A randomized comparison of combined ticlopidine and aspirin therapy versus aspirin therapy alone after successful intravascular ultrasound-guided stent implantation

The Effects of Clopidogrel Duration On Carotid Artery In-stent Restenosis

OBJECTIVE

There is limited data supporting a specific duration for dual antiplatelet therapy in carotid artery stenting (CAS), and most clinical evidence is derived from studies involving coronary interventions. As a result, the appropriate duration of dual antiplatelet therapy after CAS has yet to be determined. We aimed to elucidate whether the duration of dual antiplatelet therapy played a role in the rate of carotid in-stent restenosis.

METHODS

A retrospective analysis of all patients who underwent CAS at our institution over a 20-year period (1996-2016) was performed (n=279). Patients who did not complete their follow-up duplex studies or were not discharged on clopidogrel were excluded from the study. Patients were separated into short-term (<6 weeks, n=159) and long-term (>6 weeks, n=112) clopidogrel users based on duration of therapy. We defined clinically significant in-stent restenosis as >50% restenosis (PSV = 224 cm/s) in symptomatic patients and >80% restenosis (PSV = 325 cm/s) in asymptomatic patients status-post prior CAS based on published velocity criteria. Rates of in-stent restenosis at 1-year, 2-year, and 5-year intervals were analyzed between the two groups using chi-squared analysis.

RESULTS

Demographic information was largely similar between the two groups; however, short-term clopidogrel users were more likely to have a history of atrial fibrillation (9.43% vs. 1.68%, p=0.008) and were less likely to have a history of CABG (16.35% vs. 29.41%, p=0.009), diabetes (33.34% vs. 49.58%, p=0.006) and CAD (50.31% vs. 63.03%, p=0.035). All patients were on long-term aspirin therapy. There was no significant difference between overall rates of in-stent restenosis between the short-term and long-term clopidogrel users (5.03% vs. 9.24%, p=0.168) within 5 years of the index procedure. Similar results were observed when these groups were evaluated at 1-year (5.61 % vs. 3%, p=0.321), 2-year (2.02% vs. 6.59%, p=0.072), and 5-year (2.24% vs. 3.57%, p=0.635) follow-up.

CONCLUSION

No statistically significant difference was observed in the rate of in-stent restenosis after CAS between short-term and long-term clopidogrel therapy. Patients in whom there is no other indication for longer duration clopidogrel therapy may be considered for shorter duration course of dual antiplatelet therapy following CAS.

Efficacy and safety of single versus dual antiplatelet therapy in carotid artery stenting

OBJECTIVE

Current guidelines recommend dual antiplatelet (AP) therapy (DAPT) before carotid artery stenting (CAS); however, the true clinical effect of single AP therapy vs DAPT is unknown. We examined the efficacy and safety of preoperative single AP therapy vs DAPT in patients who had undergone transfemoral CAS (tfCAS) or transcarotid artery revascularization (TCAR).

METHODS

We identified all patients who had undergone tfCAS or TCAR in the Vascular Quality Initiative database from 2016 to 2021. We stratified the patients by procedure and identified those who had received the following preoperative AP regimens: DAPT (acetylsalicylic acid [ASA] + P2Y12 inhibitor [P2Yi]), no AP therapy, ASA only, ASA + AP loading dose, P2Yi only, and P2Yi + AP loading dose. The AP loading dose was given within 4 hours of CAS. We generated propensity scores for each treatment regimen and assessed in-hospital outcomes using inverse probability weighted log binomial regression, with DAPT as the reference and adjusting for intraoperative protamine use. The primary efficacy outcome was a composite end point of stroke and death, and the primary safety outcome was access-related bleeding.

RESULTS

Of the 18,570 tfCAS patients, 70% had received DAPT, 5.6% no AP therapy, 10% ASA only, 8.0% ASA + AP loading dose, 4.6% P2Yi only, and 2.9% P2Yi + AP loading dose. The corresponding unadjusted rates of stroke/death were 2.2%, 6.8%, 4.1%, 5.1%, 2.4%, and 2.3%. After adjustment, compared with DAPT, the incidence of stroke/death was higher with no AP therapy (relative risk [RR], 2.3; 95% confidence interval [CI], 1.7-3.2), ASA only (RR, 1.6; 95% CI, 1.2-2.1), and ASA + AP loading dose (RR, 2.0; 95% CI, 1.5-2.7) but was similar with P2Yi only (RR, 0.99; 95% CI, 0.58-1.7) and P2Yi + AP loading dose (RR, 1.1; 95% CI, 0.49-2.5). Of the 25,459 TCAR patients, 81% had received DAPT, 2.0% no AP therapy, 5.5% ASA only, 3.5% ASA + AP loading dose, 4.9% P2Yi only, and 2.4% P2Yi + AP loading dose. The corresponding unadjusted rates of stroke/death were 1.5%, 3.3%, 3.3%, 2.9%, 1.2%, and 1.1%. After adjustment, compared with DAPT, the incidence of stroke/death was higher with no AP therapy (RR, 2.0; 95% CI, 1.2-3.3) and ASA only (RR, 2.2; 95% CI, 1.5-3.1), with a trend toward a higher incidence with ASA + AP loading dose (RR, 1.6; 95% CI, 0.99-2.6), and was similar with P2Yi only (RR, 0.98; 95% CI, 0.54-1.8) and P2Yi + AP loading dose (RR, 0.66; 95% CI, 0.27-1.6). No differences were found in the incidence of access-related bleeding between the treatment groups after tfCAS or TCAR.

CONCLUSIONS

Compared with DAPT, no AP therapy or ASA monotherapy was associated with higher rates of stroke/death after CAS and should be discouraged as unsafe practice. Meanwhile, P2Yi monotherapy was associated with similar rates of stroke/death. No differences were found in the incidence of bleeding complications, and adding an AP loading dose to ASA or P2Yi monotherapy within 4 hours of the procedure did not affect the outcomes. Overall, these findings support the current guidelines recommending DAPT before CAS but also suggest that P2Yi monotherapy might confer thromboembolic benefits similar to those with DAPT. However, an immediate preoperative AP loading dose might not provide additional thromboembolic benefits.

Antiplatelet Therapy in Patients Undergoing Elective Percutaneous Coronary Intervention

PURPOSE OF REVIEW

The evidence for use of dual antiplatelet therapy (DAPT) for patients undergoing percutaneous coronary intervention (PCI) in the elective setting is relatively sparse and is based on data from more than two decades ago. We will review the evidence supporting the use of DAPT with focus on stable patients undergoing elective PCI, including the role of potent P₂Y₁₂ inhibitors, modified DAPT durations, and more recently, aspirin discontinuation.

RECENT FINDINGS

Clopidogrel is the recommended P₂Y₁₂ inhibitor in the elective PCI setting. The benefit of more potent P₂Y₁₂ inhibitors such as ticagrelor or prasugrel in stable patients is unproven, but their use might be reasonable in those with high clinical or angiographic features of increased ischemic risk without increased risk of bleeding. Moreover, extending DAPT beyond 12 months is associated with a reduction in ischemic events but also increased bleeding. In contrast, shortening DAPT (3-6 months) reduces bleeding compared with 1 year of treatment, but it is also probably associated with increased ischemic events, mainly in higher-risk patients undergoing complex PCI. Recently, early aspirin discontinuation at 3 months (and perhaps as early as 1 month) following PCI reduces bleeding, with no evidence to suggest an increase in ischemic events. Clopidogrel is the P₂Y₁₂ inhibitor of choice, while more data are required to support the use of more potent P₂Y₁₂ inhibitors in stable patients. The duration of DAPT should be tailored to individual patient ischemic and bleeding risks. New strategies, such as early aspirin discontinuation, are promising to reduce bleeding risk without increase in ischemic risk.

Efficacy of aspirin, clopidogrel, and ticlopidine in stroke prevention: A population-based case-cohort study in Taiwan

Background

In real-world practice settings, there is insufficient evidence on the efficacy of antiplatelet drugs, including clopidogrel, aspirin, and ticlopidine, in stroke prevention.

Purpose

To compare the efficacies between aspirin and clopidogrel and aspirin and ticlopidine in stroke prevention.

Methods

This population-based case-cohort study utilized the data obtained from a randomized sample of one million subjects in the Taiwan National Health Insurance Research Database. Patients who were hospitalized owing to the primary diagnosis of ischemic stroke from January 1, 2000 to December 31, 2010 and treated with aspirin, ticlopidine, or clopidogrel were included in the study. Propensity score matching with a 1:4 ratio was performed to compare aspirin with ticlopidine and clopidogrel. The criteria for inclusion were the use of one of the three antiplatelet drugs for more than 14 days within the first month after the stroke and then continued use of the antiplatelet drugs until the study endpoint of recurrent stroke.

Results

During the 3-year follow-up period, the recurrent stroke rates were 1.62% (42/2585), 1.48% (3/203), and 2.55% (8/314) in the aspirin, ticlopidine, and clopidogrel groups, respectively. Compared with the patients treated with aspirin, those treated with clopidogrel and ticlopidine showed competing risk-adjusted hazard ratios of recurrent stroke of 2.27 (1.02–5.07) and 0.62 (0.08–4.86), respectively.

Conclusion

Compared with the patients treated with aspirin, those treated with clopidogrel were at a higher risk of recurrent stroke. For stroke prevention, aspirin was superior to clopidogrel whereas ticlopidine was not inferior to aspirin.

Omitting aspirin in PCI patients: Myth or reality?

In the current era of percutaneous coronary intervention (PCI), with the use of contemporary drug-eluting stents, refined techniques, and adjunctive pharmacotherapy, the role of aspirin peri-PCI remains undisputable. Beyond the initial period, dual antiplatelet therapy (DAPT) consisting of aspirin and a P2Y₁₂ receptor inhibitor for 6 months in stable coronary artery disease and 12 months in acute coronary syndromes is the standard of care. However, concerns regarding bleeding adverse events caused by aspirin have led to shortened DAPT duration or even omission of aspirin. Aspirin free-strategies have been increasingly encountered in several studies and showed a significant reduction in bleeding events, without any sign of increased ischemic risk. Individualization of DAPT duration particularly in high bleeding risk patients appears therefore mandatory, making aspirin not necessary in several cases. Moreover, recent randomized trials have shed light on how to treat PCI patients in the presence of concomitant anticoagulant treatment with P2Y₁₂ monotherapy and excluding aspirin. These aspirin-free strategies have been proved safer than the "older" standard triple antithrombotic treatment, without compromising safety. Ongoing studies may further dispel the myths and establish real facts regarding post-PCI-tailored treatment with or without aspirin.

Comparison of heparin, bivalirudin, and different glycoprotein IIb/IIIa inhibitor regimens for anticoagulation during percutaneous coronary intervention: A network meta-analysis

BACKGROUND/PURPOSE

Numerous GPIs are available for PCI. Although they were tested in randomized controlled trials, a comparison between the different GPI strategies is lacking. Thus, we performed a Bayesian network meta-analysis to compare different glycoprotein IIb/IIIa inhibitor (GPI) strategies with heparin and bivalirudin for percutaneous coronary intervention (PCI).

METHODS

MEDLINE, Cochrane CENTRAL, and ClinicalTrials.gov were searched by two independent reviewers for randomized controlled trials comparing high-dose bolus tirofiban, abciximab, eptifibatide, heparin with provisional glycoprotein IIb/IIIa inhibitors, and bivalirudin with provisional GPI that reported clinical outcomes. Mixed treatment comparison model generation was performed to directly and indirectly compare between different anticoagulation strategies for all-cause mortality, myocardial infarction, major adverse cardiovascular events, major bleeding, minor bleeding, need for transfusion, and thrombocytopenia.

RESULTS

A total of 41 randomized controlled trials with 38,645 patients were included in the analysis, among which 2654 were randomized to high-dose bolus tirofiban, 6752 to abciximab, 1669 to eptifibatide, 16,500 to heparin, and 11,070 to bivalirudin. Mean age was 64±11years, 75% were male, 91% were treated with stenting, 71% with clopidogrel, and 74% for acute coronary syndrome. High-dose bolus tirofiban was associated with a significant reduction in all-cause mortality compared with heparin (OR 0.57 [credible intervals 0.37, 0.9]) and eptifibatide (OR 0.44 [credible intervals 0.19, 1.0]). GPI regimens had less myocardial infarction and major adverse cardiovascular events but greater bleeding compared with heparin and bivalirudin. There was no difference among the GPI therapies for other outcomes, including myocardial infarction, major adverse cardiovascular events, and major bleeding.

CONCLUSIONS

Our network meta-analysis of 38,645 patients demonstrated that GPI regimens were associated with a reduction in recurrent myocardial infarction or major adverse cardiovascular events for PCI, while bivalirudin was associated with the lowest risk of bleeding.

Coronary Stenting or Balloon Angioplasty for Chronic Total Coronary Occlusions: The Taiwan Experience (A Single-Center Report)

The authors conducted this study to compare the restenosis and reocclusion rates of primary balloon angioplasty alone versus angioplasty followed by stenting in Taiwanese patients with chronic total occlusions. They also evaluated whether stenting reduced the incidence of restenosis and improved left ventricular function in these patients. From October 1998 to April 2000, a total of 294 patients with chronic total occlusion (Thrombolysis in Myocardial Infarction grade 0 flow) underwent recanalization using balloon angioplasty alone or followed by stent implantation. Of these, only 129 patients were included after procedural failure and patients lost to follow-up; 62 patients were placed in the stent group, while 67 patients were assigned to the percutaneous transluminal coronary angioplasty (PTCA) group. Coronary angiography was performed at baseline and at 6 months follow-up or earlier if angina or objective evidence of ischemia involving the target vessel or other vessels was present. Procedural success was 60%. Minimal lumen diameter increased significantly after stenting: 2.97 ±0.41 vs 2.24 ±0.41 (p<0.001); 60% of patients in the stent group were free of restenosis, whereas only 33% in the PTCA group were free of restenosis at follow-up. Only 1 patient in the stent group had reocclusion, as opposed to 17 (25%) patients in the PTCA group (p<0.001). The follow-up minimal lumen diameter (MLD) at 6 months was significantly larger in the stent group: 1.80 ±0.85 mm vs 1.08 ±0.82 mm (p<0.001). Left ventricular function improved in the stent group, but not in the PTCA group (58.44 ±16.58% to 63.60 ±14.59% [p<0.001] vs 54.13 ±15.66% to 54.31 ±15.60% [p=0.885]). More patients had angina in the PTCA group than in the stented group 43 vs 29 (p=0.053). The postprocedural MLD and reference vessel diameter (RVD) were the strong predictors of restenosis and follow-up MLD (p<0.001). Stenting of chronically occluded arteries significantly reduced the incidence of reocclusion and restenosis, at the same time improving left ventricular function in these patients. This should be the procedure of choice after successful angioplasty of chronically occluded vessels.

Antiplatelet Effects of the Addition of Acetylsalicylic Acid 40 Mg Daily to Ticlopidine in Human Healthy Volunteers

Clinical studies have shown that acetylsalicylic acid (ASA) or ticlopidine (T) bring a partial clinical benefit in a subset of patients threatened by thrombosis on atherosclerotic plaques. Acetylsalicylic acid and T have different impacts on platelet function and the combination of the drugs seems logical to achieve a greater antiplatelet effect. Healthy volunteers were randomly allocated to any of the three treatment groups: T 250-placebo; T 250-T 250; placebo-placebo (treatment was administered in a double blind manner). Acetylsalicylic acid 40 mg was openly administered once a day to the subjects of the three groups after the first week of treatment. Simplate I bleeding time and platelet aggregation testing were performed before treatment and at the end of the two treatment periods. We confirmed that T alone prolongs bleeding time and impairs, in a dose-dependent manner, ADP-induced aggregation; platelet responses that depend on released ADP were also affected. Inhibition of thromboxane-dependent aggregation, associated with a doubling of the bleeding time, was observed after one week of low-dose ASA inhibition of thromboxane synthesis. An additive effect of ASA 40 mg to T 250 mg on the bleeding time was evidenced. There was also a wider alteration of platelet aggregation, with a trend towards an inhibition of the response to a high concentration of collagen as compared to ASA or T used alone. Such a powerful, logical drug combination is in good agreement with preliminary encouraging results obtained after coronary stent implantation and deserves further studies in patients at high risk for arterial thrombosis to define its benefit-risk profile. Key Words: Aspirin—Ticlopidine— Drug combination—Bleeding time—Platelet aggregation.

Carotid stent-assisted thrombectomy in acute ischemic stroke

Acute carotid occlusion or near-occlusion with concomitant intracranial embolism cause severe acute ischemic strokes in patients. These concomitant occlusions have suggested poor response to intravenous thrombolysis and complicate endovascular treatment. Nevertheless, endovascular stent-assisted thrombectomy may improve outcome in patients but the treatment is not without concerns. Required antiplatelet therapy to prevent stent thrombosis may increase the rate of intracranial hemorrhage, especially after recent thrombolysis. Furthermore, technical difficulties in access of the intracranial vasculature may cause adverse events, even in the hands of experienced interventionalists. These concerns currently defy the treatment in being recommended for general use and only on a compassionate basis. However, recent patient series have suggested reasonable safety and efficacy for carotid stent-assisted thrombectomy.

Comparison of prasugrel and bivalirudin vs clopidogrel and heparin in patients with ST-segment elevation myocardial infarction: Design and rationale of the Bavarian Reperfusion Alternatives Evaluation (BRAVE) 4 trial

Primary percutaneous coronary intervention (PCI) is the preferred reperfusion strategy for patients with ST-segment elevation myocardial infarction (STEMI). Effective and safe adjunct antithrombotic therapy is a major determinant for short- and long-term outcomes after primary PCI. Two separate studies have shown significant benefits vs conventional therapy for 2 recently approved drugs. In the Harmonizing Outcomes With Revascularization and Stents in Acute Myocardial Infarction (HORIZONS-AMI) trial, bivalirudin after pretreatment with clopidogrel resulted in improved net clinical outcome compared with heparin plus glycoprotein IIb/IIIa inhibitors. However, during the first 24 hours after PCI, there was an increase in stent thrombosis rates with bivalirudin. In the Trial to Assess Improvement in Therapeutic Outcomes by Optimizing Platelet Inhibition With Prasugrel-Thrombolysis In Myocardial Infarction (TRITON-TIMI) 38 trial, prasugrel was superior to clopidogrel in patients with acute coronary syndrome with and without ST-segment elevation. The synergic actions of prasugrel and bivalirudin may maximize the benefit of antithrombotic therapy for STEMI patients undergoing primary PCI. However, no specifically designed studies have so far compared the combination of prasugrel plus bivalirudin with that of clopidogrel plus unfractionated heparin in these patients. The Bavarian Reperfusion Alternatives Evaluation (BRAVE) 4 study is a randomized, open-label, multicenter trial aimed to test the hypothesis that a strategy based on prasugrel plus bivalirudin is superior to a strategy based on clopidogrel plus unfractionated heparin in terms of net clinical outcome in STEMI patients with planned primary PCI.

Vitamin K antagonists in heart disease: current status and perspectives (Section III). Position paper of the ESC Working Group on Thrombosis--Task Force on Anticoagulants in Heart Disease

Oral anticoagulants are a mainstay of cardiovascular therapy, and for over 60 years vitamin K antagonists (VKAs) were the only available agents for long-term use. VKAs interfere with the cyclic inter-conversion of vitamin K and its 2,3 epoxide, thus inhibiting γ-carboxylation of glutamate residues at the amino-termini of vitamin K-dependent proteins, including the coagulation factors (F) II (prothrombin), VII, IX and X, as well as of the anticoagulant proteins C, S and Z. The overall effect of such interference is a dose-dependent anticoagulant effect, which has been therapeutically exploited in heart disease since the early 1950s. In this position paper, we review the mechanisms of action, pharmacological properties and side effects of VKAs, which are used in the management of cardiovascular diseases, including coronary heart disease (where their use is limited), stroke prevention in atrial fibrillation, heart valves and/or chronic heart failure. Using an evidence-based approach, we describe the results of completed clinical trials, highlight areas of uncertainty, and recommend therapeutic options for specific disorders. Although VKAs are being increasingly replaced in most patients with non-valvular atrial fibrillation by the new oral anticoagulants, which target either thrombin or FXa, the VKAs remain the agents of choice for patients with atrial fibrillation in the setting of rheumatic valvular disease and for those with mechanical heart valves.

Patients who require non-cardiac surgery in acute coronary syndrome

The coexistence of an acute coronary syndrome (ACS) and non-cardiac surgery (NCS) in an individual patient can be summarized in two challenging clinical scenarios for the treating physician: 1) Post-operative patients who develop ACS and 2) Patients with ACS who subsequently require NCS. Both settings are characterized by a struggle on the part of treating physicians attempting to optimize antithrombotic therapies for ACS while minimizing post-surgical bleeding risk. In this review we address specific clinical issues related to patients with coexistent NCS and ACS, discussing possible management strategies balancing ischemic and bleeding risk in these complex patient scenarios.

Dual antiplatelet therapy with aspirin and clopidogrel: what is the risk in noncardiac surgery? A narrative review

Clopidogrel is one of the most commonly prescribed medications and is currently recommended along with aspirin as treatment to be used for 1 year in all patients without contraindications following an acute coronary syndrome. Patients who are committed to clopidogrel therapy due to recent coronary artery stent implantation may require noncardiac surgery during this recommended period of dual antiplatelet therapy (DAPT). Due to differing rates of endothelialization, patients who undergo bare-metal stent implantation generally require ≥ 1 month of uninterrupted DAPT, and those who undergo drug-eluting stent implantation require ≥ 12 months. Many surgeons ask their patients to stop taking clopidogrel in advance of their procedure to decrease perioperative bleeding. This practice is based largely on anecdotal experience and extrapolated from limited data in cardiac surgery. Premature cessation of aspirin and/or clopidogrel following coronary artery stenting, however, has been associated with acute stent thrombosis, myocardial infarction, and death. We searched PubMed for English language articles published from 1960 to 2012, using the keywords aspirin, clopidogrel, surgery, general, vascular, genitourinary, thoracic, orthopedic, ophthalmologic, dermatologic, endoscopy, colonoscopy, cardiac device implantation, pacemaker, defibrillator, bronchoscopy, bridging, bleeding complications, and transfusion, including various combinations. s were reviewed to confirm relevance, and then the full articles were extracted. References from extracted articles were also reviewed for relevant articles. Literature regarding perioperative clopidogrel continuation is predominantly composed of small, nonrandomized data, but suggests that most noncardiac surgeries or procedures can be performed safely while patients are taking clopidogrel. In this article, we review the current best evidence on the risk for bleeding with clopidogrel therapy in noncardiac surgery, summarize recent guidelines on appropriate duration of DAPT, and make recommendations on the management of perioperative DAPT.

Aspirin and platelet adenosine diphosphate receptor antagonists in acute coronary syndromes and percutaneous coronary intervention: role in therapy and strategies to overcome resistance

Platelet activation and aggregation are key components in the cascade of events causing thrombosis following plaque rupture. Antiplatelet therapy is essential in the treatment of patients with acute coronary syndromes (ACS) and for those requiring percutaneous coronary intervention (PCI). Aspirin (acetylsalicylic acid) is a well established antiplatelet therapy and is mandated for secondary prevention of cardiovascular events following ACS. In patients with ACS, the addition of clopidogrel to aspirin is more effective than aspirin alone. For patients undergoing PCI, dual antiplatelet therapy with aspirin and clopidogrel is warranted. Aspirin should be continued indefinitely after PCI. Pretreatment of patients with clopidogrel prior to PCI lowers the incidence of cardiovascular events, yet the optimum timing of drug administration and dose are still being investigated, as is the duration of therapy following PCI. Late-stent thrombosis with drug-eluting stents has pushed the recommendation for duration of clopidogrel therapy up to 1 year and perhaps beyond, in patients without risks for bleeding. The concepts of aspirin and clopidogrel resistance are important clinical questions. No uniform definition exists for aspirin or clopidogrel resistance. Measurements of resistance are often highly variable and do not necessarily correlate with clinical resistance. Noncompliance remains the most prominent mode of resistance. Screening of selected patient populations for resistance or pharmacologic intervention of those patients termed 'resistant' warrants further study.

A Study on the Effects of Covered Stents on Tissue Prolapse

Polyvinyl alcohol (PVA) cryogel covered stents may reduce complications from thrombosis and restenosis by decreasing tissue prolapse. Finite element analysis was employed to evaluate the effects of PVA cryogel layers of varying thickness on tissue prolapse and artery wall stress for two common stent geometries and two vessel diameters. Additionally, several PVA cryogel covered stents were fabricated and imaged with an environmental scanning electron microscope. Finite element results showed that covered stents reduced tissue prolapse up to 13% and artery wall stress up to 29% with the size of the reduction depending on the stent geometry, vessel diameter, and PVA cryogel layer thickness. Environmental scanning electron microscope images of expanded covered stents showed the PVA cryogel to completely cover the area between struts without gaps or tears. Overall, this work provides both computational and experimental evidence for the use of PVA cryogels in covered stents.

Direct vasoactive properties of thienopyridine-derived nitrosothiols

Thienopyridines (ticlopidine, clopidogrel, and prasugrel) require in vivo metabolism to exhibit a critical thiol group in the active form that binds to the P2Y12 platelet receptor to inhibit platelet activation. We hypothesized that formation of thienopyridine-derived nitrosothiols (ticlopidine-SNO, clopidogrel-SNO, and prasugrel-SNO) occurs directly from the respective parent drug. Pharmaceutical-grade thienopyridine (ticlopidine, clopidogrel chloride, clopidogrel sulfate, clopidogrel besylate, or prasugrel) was added to nitrite in aqueous solution to form the respective thienopyridine-SNO (Th-SNO). An isolated aortic ring preparation was used to test vasoactivity of the Th-SNO derivatives. Increasing nitrite availability resulted in increased Th-SNO formation for all drugs (other than ticlopidine). Th-SNO induced significant endothelium-independent relaxation of preconstricted aortic rings. Clopidogrel-chloride-SNO displayed rapid-release kinetics in a chemical environment, which was reflected by immediate and transient vasorelaxation when compared with the SNO derivatives of the other thienopyridines. Accounting for differences in yield, clopidogrel-chloride-SNO exhibited the greatest propensity to immediately relax vascular tissue. Th-SNO derivatives exhibit nitrovasodilator properties by supplying NO that can directly activate vascular soluble guanylate cyclase to induce vasorelaxation. Differences in SNO yield and vasoactivity exist between thienopyridine preparations that might be important to our understanding of the direct pharmacological effectiveness of thienopyridines on vascular and platelet function.

The evolution of antiplatelet therapy in cardiovascular disease

The platelet--an anucleate cell--is the bedrock of thrombosis, both physiologically and pathologically. Antagonism of the P2Y(12) receptor for ADP is one of several pathways inhibiting the activation and aggregation of platelets, thereby attenuating coronary thrombosis in response to spontaneous plaque rupture or percutaneous revascularization. The addition of clopidogrel to a background of aspirin therapy was a revolutionary change in the management of ischemic coronary syndromes. Despite this paradigm shift, clopidogrel has certain limitations, including variability in platelet inhibitory effect, which is associated with adverse thrombotic events. In the evolution of antiplatelet treatment strategies, two new P2Y(12) receptor antagonists--prasugrel and ticagrelor--have been added to the armamentarium in the past few years. Both of these drugs confer greater platelet inhibition than clopidogrel. Nevertheless, more-potent platelet inhibition comes with an increased risk of hemorrhagic complications. Cangrelor and elinogrel are novel P2Y(12) inhibitors that show potential in the periprocedural setting with their rapid onset and offset of activity. Successes in P2Y(12) inhibitory therapies have reduced use of glycoprotein IIb/IIIa inhibitors, which block the final pathway leading to platelet aggregation and thrombosis. Newer therapies aimed at various molecular factors are under clinical investigation. Pharmacodynamic platelet function assays and pharmacogenetic testing to individualize and optimize antiplatelet therapy may find their way into clinical use, although much more study is needed.

Antiplatelet therapy in acute coronary syndromes

Antiplatelet therapy is integral to the acute and long-term management of acute coronary syndromes (ACSs) and for minimizing the thrombotic complications of percutaneous coronary intervention (PCI). This article reviews the most commonly used antiplatelet agents in ACS therapy--aspirin, adenosine diphosphate (ADP)-receptor blockers, and glycoprotein IIb/IIIa inhibitors. More recent data are also reviewed on novel ADP-receptor blockers and thrombin inhibitors before addressing issues of adherence to antiplatelet regimens.

Platelet interactions as therapeutic targets for prevention of atherothrombosis

Physiologically, platelets perform important tasks to maintain the homeostasis of the vascular wall and the surrounding environment. In pathologic conditions, however, platelets contribute to the formation of atherosclerotic plaques as well as to atherothrombotic events (i.e., acute myocardial infarction). This review aims to elucidate the role of platelets in atherogenesis and atherothrombosis and to provide an insight into current and future strategies for platelet inhibition.

Combining antiplatelet and anticoagulant therapies

Antiplatelet therapy is the cornerstone for both primary and secondary prevention therapies for ischemic events resulting from coronary atherosclerotic disease. Dual antiplatelet therapy (aspirin plus a thienopyridine, usually clopidogrel) has assumed a central role in the treatment of acute coronary syndromes and after coronary stent deployment. In addition to antiplatelet therapy, anticoagulant therapy might be indicated for stroke prevention in a variety of conditions that include atrial fibrillation, profound left ventricular dysfunction, and after mechanical prosthetic heart valve replacement. For this reason, the use of triple antithrombotic therapy (a dual antiplatelet regimen plus warfarin) is expected to become more prominent, given an aging patient population. But although triple therapy can prevent both thromboembolism and stent thrombosis, it is also associated with significant bleeding hazards. Furthermore, when bleeding events do occur, the challenge of balancing the risk of stent thrombosis or stroke and the need for hemostasis requires considerable expertise. It is both prudent and timely to review treatment strategies that employ combinations of antiplatelet and anticoagulant therapies as well as strategies aimed at reducing bleeding risk in patients treated with these therapies.

The effect of intended duration of clopidogrel use on early and late mortality and major adverse cardiac events in patients with drug-eluting stents

BACKGROUND

The optimal duration of clopidogrel use for prevention of stent thrombosis with drug-eluting stent (DES) use is uncertain. Our objective was to determine whether the planned duration of clopidogrel at the time of percutaneous coronary intervention affected patient outcomes.

METHODS

We analyzed data from 2,980 patients who underwent percutaneous coronary intervention in the Melbourne Interventional Group registry who had 12-month follow-up. We compared outcomes at 30 days and 12 months according to planned duration of clopidogrel use.

RESULTS

Twelve-month mortality was significantly lower in patients with a DES with a longer (>or=12 months) planned duration of clopidogrel when compared with a shorter (<or=6 months) planned duration (2.8% vs 5.3%, P = .012). However, myocardial infarction, target-vessel revascularization, and overall major adverse cardiac events were similar in the longer- and shorter-duration clopidogrel strategies. In contrast, in patients receiving a bare-metal stent, mortality at 12 months was similar among the clopidogrel-duration strategies. Kaplan-Meier analysis demonstrated improved cumulative survival with planned clopidogrel use of >or=12 months (log rank P = .017), and the propensity score-adjusted odds ratio was 0.59 (95% confidence interval 0.35-0.99, P = .04). Premature cessation of clopidogrel in DES patients was documented in 5.2% of patients alive at 30-day follow-up, and these patients had increased 12-month mortality (10.6% vs 1.4%, P < .0001) and major adverse cardiac events (22.4% vs 12.0%, P = .005).

CONCLUSIONS

These data suggest that in patients treated with DES, longer (>or=12 months) planned duration of clopidogrel results in reduced 12-month mortality and that premature cessation of clopidogrel results in significantly higher event rates. Randomized studies are urgently needed to address this issue.

High-residual platelet activity despite dual antiplatelet treatment associated with subacute stent thrombosis

High-residual platelet activity despite the dual antiplatelet treatment with aspirin and clopidogrel is associated with major adverse cardiac events, including stent thrombosis. Acute and subacute stent thrombosis is rare, but presents itself with serious complications including high mortality and morbidity rates. Light transmittance aggregometry with specific agonists — arachidonic acid and 5-adenosin diphosphate — is still considered a standard for the assessment of platelet reactivity, besides novel methods like vasodilator-stimulated phosphoprotein phosphorylation. In our case study, we report the coincidence of high-residual platelet activity with subacute stent thrombosis despite the recommended doses of antiplatelet agents — aspirin and clopidogrel. Stent thrombosis was treated by aspiration thrombectomy, and antiplatelet treatment was modified by increasing the dose of aspirin and substituting clopidogrel with a firstgeneration thienopyridin — ticlopidin. The effect of the treatment was documented by reaching the optimal inhibition of platelet reactivity. In the 6- and 12-month follow-up, the patient presented no ischemic events.

A new wave in treatment of vascular occlusive disease: biodegradable stents--clinical experience and scientific principles

Stent-based therapies in percutaneous vascular intervention are associated with significant long-term complications related to in-stent restenosis. A growing body of literature demonstrates the feasibility of biodegradable materials for endovascular stents, which may, in theory, circumvent many of the immunologic and inflammatory response issues seen with long-term metallic stent failure in coronary and peripheral applications. This review describes the history of endovascular stents and the challenges encountered with metallic, drug-eluting, and biodegradable stents. A review of the basic engineering principles of biodegradable stents is provided, along with a discussion of the cellular mechanisms of restenosis.

Overview of advances in cardiovascular disease treatment and prevention: the evolving role of antiplatelet therapy

PURPOSE

The role of antiplatelet therapy in preventing and treating cardiovascular disease is reviewed.

SUMMARY

Cardiovascular disease, especially coronary heart disease, contributes to substantial morbidity and mortality in the United States and raises healthcare costs. Current guidelines from the American College of Cardiology and the American Heart Association, in conjunction with the Society for Cardiovascular Angiography and Interventions, recommend percutaneous coronary intervention (PCI) and stent placement to improve cardiovascular outcomes in patients with acute coronary syndrome, which encompasses unstable angina and myocardial infarction. Following stent placement, dual antiplatelet therapy with aspirin and a thienopyridine (clopidogrel or ticlopidine) significantly reduces the incidence of early major adverse cardiac events and mortality compared with aspirin alone or in combination with warfarin, and is the current standard of care for patients undergoing PCI. Maintenance therapy should be continued for at least one month after placement of a bare-metal stent, and at least three months or six months after placement of a sirolimus- or paclitaxel-eluting stent; ideally, therapy should be continued for one year following PCI. Even utilizing this standard, however, adverse clinical events do occur. In addition, treatment is often discontinued within the first year after stent placement by either the healthcare provider or the patient.

CONCLUSION

Premature discontinuation of antiplatelet therapy is associated with an increased risk of adverse outcomes and can be avoided through better understanding of these risks by healthcare professionals and improved patient education.

Prognostic significance of post-clopidogrel platelet reactivity assessed by a point-of-care assay on thrombotic events after drug-eluting stent implantation

AIMS

The aim of this study was to determine whether platelet reactivity on clopidogrel therapy, as measured by a point-of-care platelet function assay, is associated with thrombotic events after percutaneous coronary intervention (PCI) with drug-eluting stents (DESs).

METHODS AND RESULTS

Platelet reactivity on clopidogrel (post-treatment reactivity) was measured with the VerifyNow P2Y12 assay (Accumetrics Inc., San Diego, CA, USA) in 380 patients undergoing PCI with sirolimus-eluting stents. Receiver-operating characteristic curve analysis was used to derive the optimal cut-off value for post-treatment reactivity in predicting 6 month out-of-hospital cardiovascular (CV) death, non-fatal MI, or stent thrombosis. The mean post-treatment reactivity was 184 +/- 85 PRU (P2Y12 reaction units). The optimal cut-off for the combined endpoint was a post-treatment reactivity > or =235 PRU [area under the curve 0.711 (95% confidence interval 0.529-0.893), P = 0.03], which was similar to the threshold of the upper tertile (231 PRU). Patients with post-treatment reactivity greater than the cut-off value had significantly higher rates of CV death (2.8 vs. 0%, P = 0.04), stent thrombosis (4.6 vs. 0%, P = 0.004), and the combined endpoint (6.5 vs. 1.0%, P = 0.008).

CONCLUSION

High post-treatment platelet reactivity measured with a point-of-care platelet function assay is associated with post-discharge events after PCI with DES, including stent thrombosis. Investigation of alternative clopidogrel dosing regimens to reduce ischaemic events in high-risk patients identified by this assay is warranted.

Antiplatelet therapy in patients undergoing coronary stent implantation: Italian Society of Interventional Cardiology consensus document

The Italian Society of Interventional Cardiology is aware of the existence of significant local and individual disparities and discordant prescriptions in antiplatelet therapy administered with coronary stents, a critical issue due to the large use of drug-eluting stents (DES), the increasing complexity of percutaneous coronary interventions and the more stringent requirement to avoid stent thrombosis. Current percutaneous coronary intervention is attempting more aggressively to treat difficult lesions and patient cohorts with a high procedural success rate. Double antiplatelet therapy with aspirin (ASA) and thienopyridine is the best current treatment to reduce the risk of coronary stent thrombosis. Due to the lower incidence of side-effects compared to ticlopidine, clopidogrel should be the thienopyridine of choice in association with ASA in the double antiplatelet regimen. However, the combination of delayed healing with DES and the increasing complexity of the stent implantation raises more demanding safety concerns about the dosage and duration of dual antiplatelet therapy.

Aspirin "failures," clopidogrel added to aspirin, and secondary stroke prevention in veterans presenting with TIA or mild-to-moderate ischemic stroke

Our objective was to investigate whether clopidogrel added to low-dose aspirin reduced vascular events in male patients at our VA hospital who had "failed" aspirin therapy because of a mild-to-moderate stroke or a transient ischemic attack. Of 179 consecutive patients who both reported daily aspirin usage at the time of their newest ischemic event as well as were then operationally defined as aspirin "failures," 134 (group A) were treated with combined aspirin-clopidogrel, 15 (group B) underwent an early arterial procedure, 25 (group C) were anticoagulated, and 5 were not entered or continued because of either non-compliance or a refusal to participate. Study therapies were modified because of a vascular event in 4.5% of group A (one non-fatal ischemic stroke, one non-fatal myocardial infarction, and four transient ischemic attacks) and 33% of group B (one non-fatal ischemic stroke, one non-fatal myocardial infarction, and three transient ischemic attacks). No major or fatal bleeding events occurred in any of those on combined aspirin-clopidogrel therapy, with minor bleeding in 10 of 134 (7.5%) and 2 of 15 (13.3%) of group A and B patients, respectively. Patients were followed for 18 +/- 9.7 months. Combined aspirin-clopidogrel therapy appears both safe as well as effective in this single-center, observational study.

Increased incidence of stent thrombosis in patients with cocaine use

INTRODUCTION

Coronary stent thrombosis is a rare occurrence in the era of dual-antiplatelet therapy. It is not known whether patients who use cocaine have a higher risk of thrombosis following coronary stent placement.

METHODS

We studied 247 consecutive patients who underwent coronary stent placement at an inner-city hospital.

RESULTS

Twelve patients (4.9%) were actively using cocaine at the time of PCI. Of these twelve patients, four patients presented with stent thrombosis (33%) at a mean of 51 +/- 40 days (median 45 days), after the index revascularization procedure. Only 2 of the 235 patients without documented cocaine use (0.85%) had stent thrombosis during the same period (P < 0.0001).

CONCLUSION

The patients who actively use cocaine have a markedly higher risk of stent thrombosis when compared with patients without a documented history of cocaine use. We discuss various factors that potentially predispose cocaine users to stent thrombosis.

Prevention of premature discontinuation of dual antiplatelet therapy in patients with coronary artery stents: a science advisory from the American Heart Association, American College of Cardiology, Society for Cardiovascular Angiography and Interventions, American College of Surgeons, and American Dental Association, with representation from the American College of Physicians

Dual antiplatelet therapy with aspirin and a thienopyridine has been shown to reduce cardiac events after coronary stenting. However, many patients and healthcare providers prematurely discontinue dual antiplatelet therapy, which greatly increases the risk of stent thrombosis, myocardial infarction, and death. This advisory stresses the importance of 12 months of dual antiplatelet therapy after placement of a drug-eluting stent and educating the patient and healthcare providers about hazards of premature discontinuation. It also recommends postponing elective surgery for 1 year, and if surgery cannot be deferred, considering the continuation of aspirin during the perioperative period in high-risk patients with drug-eluting stents.

Prevention of premature discontinuation of dual antiplatelet therapy in patients with coronary artery stents: A science advisory from the American Heart Association, American College of Cardiology, Society for Cardiovascular Angiography and Interventions, American College of Surgeons, and American Dental Association, with representation from the American College of Physicians

Dual antiplatelet therapy with aspirin and a thienopyridine has been shown to reduce cardiac events after coronary stenting. However, many patients and healthcare providers prematurely discontinue dual antiplatelet therapy, which greatly increases the risk of stent thrombosis, myocardial infarction, and death. This advisory stresses the importance of 12 months of dual antiplatelet therapy after placement of a drug-eluting stent and educating the patient and healthcare providers about hazards of premature discontinuation. It also recommends postponing elective surgery for 1 year, and if surgery cannot be deferred, considering the continuation of aspirin during the perioperative period in high-risk patients with drug-eluting stents.

Incremental effect of clopidogrel on important outcomes in patients with cardiovascular disease: a meta-analysis of randomized trials

OBJECTIVES

To quantify the impact of clopidogrel plus aspirin on the individual outcomes of death, myocardial infarction, or stroke in patients with established cardiovascular disease, or in patients with multiple risk factors for vascular disease.

BACKGROUND

Randomized trials have demonstrated a reduction in composite outcomes when clopidogrel is added to aspirin therapy in patients with coronary artery disease; however, the magnitude of benefit on individual outcomes is unknown.

METHODS

We conducted a meta-analysis on randomized, controlled trials that compared aspirin plus clopidogrel with aspirin plus placebo for the treatment of coronary artery disease.

RESULTS

This analysis included five randomized trials (CURE, CREDO, CLARITY, COMMIT, and CHARISMA) in 79 624 patients. The incidence of all-cause mortality was 6.3% in the aspirin plus clopidogrel group versus 6.7% in the aspirin group (odds ratio [OR] 0.94; 95% CI 0.89, 0.99; p = 0.026). The incidence of myocardial infarction was 2.7% and 3.3% (OR 0.82; 95% CI 0.75, 0.89; p < 0.0001), and stroke was 1.2% and 1.4% (OR 0.82; 95% CI 0.73, 0.93; p = 0.002). Similarly, the incidence of major bleeding was 1.6% and 1.3% (OR 1.26; 95% CI 1.11, 1.41; p < 0.0001), and fatal bleeding was 0.28% and 0.27% (OR 1.04; 95% CI 0.76, 1.43; p = 0.79).

CONCLUSION

The addition of clopidogrel to aspirin results in a small reduction in all-cause mortality in patients with ST-elevation myocardial infarction and a modest reduction in myocardial infarction and stroke in patients with cardiovascular disease. The overall incidence of major bleeding however is increased, although there is no excess of fatal bleeds or hemorrhagic strokes.

Oral platelet glycoprotein IIb/IIIa receptor inhibitors--Part I

With the central importance of antiplatelet therapy in patients with coronary artery disease and the numerous positive trials with glycoprotein (GP) IIb/IIa inhibitors given intravenously, it was hoped that one could extend the benefit of IIb/IIIa inhibition to long-term treatment. Although the hypothesis that prolonged oral IIb/IIIa inhibition was appealing, many issues have been identified in the initial Phase II trials that would limit the usefulness of these compounds. Variability of the level of platelet inhibition was one major culprit that distinguished the oral compounds from intravenous ones. The problems that arose were that increased bleeding has been seen when levels of platelet inhibition are high (e.g., > 90%) and that, conversely, efficacy would likely be limited when levels of platelet inhibition were low. If further development of this class of drugs is undertaken, formal dosing studies would have to establish an oral dosing strategy that achieves appropriately high (80-95% inhibition) and steady levels of inhibition.