Shunnosuke Handa

Cilostazol for prevention of secondary stroke (CSPS 2): an aspirin-controlled, double-blind, randomised non-inferiority trial

BACKGROUND The antiplatelet drug cilostazol is efficacious for prevention of stroke recurrence compared with placebo. We designed the second Cilostazol Stroke Prevention Study (CSPS 2) to establish non-inferiority of cilostazol versus aspirin for prevention of stroke, and to compare the efficacy and safety of cilostazol and aspirin in patients with non-cardioembolic ischaemic stroke. METHODS Patients aged 20-79 years who had had a cerebral infarction within the previous 26 weeks were enrolled at 278 sites in Japan and allocated to receive 100 mg cilostazol twice daily or 81 mg aspirin once daily for 1-5 years. Patients were allocated according to a computer-generated randomisation sequence by means of a dynamic balancing method using patient information obtained at registration. All patients, study personnel, investigators, and the sponsor were masked to treatment allocation. The primary endpoint was the first occurrence of stroke (cerebral infarction, cerebral haemorrhage, or subarachnoid haemorrhage). The predefined margin of non-inferiority was an upper 95% CI limit for the hazard ratio of 1·33. Analyses were by full-analysis set. This trial is registered with ClinicalTrials.gov, number NCT00234065. FINDINGS Between December, 2003, and October, 2006, 2757 patients were enrolled and randomly allocated to receive cilostazol (n=1379) or aspirin (n=1378), of whom 1337 on cilostazol and 1335 on aspirin were included in analyses; mean follow-up was 29 months (SD 16). The primary endpoint occurred at yearly rates of 2·76% (n=82) in the cilostazol group and 3·71% (n=119) in the aspirin group (hazard ratio 0·743, 95% CI 0·564-0·981; p=0·0357). Haemorrhagic events (cerebral haemorrhage, subarachnoid haemorrhage, or haemorrhage requiring hospital admission) occurred in fewer patients on cilostazol (0·77%, n=23) than on aspirin (1·78%, n=57; 0·458, 0·296-0·711; p=0·0004), but headache, diarrhoea, palpitation, dizziness, and tachycardia were more frequent in the cilostazol group than in the aspirin group. INTERPRETATION Cilostazol seems to be non-inferior, and might be superior, to aspirin for prevention of stroke after an ischaemic stroke, and was associated with fewer haemorrhagic events. Therefore, cilostazol could be used for prevention of stroke in patients with non-cardioembolic stroke. FUNDING Otsuka Pharmaceutical.

Platelet Spontaneous Aggregation in Platelet-Rich Plasma Is Increased in Habitual Smokers

Cigarette smoking is a well-known risk factor for atherosclerotic disorders. Several authors have suggested that platelet aggregability is important in smoking-induced vascular injury. When platelet-rich plasma is stirred at 37 degrees C in the absence of chemical stimulants, small aggregates of platelets may be formed, but it was difficult to detect small aggregates by conventional aggregometer using optical density. Recent technological advances have made it possible to detect small aggregates by using a newly developed assay system that employs laser light scattering. In the present study, we attempted to measure platelet aggregation by this method, using laser light scattering in 54 nonsmoking healthy males and 51 healthy male habitual smokers who were age matched. In smokers, blood was obtained after 10 hours of smoking abstinence. No significant difference in platelet aggregation was induced by 1 microM or 5 microM of ADP between smokers and nonsmokers. In smokers, plasma fibrinogen levels and the number of small aggregates formed in the absence of chemical stimulants was significantly higher than in nonsmokers. Small aggregates formed in the absence of stimulants correlated positively with the concentrations of von Willebrand factor (vWF) antigen (r=0.2654, p<0.01) and of fibrinogen (r=0.2834, p<0.01). The formation of these small aggregates was inhibited by monoclonal antibody against GPIIb/IIIa blocking fibrinogen binding to GPIIb/IIIa but not inhibited at all by monoclonal antibody against GPIb blocking vWF binding to GPIb. From these results, enhanced platelet aggregability in smokers was confirmed, and it was suggested that GPIIb/IIIa is concerned in platelet spontaneous aggregation, although vWF may not directly influence on the platelet spontaneous aggregation. Since the mechanism of spontaneous aggregation and the effect of increased spontaneous aggregability on the progression of atherosclerosis remains unclear, further study was considered necessary.

Involvement of Glycoprotein VI in Platelet Thrombus Formation on Both Collagen and von Willebrand Factor Surfaces Under Flow Conditions

Background—We studied the role of glycoprotein (GP) VI in platelet adhesion and thrombus formation on the immobilized collagen and von Willebrand factor (vWF) surface under flow conditions. Methods and Results—Whole blood obtained from 2 patients with GP VI–deficient platelets and the effects of the Fab of anti–GP VI antibody (Fab/anti–GP VI) were tested. Blood containing platelets rendered fluorescent by mepacrine was perfused on immobilized type I collagen or vWF under controlled wall shear rate. Platelet adhesion and thrombus formation were detected by epifluorescent videomicroscopy. The percentage of surface coverage by the platelets was calculated. Fc receptor &ggr;-chain and spleen tyrosine kinase (Syk) were immunoprecipitated from the lysate of platelets stimulated by vWF plus ristocetin and then analyzed by antiphosphotyrosine immunoblotting. No platelet attachment was seen on the surface of collagen even after 9 minutes of perfusion of blood at relatively low (100 s−1) or high (1500 s−1) wall shear rate, either in the case of blood containing GP VI–deficient platelets or in the presence of Fab/anti–GP VI, whereas significant platelet thrombus formation was noted after control blood perfusion. Such interference with the actions of GP VI also reduced firm platelet adhesion on immobilized vWF. vWF-induced tyrosine phosphorylation of GP VI–associated Fc receptor &ggr;-chain followed by Syk activation occurred in normal platelets, but little activation of Syk occurred in GP VI–deficient platelets. Conclusions—GP VI plays crucial roles in platelet thrombus formation on the surface of collagen under flow conditions in humans and is also involved in the process of firm platelet adhesion on the surface of vWF.

Preinfarction angina as a major predictor of left ventricular function and long-term prognosis after a first Q wave myocardial infarction

OBJECTIVES The purpose of this study was to assess the prognostic significance of preinfarction angina after a first Q wave myocardial infarction. Patients with anterior or inferior myocardial infarction were compared. BACKGROUND The effect of preinfarction angina on prognosis after anterior and inferior myocardial infarction remains unclear. METHODS A total of 291 patients with a first Q wave anterior (n = 171) or inferior (n = 120) myocardial infarction were examined to assess the effect of preinfarction angina on short- and long-term prognosis. The relation between predischarge left ventriculographic findings and preinfarction angina was also examined. RESULTS The presence of preinfarction angina was associated with lower peak creatine kinase activity, a lower in-hospital incidence of sustained ventricular tachycardia and fibrillation and a lower incidence of pump failure and cardiac mortality in patients with either anterior or inferior infarction. Among patients with anterior infarction, preinfarction angina was associated with a lower incidence of cardiac rupture and less need for readmission for heart failure within 1 year after the onset of infarction. In this subgroup it was also associated with a higher ejection fraction, a smaller end-diastolic volume and a lower incidence of aneurysm formation noted on ventriculography during convalescence. In patients with inferior infarction, these variables did not differ significantly in the presence or absence of preinfarction angina. Multivariate analysis confirmed that the presence of preinfarction angina was an independent predictor of development of ventricular aneurysm, late phase heart failure and 1-year cardiac mortality. CONCLUSIONS The presence of preinfarction angina has a favorable effect on infarct expansion and late phase left ventricular function, especially in patients with anterior myocardial infarction. The mechanisms responsible for this phenomenon are not known but may be secondary to limitations of infarct size through unidentified mechanisms other than collateralization (e.g., ischemic preconditioning).

Functional Significance of Adenosine 5′-Diphosphate Receptor (P2Y12) in Platelet Activation Initiated by Binding of von Willebrand Factor to Platelet GP Ibα Induced by Conditions of High Shear Rate

Background—The role of the adenosine 5′-diphosphate receptor P2Y12 in platelet activation initiated by the von Willebrand factor (VWF)–GP Ib&agr; interaction under high shear rate was investigated. Methods and Results—Blood samples were obtained from 11 donors. Shear-induced platelet aggregation was detected by optically modified cone-plate viscometer. Shear-induced VWF binding, P-selectin expression, and microparticle release were detected by flow cytometry. Platelet interaction with immobilized VWF was also investigated by parallel-plate flow chamber equipped with epifluorescent videomicroscopy. Effects of a selective P2Y12 antagonist AR-C69931 MX were tested. AR-C69931 MX inhibited shear-induced platelet aggregation in a dose-dependent manner, achieving the maximum inhibition at 100 nmol/L. The extent of aggregation after exposure to a shear rate of 10 800 s−1 for 6 minutes in the presence of 100 nmol/L AR-C69931 MX was 32.4±8.2% (mean±SD), which was significantly lower than the value in the controls of 69.7±9.6% (P <0.01). The inhibiting effects of AR-C69931 MX were reversed by exogenous addition of adenosine 5′-diphosphate. Shear-induced VWF binding and P-selectin surface translocation, which occurred in 4696±911 and 5964±784, respectively, of 10 000 measured platelets, was also inhibited by AR-C69931 MX (100 nmol/L) to 1948±528 and 2797±718, respectively (P =0.0018 and P =0.0009). Microparticle release was similarly inhibited. In a flow chamber experiment, firm platelet attachment on immobilized VWF was inhibited by AR-C69931 MX, whereas transient interaction was not influenced. All the above reactions were completely inhibited by blocking VWF–GP Ib&agr; interaction. Conclusions—We have demonstrated that the stimulation of P2Y12 is involved in platelet activation initiated by the binding of VWF to GP Ib&agr; induced by a high shear rate.

Enhanced Shear-Induced Platelet Aggregation in Acute Myocardial Infarction

BACKGROUND Experiments under controlled flow conditions indicate that the binding of von Willebrand factor (vWF) to platelet glycoprotein (GP) Ibalpha and integrin alphaIIbbeta3 (GP IIb/IIIa complex) is crucial for aggregation at elevated shear rates. We have tested how the plasma of patients with acute myocardial infarction affects this process. METHODS AND RESULTS Citrated plasma was obtained from 18 patients with acute myocardial infarction within 6 hours from the onset of symptoms and from 26 control subjects with chest pain syndrome without evidence of ischemia. Aggregation of normal platelets at high shear rates was significantly greater in the presence of patient than control plasma and was inhibited by both anti-GP Ibalpha and anti-alphaIIbbeta3 monoclonal antibodies. The observed values (mean+/-SD) were 47.6+/-17.8% versus 30.1+/-9.9% at 10 800 s-1 (P<0.01) and 32.9+/-14.1% versus 17.5+/-9.5% at 7200 s-1 (P<0.01), respectively, and were positively correlated with plasma vWF antigen levels and ristocetin cofactor activities. In contrast, at the lower shear rate of 1200 s-1, aggregation was similar in the presence of control or patient plasma and was not inhibited by the anti-GP Ibalpha antibody. Both vWF antigen and platelet aggregation decreased 2 weeks after the onset of myocardial infarction. CONCLUSIONS Shear-induced platelet aggregation is enhanced in plasma in the presence of acute myocardial infarction, apparently as a result of increased vWF concentration. This may contribute to the onset of acute coronary artery thrombosis and early reocclusion after reperfusion treatment.

Sarpogrelate-Aspirin Comparative Clinical Study for Efficacy and Safety in Secondary Prevention of Cerebral Infarction (S-ACCESS): A randomized, double-blind, aspirin-controlled trial.

Background and Purpose— The antiplatelet agent sarpogrelate is a selective inhibitor of 5-hydroxytryptamine receptors. The purpose of this study was to compare the efficacy and safety of sarpogrelate with those of aspirin in Japanese ischemic stroke patients. Methods— In total, 1510 patients with recent cerebral infarction (1 week to 6 months after onset) were randomly assigned to receive either sarpogrelate (100 mg TID) or aspirin (81 mg/d). Mean follow-up period was 1.59 years. The primary efficacy end point was recurrence of cerebral infarction. Clusters of serious vascular events (stroke, acute coronary syndrome, or vascular event–related death) were selected as secondary end points. The aim of the primary efficacy analysis was to demonstrate the noninferiority of sarpogrelate with respect to aspirin, with the criterion that the upper limit of the 95% CI of the hazard ratio (sarpogrelate vs aspirin) for recurrence of cerebral infarction should not exceed 1.33. Results— Cerebral infarction recurred in 72 patients (6.09%/y) in the sarpogrelate group and in 58 (4.86%/y) in the aspirin group (hazard ratio=1.25; 95% CI, 0.89 to 1.77; P=0.19). A serious vascular event occurred in 90 (7.61%/y) and in 85 (7.12%/y) patients, respectively (hazard ratio=1.07; 95% CI, 0.80 to 1.44; P=0.65). The overall incidences of bleeding events were 89 (11.9%) and 131 (17.3%), respectively (P<0.01). Conclusions— Sarpogrelate was not noninferior to aspirin for prevention of recurrence of cerebral infarction. Bleeding events were significantly fewer with sarpogrelate than aspirin. The effect of aspirin in Japanese patients was similar to that in Western studies.

Different effects of various anti‐GPIIb‐IIIa agents on shear‐induced platelet activation and expression of procoagulant activity

Summary.  Inhibitors of the platelet glycoprotein (GP)IIb‐IIIa receptor (integrin αIIbβ3) reduce acute thrombotic events in patients with coronary artery disease. To characterize the mechanism of action of these drugs, we evaluated the effects of different GPIIb‐IIIa antagonists on shear‐induced platelet aggregation, activation, and the expression of procoagulant activity. Samples of platelet‐rich plasma from 16 volunteers were exposed to the shear rate of 10 800 s−1 for 6 min in an optically modified cone‐plate viscometer. Abciximab, tirofiban and eptifibatide inhibited aggregation to a similar extent (mean ± SD: 74.1 ± 8.5%, 69.5 ± 13.6%, 65.6 ± 17.0%, respectively), but only abciximab inhibited significantly microparticle release associated with shear‐induced platelet activation (64.4 ± 13.6%, P = 2.2 × 10−7; tirofiban = 20.0 ± 23.4%; eptifibatide = 23.9 ± 17.4%). P‐selectin platelet surface translocation was also strongly inhibited by abciximab, weakly by eptifibatide, but not by tirofiban. The addition of anti‐αvβ3 to tirofiban enhanced the inhibiting effects on shear‐induced P‐selectin translocation and microparticle release. Shearing of platelet‐rich plasma shortened the re‐calcification clotting time after addition of kaolin from 106.9 ± 14.3 to 94.2 ± 10.7 s (mean ± SD; P = 0.0013). This effect, which is mediated by the appearance of procoagulant phospholipids on the surface of sheared platelets and microparticles, was prevented by abciximab and by the combination of tirofiban and anti‐αvβ3, but not by tirofiban alone or eptifibatide. The ability to inhibit shear‐induced platelet activation, as evidenced by microparticle release and P‐selectin surface translocation as well as the expression of procoagulant activity, differentiates the effects of anti‐GPIIb‐IIIa agents, which may explain the distinct antithrombotic efficacy of the agents.

Epinephrine augments von Willebrand factor-dependent shear-induced platelet aggregation.

BackgroundShear-induced platelet aggregation (SIPA) is an important mechanism in thrombogenesis. von Willebrand factor (vWF) binding to platelet glycoprotein lb (GP Ib) has been found to be crucial for platelet aggregation under the high shear force probably generated in stenosed coronary artery. The physiological significance of vWF-dependent SIPA has not been clarified. Methods and ResultsBlood samples were collected from 23 normal volunteers. SIPA was continuously monitored using a modified cone-plate viscometer adapted for measuring the transmitted light intensity of the material. The effects of low concentrations of epinephrine, ADP, and collagen on SIPA under both low shear (12 dyne/cm2) and high shear (108 dyne/cm2) force were investigated. All agonists tested enhanced SIPA under low shear force, whereas only epinephrine augmented SIPA under high shear force. The maximum extents of SIPA under high shear force in the absence and presence of epinephrine (10 ng/ml) were 37.9 ± 11.5% and 59.7 ± 13.9%, respectively. The antagonist of the a2-adrenergic receptor yohimbine (1,μg/ml) antagonized the effects of epinephrine. The monoclonal antibody NMC-4 against vWF, which was shown to inhibit its binding to GP Ib, completely abolished SIPA under high shear force, even in the presence of epinephrine. However, this antibody only partially inhibited SIPA under low shear force. ConclusionsOur findings suggest that epinephrine is the agonist that enhances SIPA mediated by vWF through its specific receptor. This may be clinically important because occlusion of the coronary artery often occurs in stenosed atherosclerotic vessels under sympathetic stimulation.

Platelets, after Exposure to a High Shear Stress, Induce IL-10-Producing, Mature Dendritic Cells In Vitro

There is evidence for immune system involvement in atherogenesis. In the present study the effect of platelets on dendritic cells (DC), an important immunologic regulator, was examined in vitro. Platelet-rich plasma, after exposure to shear stress, was added to human monocyte-derived immature DC, which were then examined for surface Ag expression, allogeneic T lymphocyte stimulatory activity, and cytokine production. After exposure, the number of anti-CD40 ligand (anti-CD40L) and anti-P-selectin IgG molecules bound per platelet was increased. These activated platelets induced DC maturation, as revealed by significant up-regulation of CD83, CD80, and CD86 Ags. The addition of platelets in the presence of IFN-γ plus LPS significantly enhanced IL-10 production from immature DC. After platelet addition, mature DC provoked a significant proliferation of allogeneic naive T lymphocytes. These activated T cells showed lower IFN-γ production than those stimulated by LPS- and IFN-γ-treated DC. CD40L on the platelet surface was not involved in maturation of DC, as mAb to CD40L failed to block maturation. The effect of platelets was observed even if platelets and DC were separated using large pore-sized membranes or when platelets were depleted from plasma by centrifugation. Furthermore, it was abrogated after the depletion of protein fraction. Thus, soluble protein factors excreted from activated platelets contribute to IL-10-producing DC maturation.