who received GP IIb/IIIa inhibitors and underwent percutaneous coronary intervention in a large community hospital. They used Thrombolysis in Myocardial Infarction (TIMI) criteria to define major or minor bleeding complications. Bleeding complications developed in 214 (21%) patients, with major bleeding in 89 (9%). Univariate predictors of bleeding were older age, lower body weight, elevated serum creatinine, higher activated partial thromboplastin time (aPTT) level, history of diabetes mellitus (DM), peripheral vascular disease (PVD), congestive heart failure (CHF), and emergency procedure for acute myocardial infarction (AMI). Multivariate predictors of major bleeding were PVD (20% in bleeding group vs 11% in nonbleeders, odds ratio [OR] = 1.8, 95% confidence interval [CI] = 1.2-2.6, P < .004), age (68 +/- 2 years, 95% CI = 66-70 in bleeding group vs 63 +/- 13 years, 95% CI = 61.2-63 in nonbleeders, P < .001), and higher aPTT level (66 +/- 27 seconds, 95% CI = 63-70 in bleeding group vs 53 +/- 28 seconds, 95% CI = 51-56 in nonbleeders, P < .001). The risk of bleeding in the large community hospital setting may be higher than in randomized clinical trials. This increased risk is associated with higher hospitalization costs. Recognition of predictors of bleeding should further enhance the safety of these antiplatelet agents.

Antiplatelet agents for chronic kidney disease

BACKGROUND

Antiplatelet agents are widely used to prevent cardiovascular events. The risks and benefits of antiplatelet treatment may be different in people with chronic kidney disease (CKD) for whom occlusive atherosclerotic events are less prevalent, and bleeding hazards might be increased.

OBJECTIVES

To summarise the effects of antiplatelet treatment (antiplatelet agent versus control or other antiplatelet agent) for the prevention of cardiovascular and adverse kidney outcomes in individuals with CKD.

SEARCH METHODS

In January 2011 we searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and the Cochrane Renal Group's Specialised Register without language restriction.

SELECTION CRITERIA

We selected randomised controlled trials of any antiplatelet treatment versus placebo or no treatment, or direct head-to-head antiplatelet agent studies in people with CKD. Studies were included if they enrolled participants with CKD, or included people in broader at-risk populations in which data for subgroups with CKD could be disaggregated.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data from primary study reports and any available supplementary information for study population, interventions, outcomes, and risks of bias. Risk ratios (RR) and 95% confidence intervals (CI) were calculated from numbers of events and numbers of participants at risk which were extracted from each included study. The reported RRs were extracted where crude event rates were not provided. Data was pooled using the random-effects model.

MAIN RESULTS

We included 50 studies, enrolling 27,139 participants; 44 studies (21,460 participants) compared an antiplatelet agent with placebo or no treatment, and six studies (5679 participants) directly compared one antiplatelet agent with another. Compared to placebo or no treatment, antiplatelet agents reduced the risk of myocardial infarction (17 studies; RR 0.87, 95% CI 0.76 to 0.99), but not all-cause mortality (30 studies; RR 0.93, 95% CI 0.81 to 1.06), cardiovascular mortality (19 studies; RR 0.89, 95% CI 0.70 to 1.12) or stroke (11 studies; RR 1.00, 95% CI 0.58 to 1.72). Antiplatelet agents increased the risk of major (27 studies; RR 1.33, 95% CI 1.10 to 1.65) and minor bleeding (18 studies; RR 1.49, 95% CI 1.12 to 1.97). In terms of dialysis access outcomes, antiplatelet agents reduced access thrombosis or patency failure but had no effect on suitability for dialysis. Meta-regression analysis indicated no differences in the relative benefit or harms of treatment (risk of all-cause mortality, myocardial infarction, or major bleeding) by type of antiplatelet agent or stage of CKD. Limited data were available for direct head-to-head comparisons of antiplatelet drugs, treatment in kidney transplant recipients, primary prevention, or risk of ESKD.

AUTHORS' CONCLUSIONS

Antiplatelet agents reduce myocardial infarction but increase major bleeding. Risks may outweigh harms among people with low annual risks of cardiovascular events, including those with early stages of CKD who do not have clinically-evident occlusive cardiovascular disease.

Blood transfusion and the risk of acute kidney injury after transcatheter aortic valve implantation

BACKGROUND

Blood transfusion is associated with acute kidney injury (AKI) after transcatheter aortic valve implantation (TAVI). We sought to elucidate in more detail the relation between blood transfusion and AKI and its effects on short- and long-term mortality.

METHODS AND RESULTS

Nine hundred ninety-five patients with aortic stenosis underwent TAVI with the Medtronic CoreValve or the Edwards Valve in 7 centers. AKI was defined by the Valve Academic Research Consortium (absolute increase in serum creatinine ≥0.3 mg/dL [≥26.4 μmol/L] or ≥50% increase ≤72 hours). Logistic and Cox regression was used for predictor and survival analysis. AKI occurred in 20.7% (n=206). The number of units of blood transfusion ≤24 hours was the strongest predictor of AKI (≥5 units, OR, 4.81 [1.45-15.95], 3-4 units, OR, 3.05 [1.24-7.53], 1-2 units, OR, 1.47 [0.98-2.22]) followed by peripheral vascular disease (OR, 1.48 [1.05-2.10]), history of heart failure (OR, 1.43 [1.01-2.03]), leucocyte count ≤72 hours after TAVI (OR, 1.05 [1.02-1.09]) and European System for Cardiac Operative Risk Evaluation (EuroSCORE; OR, 1.02 [1.00-1.03]). Potential triggers of blood transfusion such as baseline anemia, bleeding-vascular complications, and perioperative blood loss were not identified as predictors. AKI and life-threatening bleeding were independent predictors of 30-day mortality (OR, 3.15 [1.56-6.38], OR, 6.65 [2.28-19.44], respectively), whereas transfusion (≥3 units), baseline anemia, and AKI predicted mortality beyond 30 days.

CONCLUSIONS

AKI occurred in 21% of the patients after TAVI. The number of blood transfusions but not the indication of transfusion predicted AKI. AKI was a predictor of both short- and long-term mortality, whereas blood transfusion predicted long-term mortality. These findings indicate that outcome of TAVI may be improved by more restrictive use of blood transfusions.

Stenting in Acute STEMI Intervention

Stenting in acute myocardial infarction (AMI) has the benefits of achieving acute optimal angiographic results and correcting residual dissection to decrease the incidence of restenosis and reocclusion. Studies have shown that percutaneous transluminal coronary angioplasty for primary treatment after AMI is superior to thrombolytic therapy regarding the restoration of normal coronary blood flow. Coronary stenting improves initial success rates, decreases the incidence of abrupt closure, and is associated with a reduced rate of restenosis. In the presence of thrombus-containing lesions, coronary stenting constitutes an effective therapeutic strategy, either after failure of initial angioplasty or electively as the primary procedure.

Review of Currently Available GP IIb/IIIa Inhibitors and Their Role in Peripheral Vascular Interventions

The glycoprotein IIb/IIIa (GP IIb/IIIa) antagonists are the most recent additions to the antiplatelet agents available to the interventional radiologist. The currently available GP IIb/IIIa antagonists are abciximab, eptifibatide, and tirofiban. These medications have demonstrated excellent safety and efficacy in the setting of coronary arterial interventions. The fundamental benefit of the GP IIb/IIIa antagonists lies in their unique mechanism of action: the ability to prevent platelet aggregation, thrombus formation, and distal thromboembolism while preserving initial platelet binding to damaged vascular surfaces. A paucity of data exists regarding the role of GP IIb/IIIa inhibitors in peripheral vascular interventions. The GP IIb/IIIa antagonists would theoretically provide excellent antiplatelet therapy in patients undergoing any of a variety of endovascular interventions during which thrombosis or thromboembolism may endanger distal perfusion in patients with peripheral vascular disease. The goal of this summary is to review the indications for use, pharmacology, and evidence for efficacy of the GP IIb/IIIa antagonists in hopes of translating these data for application in the peripheral arterial circulation. Further research is necessary to determine how these agents may be safely used in combination with other anticoagulants or with stents, efficacy compared with standard regimens, success at preventing distal thromboembolism, and cost effectiveness.

High Bolus Tirofiban vs Abciximab in Acute STEMI Patients Undergoing Primary PCI - The Tamip Study

BACKGROUND

Primary percutaneous coronary intervention (PCI) has been shown to be an effective therapy for patients with acute myocardial infarction (MI). Glycoprotein (GP) IIb/IIIa receptor blockers reduce thrombotic complications in patients undergoing PCI. Most available data relate to Reopro, which has been registered for this indication. GP IIb/IIIa reduce unfavorable outcome in U/A and non ST-elevation myocardial infarction (STEMI) patients. Only few studies focused on high dose Aggrastat for STEMI patients in the emergency department (ED) before PCI. The aim is to increase the patency during the time awaiting coronary angioplasty in patients with acute MI.

OBJECTIVES

To study the effect of upfront high bolus dose (HDR) of tirofiban on the extent of residual ST segment deviation 1 hour after primary PCI and the incidence of TIMI 3 flow of the infarct-related artery (IRA).

MATERIALS AND METHODS

A randomized, open label, single center study in the ED. A total of 90 patients with acute ST-elevation MI, diagnosed clinically by ECG criteria (ST segment elevation of >2 mm in two adjacent ECG leads), and with an expectation that a patient will undergo primary PCI. Patients were aged 21-85 years and all received heparin 5000 u, aspirin 160 mg, and Plavix 600 mg. Patients were divided in two groups (group I: triofiban high bolus vs group II: Reopro) with 45 patients in each group. In group I, high bolus triofiban 25 mcg/kg over 3 min was started in the ED with maintenance infusion of 0.15 mcg/ kg/min continued for 12 hours and transferred to cath lab for PCI. Patients in group II were transferred to cath lab, where a standard dose of Reopro was given with a bolus of 0.25 mcg/kg and maintenance infusion of 0.125 mcg/kg/min over 12 hours.

RESULTS

ST segment resolution and TIMI flow were evaluated in both groups before and after PCI. Thirty-five patients (78%) enrolled in group I and 29 patients (64%) in group II had resolution of ST segment (P-value 0.24). Twenty-one patients (47% group I) vs 23 patients (51% group II) with P-value 0.83 achieved TIMI 0 flow. Twenty-four patients (53% group I) compared with 22 patients (49% group II) with P-value 0.83 had TIMI 1 to 3 flow before PCI. TIMI 3 flow was achieved in 40 patients (89% group I) compared with 38 patients (84% group II) with P-value 0.76.

CONCLUSION

In this study there was a trend toward better ST segment resolution and patency of IRA (i.e., improved TIMI flow) in patients given high bolus dose Aggrastat in the ED. Larger studies are needed to confirm this finding.

Intravascular ultrasound findings that are predictive of no reflow after percutaneous coronary intervention for saphenous vein graft disease

The aim of this study was to investigate the relation between intravascular ultrasound (IVUS) findings and the no-reflow phenomenon and long-term outcome after percutaneous coronary intervention (PCI) of saphenous vein graft (SVG) lesions. No reflow was defined as Thrombolysis In Myocardial Infarction grade 0, 1, or 2 flow after PCI. Of 311 patients who underwent IVUS before and after stenting, no reflow was observed in 39 patients (13%). Degenerated SVG (62% vs 36%, p = 0.002), IVUS-detected intraluminal mass (82% vs 43%, p <0.001), culprit lesion multiple plaque ruptures (23% vs 6%, p <0.001), and tissue prolapse (51% vs 35%, p = 0.043) were observed more frequently in patients with no reflow. In multivariate logistic regression analysis, an intraluminal mass (odds ratio [OR] 4.84, 95% confidence interval [CI] 1.98 to 10.49, p = 0.001), culprit lesion multiple plaque ruptures (OR 3.46, 95% CI 1.46 to 8.41, p = 0.014), and degenerated SVGs (OR 3.17, 95% CI 1.17 to 6.56, p = 0.024) were the independent predictors of no reflow after PCI. At 5-year clinical follow-up, rates of death (14, 36%, vs 55, 20%, p = 0.036) and myocardial infarction (13, 33%, vs 52, 19%, p = 0.039) were significantly higher in the no-reflow group. However, rate of target vessel revascularization was not significantly different between the 2 groups (15, 38%, vs 90, 33%, p = 0.3). IVUS-detected intraluminal mass, multiple plaque ruptures, and degenerated SVGs were associated with no reflow in SVG lesions after PCI. In conclusion, no reflow was associated with poor long-term clinical outcomes after PCI for SVG lesions.

Frequency and causes of stroke during or after transcatheter aortic valve implantation

Transcatheter aortic valve implantation (TAVI) is invariably associated with the risk of clinically manifest transient or irreversible neurologic impairment. We sought to investigate the incidence and causes of clinically manifest stroke during TAVI. A total of 214 consecutive patients underwent TAVI with the Medtronic-CoreValve System from November 2005 to September 2011 at our institution. Stroke was defined according to the Valve Academic Research Consortium recommendations. Its cause was established by analyzing the point of onset of symptoms, correlating the symptoms with the computed tomography-detected defects in the brain, and analyzing the presence of potential coexisting causes of stroke, in addition to a multivariate analysis to determine the independent predictors. Stroke occurred in 19 patients (9%) and was major in 10 (5%), minor in 3 (1%), and transient (transient ischemic attack) in 6 (3%). The onset of symptoms was early (≤24 hours) in 8 patients (42%) and delayed (>24 hours) in 11 (58%). Brain computed tomography showed a cortical infarct in 8 patients (42%), a lacunar infarct in 5 (26%), hemorrhage in 1 (5%), and no abnormalities in 5 (26%). Independent determinants of stroke were new-onset atrial fibrillation after TAVI (odds ratio 4.4, 95% confidence interval 1.2 to 15.6), and baseline aortic regurgitation grade III or greater (odds ratio 3.2, 95% confidence interval 1.1 to 9.3). In conclusion, the incidence of stroke was 9%, of which >1/2 occurred >24 hours after the procedure. New-onset atrial fibrillation was associated with a 4.4-fold increased risk of stroke. In conclusion, these findings indicate that improvements in postoperative care after TAVI are equally, if not more, important for the reduction of periprocedural stroke than preventive measures during the procedure.

Antiplatelet drugs: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

The article describes the mechanisms of action, pharmacokinetics, and pharmacodynamics of aspirin, dipyridamole, cilostazol, the thienopyridines, and the glycoprotein IIb/IIIa antagonists. The relationships among dose, efficacy, and safety are discussed along with a mechanistic overview of results of randomized clinical trials. The article does not provide specific management recommendations but highlights important practical aspects of antiplatelet therapy, including optimal dosing, the variable balance between benefits and risks when antiplatelet therapies are used alone or in combination with other antiplatelet drugs in different clinical settings, and the implications of persistently high platelet reactivity despite such treatment.

Management of bleeding complications in the anticoagulated patient

As new anticoagulants become available, and the number of anticoagulated patients continues to rise, it is necessary to know how to deal with associated bleeding complications. In this review, reversal strategies for traditional anticoagulants (warfarin and heparin) as well as newer anticoagulants are described. Prothrombin complex concentrates (PPCs) can be used to reverse vitamin K antagonists (VKA), and plasma may be used where they are not available. Recombinant activated factor VII (rFVIIa) may be useful to reverse pentasaccharide anticoagulants. 1-Desamino-8-D-arginine vasopressin (DDAVP), cryoprecipitate, PCCs, and dialysis may help to reverse direct thrombin inhibitors, while rFVIIa seems to be ineffective. The effect of direct factor Xa inhibitors may be reversed by PCCs, FVIIa, or factor Xa concentrates.

Meta-analysis of prospective randomized controlled trials comparing intracoronary versus intravenous abciximab in patients with ST-elevation myocardial infarction undergoing primary percutaneous coronary intervention

Abciximab is a glycoprotein IIb/IIIa receptor inhibitor that has been shown to improve outcomes in patients with ST-segment elevation myocardial infarction who undergo primary percutaneous coronary intervention (pPCI). An earlier study reported better efficacy with intracoronary (IC) compared to intravenous (IV) administration, but this finding has not been duplicated in other studies, thus leaving a great deal of uncertainty as to the most efficacious route of administration. To investigate if IC abciximab compared to IV administration decreases mortality and major adverse cardiac events in patients with ST-segment elevation myocardial infarction who undergo pPCI, a meta-analysis was performed consisting only of prospective randomized controlled trials. Subgroup analysis was performed to investigate the source of difference in efficacy between the 2 strategies. A meta-analysis of 4 trials including 1,148 subjects revealed that IC abciximab significantly reduced mortality compared to IV administration (1.5% vs 3.6%, odds ratio 0.44, 95% confidence interval 0.20 to 0.95, p = 0.04). Major adverse cardiac events were also reduced in a subgroup in which <30% of patients received aspiration thrombectomy (6.1% vs 16.2%, odds ratio 0.33, 95% confidence interval 0.18 to 0.61, p = 0.0004). In conclusion, the totality of the data available from relatively small but high-quality studies shows a significant mortality reduction associated using IC abciximab for pPCI compared to IV abciximab. IC abciximab in the setting of pPCI for ST-segment elevation myocardial infarction may be beneficial for patients with higher risk profiles.

Treatment with tirofiban for acute coronary syndrome (ACS): a systematic review and network analysis

OBJECTIVE

To assess the efficacy of tirofiban in comparison to usual care or other GPIIb/IIIa antagonists (eptifibatide and abciximab). Results were analysed by drug administration with planned percutaneous coronary intervention (PCI) or as medical management without planned PCI, and separately for STEMI or NSTE ACS patients.

RESEARCH DESIGN AND METHODS

A systematic review was performed of randomized controlled trials of tirofiban, abciximab, eptifibatide or usual care given to patients with acute coronary syndrome. Nine databases were searched up to March 2010. Pair-wise meta-analysis was used to combine all available direct comparisons; indirect comparisons and network analysis were performed when this was not possible. The primary outcome was MACE (major adverse cardiac event).

RESULTS

The search yielded 8, 119 records and 50 trials were included (total number of patients = 52,958). Compared to usual care, high and medium-dose tirofiban (25 and 10 µg/kg/min) administered with planned PCI reduced MACE at 30 days for patients with STEMI (RR 0.67, 95% CI 0.45, 0.99; RR 0.28, 95% CI 0.10, 0.80), but was not effective as a medical management. Medium-dose tirofiban (10 µg/kg/min) administered with planned PCI or low dose (0.4 µg/kg/min) as medical management reduced the risk of MACE for patients with NSTE ACS (RR 0.39, 95% CI 0.21, 0.75; RR 0.58, 95% CI 0.41, 0.83) in comparison to usual care, but at the expense of increased thrombocytopenia (RR 3.26, 95% CI 1.31, 8.13). Evidence from RCTs and network analysis indicated tirofiban and abciximab were equally effective and safe. Comparing tirofiban and eptifibatide treatment by indirect and network analysis produced inconclusive results.

CONCLUSIONS

Tirofiban was more effective than usual care for STEMI and NSTE ACS patients receiving planned PCI, and NSTE ACS patients receiving medical management. Tirofiban and abciximab were equally effective. Comparisons of tirofiban and eptifibatide were inconclusive.

Parenteral anticoagulants: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

This article describes the pharmacology of approved parenteral anticoagulants. These include the indirect anticoagulants, unfractionated heparin (UFH), low-molecular-weight heparins (LMWHs), fondaparinux, and danaparoid, as well as the direct thrombin inhibitors hirudin, bivalirudin, and argatroban. UFH is a heterogeneous mixture of glycosaminoglycans that bind to antithrombin via a unique pentasaccharide sequence and catalyze the inactivation of thrombin, factor Xa, and other clotting enzymes. Heparin also binds to cells and plasma proteins other than antithrombin causing unpredictable pharmacokinetic and pharmacodynamic properties and triggering nonhemorrhagic side effects, such as heparin-induced thrombocytopenia (HIT) and osteoporosis. LMWHs have greater inhibitory activity against factor Xa than thrombin and exhibit less binding to cells and plasma proteins than heparin. Consequently, LMWH preparations have more predictable pharmacokinetic and pharmacodynamic properties, have a longer half-life than heparin, and are associated with a lower risk of nonhemorrhagic side effects. LMWHs can be administered once daily or bid by subcutaneous injection, without coagulation monitoring. Based on their greater convenience, LMWHs have replaced UFH for many clinical indications. Fondaparinux, a synthetic pentasaccharide, catalyzes the inhibition of factor Xa, but not thrombin, in an antithrombin-dependent fashion. Fondaparinux binds only to antithrombin. Therefore, fondaparinux-associated HIT or osteoporosis is unlikely to occur. Fondaparinux exhibits complete bioavailability when administered subcutaneously, has a longer half-life than LMWHs, and is given once daily by subcutaneous injection in fixed doses, without coagulation monitoring. Three additional parenteral direct thrombin inhibitors and danaparoid are approved as alternatives to heparin in patients with HIT.

Anti-platelet therapy: glycoprotein IIb-IIIa antagonists

Glycoprotein (GP) IIb-IIIa antagonists inhibit the aggregation of activated platelets. Three agents are approved for clinical use. In this review, the characteristics of each agent, their pharmacodynamic profile, results in pivotal clinical trials and the associated clinical implications are discussed. GP IIb-IIIa antagonists have greatest benefit when used as adjunctive therapy during percutaneous coronary intervention (PCI) when the patient has intra-coronary thrombosis. These agents appear to provide greatest benefit when used in combination with heparin. The clinical niche for parenteral GP IIb-IIIa antagonists is evolving. The rapid onset and offset of GP IIb-IIIa antagonists plus dosing designed to inhibit extensively platelet aggregation differentiates them from oral agents. The contemporary niche appears to include patients in transition, such as individuals requiring emergent PCI before oral agents are fully active and for unstable patients requiring transport to PCI centres, particularly in patients likely to have intracoronary thrombus. Subsequent studies should evaluate the optimal duration of therapy with GP IIb-IIIa antagonists.

Contemporary use of glycoprotein IIb/IIIa inhibitors

Platelet glycoprotein IIb/IIIa inhibitors (GPI) are antithrombotic agents preventing the binding of fibrinogen to GP IIb/IIIa receptors. Thus, GPI interfere with interplatelet bridging mediated by fibrinogen. Currently, three generic GPI with different antithrombotic properties are available for intravenous administration: abciximab, eptifibatide, and tirofiban. The development of oral GPI was abandoned, whereas intravenous GPI were introduced in various clinical settings during the 1990s, yielding substantial benefit in the treatment of acute coronary syndromes, particularly during percutaneous coronary interventions. Results of the many randomised trials evidenced the efficacy of this drug class, though these trials were conducted prior to the emergence of modern oral antiplatelet therapy with efficient P2Y(12) inhibitors. Subsequent trials failed to consolidate the strongly favourable impression of GPI, and indications for their use have been more restricted in recent years. Nonetheless, GPI may still be beneficial during coronary interventions among high-risk patients including acute ST-elevation and non-ST-elevation myocardial infarctions, particularly in the absence of adequate pretreatment with oral antiplatelet drugs or when direct thrombin inhibitors are not utilised. Intracoronary GPI administration has been suggested as adjunctive therapy during primary percutaneous coronary intervention, and the results of larger ongoing trials are expected to elucidate its clinical potential. The present review outlines the key milestones of GPI development and provides an up-to-date overview of the clinical applicability of these drugs in the era of refined coronary stenting, potent antithrombotic drugs, and novel thrombin inhibiting agents.

Optimal use of platelet glycoprotein IIb/IIIa receptor antagonists in patients undergoing percutaneous coronary interventions

Discovery of the central role of platelets in the pathogenesis of acute coronary syndromes (ACS) and ischaemic complications of percutaneous coronary interventions (PCI) has led to the widespread use of oral and parenteral platelet inhibitors to treat these conditions. Glycoprotein (GP) IIb/IIIa (also known as α(IIb)β(3)) receptors on the surface of platelets play an essential role in platelet aggregation and serve as a key mediator in the formation of arterial thrombus. When activated, GP IIb/IIIa receptors bind to fibrinogen, which serves as the 'final common pathway' in platelet aggregation. Of the numerous agents developed for modulating platelet activity, intravenous platelet GP IIb/IIIa receptor antagonists are the most potent. There are four agents in clinical use, including abciximab, eptifibatide, tirofiban and lamifiban, although lamifiban is not approved for use in the US. While all agents block fibrinogen binding to GP IIb/IIIa, they do so by different mechanisms. Abciximab is a humanized form of a murine monoclonal antibody directed against GP IIb/IIIa, eptifibatide is a synthetic, cyclic heptapeptide that contains a lysine-glycine-aspartic acid (KGD) sequence that mimics the arginine-glycine-aspartic acid (RGD) sequence found on GP IIb/IIIa, tirofiban is a non-peptide antagonist derived by optimization of the tyrosine analogue that structurally mimicks the RGD-containing loop of the disintegrin echistatin, and lamifiban is a synthetic, non-cyclic, non-peptide, low-molecular-weight compound. In clinical trials, use of these agents reduces ischaemic adverse cardiovascular events in patients with ACS undergoing PCI, but at a cost of increased bleeding.

Tirofiban versus abciximab: tirofiban is administered at suboptimal dosages when evaluated in an arterial thrombosis model in non-human primates

To prevent thrombosis in high-risk acute coronary syndrome patients undergoing percutaneous coronary intervention for re-vascularisation, concomitant administration of a glycoprotein IIb/IIIa inhibitor, such as abciximab, tirofiban or eptifibatide, is recommended. Abciximab and eptifibatide are mostly preferred over tirofiban, which is less effective in preventing ischaemic events. We compared the efficacy and bleeding potential of escalating doses of tirofiban and abciximab in non-human primates. The efficacy of tirofiban and abciximab in inhibiting cyclic flow reductions (CFRs) was tested in a high shear arterial thrombosis model. Bleeding was evaluated with the template bleeding time and an incision bleeding model. Abciximab completely inhibited arterial thrombosis after injection of its therapeutic bolus dose. With tirofiban, a dose three times higher than the recommended therapeutic dose caused weak inhibition characterised by a return of CFRs after re-injury. At nine times the recommended therapeutic dose, complete inhibition was observed, and the efficacy of tirofiban was comparable to abciximab at its therapeutic bolus dose. Blood loss was less than with abciximab at its effective dose. In this model, tirofiban compared favourably with abciximab, although only at a dose of 3-9 times the therapeutic dose, and caused less bleeding than abciximab.

Improved clinical outcome after invasive management of patients with recent myocardial infarction and proven myocardial viability: primary results of a randomized controlled trial (VIAMI-trial)

Background

Patients with ST-elevation myocardial infarction (STEMI) not treated with primary or rescue percutaneous coronary intervention (PCI) are at risk for recurrent ischemia, especially when viability in the infarct-area is present. Therefore, an invasive strategy with PCI of the infarct-related coronary artery in patients with viability would reduce the occurrence of a composite end point of death, reinfarction, or unstable angina (UA).

Methods

Patients admitted with an (sub)acute myocardial infarction, who were not treated by primary or rescue PCI, and who were stable during the first 48 hours after the acute event, were screened for the study. Eventually, we randomly assigned 216 patients with viability (demonstrated with low-dose dobutamine echocardiography) to an invasive or a conservative strategy. In the invasive strategy stenting of the infarct-related coronary artery was intended with abciximab as adjunct treatment. Seventy-five (75) patients without viability served as registry group. The primary endpoint was the composite of death from any cause, recurrent myocardial infarction (MI) and unstable angina at one year. As secondary endpoint the need for (repeat) revascularization procedures and anginal status were recorded.

Results

The primary combined endpoint of death, recurrent MI and unstable angina was 7.5% (8/106) in the invasive group and 17.3% (19/110) in the conservative group (Hazard ratio 0.42; 95% confidence interval [CI] 0.18-0.96; p = 0.032). During follow up revascularization-procedures were performed in 6.6% (7/106) in the invasive group and 31.8% (35/110) in the conservative group (Hazard ratio 0.18; 95% CI 0.13-0.43; p < 0.0001). A low rate of recurrent ischemia was found in the non-viable group (5.4%) in comparison to the viable-conservative group (14.5%). (Hazard-ratio 0.35; 95% CI 0.17-1.00; p = 0.051).

Conclusion

We demonstrated that after acute MI (treated with thrombolysis or without reperfusion therapy) patients with viability in the infarct-area benefit from a strategy of early in-hospital stenting of the infarct-related coronary artery. This treatment results in a long-term uneventful clinical course. The study confirmed the low risk of recurrent ischemia in patients without viability.

Trial registration

ClinicalTrials.gov: NCT00149591.

Glycoprotein IIb/IIIa antagonists

Mortality from ischemic cardiac disease in adults has been dramatically reduced by the development of novel therapies for inhibiting platelet function. Circulating platelets are maintained in a resting state and are activated at sites of vascular injury by exquisitely controlled mechanisms, thereby maintaining vascular integrity without causing intravascular thrombosis. As it became clear that platelets play a central role in arterial thrombosis, the processes of platelet activation, adhesion, and aggregation became logical targets for the development of antithrombotic agents.

Safety of immediate reversal of anticoagulation by protamine to reduce bleeding complications after infarct artery stenting for acute myocardial infarction and adjunctive abciximab therapy

Infarct artery stenting with adjunctive abciximab therapy is widely used treatment for patients with acute myocardial infarction (AMI). However, bleeding complications have been associated with a worse clinical outcome. Randomized trials in elective patients have shown that postprocedural protamine administration is safe and associated with a significant reduction in bleeding complications. The aim of the current study was to evaluate in STEMI patients undergoing primary percutaneous coronary intervention (PCI) with abciximab and stenting whether immediate reversal of anticoagulation by protamine is safe and associated with a reduction in the occurrence of bleeding complications. From January 2004 to June 2005, 254 patients with STEMI had immediate reversal of anticoagulation by protamine administration after infarct artery stenting and received abciximab therapy without heparin infusion (Group 1). These patients were compared with a control group of 265 patients (June 2002-December 2003) treated with the standard heparin therapy: bolus in order to achieve an activated coagulation time of 250-300 s during PCI plus 12-h infusion (7 UI/kg/h; Group 2). We excluded patients undergoing IABP implantation. The two groups were similar in all baseline characteristics. There were no differences in in-hospital mortality, reinfarction, urgent target vessel revascularization, stroke or acute or subacute stent thrombosis, while Group 1 patients showed a lower incidence of major bleeding complications (ACUITY scale: 1.1 vs. 4.0%, P = 0.035) and a shorter length of hospital stay (3.5 ± 1.7 vs. 4.0 ± 1.6 days, P = 0.002) as compared with heparin treated patients. Among patients undergoing primary stenting with abciximab administration, immediate post-PCI reversal anticoagulation by protamine without associated heparin infusion is safe and associated with a significant reduction in major bleeding complications.