What is the role for improved long-term antiplatelet therapy after percutaneous coronary intervention?

The dogma of aspirin: a critical review of evidence on the best monotherapy after dual antiplatelet therapy

Dual antiplatelet therapy based on the combination of an adenosine diphosphate (ADP)-receptor antagonist plus aspirin has demonstrated to be more effective in reducing the rate of major ischemic vascular events compared to aspirin monotherapy in some clinical settings. The current controversy on the duration of dual antiplatelet therapy should not conceal another major issue: the choice of the more appropriate antiplatelet monotherapy after the dual treatment phase. The aim of this article is to critically analyze the available evidence in this topic.

Data from studies like CAPRIE, MATCH, PROFESS, CHANCE, DAPT and others, raise questions as why antiplatelet monotherapy after the dual phase should only be based on aspirin, in spite of a lack of evidence surprisingly not highlighted by key opinion leaders and experts.

We conclude that, whether ADP-receptor antagonist rather than aspirin may be proposed as monotherapy seems not only have no answer but also not place in the current specialists’ analysis, as if a dogmatic approach were prevalent. Perhaps the time for an open debate on these topics is ripe.

Is there an alternative to systemic anticoagulation, as related to interventional biomedical devices?

To reduce the toxic effects, related clinical problems and complications such as bleeding disorders associated with systemic anticoagulation, it has been hypothesized that by coating the surfaces of medical devices, such as stents, bypass grafts, extracorporeal circuits, guide wires and catheters, there will be a significant reduction in the requirement for systemic anticoagulation or, ideally, it will no longer be necessary. However, current coating processes, even covalent ones, still result in leaching followed by reduced functionality. Alternative anticoagulants and related antiplatelet agents have been used for improvement in terms of reduced restenosis, intimal hyperphasia and device failure. This review focuses on existing heparinization processes, their application in clinical devices and the updated list of alternatives to heparinization in order to obtain a broad overview, it then highlights, in particular, the future possibilities of using heparin and related moieties to tissue engineer scaffolds.

Drug-eluting stents: from evidence to policy

Drug-eluting stents are a major breakthrough in cardiology, with the Cypher (Cordis Corporation) and Taxus (Boston Scientific) stents preventing 60-70% of repeat coronary revascularizations, compared with bare metal stents. Both evidence- and risk-based application of drug-eluting stents is expected to create relevant financial and equity problems to most public hospitals, as the cost of drug-eluting stents is over 1000 higher than traditional stents. In the perspective of third-party payers, drug-eluting stents are cost-effective revascularization strategies for a large portion of patients actually undergoing stenting. However, adequate guidelines and reimbursement strategies are still awaited in several countries.

Effects of Preoperative Abciximab and Eptifibatide on Bleeding Indices in Coronary Artery Bypass Graft Patients

Background:

Glycoprotein (GP) IIb/IIIa antagonists are used routinely for the treatment of acute coronary syndrome and to prevent thromboses during percutaneous coronary interventions. It is not uncommon for patients who initially require a GP IIb/IIIa inhibitor to eventually receive a surgical intervention.

Objective:

To compare the difference in bleeding indices in patients who undergo coronary artery bypass grafting (CABG) after receiving either eptifibatide or abciximab.

Methods:

A retrospective chart review was completed on all adults who received abciximab or eptifibatide within 24 hours prior to undergoing CABG. Patients were excluded if they had received a dose of warfarin within 96 hours prior to the procedure or if they had an incomplete medical record, an off-pump procedure, a known hypercoagulable disorder, or hemophilia. A total of 54 patients were included and preoperative data, including doses of anticoagulant and antiplatelet agents, were recorded. Intraoperative and postoperative data collected for analysis included hemoglobin level, chest tube output, and the amount of blood products transfused for 24 hours postprocedure.

Results:

There was a statistically significant difference between the eptifibatide and abciximab groups in the amount of fresh frozen plasma (mean ± SD, 21 ± 31 vs 187 ± 125 mL, respectively; p < 0.05) and platelets (212 ± 81 vs 433 ± 118 mL, respectively; p < 0.01) transfused during the intraoperative period. However, when the total amount of blood products transfused intraoperatively (769 ± 243 vs 1395 ± 316 mL, respectively; p = 0.47) was evaluated, no significant difference was detected. Likewise, markers for bleeding that were collected during the 24-hour postoperative window (immediate and 24-h postoperative hemoglobin and total 24-h chest tube output) were not significantly different.

Conclusions:

Although there is an increased risk of bleeding when abciximab or eptifibatide is administered prior to CABG, no significant difference in the total amount of blood products used was detected between the 2 agents in this study.

Clopidogrel nonresponsiveness in patients undergoing percutaneous coronary intervention with stenting: a systematic review and meta-analysis

BACKGROUND

Despite clopidogrel therapy, patients undergoing percutaneous coronary intervention (PCI) with stenting are at risk of recurrent coronary events. This could be partly explained by a reduced efficacy of clopidogrel to inhibit platelet aggregation, an ex vivo defined phenomenon called clopidogrel nonresponsiveness or resistance. However, both prevalence and associated cardiovascular risks remain unclear. We systematically reviewed evidence on prevalence and clinical consequences of laboratory clopidogrel nonresponsiveness in patients undergoing PCI.

METHODS

Using predefined strategies, we searched electronic databases. To be included, articles should report on PCI patients treated with clopidogrel, contain a clear description of the method used to establish the effects of clopidogrel, and report the prevalence of clopidogrel nonresponsiveness or incidence of cardiovascular events. We analyzed prevalences with a linear mixed model that accounts for study covariates and we pooled odds ratios of clinical consequences with a random-effects model.

RESULTS

We identified 25 eligible studies that included a total of 3688 patients. Mean prevalence of clopidogrel nonresponsiveness was 21% (95% CI, 17%-25%) and was inversely correlated with time between clopidogrel loading and determination of nonresponsiveness and used loading dose. The pooled odds ratio of cardiovascular outcome was 8.0 (95% CI, 3.4-19.0).

CONCLUSIONS

Laboratory clopidogrel nonresponsiveness can be found in approximately 1 in 5 patients undergoing PCI. Patients ex vivo labeled nonresponsive are likely to be also "clinically nonresponsive," as they exhibit increased risks of worsened cardiovascular outcomes. Our results indicate that use of a 600-mg clopidogrel loading dose will reduce these risks, which needs to be confirmed in large prospective studies.

The cost-effectiveness of dual oral antiplatelet therapy following percutaneous coronary intervention: a Swedish analysis of the CREDO trial

The CREDO trial demonstrated the clinical efficacy of 12-month antiplatelet therapy with clopidogrel compared to standard 28-day treatment with a 27% relative reduction in the combined risk of death, myocardial infarction, or stroke in patients undergoing percutaneous coronary intervention (PCI) and being treated with aspirin. This study evaluated the long-term cost-effectiveness of 12-month vs. 28-day therapy with clopidogrel in Sweden. A Markov model was developed which assumed a hypothetical cohort of patients in a post-PCI state to have certain risks of suffering one of the endpoints of the CREDO trial: stroke, myocardial infarction, or death. The model predicted a mean survival of 12.098 years in the 12-month arm vs. 12.026 in the 28-day arm, an incremental gain of 0.072 life-years. The gain in survival came at a predicted incremental cost of Euro 217, resulting in an incremental cost-effectiveness ratio of Euro 3,022. Thus the predicted cost-effectiveness ratio of long-term treatment with clopidogrel in patients undergoing PCI is well below the threshold values currently considered cost-effective.

Clopidogrel: How good is it and how does it work?

Until recently, long-term antiplatelet therapy for the treatment and prevention of the complications of atherothrombotic disease was limited to aspirin. Although an incredibly cost-effective therapy, in placebo-controlled clinical trials approximately 75% of patients at risk continue to experience thrombotic events despite chronic aspirin therapy. The availability of the thienopyridines, in particular clopidogrel, represents an important addition to the physician's armamentarium. A number of clinical trials have confirmed the efficacy of the combination of clopidogrel and aspirin therapy compared with aspirin alone, with multiple other important large-scale clinical trials currently ongoing. The exact mechanism of this benefit is still being elucidated but is clearly related to the inhibition of the many consequences of platelet activation--vascular inflammation, endothelial dysfunction, and localized angiogenesis/mitogenesis--and not just aggregation.