Changes in membrane glycoproteins of circulating platelets after coronary stent implantation

Proteomic study of apheresis platelets made HLA class I deficient for transfusion of refractory patients

PURPOSE

Refractoriness can occur after repeated platelet (PLT) transfusions because of alloimmunization to HLA class I antigens on transfused PLTs and generation of anti-HLA antibodies that bind to the foreign PLTs and initiate their destruction. Such refractoriness can be overcome by provision of HLA-matched PLTs from HLA typed donors. However, since the procedure is both expensive and time-consuming, an alternative approach is to deplete PLTs of HLA class I molecules by a brief treatment with citric acid, on ice. This is shown to be feasible without damaging PLT function. We used label free quantitative mass spectrometry (MS)-based proteomics to investigate the effect of acid treatment on apheresis PLTs for combatting immunologic PLT refractoriness.

EXPERIMENTAL DESIGN

Proteomic analyses are undertaken using PLTs from seven apheresis concentrates, which were split in two with or without acid treatment.

RESULTS

In total 1717 proteins in apheresis PLTs were quantified using proteomics. Data are available via ProteomeXchange with identifier PXD027893 . Of these, the amount of 80 proteins changed significantly after acid treatment, but overall there were not any major differences in proteomes between samples with and without acid treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

In general, the changes of PLT proteins after treatment with citric acid were quite small and functionally safe. Hence, this result taken together with our previously published data indicates that acid treated PLTs can be used for treatment of patients with PLT refractoriness and opens up for a clinical trial.

Inhibition of in-stent restenosis after graphene oxide double-layer drug coating with good biocompatibility

In this study, we designed a double layer-coated vascular stent of 316L stainless steel using an ultrasonic spray system to achieve both antiproliferation and antithrombosis. The coating included an inner layer of graphene oxide (GO) loaded with docetaxel (DTX) and an outer layer of carboxymethyl chitosan (CMC) loaded with heparin (Hep). The coated surface was uniform without aggregation and shedding phenomena before and after stent expanded. The coating treatment was able to inhibit the adhesion and activation of platelets and the proliferation and migration of smooth muscle cells, indicating the excellent biocompatibility and antiproliferation ability. The toxicity tests showed that the GO/DTX and CMC/Hep coating did not cause deformity and organ abnormalities in zebrafish under stereomicroscope. The stents with GO double-layer coating were safe and could effectively prevent thrombosis and in-stent restenosis after the implantation into rabbit carotid arteries for 4–12 weeks.

Pharmacological prevention of peri-, and post-procedural myocardial injury in percutaneous coronary intervention

In recent years, percutaneous coronary intervention (PCI) has become a well-established technique for the treatment of coronary artery disease. PCI improves symptoms in patients with coronary artery disease and it has been increasing safety of procedures. However, peri- and post-procedural myocardial injury, including angiographical slow coronary flow, microvascular embolization, and elevated levels of cardiac enzyme, such as creatine kinase and troponin-T and -I, has also been reported even in elective cases. Furthermore, myocardial reperfusion injury at the beginning of myocardial reperfusion, which causes tissue damage and cardiac dysfunction, may occur in cases of acute coronary syndrome. Because patients with myocardial injury is related to larger myocardial infarction and have a worse long-term prognosis than those without myocardial injury, it is important to prevent myocardial injury during and/or after PCI in patients with coronary artery disease. To date, many studies have demonstrated that adjunctive pharmacological treatment suppresses myocardial injury and increases coronary blood flow during PCI procedures. In this review, we highlight the usefulness of pharmacological treatment in combination with PCI in attenuating myocardial injury in patients with coronary artery disease.

Effects ofad hocclopidogrel loading versus pre-treatment on P-selectin expression after coronary stent implantation

Stents represent a thrombogenic surface where one of the earliest events is the deposition of platelets. Activated platelets express neoepitopes that enable them to form homo- and heterotypic aggregates and activate the coagulation system. In this study, we investigated the effects of ad hoc clopidogrel treatment compared to a clopidogrel pretreated group on platelet P-selectin expression. We found that after stent implantation in the ad hoc treated group, P-selectin expression decreased after 1 h, while the initial decrease in platelet count normalized after 4 h. Aspirin non-responsiveness did not influence the results. These data point to the beneficial effect of clopidogrel treatment in reducing platelet reactivity during stenting.

Glycoprotein IIb/IIIa antagonists in acute ischaemic stroke: current status and future directions

Glycoprotein (GP) IIb/IIIa receptors on the surface of platelets play a critical role in thrombosis. Intravenous GP IIb/IIIa antagonists abciximab, tirofiban and eptifibatide have demonstrated efficacy in acute coronary syndromes when combined with heparin, aspirin, clopidogrel and percutanous coronary interventions. Results have been less consistent in acute ischaemic stroke. Preclinical data support the potential benefit of these agents both in the microcirculation and in aiding clot lysis. While phase I and II trials of abciximab as the sole agent employing dosages comparable with those used in coronary syndromes were promising, the pivotal phase III trial was abandoned because of an unfavourable benefit-to-risk ratio. New preliminary platelet inhibition measurements from our group suggest that cardiac dosages were likely to be too high for stroke patients. Exploration of lower dosages of abciximab and potentiation with time-limited weight-based heparin along with platelet aggregation inhibition measurement is continuing on a smaller scale. At present, the most common usage of GP IIb/IIIa antagonists in stroke are as adjunctive agents to thrombolysis by intravenous and intra-arterial routes. Substantial progress is likely to require a better understanding of the mechanism of actions and unique pharmacology of GP IIb/IIIa antagonists in ischaemic stroke.

Optimal management of platelet function after coronary stenting

Coronary stenting elicits vessel wall damage, and subsequent activation of platelets is implicated as a major component of complications such as acute, subacute, and late stent thrombosis. As such, dual antiplatelet therapy using aspirin and clopidogrel has become a routine adjunct to coronary stenting. Use of aspirin and clopidogrel with or without glycoprotein IIb/IIIa inhibitors after coronary stenting reduces the complication rate and improves long-term outcomes. Dual antiplatelet therapy using aspirin and clopidogrel is recommended for at least 4 weeks with bare metal stents, and for 3 to 6 months with drug-eluting stents for prevention of major adverse cardiac events. After coronary stenting, 1 year of dual antiplatelet therapy is recommended for prevention of future cardiac events. However, despite the use of antiplatelet agents, stent thrombosis occurs in approximately 1% of patients, with an increased likelihood of occurrence in high-risk patients or a lesion subset of patients. Although the incidence of stent thrombosis is low, stent thrombosis usually presents as acute coronary syndrome and the mortality rate is up to 45%. Thus, considering the widespread use of stents, a considerable number of people are inadequately protected from thrombotic events despite current standard antiplatelet therapy using aspirin and clopidogrel. A concern with clopidogrel is the loading time and loading dose required to achieve and maintain optimal inhibition of platelet aggregation. The current recommendation for ensuring maximum antiplatelet activity is administration of a 300-mg loading dose of clopidogrel initiated at least 6 hours prior to percutaneous coronary intervention (PCI), and ideally the day before. If this is not possible, a loading dose of 600 mg of clopidogrel should be administered at least 2 hours before PCI. Recently, new combinations of antiplatelet agents (ie, triple therapy using aspirin, clopidogrel, and cilostazol) and new drugs with potent antiplatelet effects (ie, Prasugrel , Cangrelor , and AZD6140) have been evaluated in clinical trials; such treatments may help reduce the number of cardiac events after coronary stenting.

Long-term care after percutaneous coronary intervention: focus on the role of antiplatelet therapy

Arterial wall injury caused by percutaneous coronary intervention (PCI) triggers transient platelet activation and mural thrombosis; these effects are superimposed on the preexisting platelet hyperreactivity associated with underlying atherothrombosis. Platelet activation has been implicated in the major complications of PCI: acute and subacute thrombosis and restenosis. Antithrombotic and anticoagulant therapy minimizes thrombotic complications after PCI. Aspirin plus a thienopyridine (ticlopidine or clopidogrel) is more effective than aspirin plus heparin and extended warfarin therapy in preventing periprocedural ischemic events and subsequent stent thrombosis and results in less major and minor bleeding. Dual antiplatelet therapy with aspirin and clopidogrel (the preferred thienopyridine because of its superior hematologic safety) is recommended for at least 4 weeks to prevent subacute stent thrombosis with bare-metal stents and 3 to 6 months to prevent late-stent thrombosis with drug-eluting stents. Coronary atherothrombosis is a diffuse vascular disease, and reduction of the risk of future ischemic events requires strategies that extend beyond the focal treatment of stenotic lesions. Optimal long-term care after PCI requires aggressive systemic pharmacotherapy (antiplatelet agents, statins, beta-blockers, and angiotensin-converting enzyme Inhibitors) in conjunction with therapeutic lifestyle changes (smoking cessation, weight reduction, dietary measures, and exercise). In this context, dual antiplatelet therapy (aspirin plus clopidogrel) is recommended for at least 12 months after PCI for prophylaxis of future atherothrombotic events.

The Benefits of Combined Anti-platelet Treatment in Carotid Artery Stenting

OBJECTIVE

To assess the benefits of a combined anti-platelet regime of aspirin and clopidogrel in carotid artery stenting.

METHODS

A randomised controlled trial was performed comparing aspirin and 24-h heparin with aspirin and clopidogrel for patients undergoing carotid artery stenting. Outcome measures included 30-day bleeding and neurological complications and 30-day stenosis rates.

RESULTS

Bleeding complications (groin haematoma or excessive bleeding at the groin site) occurred in 17% of the heparin and 9% of the clopidogrel group (p=0.35; n.s). The neurological complication rate in the 24-h heparin group was 25% compared to 0% in the clopidogrel group (p=0.02). The 30-day 50-100% stenosis rates were 26% in the heparin group and 5% in the clopidogrel group (p=0.10; n.s).

CONCLUSIONS

The dual anti-platelet regime has a significant impact on reducing adverse neurological outcomes without an additional increase in bleeding complications. This study was terminated prematurely due to an unacceptable level of complications in the heparin arm of the trial.

Therapeutic potential of platelet glycoprotein IIb/IIIa receptor antagonists in acute ischaemic stroke: scientific rationale and available evidence

Acute ischaemic stroke is the result of an abrupt interruption of focal cerebral blood flow. In the majority of cases, this interruption is caused by an acute thromboembolism. Based on clinical experience in the treatment of acute coronary syndromes, platelet glycoprotein (GP) IIb/IIIa receptor antagonists alone, in combination with reduced doses of thrombolytic agents, or as complementary therapy for short-term mechanical interventions merit consideration as a class of agents with potential use in ischaemic stroke. Research to date and extrapolation from the cardiac literature suggest significant, but as yet unproven, potential for the use of GP IIb/IIIa receptor antagonists in the treatment of acute ischaemic stroke. This potential exists both at the site of the thromboembolic occlusion and at the distal microvascular level. This article reviews the scientific rationale and available evidence for the potential use of platelet GP IIb/IIIa receptor antagonists in acute ischaemic stroke.

P-selectin in arterial thrombosis

P-selectin is a transmembrane protein present in the alpha granules of platelets and the Weibel-Palade bodies of endothelial cells. Following activation, it is rapidly translocated to the cell surface. P-selectin expression in platelets has been shown to be elevated in disorders associated with arterial thrombosis such as coronary artery disease, acute myocardial infarction, stroke, and peripheral artery disease. P-selectin mediates rolling of platelets and leukocytes on activated endothelial cells as well as interactions of platelets with leukocytes. Platelet P-selectin interacts with P-selectin glycoprotein ligand-1 (PSGL-1) on leukocytes to form platelet-leukocyte aggregates. Furthermore, this interaction of P-selectin with PSGL-1 induces the upregulation of tissue factor, several cytokines in leukocytes and the production of procoagulant microparticles, thereby contributing to a prothrombotic state. P-selectin is also involved in platelet-platelet interactions, i. e. platelet aggregation which is a major factor in arterial thrombosis. P-selectin interacts with platelet sulfatides, thereby stabilizing initial platelet aggregates formed by GPIIb/IIIa-fibrinogen bridges. Inhibtion of the P-selectin-sulfatide interaction leads to a reversal of platelet aggregation. Thus, P-selectin plays a significant role in platelet aggregation and platelet- leukocyte interactions, both important mechanisms in the development of arterial thrombosis.

Molecular and cellular basis of restenosis after percutaneous coronary intervention: the intertwining roles of platelets, leukocytes, and the coagulation-fibrinolysis system

The major limitation of percutaneous coronary intervention (PCI) is restenosis. Restenosis is considered to be an overreaction of the natural healing process after traumatic balloon dilatation. An elaborate web of cellular and molecular responses, including the interaction of platelets, leukocytes, and the coagulation-fibrinolysis system, as well as the secretion of various growth factors and pro-inflammatory cytokines, contributes to neointimal hyperplasia and the development of restenosis. Moreover, platelet and neutrophil activation after stenting appears to be different from that after balloon angioplasty alone. Pharmacotherapy targeting the cell-to-cell interaction between platelets and neutrophils may potentially offer an effective treatment strategy against restenosis after PCI.

Distinct yet complementary mechanisms of heparin and glycoprotein IIb/IIIa inhibitors on platelet activation and aggregation: implications for restenosis during percutaneous coronary intervention

OBJECTIVE

To study the effect of unfractionated heparin (UFH) versus low molecular weight heparin (LMWH) in combination with glycoprotein (Gp) IIb/IIIa blockers on platelet activation and aggregation.

METHODS

Washed platelets were stimulated with thrombin in the presence or absence of UFH (monoparin), LMWH (enoxaparin), and a Gp IIb/IIIa blocker (abciximab, eptifibatide, or tirofiban).

RESULTS

Although Gp IIb/IIIa antagonists blocked the final common pathway of thrombin induced platelet aggregation, UFH and LMWH were better at blocking upstream platelet activation. UFH was significantly more effective than LMWH at inhibiting P selectin expression (p = 0.001) and platelet derived growth factor release from thrombin activated platelets (p = 0.012).

CONCLUSIONS

UFH and LMWH exert complementary effects to Gp IIb/IIIa blockers by inhibiting afferent pathways of platelet activation. Coadministration of heparin with Gp IIb/IIIa blockers provides improved protection against persistent platelet activation, thereby improving outcome after percutaneous coronary intervention. Judging from these data, UFH may be more effective in this regard than LMWH, at least in vitro. The use of LMWH in preference to UFH during percutaneous coronary intervention, although initially attractive, may inadequately protect against platelet activation despite the presence of Gp IIb/IIIa blockers.

Effects of Antiplatelet Agents on Subacute Thrombosis and Restenosis After Successful Coronary Stenting-A Randomized Comparison of Ticlopidine and Cilostazol-

BACKGROUND

A prospective randomized study compared the preventive effects of ticlopidine plus aspirin therapy versus cilostazol plus aspirin therapy on subacute thrombosis (SAT) and restenosis after coronary stenting.

METHODS AND RESULTS

After successful stenting of 327 coronary lesions in 282 consecutive patients, the patients were randomized to receive ticlopidine (200 mg/day) or cilostazol (200 mg/day). Aspirin (81 mg/day) was administered concomitantly in both groups. SAT occurred in 1 patient in the ticlopidine group (0.7%) and in 8 patients in the cilostazol group (5.6%, p=0.037). Based on follow-up angiography, restenosis occurred in 30 patients (23.3%) in the ticlopidine group and 35 patients (26.9%) in the cilostazol group (NS). The late loss was significantly smaller in the cilostazol group than the ticlopidine group (1.08+/-0.95 mm vs 0.78+/-0.93 mm, respectively, p=0.037). No significant differences between the 2 groups were observed with respect to the rates of total death, non-fatal cardiovascular events, or bleeding complications.

CONCLUSION

The ticlopidine group showed significantly less SAT after stenting compared with the cilostazol group. After 6 months of treatment, the inhibition of neointimal proliferation was greater in the cilostazol group than in the ticlopidine group, but the prevention of restenosis was not confirmed.

Abciximab Reduces Monocyte Tissue Factor in Carotid Angioplasty and Stenting

Background and Purpose— Abciximab, a nonselective glycoprotein IIb/IIIa inhibitor, was shown to reduce peri-interventional stroke rate in carotid stenting. We evaluated the effect of adjunct abciximab therapy on monocyte-platelet cross talk and neurological deficit in unprotected carotid stenting and compared its efficacy with distal filter protection.

Methods— Fifty patients were randomized to either standard antithrombotic therapy (n=30) consisting of aspirin, clopidogrel, and heparin or adjunct bolus (0.25 mg/kg) and 12-hour infusion (0.125 μg · kg −1 · min −1 ) of abciximab (n=20). A third cohort of patients was stented with filter protection (n=30). Monocyte-platelet aggregate formation and monocyte tissue factor expression were determined by whole blood flow cytometry, and F1.2 generation and soluble CD40 ligand (sCD40L) were determined by immunoassay.

Results— The incidence of peri-interventional ischemic episodes (23% versus 10%; P =0.2) and the number of de novo ischemic lesions detected by diffusion-weighted MRI (47% versus 30%; P =0.17) were not significantly different between standard antithrombotic therapy and adjunct abciximab but were reduced with filter protection ( P =0.023). However, the number of transient ischemic attacks was lower ( P =0.05) and the National Institutes of Health Stroke Score rapidly decreased in patients with adjunct abciximab. This clinical improvement was paralleled by a reduction in the postinterventional percentage of activated monocyte-platelet aggregates (CD62P+/CD14+; P =0.018) and the number of tissue factor–positive monocytes (TF+/CD14+; P =0.005). Both abciximab and filter protection suppressed F1.2 generation and significantly reduced sCD40L.

Conclusions— Abciximab limits thrombus propagation and thrombus stabilization after carotid stenting by reducing monocyte-platelet cross talk and sCD40L. Although abciximab seems inferior to filter devices in peri-interventional cerebral protection, it may be considered in patients who do not allow placement of protection devices.

Parameters of the tissue factor pathway with coumadin/dipyridamole versus ticlopidine as adjunct antithrombotic-drug regimen in coronary artery stenting

A different rate and timing of subacute stent thrombosis after percutaneous coronary intervention was reported with various peri-interventional antithrombotic regimens. Next to platelet activation, coagulation triggered by tissue factor (TF) may play a key role in this process. Thirty-one consecutive patients with stable and unstable angina undergoing coronary stenting were randomly assigned to adjunct oral anticoagulation/anti-platelet therapy (coumadin, dipyridamole, aspirin and heparin; n = 16) or adjunct anti-platelet therapy with thienopyridin (ticlopidine, aspirin and heparin; n = 15). Antigen levels of plasma TF, total tissue factor pathway inhibitor (TFPI) and TFPI/ activated factor X (TFPI/FXa) complex were determined before and for up to 6 days after intervention by immunoassay. At baseline, significantly higher levels of plasma TF and TFPI/FXa were found in patients with unstable angina [TF, 161 pg/ml (126-191 pg/ml); TFPI/FXa, 7.8 ng/ml (6.1-9.6 ng/ml)] compared with stable angina [TF, 62 pg/ml (46-82 pg/ml), P < 0.0001; TFPI/FXa, 4.5 ng/ml (3-7.6 ng/ml), P= 0.003]. One hour after intervention, an increase of plasma TF and TFPI/FXa was seen in both treatment groups. In unstable angina patients, plasma levels of TF, TFPI and TFPI/FXa were more efficiently reduced by adjunct ticlopidine therapy compared with adjunct coumadin/dipyridamole. These data suggest reduced release of circulating TF by combined anti-platelet therapy with ticlopidine and aspirin after coronary artery stenting, which may-contribute to the lower incidence of subacute stent thrombosis previously observed.

Platelet activity and sensitivity to agonists after exhaustive treadmill exercise

The extent of platelet activation after exhaustive exercise remains under discussion. Previous studies have provided contrary data, probably due to differences in the methodologies and the enrolled subjects. In the present study a maximal treadmill exercise (TR) was used to test platelet activity and -reactivity in 13 healthy non-smoking men. Blood samples were taken after a 30min rest, immediately before and after exercise, and 1h after completion of exercise. Platelets were analysed by whole blood flow cytometry either directly or after in vitro stimulation by incubating the blood samples for 10min with TRAP-6 (10µM) or ADP (5µM or 2,5µM). Binding of an anti-CD62P antibody or a PAC1 antibody directed against the activated fibrinogen receptor GPIIb/IIIa were used as a measure of platelet activation. Immediately after TR the percent CD62P positive platelets (%PC) unstimulated increased (p<0.01) from 0.77±0.06 to 1.12± 0.09 %PC and in PAC1 (p<0.05) from 2.32 ±0.54 to 3.83±0.81 %PC (mean±SEM). After ADP-stimulation an increase from 4.18±1.02 to 5.69±1.40 %PC in CD62P (p<0.01) and from 45.7±3.4 to 57.9±6.6 %PC in PAC1 (p<0.05) after TR were detected. Using TRAP-6-stimulation only the increase of PAC1 (p<0.01) after TR was different in comparison with the control experiment without exercise. Soluble CD62P in plasma as a marker of platelet and endothelial cell activation was also enhanced (p<0.05) after TR. Although these results indicate that exhaustive exercise lead to a small platelet activation and an increase in platelet reactivity, it is rather doubtful that these changes alone implicate a prothrombotic situation in healthy young non-smokers.

The prevention of minor myocardial injury with ticlopidine pretreatment in patients undergoing elective coronary stenting

The aim of the study was to determine whether ticlopidine treatment prior the coronary stenting would be associated with lower rates of procedure-related minor myocardial injury (MMI) in patients undergoing elective coronary stenting. In this retrospective, nonrandomized, uncontrolled study, a total of 153 consecutive patients with a mean age of 63.4+/-8.9 years were divided into two groups based on the duration of ticlopidine treatment: group I (n=81), ticlopidine >/=3 days before the procedure, group II (n=72), on the same day as stent placement. Cardiac troponin T (cTnT) was measured immediately before and 12 h after the procedures. All patients were followed-up during the hospital stay with respect to MMI and major clinical events (MCE). The increase frequency and the amount of cTnT level in group I was found to be significantly lower compared with group II (4 vs. 13; P<0.01, and 0.35+/-0.06 vs. 0.52+/-0.11 ng/ml; P<0.01, respectively). In general, patients with elevated cTnT levels are more likely to have C type lesion and multivessel procedure than those of normal cTnT level (41 vs.10%; P<0.002 and 47 vs. 17%; P<0.009, respectively). Though there was a trend toward increased MCE rates in group II than that of group I, this did not reached statistical significance (3 vs.1; P=NS). The present study shows that an anti-platelet treatment with ticlopidine prior the coronary stenting of adequate duration to allow for the development of maximal inhibition is associated with a markedly decreased incidence of procedure-related MMI. Therefore, ticlopidine pretreatment may be a cost alternative for the prevention of platelet-rich microembolism in patients undergoing elective coronary stenting.

Comparison of clopidogrel versus ticlopidine for prevention of minor myocardial injury after elective coronary stenting

We searched a randomized, double-blinded, prospective study that compared the effectiveness of clopidogrel versus ticlopidine for prevention of minor myocardial injury (MMI) and major clinical events (MCEs) after elective coronary stenting. A total of 158 consecutive patients (98 male, 60 female patients with a mean age of 59.3+/-5.4 years) were divided into two arms based on treatment with thienopyridines: group I, clopidogrel 1 x 300 mg as a loading dose, and 1 x 75 mg per day thereafter, group II, ticlopidine 2 x 250 mg daily. Both thienopyridines were started on the same day as stent placement. Cardiac troponin T (cTnT) was measured immediately before and 12 h after the procedures. All patients were followed-up during the hospital stay (6+/-2 days) with respect to MMI and MCEs. The increase frequency and the amount of cTnT level in group I was found significantly lower compared with group II (5 vs.15; P<0.01; 0.38+/-0.11 vs. 0.44+/-0.12 ng/ml; P<0.001, respectively). Patients with elevated cTnT levels more likely to have C type lesion (P<0.004). Though there was a trend toward increased major clinical events rate in group II than those of group I, the statistical difference was not different (4 vs. 1.3%; P>0.05). The present study showed that the combination of clopidogrel and aspirin was more effective than the combination of ticlopidine and aspirin in decreasing the rate of MMI.

Randomized comparison of platelet–leukocyte aggregates and platelet activation in blood: heparin-coated coiled wire stent implantation versus balloon angioplasty in acute myocardial infarction

INTRODUCTION

Stent implantation has been shown to be superior to balloon angioplasty in patients with acute myocardial infarction (AMI). Newer trials indicate that platelet-leukocyte aggregates are a more sensitive marker for platelet activation than platelet surface marker. Our study examined platelet activation and platelet-leukocyte interaction in blood in patients with AMI randomized to heparin-coated stent implantation versus balloon angioplasty.

MATERIALS AND METHODS

Forty-seven patients with AMI were included into our study. Patients were randomized to heparin-coated stent implantation (n=31) or balloon angioplasty (n=16). Platelet activation, total platelet-leukocyte aggregates and aggregate composition in blood were assessed by flow cytometry before, immediately after and 24 h after intervention.

RESULTS

No differences in platelet activation, total platelet-leukocyte aggregates and aggregate composition were found between both groups before intervention. Immediately after intervention, platelet activation was comparably increased in both groups. Patients treated with heparin-coated stent showed a decrease in total platelet-leukocyte aggregates 24 h after intervention (3.9% [2.8; 4.7] versus 3.2% [2.4; 4.1]; p<0.01). Platelet-monocyte conjugates decreased 24 h after heparin-coated stent implantation compared to balloon angioplasty alone (0.28% [0.17; 0.42] versus 0.49% [0.45; 0.79]; p<0.05). No difference in total platelet-leukocyte aggregates was found in patients treated with balloon angioplasty alone.

CONCLUSIONS

An inhibitory effect of heparin-coated stent implantation on total platelet-leukocyte aggregates and platelet-monocyte conjugates in blood was demonstrated in patients with AMI. This reflects heparin-coated stent implantation to be less thrombogenic than balloon angioplasty alone.

Glycoprotein IIb/IIIa antagonists in the setting of rescue percutaneous coronary intervention

It is clear that survival and better outcomes after acute myocardial infarction (AMI) are dependent on rapid, complete, and sustained reperfusion of the affected myocardium. Thrombolytic therapy is currently the most common reperfusion strategy in AMI, however, a significant proportion of patients fail to reach reperfusion with this form of therapy. There is evidence from randomized trials that rescue percutaneous coronary intervention (PCI) for failed thrombolysis may convey better outcomes to patients when compared to a conservative management. Nevertheless, it is not surprising that in this inherently thrombogenic milieu, rescue PCI has a lower success rate and a high incidence of rethrombosis, which have a profoundly negative impact on the outcome of patients. Platelets are thought to play a central role in the pathophysiology of failed thrombolysis and in the thrombotic complications following PCIs. Therefore, platelet glycoprotein (GP) IIb/IIIa antagonist may be of benefit in the setting of rescue PCI. Two retrospective subgroup analyses have suggested that these potent antiplatelet agents may improve the outcome of patients undergoing rescue PCI after failed full-dose thrombolytic therapy. An increase in major bleeding, however, has also been noted. Therefore, in light of the lack of evidence deriving from randomized, placebo-controlled trials, careful consideration of several aspects relevant to this setting is needed before GP IIb/IIIa antagonists are administered in rescue percutaneous coronary procedures.

Leukocyte-platelet aggregation, platelet surface P-selectin, and platelet surface glycoprotein IIIa after percutaneous coronary intervention: Effects of dalteparin or unfractionated heparin in combination with abciximab

BACKGROUND

Plaque disruption with resultant platelet activation and leukocyte-platelet aggregation is a pathophysiologic process common to both acute coronary syndromes and percutaneous coronary interventions. Unfractionated heparin is a standard antithrombotic therapy in patients with both acute coronary syndromes and in those undergoing percutaneous coronary interventions. Low-molecular-weight heparins have been reported to cause less platelet activation than unfractionated heparin.

METHODS

Monocyte-platelet aggregates, neutrophil-platelet aggregates, platelet surface P-selectin, and platelet surface glycoprotein (GP) IIIa were measured serially by whole blood flow cytometry in 40 patients with unstable angina (randomly assigned to either unfractionated heparin 70 U/kg or the low-molecular-weight heparin dalteparin 60 IU/kg) undergoing coronary intervention with planned abciximab administration (in 2, one-half-dose boluses). Assays were performed at baseline, 5 minutes after administration of either type of heparin, 10 minutes after the first bolus of abciximab, 10 minutes after second bolus of abciximab, and 8 to 10 and 16 to 24 hours after administration of either heparin.

RESULTS

No significant differences in clinical outcomes were observed between patients receiving either unfractionated heparin or dalteparin. The number of circulating P-selectin-positive platelets was increased by unfractionated heparin but not dalteparin, and abciximab reversed this increase. The number of circulating P-selectin-positive platelets was reduced below baseline levels in both treatment groups 8 to 10 and 16 to 24 hours after study drug administration. At 8 to 10 and 16 to 24 hours after administration of study drug, platelet degranulation in response to iso-thrombin receptor agonist peptide 1.5 mmol/L was significantly reduced by almost 50% (compared with immediately after study drug administration). Both unfractionated heparin and dalteparin significantly increased the numbers of circulating monocyte-platelet and neutrophil-platelet aggregates, which were subsequently reduced to baseline levels after administration of the second abciximab bolus and to below baseline at both 8 to 10 and 16 to 24 hours in all patients. After both unfractionated heparin and dalteparin administration, platelet surface GP IIIa expression was significantly increased compared with baseline at both 8 to 10 and 16 to 24 hours.

CONCLUSIONS

Dalteparin in combination with abciximab in patients with unstable angina undergoing coronary intervention appears to be safe. Unfractionated heparin, but not dalteparin, degranulates platelets in patients with unstable angina. Both heparins increase the number of circulating monocyte-platelet and neutrophil-platelet aggregates. Abciximab therapy during coronary interventions rapidly reduces the number of degranulated platelets and leukocyte-platelet aggregates.

Initial experience of platelet glycoprotein IIb/IIIa inhibition with abciximab during carotid stenting: a safe and effective adjunctive therapy

BACKGROUND AND PURPOSE

Abciximab has been shown to decrease periprocedural ischemic complications after coronary intervention. However, the adjunctive use of abciximab in carotid stenting has not been adequately studied. We sought to determine the efficacy and safety of abciximab in carotid stenting.

METHODS

Carotid stenting was performed in 151 consecutive patients determined to be at high surgical risk by a vascular surgeon. Of these, 128 consecutive patients received adjuvant therapy with abciximab (0.25 mg/kg bolus before the lesion was crossed with guidewire and 0.125 micro. kg(-1). min(-1) infusion for 12 hours.). A heparin bolus of 50 U/kg was given, and activated clotting time was maintained between 250 to 300 seconds. All patients received aspirin and thienopyridine. Procedural and 30-day outcomes were compared between the control (n=23) and abciximab (n=128) groups.

RESULTS

The 2 groups had similar baseline characteristics. Procedural events were more frequent in the control group (8%; 1 major stroke and 1 neurological death) compared with the abciximab group (1.6%; 1 minor stroke and 1 retinal infarction; P=0.05). On 30-day follow-up, 1 patient presented with delayed intracranial hemorrhage in the abciximab group. There were no other major bleeding complications.

CONCLUSIONS

Adjunctive use of abciximab for carotid stenting is safe with no increase in the risk of intracranial hemorrhage. This adjunctive therapy with potent glycoprotein IIb/IIIa inhibition may help to reduce periprocedural adverse events in patients undergoing carotid stenting.

Glycoprotein Ia C807T polymorphism and risk of restenosis following coronary stenting

Platelets are thought to contribute to development of restenosis following percutaneous coronary interventions. The glycoprotein Ia/IIa complex is a major platelet collagen receptor, its surface expression being influenced by two, linked single nucleotide polymorphisms (C807T and G873A) in the glycoprotein Ia gene. T807 is associated with increased expression of this integrin receptor. We assessed whether T807 is associated with an increased risk of restenosis in 1769 consecutive patients treated with coronary stenting. 6-month follow-up angiograms were available in 82.4% of the patients. C807T genotype distribution was CC in 35.8%, CT in 47.6% and TT in 16.6% of the patients. Restenosis (diameter stenosis > or =50% at follow-up angiography) occurred in 32.9% of CC, 31.5% of CT and 32.1% of TT patients (P=0.87). The rate of major adverse cardiac events (death, myocardial infarction or need of reintervention) within 1 yr was 21.6% for CC, 21.7% for CT and 21.2% for TT patients (P=0.98). Thus, carriage of the GP Ia T807 allele is not associated with an increased risk of restenosis or unfavorable late outcome following coronary artery stenting.

Multilink Stent Promotes Less Platelet and Leukocyte Adhesion Than a Traditional Stainless Steel Stent

BACKGROUND

Platelet and leukocyte deposition onto metallic struts can be a crucial factor in the outcome of a coronary stenting procedure. By means of an in vitro, closed-loop circulation model, we aimed to assess blood-stent interaction patterns for a new stainless steel stent (MultiLink, Guidant Nederland BV, Nieuwegein, the Netherlands).

METHODS

The effect of MultiLink (n=20) on blood cells and blood activation was studied by biochemical assays. Platelet and leukocyte adhesion to MultiLink were studied by immunofluorocytometric assays (anti-GpIIIa [CD 61] and anti-CD11b labeled antibodies, respectively), and by scanning electron microscopy. MultiLink was compared with empty circuits (n=20) and to the Palmaz Schatz stent (n=20). Experiments were performed both in the presence and in the absence of an antiplatelet agent (15 microg/mL of indomethacin).

RESULTS

No significant effect on blood cells and blood activation was demonstrated for MultiLink. Antiplatelet treatment significantly reduced platelet adhesion to MultiLink (from 3.78+/-1.28 to 2.23+/-0.57 x 10(6) count per second [cps]/stent) but not to the Palmaz Schatz stent (from 4.11+/-0.31 to 5.02+/-1.29 x 10(6) cps/stent)(P=0.011). Leukocyte adhesion to MultiLink was significantly less than adhesion to the Palmaz Schatz stent (7.95+/-1.59 vs. 9.16+/-1.36 x 10(6) cps/stent, respectively; P=0.016), regardless of the presence of antiplatelet treatment.

CONCLUSIONS

When compared with a traditional stainless steel stent, MultiLink seems to have features of improved hemocompatibility, and single antiplatelet treatment is proposed as the treatment of choice to prevent platelet deposition.

Platelet and leukocyte deactivation after intracoronary stent placement in patients receiving combined antiplatelet therapy

Activated platelets and leukocytes have been demonstrated to play a role in the development of stent thrombosis, and coronary angioplasty has been shown to result in activation of platelets, leukocytes, and endothelial cells. We aimed to evaluate the effects of intracoronary stent placement and aspirin plus ticlopidine treatment on platelets, leukocytes, and endothelial cells via observing the serial changes in the circulating soluble forms of adhesion molecules in 54 patients with coronary artery disease, who had elective coronary angioplasty and stent implantation for a single lesion of the left anterior descending artery. After stent placement, intravenous heparin infusion was administered only for 24 hours, and aspirin plus ticlopidine treatment was applied for 1 month. Venous blood samples were drawn before stent placement, and repeated 24 and 48 hours after the procedure. Patients were excluded if they had had recent cardiovascular events or any illness that might influence platelet, leukocyte, and endothelial cell function. The plasma level of sL-selectin was significantly decreased 48 hours after coronary stenting (636+/-110 ng/mL vs 567+/-93 ng/mL; P = 0.001, respectively). Likewise, the plasma level of sP-selectin was also decreased significantly 48 hours after the procedure (260+/-61 ng/mL vs 233+/-83 ng/mL, P = 0.01). The sE-selectin level was found to be significantly increased 24 hours (31+/-9 ng/mL vs 39+/-12 ng/mL, P = 0.0001) and 48hours(31+/-9 ng/mL vs 42+/-15 ng/mL, P = 0.001) after coronary stenting. The results of our study suggest that significant platelet and leukocyte deactivation take place in patients treated with combined antiplatelet therapy after stenting; endothelial cell activation also occurs during this treatment.

Effects of stent coating on platelets and endothelial cells after intracoronary stent implantation

BACKGROUND

Adhesion molecules are known to be important in the regulation of endothelial cell and platelet functions. Increased platelets P-selectin expression is a marker of stent thrombosis after uncoated stent placement.

HYPOTHESIS

The aim of this study was to compare the effects of intracoronary placement of phosphorylcholine (PC)-coated, versus heparin-coated, versus uncoated stents on platelets and endothelial activity.

METHODS

Thirty patients (age 55 +/- 10, 27 men) with significant proximal left anterior descending coronary artery stenoses were randomized to elective implantation of PC-coated, versus heparin-coated, versus uncoated stents. Following stent placement, intravenous heparin and aspirin plus ticlopidine were administered. Venous plasma soluble E-selectin, sP-selectin, and intercellular adhesion molecule-l levels were measured before the procedure and 24 and 48 h thereafter as markers of platelet and endothelial cell activation. Patients were excluded if they had a disease known to influence platelet and endothelial cell function.

RESULTS

Plasma sP-selectin levels decreased significantly after implantation of PC- and heparin-coated stents (p = 0.04), but remained unchanged in patients randomized to uncoated stents. Plasma sE-selectin levels increased significantly after uncoated stent placement (p = 0.04) and remained unchanged after coated stent implantation.

CONCLUSION

In patients treated with combined antiplatelet therapy, implantation of PC- and heparin-coated stents decreased platelet activity without activating endothelial cells, whereas placement of uncoated stents led to endothelial activation without changing platelet activity. These results suggest that PC-coated and heparin-coated stents may be advantageous in limiting thrombotic complications.

Novel approaches for the prevention of restenosis

Restenosis, the re-narrowing of the lumen of the coronary artery, in the months following a successful percutaneous balloon angioplasty or stenting, remains the main limitation to percutaneous coronary revascularisation. Serial intravascular ultrasound studies have shown that restenosis after conventional balloon angioplasty represents a complex interplay between elastic recoil, smooth muscle proliferation and vascular remodelling, while restenosis after stent deployment is due almost entirely to smooth muscle hyperplasia and matrix proliferation. Despite intensive investigation in animal models and in clinical trials, most pharmacological agents have been found to be ineffective in preventing restenosis after percutaneous balloon angioplasty or stenting. Although studies frequently report success in the suppression of neointimal proliferation in animal models of balloon vascular injury, few of them have been successful in clinical trials. Lately, the advent of endovascular radiation, new antiproliferative agents, recombinant DNA, growth factor regulators and novel local drug delivery systems have shown promising results. In the past five years, intracoronary radiation with gamma- and beta-emitting sources has been evaluated intensively with very encouraging results. This is the first potent non-pharmacological approach that has been successful in a large number of patients in controlling excessive tissue proliferation. It is very likely that a combination of stents and pharmacological and/or non-pharmacological inhibition of neointimal hyperplasia will likely result in further reductions in the incidence if restenosis. The continued attractiveness of percutaneous coronary revascularisation, as an alternative to medical treatment or bypass surgery for patients with coronary artery disease, will depend upon our ability to control the restenotic process. Due to the vast literature on the subject, this review will focus mainly on clinical trials that show the most promise and will highlight those that warrant further investigation.

A direct comparison of tirofiban and abciximab during percutaneous coronary revascularization and stent placement: rationale and design of the TARGET study

BACKGROUND

Trials testing intravenous platelet glycoprotein IIb/IIIa antagonists in the setting of percutaneous coronary revascularization and empirically during acute coronary syndromes have consistently demonstrated a reduction in ischemic events. These trials, however, have varied regarding patient population, type, duration and timing of IIb/IIIa therapy, adjunct therapies, and methods for collection and adjudication of end points. All trials were placebo-controlled, and none involved a direct comparison of IIb/IIIa inhibitors. Whether these agents produce a similar clinical outcome in the contemporary practice of coronary interventions is uncertain.

METHODS AND RESULTS

To evaluate the efficacy of tirofiban in patients undergoing percutaneous revascularization with stent placement, a randomized, multicenter, double-blind, double-dummy, abciximab-controlled study is currently underway. All patients will receive preprocedural clopidogrel, weight-adjusted heparin, and aspirin. In 18 countries, 4750 patients undergoing nonemergency percutaneous coronary revascularization will be studied. The primary end point will be the composite 30-day occurrence of death, myocardial infarction, or urgent target vessel revascularization. Secondary end points will include 6-month death, myocardial infarction, or any myocardial revascularization and 1-year death.

CONCLUSION

This is the first large-scale, head-to-head comparison of 2 established IIb/IIIa inhibitors in interventional cardiology. Enrollment is expected to be complete by mid-2000.

PlA polymorphism of glycoprotein IIIa and risk of adverse events after coronary stent placement

OBJECTIVE

We designed this prospective study to test the hypothesis that platelet antigen (PlA) polymorphism of glycoprotein (GP) IIIa is associated with an increased risk for adverse events after coronary stent placement.

BACKGROUND

Platelets play a central role in arterial thrombosis. The PlA polymorphism of GP IIIa, a constituent of the fibrinogen receptor, may influence the platelet function and, thereby, the early outcome of patients after coronary stent placement.

METHODS

The study included 1,759 consecutive patients with stable or unstable angina and successful coronary stent placement. Platelet antigen genotypes were determined by allele-specific restriction enzyme analysis. The end point of the study was a composite of death, myocardial infarction and urgent revascularization during the first 30 days after stent placement.

RESULTS

The PlA1 genotype of the patients included was: 70.2% were homozygous for platelet antigen 1 (PlA1), 2.6% homozygous for platelet antigen 2 (PlA1), and 27.2% were heterozygous (PlA1/A2). The incidence of the composite end point was 5.5% among PlA2 carriers and 5.4% in homozygous PlA1 subjects (p = 0.94). It was 5.4% in PlA1/A1 patients, 4.8% in PlA1/A2 patients and 13.0% in PlA2A2 patients (p = 0.06). The combined incidence of death or myocardial infarction was 4.3% in PlA1/A1 patients, 4.2% in PlA1/A2 patients and 13.0% in PlA2/A2 patients (p = 0.02).

CONCLUSIONS

The isolated presence of the PlA2 allele in heterozygous patients is not associated with any detectable increase in the risk for an adverse 30-day outcome after coronary stenting. This study suggests also that an increased risk is likely to be present in homozygous carriers of the PlA2 allele, but this should be confirmed in a much larger series of patients.

Glycoprotein Ia gene C807T polymorphism and risk for major adverse cardiac events within the first 30 days after coronary artery stenting

The glycoprotein complex Ia/IIa (GP Ia/IIa) is a major collagen receptor on platelets and other cell types. Recently, linked polymorphisms within the coding region of the GP Ia gene (C807T and G873A) were identified that are related to GP Ia/IIa surface expression. The T807/A873 allele is associated with high expression, whereas the C807/G873 allele is associated with low surface expression of GP Ia/IIa. Subsequently, the T807 allele was found to be associated with coronary and cerebral infarction in younger patients. Platelet adhesion to the vessel wall plays a pivotal role in thrombosis after coronary artery stent placement. The goal of this study was to test whether C807T polymorphism is associated with a higher incidence of thrombotic events following coronary stenting. Consecutive patients treated with coronary stent placement (n = 1797) were genotyped for C807T polymorphism with polymerase chain reaction and allele-specific fluorogenic probes. The composite end point was defined as death, myocardial infarction, or urgent target vessel revascularization within 30 days of stent implantation. The genotype distribution of the study population was CC in 36.5%, CT in 46.7%, and TT in 16.8% of the patients. The incidence of the composite end point was 6.5% in T allele carriers and 5.3% in noncarriers (odds ratio for T allele carriage 1.23 [95% confidence interval, 0.81-1.86],P = .33). After adjusting for other baseline characteristics, the odds ratio for the composite end point was 1.15 (0.76-1.75). Therefore, C807T genotype has no significant influence on the major adverse events occurring after coronary artery stenting.

Glycoprotein Ia gene C807T polymorphism and risk for major adverse cardiac events within the first 30 days after coronary artery stenting

The glycoprotein complex Ia/IIa (GP Ia/IIa) is a major collagen receptor on platelets and other cell types. Recently, linked polymorphisms within the coding region of the GP Ia gene (C807T and G873A) were identified that are related to GP Ia/IIa surface expression. The T807/A873 allele is associated with high expression, whereas the C807/G873 allele is associated with low surface expression of GP Ia/IIa. Subsequently, the T807 allele was found to be associated with coronary and cerebral infarction in younger patients. Platelet adhesion to the vessel wall plays a pivotal role in thrombosis after coronary artery stent placement. The goal of this study was to test whether C807T polymorphism is associated with a higher incidence of thrombotic events following coronary stenting. Consecutive patients treated with coronary stent placement (n = 1797) were genotyped for C807T polymorphism with polymerase chain reaction and allele-specific fluorogenic probes. The composite end point was defined as death, myocardial infarction, or urgent target vessel revascularization within 30 days of stent implantation. The genotype distribution of the study population was CC in 36.5%, CT in 46.7%, and TT in 16.8% of the patients. The incidence of the composite end point was 6.5% in T allele carriers and 5.3% in noncarriers (odds ratio for T allele carriage 1.23 [95% confidence interval, 0.81-1.86],P = .33). After adjusting for other baseline characteristics, the odds ratio for the composite end point was 1.15 (0.76-1.75). Therefore, C807T genotype has no significant influence on the major adverse events occurring after coronary artery stenting.

Increased platelet surface expression of P-selectin and thrombospondin as markers of platelet activation in essential thrombocythaemia

Essential thrombocythaemia (ET) is a clonal myeloproliferative disorder associated with an increased risk of both thromboembolic and bleeding complications. Platelet activation plays a crucial role in the pathogenesis of prethrombotic conditions. The platelet surface expression of p-selectin (CD62p) and thrombospondin (TSP) has been shown to correlate with platelet activation. In the present study, we used a flow cytometric assay to study whether the fraction of platelets expressing CD62p and TSP is increased in newly diagnosed ET. Thirty-four patients with newly diagnosed ET and 25 healthy control subjects were investigated. The proportion of platelets expressing the activation-dependent antigens CD62p and TSP was higher in patients with ET (CD62p: 14.7+/-15.0%; TSP: 12.4+/-9.9%) as compared with healthy control subjects (CD62p: 3.0+/-4.0%; TSP: 3.2+/-3.2%; p< 0.001). In ET, there was a linear correlation between platelet surface expression of CD62p and TSP (p<0.0001, r=0.83). At diagnosis of ET, 20 patients were symptomatic and 14 asymptomatic. Compared with asymptomatic ET patients there was no difference in the expression of CD62p (18.3+/-16.2% vs. 14.5+/-13.4%) and TSP (14.4+/-9.8% vs. 12.8+/-9.5%) in symptomatic ET patients. In conclusion, increased expression of platelet neoantigens is present at the diagnosis of ET. Both activation-dependent epitopes CD62p and TSP are increasingly expressed on the platelet surface in newly diagnosed ET patients.

Ticlopidine and clopidogrel

The thienopyridines ticlopidine and clopidogrel are inhibitors of platelet function in vivo. Their mode of action has not been defined, but it appears that they require conversion to as yet unidentified metabolites that are noncompetitive antagonists of the platelet ADP receptor. Inhibition of platelet aggregation with these compounds is delayed until 24 to 48 hours after administration. Maximum inhibition occurs after 3 to 5 days, and recovery is slow after drug withdrawal. Ticlopidine is effective in preventing cardiovascular events in cerebrovascular, cardiovascular, and peripheral vascular disease, with an efficacy that is similar to aspirin. However, its use is associated with significant and sometimes fatal adverse reactions, specifically neutropenia and bone marrow aplasia. Gastrointestinal side effects and skin rashes are common and result in discontinuation of therapy in up to 10% of patients. Clopidogrel is at least as effective as aspirin in preventing cardiovascular events in patients with a history of vascular disease. It appears to be safer than ticlopidine, although its efficacy in acute coronary syndromes or post-coronary-stent insertion has not been reported. Important outstanding issues are whether clopidogrel adds to the benefit of aspirin and whether the combination of these agents is safe. If so, this combination may become the standard for antithrombotic therapy in cardiovascular disease.

Clopidogrel: the future choice for preventing platelet activation during coronary stenting?

Ticlopidine has become an established therapy in patients with stroke, and during stenting in patients with coronary artery disease. Clopidogrel, another thienopyridine, is a safe and promising alternative, that irreversibly inhibits ADP-induced platelet aggregation, and reduces formation of both arterial and venous thrombi. In a recent, large, well-controlled trial (CAPRIE), clopidogrel has been shown to be superior to aspirin in terms of prevention of ischaemic stroke, myocardial infarction and death in patients with atherosclerotic vascular disease. Clopidogrel provides a safe opportunity to enhance reperfusion when administered during stent placement, by protecting platelets from excessive activation. However, the ability of clopidogrel to be superior to ticlopidine in terms of its antiplatelet properties in the clinical setting of coronary stenting, is unknown. The effects of clopidogrel versus ticlopidine on platelet and endothelial function are yet to be determined and may strongly affect the outcome, benefits, and complications following coronary stent placement. Further clinical trials, well-designed, and carefully conducted, should elucidate possible benefits of clopidogrel during coronary interventions, especially in conjunction with new and aggressive reperfusion techniques. The benefits of clopidogrel in an expanding array of clinical conditions, including myocardial infarction, may be directly related to platelet inhibition. Moreover, marginal clinical benefits, and recently reported severe bleeding events in some patients after oral platelet glycoprotein IIb/IIIa therapy, may advance clopidogrel as a safe, and efficient alternative during coronary interventions. This review summarises the latest, and often confusing data on the effects of thienopyridines on certain haemostatic characteristics in interventional cardiology. 1999 Academic Press.

PlA polymorphism of platelet glycoprotein IIIa and risk of restenosis after coronary stent placement

BACKGROUND

Platelets play a central role in the process of restenosis after percutaneous coronary interventions. A polymorphism of platelet glycoprotein IIIa (PlA) has been associated with a higher risk of coronary thrombosis. We designed this prospective study to test the hypothesis that PlA polymorphism of glycoprotein IIIa is associated with an increased risk for restenosis after coronary stent placement.

METHODS AND RESULTS

The study included 1150 consecutive patients with successful coronary stent placement and 6-month follow-up with coronary angiography. The end point of the study was the incidence of angiographic restenosis (>/=50% diameter stenosis) at follow-up. Of the 1150 patients, 72.5% were homozygous for PlA1, 24.7% were heterozygous (PlA1/A2), and 2.8% were homozygous for PlA2. Patients with the PlA2 allele demonstrated a significantly higher restenosis rate than did those without (47% versus 38%; OR, 1.42; 95% CI, 1.09 to 1.84). The risk was highest in homozygous carriers of PlA2 (53.1% restenosis rate). After adjustment for several clinical and angiographic characteristics, the presence of the PlA2 allele remained a significantly independent risk factor for restenosis (adjusted OR, 1.35; 95% CI, 1.07 to 1.70). The influence of the PlA2 allele on restenosis was stronger in women. Women with PlA2 had a restenosis rate of 52% compared with the 33% incidence among women homozygous for PlA1 (OR, 2.21; 95% CI, 1.27 to 3.85).

CONCLUSIONS

This study showed a significant association between the PlA polymorphism of glycoprotein IIIa and the risk of restenosis after coronary stent placement. The risk was more pronounced in patients homozygous for PlA2 allele and in female patients.

The duration of pretreatment with ticlopidine prior to stenting is associated with the risk of procedure-related non-Q-wave myocardial infarctions

OBJECTIVES

This study sought to determine whether the duration of pretreatment with the adenosine diphosphate receptor antagonist ticlopidine prior to intracoronary stenting is associated with the incidence of procedure-related non-Q-wave myocardial infarctions (MIs).

BACKGROUND

Dual antiplatelet therapy with ticlopidine and aspirin is routinely used with stenting, although ticlopidine is commonly not begun until the day of the procedure. Periprocedural MIs are at least partially platelet-dependent events. As the maximal platelet inhibitory effects of this drug take 2 to 3 days to be realized, we hypothesized that longer treatment prior to stenting would be associated with lower rates of procedure-related MIs.

METHODS

We reviewed outcomes in 175 consecutive patients treated with ticlopidine prior to stenting at the Cleveland Clinic Foundation. Those patients with an elevation in creatine kinase above our laboratory normal (>210 IU/L) with > or =4% MB fraction on routine evaluation were defined as having a non-Q-wave MI. RESULTS. There were 28 patients (16%) who had a non-Q-wave MI. Longer duration of ticlopidine pretreatment was strongly associated with a lower incidence of procedure-related non-Q-wave MIs (duration of pretreatment <1 day, 29% had MI; 1 to 2 days, 14%; > or =3 days, 5%; chi-square for trend=9.6; p=0.002). Ticlopidine pretreatment of > or =3 days was associated with a significant reduction in the risk of non-Q-wave MI (unadjusted odds ratio 0.18, 95% confidence interval=0.04 to 0.78, p=0.01) compared with pretreatment of <3 days.

CONCLUSIONS

Among patients undergoing intracoronary stenting, beginning ticlopidine therapy several days prior to the procedure is associated with a reduced risk of procedural non-Q-wave MIs.

Antiplatelet effect of ticlopidine after coronary stenting

OBJECTIVES

This study sought to investigate the contribution of ticlopidine to the inhibition of platelet activation after coronary stent placement.

BACKGROUND

After coronary stenting, antiplatelet therapy with aspirin and ticlopidine improves stent patency compared with anticoagulation. However, the specific role of ticlopidine has not been elucidated.

METHODS

After successful coronary stent placement, we randomized 22 patients to receive ticlopidine and aspirin (ticlopidine group) and 25 to receive aspirin alone (aspirin group). Surface expression on platelets of the activated fibrinogen receptor and of P-selectin was assessed by flow cytometry.

RESULTS

In the aspirin group the percent of platelets with activated fibrinogen receptors increased between days 1 and 5 (p = 0.001), whereas there were no substantial changes in the ticlopidine group. The percent of P-selectin-positive platelets did not change significantly in the aspirin group but decreased in the ticlopidine group (p = 0.019). At day 5 after the intervention, the percent of platelets with activated fibrinogen receptors in the ticlopidine group was significantly lower (median [interquartile range]: 8.5 [3.1 to 17.8] vs. 18.1 [8.5 to 35.5], p = 0.025), and there was a trend to fewer P-selectin-positive platelets than in the aspirin group (5.8 [3.4 to 9.5] vs. 8.8 [4.0 to 15.8], p = 0.073).

CONCLUSIONS

Combined antiplatelet therapy with ticlopidine plus aspirin is superior to treatment with aspirin alone in suppressing platelet activation after coronary stenting.