Effect of abciximab on myocardial salvage in patients with acute myocardial infarction undergoing primary angioplasty

What do we know about platelets in myocardial ischemia-reperfusion injury and why is it important?

Myocardial ischemia-reperfusion injury (MIRI), the joint result of ischemic injury and reperfusion injury, is associated with poor outcomes in patients with acute myocardial infarction undergoing primary percutaneous coronary intervention. Accumulating evidence demonstrates that activated platelets directly contribute to the pathogenesis of MIRI through participating in the formation of microthrombi, interaction with leukocytes, secretion of active substances, constriction of microvasculature, and activation of spinal afferent nerves. The molecular mechanisms underlying the above detrimental effects of activated platelets include the homotypic and heterotypic interactions through surface receptors, transduction of intracellular signals, and secretion of active substances. Revealing the roles of platelet activation in MIRI and the associated mechanisms would provide potential targets/strategies for the clinical evaluation and treatment of MIRI. Further studies are needed to characterize the temporal (ischemia phase vs. reperfusion phase) and spatial (systemic vs. local) distributions of platelet activation in MIRI by multi-omics strategies. To improve the likelihood of translating novel cardioprotective interventions into clinical practice, basic researches maximally replicating the complexity of clinical scenarios would be necessary.

Glycoprotein IIb/IIIa inhibitors with or without thienopyridine pretreatment improve outcomes after primary percutaneous coronary intervention in high-risk patients with ST elevation myocardial infarction--a meta-regression of randomized controlled trials

BACKGROUND

Recent studies have casted a doubt on usefulness of routine glycoprotein IIb/IIIA inhibitors (GPI) in patients, pretreated with aspirin and clopidogrel, undergoing primary percutaneous coronary intervention (PCI) for ST elevation myocardial infarction (STEMI).

OBJECTIVE

We aimed to investigate the effect of relevant factors, particularly thienopyridine pretreatment, on clinical benefit from GPI in randomized controlled trials (RCT).

METHODS

We searched electronic databases for RCT comparing GPI to control in patients with STEMI undergoing primary PCI. Relevant study covariates and clinical outcomes were extracted. A random effect cumulative and subgroup analyses (thienopyridine non-pretreated studies vs. pretreated studies) were performed. A weighted random effect meta-regression to determine the effect of thienopyridine pretreatment, enrollment year, control group mortality, and ischemic time on mortality benefit from GPI use was conducted.

RESULTS

Twenty studies (9 non-pretreated, 11 pretreated) with a total of 7,414 patients (3,811 GPI, 3,603 control) were included. GPI use reduces mortality (risk ratio, RR = 0.75 95% confidence interval (CI) 0.57-0.97, P = 0.03), target vessel revascularization (TVR) (RR = 0.63, 95% CI 0.50-0.80, P = 0.0002), but not reinfarction (RR = 0.66, 95% CI 0.44-1.0, P = 0.05) at 30 days. There was no effect of thienopyridine pretreatment on reduction in mortality (P = 0.39), reinfarction (P = 0.46), or TVR (P = 0.95) in subgroup analysis. Meta-regression analyses showed significant effect of control group mortality risk (B = -12.15, P = 0.034) but not of thienopyridine pretreatment, enrollment year or control group ischemic time on mortality reduction from GPI use.

CONCLUSION

The benefit from GPI use in primary PCI for STEMI appears to depend on mortality risk, and not on thienopyridine pretreatment.

Glycoprotein IIb-IIIa inhibitors

Platelets play a pivotal role in the pathogenesis of coronary artery disease and myocardial infarction. Therefore, great interests have been focused in the last decades on improvement in antiplatelet therapies, that currently are regarded as main pillars in the prevention and treatment of coronary artery disease, with special attention to glycoprotein IIb-IIIa (GP IIb-IIIa) receptors, that mediates the final stage of platelet activation. GP IIb-IIIa inhibitors, especially abciximab, have been shown to improve clinical outcome in patients undergoing primary angioplasty for STEMI. Upstream administration cannot routinely recommended, but may potentially be considered among high-risk patients within the first 4 h from symptoms onset. In case of periprocedural administration of antithrombotic therapy, Bivalirudin should be considered, especially in patients at high risk for bleeding complications. Among high-risk patients with acute coronary syndromes, an early invasive strategy with selective downstream administration of GP IIb-IIIa inhibitors is the strategy of choice, whereas bivalirudin should be considered in patients at high risk for bleeding complications. Among patients with unstable angina GP IIb-IIIa inhibitors should be considered only in case of evidence of intracoronary thrombus or in case of thrombotic complications (as provisional use). Further, randomized trials are certainly needed in the era of new oral antiplatelet therapies, and with strategies to prevent bleeding complications such as larger use of radial approach, mechanical closure devices, bivalirudin, or postprocedural protamine administration to promote early sheat removal.

Comparison of myocardial contrast echocardiography versus rest sestamibi myocardial perfusion imaging in the early diagnosis of acute coronary syndrome

BACKGROUND

It remains unclear whether myocardial contrast echocardiography (MCE) is as accurate as myocardial perfusion imaging with technetium-99m sestamibi (MPI) for the diagnosis of acute coronary syndrome (ACS). We sought to directly compare the diagnostic accuracy of MCE with resting MPI in a head-to-head fashion.

METHODS

We prospectively enrolled 98 consecutive patients (mean age; 59+/-9 years, 68 males) who presented to the emergency department with chest pain suggestive of acute myocardial ischemia. Early MCE was performed by using continuous infusion of perfluorocarbon-exposed sonicated dextrose albumin (PESDA) during intermittent power Doppler harmonic imaging. Myocardial perfusion defects observed in at least one coronary territory were considered positive. Sestamibi was injected immediately after MCE and MPI was obtained within 6 hours of tracer injection.

RESULTS

ACS was confirmed in 67 patients. There were 32 patients with acute myocardial infarction (AMI) and 35 patients with unstable angina requiring urgent revascularization. The sensitivities of MCE and MPI for the diagnosis of ACS were 72% and 61%, respectively, which were significantly higher than those of ST segment change (24%, p<0.001 vs. MCE and vs. MPI) and troponin I (27%, p<0.001 vs. MCE and vs. MPI), with similar specificities of 90% to 100%. On a receiveroperating characteristics curve demonstrating diagnostic accuracy for ACS, the area under the curve of MCE was significantly larger than that of MPI (0.86 vs. 0.77, respectively; p=0.019).

CONCLUSION

MCE and MPI overcome the low sensitivity of routine triage tests for detecting ACS, and MCE is more accurate than MPI for the diagnosis of ACS in the emergency department.

Risk profile and benefits from Gp IIb-IIIa inhibitors among patients with ST-segment elevation myocardial infarction treated with primary angioplasty: a meta-regression analysis of randomized trials

Aims

Several randomized trials and a previous meta-analysis have shown significant benefits from Gp IIb-IIIa inhibitors, especially abciximab. Recent randomized trials (BRAVE-3 and HORIZON trials) have shown no benefits from adjunctive Gp IIb-IIIa inhibitors on the top of clopidogrel administration. However, the relatively low mortality may have hampered the conclusion of these recent trials. Thus, the aim of the current study was to perform an update meta-analysis of randomized trials on adjunctive Gp IIb-IIIa inhibitors in primary angioplasty, and to evaluate by meta-regression analysis, whether the results may be related to risk profile.

Methods and results

We obtained results from all randomized trials evaluating the benefits of adjunctive Gp IIb-IIIa inhibitors among STEMI patients undergoing primary angioplasty. The literature was scanned by formal searches of electronic databases (MEDLINE and CENTRAL) from January 1990 to September 2008. The following key words were used: randomized trial, myocardial infarction, reperfusion, primary angioplasty, Gp IIb-IIIa inhibitors, abciximab, tirofiban, and eptifibatide. Clinical endpoint was mortality at 30 days. Major bleeding complications were assessed as safety endpoint. No language restriction was applied. A total of 16 randomized trials were finally included in the meta-analysis, involving 10 085 patients (5094 or 50.5% in the Gp IIb-IIIa inhibitors group and 4991 or 49.5% in the control group. Gp IIb-IIIa inhibitors did not reduce 30 day mortality (2.8 vs. 2.9%, P = 0.75) or re-infarction (1.5 vs. 1.9%, P = 0.22), but were associated with higher risk of major bleeding complications (4.1 vs. 2.7%, P = 0.0004). However, we observed a significant relationship between patient's risk profile and benefits from adjunctive Gp IIb-IIIa inhibitors in terms of death (P = 0.008) but not re-infarction (P = 0.25).

Conclusion

This meta-analysis shows a significant relationship between benefits in mortality from Gp IIb-IIIa inhibitors and patient's risk profile. Thus, Gp IIb-IIIa inhibitors should be strongly considered among high-risk patients.

Impact of early tirofiban administration on myocardial salvage in patients with acute myocardial infarction undergoing infarct-related artery stenting

BACKGROUND/AIMS

The timing of GpIIb/IIIa inhibitor administration may be important in achieving early epicardial and myocardial reperfusion. We evaluated the effect of early tirofiban on myocardial salvage and cardiovascular outcome in patients with acute myocardial infarction (AMI) undergoing infarct-related artery stenting.

METHODS

Patients (n = 66) with a first AMI presenting <6 h from onset of symptoms were randomized to either early administration of tirofiban in the emergency room (n = 32) or later administration in the catheterization laboratory (n = 34) (tirofiban bolus dose of 10 microg/kg, followed by 0.15 microg/kg for 24 h). The primary end-point was the degree of myocardial salvage, determined by means of serial scintigraphic studies with technetium-99m sestamibi. Thirty-day major adverse cardiac events were also assessed.

RESULTS

There were no significant differences in patient characteristics or in their presentation. The mean door-to-balloon time was similar in both groups (43 +/- 12 and 53 +/- 9 min, p = 0.08). The early and late treatment groups received tirofiban 18 +/- 4 and 52 +/- 10 min after admission, respectively. Angiographic analysis revealed a higher initial frequency of TIMI grade 3 flow in the early group (31% vs. 12%, p = 0.04). Procedural success was achieved in all patients. Myocardial risk area were comparable between early and late treatment groups (35.6 +/- 12.2% vs. 39.3 +/- 14.0%, p = 0.6). Scintigraphic outcomes demonstrated a significant reduction in the final infarction size (11.8 +/- 5.2% vs. 22.4 +/- 6.2%, p = 0.01), and improvement in salvage index (0.68 +/- 0.22 vs. 0.44 +/- 0.18, p = 0.003) in favor of the early tirofiban group. The thirty-day composite end-point of death, recurrent MI or rehospitalization also favored the early group (6% early, 15% late, p = 0.06).

CONCLUSION

Early tirofiban administration enhanced the degree of myocardial salvage and clinical outcome in patients with AMI undergoing infarct-related artery stenting.

Beneficial effects of abciximab in patients with primary percutaneous intervention for acute ST segment elevation myocardial infarction in clinical practice

OBJECTIVES

To assess the safety and effectiveness of abciximab in patients with ST elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI) in clinical practice.

METHODS

Data were analysed of 2184 consecutive patients treated with primary PCI for acute STEMI and either concomitant abciximab or no glycoprotein IIb/IIIa inhibitor (control group), who were prospectively enrolled in the Acute Coronary Syndromes (ACOS) registry between July 2000 and November 2002.

RESULTS

Patients who were treated with abciximab were younger than the control group, and fewer of them had a history of stroke/transient ischaemic attack and systemic hypertension, but more of them had three-vessel coronary artery disease and cardiogenic shock. Cumulated mid-term survival for patients treated with abciximab was significantly higher than in the control group (91% v 79%, log rank p < 0.05, median observational time 375 days, range 12-34 months). The Cox proportional hazards model of mid-term mortality after admission with adjustment for baseline characteristics showed that mortality was significantly lower in the abciximab group than in the control group (hazard ratio 0.68, 95% confidence interval 0.49 to 0.95). Whereas overall there was no difference in bleeding complications, patients older than 75 years had more major bleeding events with abciximab (12.5% v 3.4%, p = 0.03).

CONCLUSION

In clinical practice adjunctive treatment with abciximab in patients with primary PCI for acute STEMI was associated with a reduction in mid-term mortality. The subgroup of patients older than 75 years who were treated with abciximab had more major bleeding complications.