Antiplatelet therapy--Part I.

We summarize current information about aspirin and other antiplatelet drugs in patients with cardiac and vascular disease. For each indication, we briefly summarize the rationale for the use of antiplatelet therapy and describe the findings of relevant clinical trials. We propose recommendations for the use of these agents in clinical practice. Part I covers the use of antiplatelet therapy for the primary and secondary prevention of myocardial infarction, coronary thrombolysis, unstable and chronic stable angina, and coronary artery-saphenous vein bypass grafts. In part II we review the use of antiplatelet agents in coronary angioplasty, atrial fibrillation, artificial cardiac valves, stroke, and peripheral vascular disease.     

Anticoagulant and antiplatelet agents: their clinical and device application(s) together with usages to engineer surfaces

An essential aspect of the treatment of patients with cardiovascular disease is the use of anticoagulant and antiplatelet agents for the prevention of further ischaemic events and vascular death resulting from thrombosis. Aspirin and heparin have been the standard therapy for the management of such conditions to date. Recently, numerous more potent platelet inhibitors together with anticoagulant agents have been developed and tested in randomized clinical trials. This article reviews the current state of the art of antiplatelet and anticoagulant therapy in light of its potential clinical efficacy. It then focuses on the usages of these agents in order to improve the performance of clinical devices such as balloon catheters, coronary stents, and femoropopliteal bypass grafting and extra corporeal circuits for cardiopulmonary bypass. The article then goes on to look at the usage of these agents more specifically heparin, heparan, hirudin, and coumarin in the development of more biocompatible scaffolds for tissue engineering.     

Platelet aggregation and antiplatelet agents in acute coronary syndromes

Antiplatelet agents are the cornerstone therapy of acute coronary syndromes. In the setting of ST elevation myocardial infarction, antiplatelet therapy prevent the prothrombotic effect of reperfusion therapy including thrombolysis and primary percutaneous coronary intervention. In non ST-elevation acute coronary syndromes, antiplatelet therapy prevent s complete coronary thrombotic occlusion and therefore the occurrence of ST elevation myocardial infarction. Antiplatelet agent benefit is related to the patient's risk profile. It is well established that combined antiplatelet therapy is the most effective in high risk patients. Several important issues have to be faced including the identification of non responders, dose adjustment and the management of temporary interruption of antiplatelet agents in stable coronary artery disease patients.     

Percutaneous coronary intervention with adjunctive abciximab and clopidogrel in a patient with chronic idiopathic thrombocytopaenic purpura

The use of the antiplatelet agents abciximab and clopidogrel is now accepted therapy in percutaneous coronary intervention. We present a case in which these agents were used in a patient with idiopathic thrombocytopaenic purpura and a platelet count of 40x10(9)/l undergoing primary multivessel coronary stenting. This case shows that unstable coronary syndromes can occur in patients with thrombocytopaenia and that antiplatelet agents may be used safely in this context.     

Regenerating cardiac cells: insights from the bench and the clinic

A major challenge in cardiovascular regenerative medicine is the development of novel therapeutic strategies to restore the function of cardiac muscle in the failing heart. The heart has historically been regarded as a terminally differentiated organ that does not have the potential to regenerate. This concept has been updated by the discovery of cardiac stem and progenitor cells that reside in the adult mammalian heart. Whereas diverse types of adult cardiac stem or progenitor cells have been described, we still do not know whether these cells share a common origin. A better understanding of the physiology of cardiac stem and progenitor cells should advance the successful use of regenerative medicine as a viable therapy for heart disease. In this review, we summarize current knowledge of the various adult cardiac stem and progenitor cell types that have been discovered. We also review clinical trials presently being undertaken with adult stem cells to repair the injured myocardium in patients with coronary artery disease.     

Collaborative overview of randomised trials of antiplatelet therapy--II: Maintenance of vascular graft or arterial patency by antiplatelet therapy. Antiplatelet Trialists' Collaboration.

OBJECTIVE--To determine the efficacy of antiplatelet therapy in maintaining vascular patency in various categories of patients. DESIGN--Overviews of 46 randomised trials of antiplatelet therapy versus control and 14 randomised trials comparing one antiplatelet regimen with another. SETTING--Randomised trials that could have been available by March 1990 and in which vascular graft or arterial patency was to be studied systematically. SUBJECTS--About 8000 patients at varying degrees of risk of vascular occlusion (by virtue of disease or of having some vascular procedure) were in trials of antiplatelet therapy versus control and 4000 such patients were in trials directly comparing different antiplatelet regimens. RESULTS--Overall, antiplatelet therapy produced a highly significant (2P < 0.0001) reduction in vascular occlusion, with similar proportional reductions in several different types of patients. Hence the absolute reductions tended to be largest among patients at highest risk of occlusion, with smaller but still significant absolute reductions among lower risk patients. The proportions of patients with confirmed occlusion among those allocated antiplatelet therapy versus appropriately adjusted control proportions (and mean scheduled treatment durations and net absolute benefits) were: (a) among about 4000 patients with coronary artery grafts, 21% antiplatelet therapy v 30% control (seven month benefit about 90 patients protected per 1000 allocated antiplatelet therapy (2P < 0.00001)); (b) among about 800 patients after coronary angioplasty, 4% antiplatelet therapy v 8% control (six month benefit about 40/1000 (2P = 0.02)); (c) among about 3000 patients with peripheral artery procedures or disease, 16% antiplatelet therapy v 25% control (19 month benefit about 90/1000 (2P < 0.00001)); (d) among about 400 renal patients with a shunt or fistula placed for haemodialysis access, 17% antiplatelet therapy v 39% control (two month benefit about 200/1000 (2P < 0.00001)). Indirect comparisons between the effects of starting treatment before these vascular procedures and starting soon after them indicated similar sized benefits. As well as preventing subclinical occlusion, antiplatelet therapy produced a significant (2P = 0.002) reduction of about one quarter in the odds of suffering a "vascular event" (non-fatal myocardial infarction, non-fatal stroke, or vascular death). Various antiplatelet regimens (chiefly aspirin alone or aspirin plus dipyridamole) were studied but there was no significant evidence of differences between their effects on arterial occlusion or vascular events. Data on bleeding were incomplete but no large excess with antiplatelet therapy was apparent. CONCLUSION--Antiplatelet therapy (chiefly aspirin alone or aspirin plus dipyridamole) greatly reduces the risk of vascular occlusion in a wide range of patients at high risk of this complication. Further studies are required to determine exactly when treatment should start (to limit any perioperative bleeding while still preventing most early occlusion) and for how long it should be continued.     

2型糖尿病的系统性血管保护治疗策略

在最新研究发现的系统性血管保护的优化治疗策略表明,血管损伤机制与胰岛素抵抗、糖尿病肾病及外周动脉疾病(PAD)的发病机理相关。胰岛素抵抗机制在血管损伤方面主要表现为大血管和微血管病变。系统性动脉硬化性疾病的及时诊断和干预是至关重要的。并且,治疗方面不仅仅是改善现有疾病状况,也应注意减少心血管事件的风险。这些努力有助于降低心血管事件的风险和死亡率。PAD的治疗包括药物治疗、血管内治疗和血管重建,以及运动疗法。经典治疗药物包括血管舒张剂,如贝前列素和抗血小板药物。值得注意的是,贝前列素除血管舒张活性外还有几个其他治疗作用,包括保护血管内皮、抗血小板和抗炎作用。最近的前期临床研究表明,贝前列素不仅通过其舒张血管活性改善四肢缺血,同时改善了影响血管内皮功能的胰岛素抵抗。贝列前素的应用,在早期疾病阶段维持血管内皮功能,减少血管事件的发生率,发挥其系统性血管保护作用。这样,贝列前素最终将有助于改善患者的生存质量并可能增加PAD患者的寿命。     

Plateletworks: a novel point of care platelet function screen

Platelet function is critically important in the acute-care settings of cardiopulmonary bypass surgery and percutaneous coronary intervention, which are commonly associated with the adverse vascular events of hemorrhage and thrombosis, respectively. To improve outcomes, it has been suggested that patients should be screened for platelet count and function periprocedurally, and therapeutic intervention including the possible use of thrombolytics and adequate anticoagulation or administration of antiplatelet agents, should be utilized. Antiplatelet therapy including aspirin (acetylsalicylic acid), the thienopyridines (clopidopgrel), and parenteral anti-glycoprotein (GP) IIb/IIIa agents (abciximab, tirofiban, and eptifibatide) are recognized as clinically important in patients at risk of developing thrombotic events. Recently, it has been recognized that empiric therapeutic administration of these agents may be suboptimal in clinical environments because of interpatient variability with regard to platelet count, platelet response, receptor concentration on the platelet, and other factors. Hence there is a clinical need to monitor such therapies on an individual basis. Traditional platelet tests including light transmission aggregometry (LTA) are inconvenient for acute diagnostic testing because of the complexity of the test and the requirement for specialty training. Hence, 'near-patient' test systems have recently been introduced. Plateletworks is an in vitro diagnostic, point-of-care test platform that has demonstrated utility in monitoring platelet response to all current antiplatelet agents including aspirin and clopidogrel.     

Early antiplatelet therapy in coronary artery bypass grafting: a calculated benefit

Studies have demonstrated that antagonists of platelet activity, including aspirin and clopidogrel, reduce the risk of major adverse events in patients with acute coronary syndromes. Although antiplatelet agents also convey an increased risk of bleeding, particularly in patients proceeding to coronary artery bypass graft surgery, in most cases, the benefits of early initiation of antiplatelet therapy outweigh the risks. The purpose of this review is to distinguish perceived and actual risk versus the benefit associated with early antiplatelet therapy to help clinicians make informed decisions on using these agents in an acute setting where patients may require coronary artery bypass grafting.     

Collaborative meta-analysis of randomised trials of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high risk patients

ObjectiveTo determine the effects of antiplatelet therapy among patients at high risk of occlusive vascular events.DesignCollaborative meta-analyses (systematic overviews).ResultsOverall, among these high risk patients, allocation to antiplatelet therapy reduced the combined outcome of any serious vascular event by about one quarter; non-fatal myocardial infarction was reduced by one third, non-fatal stroke by one quarter, and vascular mortality by one sixth (with no apparent adverse effect on other deaths). Absolute reductions in the risk of having a serious vascular event were 36 (SE 5) per 1000 treated for two years among patients with previous myocardial infarction; 38 (5) per 1000 patients treated for one month among patients with acute myocardial infarction; 36 (6) per 1000 treated for two years among those with previous stroke or transient ischaemic attack; 9 (3) per 1000 treated for three weeks among those with acute stroke; and 22 (3) per 1000 treated for two years among other high risk patients (with separately significant results for those with stable angina (P=0.0005), peripheral arterial disease (P=0.004), and atrial fibrillation (P=0.01)). In each of these high risk categories, the absolute benefits substantially outweighed the absolute risks of major extracranial bleeding. Aspirin was the most widely studied antiplatelet drug, with doses of 75-150 mg daily at least as effective as higher daily doses. The effects of doses lower than 75 mg daily were less certain. Clopidogrel reduced serious vascular events by 10% (4%) compared with aspirin, which was similar to the 12% (7%) reduction observed with its analogue ticlopidine. Addition of dipyridamole to aspirin produced no significant further reduction in vascular events compared with aspirin alone. Among patients at high risk of immediate coronary occlusion, short term addition of an intravenous glycoprotein IIb/IIIa antagonist to aspirin prevented a further 20 (4) vascular events per 1000 (P<0.0001) but caused 23 major (but rarely fatal) extracranial bleeds per 1000.ConclusionsAspirin (or another oral antiplatelet drug) is protective in most types of patient at increased risk of occlusive vascular events, including those with an acute myocardial infarction or ischaemic stroke, unstable or stable angina, previous myocardial infarction, stroke or cerebral ischaemia, peripheral arterial disease, or atrial fibrillation. Low dose aspirin (75-150 mg daily) is an effective antiplatelet regimen for long term use, but in acute settings an initial loading dose of at least 150 mg aspirin may be required. Adding a second antiplatelet drug to aspirin may produce additional benefits in some clinical circumstances, but more research into this strategy is needed.

What is already known on this topic

Antiplatelet therapy is effective for short term treatment of patients with suspected acute myocardial infarction and unstable anginaLong term treatment is beneficial for patients who have had a myocardial infarction, stroke, or transient ischaemic attackDaily aspirin doses of 75-325 mg are effective

What this study adds

Antiplatelet therapy protects against vascular events among patients with stable angina, intermittent claudication, and (if oral anticoagulants are unsuitable) atrial fibrillationAntiplatelet therapy can be started promptly during acute presumed ischaemic stroke and continued long termDaily aspirin doses of 75-150 mg seem to be as effective as higher doses for long term treatments (and clopidrogel is an appropriate alternative for patients with a contraindication to aspirin)Short term addition of a glycoprotein IIb/IIIa antagonist to aspirin prevents vascular events in patients having percutaneous coronary intervention and those with unstable angina but causes increased bleeding     

A Simplified Technique for Postmortem Evaluation of Coronary Arteries

The growth of complex diagnostic and therapeutic technologies in the clinical management of cardiovascular diseases has mandated a more comprehensive and detailed analysis of cases which reach the pathology laboratory. This report describes in detail the relatively simple techniques and protocol which we have employed for postmortem evaluation of the coronary vascular bed and myocardium. The key elements include the use of a pigmented gelatin mass containing radiopaque material (Barosperse), proper injection technique with simultaneous filling of the main coronary vessels at identical pressures, postmortem arteriography, cardiac dissection, and histologic confirmation of coronary and myocardial lesions. Three cases with sharply differing cardiac diseases are presented to illustrate the kind of information which may be obtained with this approach. Our experience in terms of frequency and distribution of occlusive coronary vascular disease and the relationship to age and sex has been summarized. Significant disease (> 75% lumenal obstruction) was identified angiographically and confirmed by dissection in 46 of 57 cases of clinically suspected disease. None of six hearts from patients without clinical evidence for cardiovascular disease demonstrated actual or angiographically false-positive occlusive coronary disease. It is suggested that a more detailed analysis of the coronary vascular bed can be accomplished in the pathology laboratory with this relatively simple approach and that important information bearing on clinical management can be reliably obtained.     

阿司匹林、氯吡格雷及西洛他唑预防和治疗老年冠脉支架植入术后血小板高反应性的临床效果观察

目的:探讨阿司匹林、氯吡格雷及西洛他唑预防和治疗老年冠脉支架植入术后血小板高反应性的临床效果。方法:选择60例拟行冠脉支架植入术的老年患者,随机地分为加用或未加用200 mg西洛他唑负荷剂量组。术前、术后24小时及术后30天时检测和比较各组患者的血小板聚集功能。结果:三联抗血小板治疗组的PRU、ARU及P2Y12%inhibition值均较两联抗血小板治疗组显著降低,差异具有统计学意义(P0.05)。三联抗血小板治疗和两联负荷剂量的抗血小板治疗的给药时间(第一次投药至冠脉介入治疗的时间间隔)分别为10.2小时(95%可信区间:7.4-13.1小时)和7.8小时(95%可信区间:4.5-11.2小时),三联抗血小板治疗组术前HPPR(83.3%和46.7%,P=0.003)、术后24小时(36.7%和13.3%,P=0.018)及术后30天HPPR(40.0%和16.7%,P=0.045)的发生率均较两联抗血小板治疗组明显降低(P0.05)。在术后30天的随访观察期间,两联抗血小板治疗组2例患者出现支架内血栓,并进行了血运重建术;无1例心源性死亡、缺血性卒中及出血性并发症的发生。两组次要终点的发生率比较无显著性差异(P0.05)。结论:在两联抗血小板聚集治疗的基础上附加200 mg西洛他唑可显著降低冠状动脉支架植入术后血小板的高反应性。     

Optimal pharmacological therapy in ST-elevation myocardial infarction—a review

Antithrombotic therapy is an essential component in the optimisation of clinical outcomes in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention. There are currently several intravenous anticoagulant drugs available for primary percutaneous coronary intervention. Dual antiplatelet therapy comprising aspirin and P2Y12 inhibitor represents the cornerstone treatment for STEMI. However, these effective treatment strategies may be associated with bleeding complications. Compared with clopidogrel, prasugrel and ticagrelor are more potent and predictable, which translates into better clinical outcomes. Therefore, these agents are the first-line treatment in primary percutaneous coronary intervention. However, patients can still experience adverse ischaemic events, which might be in part attributed to alternative pathways triggering thrombosis. In this review, we provide a critical and updated review of currently available antithrombotic therapies used in patients with STEMI undergoing primary PCI. Finding a balance that minimises both thrombotic and bleeding risk is difficult, but crucial. Further randomised trials for this optimal balance are needed.     

In-hospital resource utilization in coronary angioplasty: the impact of increased coronary stenting rates and antiplatelet therapy

BACKGROUND: The technique of coronary stenting has evolved over recent years, with improved stent technology and effective antiplatelet therapies to prevent stent thrombosis. In Europe, reductions in stent and equipment costs have resulted from increased market competition. The impact of these changes on the in-hospital procedural cost of percutaneous coronary intervention (PCI) in the current clinical setting is not known. METHODS: We compared the initial equipment and pharmaceutical costs of one hundred consecutive, unselected patients undergoing PCI in 1998 to a similar population who underwent PCI in 1994. RESULTS: Similar patient characteristics were noted, yet more complex disease (multivessel, AHA type B2/C lesions) was treated in the 1998 population. The stent utilization rate (83% vs 15%, p < 0.0001) and use of intravenous and/or oral antiplatelet therapy (abciximab, ticlopidine) (64% vs 4%, p < 0.0001) was higher in 1998. Similar angiographic success was achieved in each group with low complication rates. Mean hospital stay was reduced in the 1998 group (2.6 +/- 2.8 vs 4.3 +/- 3.8 days, p < 0.001). Repeat PCI was required more frequently in the 1994 population (26% vs 9%, p < 0.001). Overall there was no significant difference in the mean equipment cost between the two groups ( pound 1551 vs pound 1422, p=ns). CONCLUSION: Despite the widespread use of coronary stenting and antiplatelet therapies there appears to be no difference in current in-hospital equipment costs for PCI compared to 1994. Improved clinical outcomes in the 1998 population imply that stenting is a cost-effective therapy.     

Cardiac evaluation and risk reduction in patients undergoing major vascular operations.

Occult coronary artery disease often accompanies symptomatic peripheral vascular disease and has an important effect on survival. Most perioperative and late fatalities after peripheral vascular operations are due to cardiac causes. Noninvasive cardiac testing can identify patients at increased risk for postoperative cardiac complications, although controversy exists regarding the optimal preoperative evaluation. Risk reduction strategies for patients known to be at high risk are also controversial. Some authors advocate coronary revascularization with coronary artery bypass grafting or percutaneous transluminal coronary angioplasty before the vascular procedure. Others believe that the combined morbidity and mortality of 2 operations exceed those of a peripheral vascular operation performed with aggressive monitoring and medical therapy. Continuous electrocardiographic monitoring after an operation has identified silent myocardial ischemia as a powerful predictor of cardiac complications. Ongoing research is likely to provide insights into the pathogenesis of postoperative cardiac complications and may lead to specific therapeutic interventions. Few prospective studies have been done in this area, and the threshold for preoperative and postoperative intervention is unknown. I review the literature and present an algorithm to guide cardiac testing and risk reduction in patients undergoing elective vascular surgical procedures.     

Urotensin-II and cardiovascular remodeling

Urotensin-II (U-II), a cyclic undecapeptide, and its receptor, UT, have been linked to vascular and cardiac remodeling. In patients with coronary artery disease (CAD), it has been shown that U-II plasma levels are significantly greater than in normal patients and the severity of the disease is increased proportionally to the U-II plasma levels. We showed that U-II protein and mRNA levels were significantly elevated in the arteries of patients with coronary atherosclerosis in comparison to healthy arteries. We observed U-II expression in endothelial cells, foam cells, and myointimal and medial vSMCs of atherosclerotic human coronary arteries. Recent studies have demonstrated that U-II acts in synergy with mildly oxidized LDL inducing vascular smooth muscle cell (vSMC) proliferation. Additionally, U-II has been shown to induce cardiac fibrosis and cardiomyocyte hypertrophy leading to cardiac remodeling. When using a selective U-II antagonist, SB-611812, we demonstrated a decrease in cardiac dysfunction including a reduction in cardiomyocyte hypertrophy and cardiac fibrosis. These findings suggest that U-II is undoubtedly a potential therapeutic target in treating cardiovascular remodeling.     

Synthesis, antiplatelet and antithrombotic activities of new 2-substituted benzopyrano[4,3-d]pyrimidin-4-cycloamines and 4-amino/cycloamino-benzopyrano[4,3-d]pyrimidin-5-ones

Atherothrombotic coronary artery disease, associated with deep vein thrombosis, is one of the most common causes of death worldwide. Recently, antiplatelet combination therapy using agents with different mechanisms of action, such as aspirin, dipyridamole, and thienopyridines, seems to be an attractive preventive approach. Moreover, several large, randomized clinical trials support combination therapy with aspirin plus warfarin in high-risk patients with atherosclerotic heart disease. Our research on the benzopyrano[4,3-d]pyrimidine system gave rise to the synthesis of a large number of compounds endowed with in vitro anti-aggregating activity. Several SAR considerations suggest that the benzopyranopyrimidine system is an appropriate scaffold to obtain molecules that are able to act simultaneously in different pathways of aggregation. Now, we report the synthesis of new 2-substituted benzopyrano[4,3-d]pyrimidin-4-cycloamines and 4-amino/cycloamino-benzopyrano[4,3-d]pyrimidin-5-ones and the results of the pharmacological study on haemostasis. Some tested compounds showed a large-spectrum antiplatelet activity in vitro, and are more potent than aspirin as antithrombotics in vivo but, at variance with aspirin, they do not increase bleeding. This paper describes novel antithrombotic compounds with an interesting pharmacological profile and a potentially attractive benefit/risk ratio, with their mechanism of action generally, but not exclusively, dependent on antiplatelet activity, deserving further investigations.     

Evidence of suboptimal management of cardiovascular risk in patients with type 2 diabetes mellitus and symptomatic atherosclerosis

Background

Given that most deaths among patients with diabetes mellitus are due to cardiovascular disease, we sought to determine the extent to which medications proven to reduce cardiovascular mortality are prescribed for patients with type 2 diabetes who have symptomatic atherosclerosis (i.e., coronary artery disease [CAD], cerebrovascular disease [CBVD] or peripheral arterial disease [PAD]).

Methods

Administrative records from Saskatchewan Health were used to evaluate the use of antiplatelet agents, statins and angiotensin-converting enzyme (ACE) inhibitors by people with treated type 2 diabetes with and without symptomatic atherosclerosis. CAD and CBVD were defined by International Classification of Diseases (ninth revision) codes, and PAD was defined on the basis of pentoxifylline use or lower limb amputation. Multivariate logistic regression analysis was used to compare medication use in patients with and without PAD, with adjustments for differences in age, sex and comorbidity.

Results

In this cohort of 12 106 patients with type 2 diabetes (mean age 64 years, 55% male, mean follow-up 5 years), fewer than 25% received an antiplatelet agent or statin, and fewer than 50% received an ACE inhibitor. Although patients with CAD were more likely to receive antiplatelet agents, statins or ACE inhibitors than people without CAD (p < 0.001 for all), the overall use of these medications was suboptimal (37%, 29% and 60% respectively among patients with symptomatic CAD). Similar patterns of practice were found for patients with symptomatic CBVD and PAD. All 3 proven efficacious therapies were prescribed for only 11% of patients with CAD, 22% with CBVD and 12% with PAD. Patients with PAD who had undergone lower limb amputation were no more likely to subsequently receive antiplatelet agents or statins than those without an amputation.

Interpretation

Diabetic patients with symptomatic atherosclerotic disease are undertreated with medications known to reduce cardiovascular morbidity and mortality, perhaps because of a “glucocentric” view of diabetes. Programs to improve the quality of cardiovascular risk reduction in these high-risk patients are needed.Diabetes mellitus in adults is associated with an annual rate of death of about 5%, approximately double the rate for age- and sex-matched control subjects without diabetes. Most of this excess mortality risk is attributable to macrovascular atherosclerotic disease.¹ Thus, it has been recommended that medical management to decrease cardiovascular risk should start when type 2 diabetes mellitus is diagnosed.^2,3 At the very least, medications proven to reduce cardiovascular risk should be prescribed for patients with diabetes and established atherosclerotic disease.In addition to smoking cessation and control of blood pressure, strategies proven to reduce cardiovascular risk in patients with diabetes and established atherosclerotic disease include therapy with antiplatelet agents, statins and angiotensin-converting enzyme (ACE) inhibitors.² Coronary artery disease (CAD), cerebrovascular disease (CBVD) and peripheral arterial disease (PAD) are all manifestations of established atherosclerosis.⁴ Recent epidemiologic studies have suggested that PAD may be present in one-quarter to one-half of all adults with type 2 diabetes and have confirmed that PAD is a powerful predictor of cardiovascular death.⁴ In fact, the survival rate for patients with PAD is worse than that for patients with breast cancer (72% v. 85% at 5 years).⁴ However, a recently published survey suggested that clinicians were less likely to prescribe antiplatelet therapy for patients with PAD than for patients with CAD.⁵We sought to evaluate the use of antiplatelet agents, statins and ACE inhibitors among diabetic patients with and without symptomatic atherosclerotic vascular disease. Given the high prevalence of symptomatic PAD among diabetic patients and suggestions that it is often neglected as a marker of atherosclerotic disease, we were particularly interested in examining patterns of care for overall cardiovascular risk reduction in patients with this condition.⁴     

Collaborative overview of randomised trials of antiplatelet therapy--I: Prevention of death,myocardial infarction,and stroke by prolonged antiplatelet therapy in various categories of patients. Antiplatelet Trialists' Collaboration.

OBJECTIVE--To determine the effects of "prolonged" antiplatelet therapy (that is, given for one month or more) on "vascular events" (non-fatal myocardial infarctions, non-fatal strokes, or vascular deaths) in various categories of patients. DESIGN--Overviews of 145 randomised trials of "prolonged" antiplatelet therapy versus control and 29 randomised comparisons between such antiplatelet regimens. SETTING--Randomised trials that could have been available by March 1990. SUBJECTS--Trials of antiplatelet therapy versus control included about 70,000 "high risk" patients (that is, with some vascular disease or other condition implying an increased risk of occlusive vascular disease) and 30,000 "low risk" subjects from the general population. Direct comparisons of different antiplatelet regimens involved about 10,000 high risk patients. RESULTS--In each of four main high risk categories of patients antiplatelet therapy was definitely protective. The percentages of patients suffering a vascular event among those allocated antiplatelet therapy versus appropriately adjusted control percentages (and mean scheduled treatment durations and net absolute benefits) were: (a) among about 20,000 patients with acute myocardial infarction, 10% antiplatelet therapy v 14% control (one month benefit about 40 vascular events avoided per 1000 patients treated (2P < 0.00001)); (b) among about 20,000 patients with a past history of myocardial infarction, 13% antiplatelet therapy v 17% control (two year benefit about 40/1000 (2P < 0.00001)); (c) among about 10,000 patients with a past history of stroke or transient ischaemic attack, 18% antiplatelet therapy v 22% control (three year benefit about 40/1000 (2P < 0.00001)); (d) among about 20,000 patients with some other relevant medical history (unstable angina, stable angina, vascular surgery, angioplasty, atrial fibrillation, valvular disease, peripheral vascular disease, etc), 9% v 14% in 4000 patients with unstable angina (six month benefit about 50/1000 (2P < 0.00001)) and 6% v 8% in 16,000 other high risk patients (one year benefit about 20/1000 (2P < 0.00001)). Reductions in vascular events were about one quarter in each of these four main categories and were separately statistically significant in middle age and old age, in men and women, in hypertensive and normotensive patients, and in diabetic and nondiabetic patients. Taking all high risk patients together showed reductions of about one third in non-fatal myocardial infarction, about one third in non-fatal stroke, and about one third in vascular death (each 2P < 0.00001). There was no evidence that non-vascular deaths were increased, so in each of the four main high risk categories overall mortality was significantly reduced. The most widely tested antiplatelet regimen was "medium dose" (75-325 mg/day) aspirin. Doses throughout this range seemed similarly effective (although in an acute emergency it might be prudent to use an initial dose of 160-325 mg rather than about 75 mg). There was no appreciable evidence that either a higher aspirin dose or any other antiplatelet regimen was more effective than medium dose aspirin in preventing vascular events. The optimal duration of treatment for patients with a past history of myocardial infarction, stroke, or transient ischaemic attack could not be determined directly because most trials lasted only one, two, or three years (average about two years). Nevertheless, there was significant (2P < 0.0001) further benefit between the end of year 1 and the end of year 3, suggesting that longer treatment might well be more effective. Among low risk recipients of "primary prevention" a significant reduction of one third in non-fatal myocardial infarction was, however, accompanied by a non-significant increase in stroke. Furthermore, the absolute reduction in vascular events was much smaller than for high risk patients despite a much longer treatment period (4.4% antiplatelet therapy v 4.8% control; five year     

Controversies and future perspectives of antiplatelet therapy in secondary stroke prevention

Antiplatelet agents are a cornerstone in the treatment of acute arterial thrombotic events and in the prevention of thrombus formation. However, existing antiplatelet agents (mainly aspirin, the combination of aspirin and dipyridamole and clopidogrel) reduce the risk of vascular events only by about one quarter compared with placebo. As a consequence, more efficacious antiplatelet therapies with a reduced bleeding risk are needed. We give an overview of several new antiplatelet agents that are currently investigated in secondary stroke prevention: adenosine 5′-diphosphonate receptor antagonists, cilostazol, sarpogrelate, terutroban and SCH 530348. There are unique features in secondary stroke prevention that have to be taken into account: ischaemic stroke is a heterogeneous disease caused by multiple aetiologies and the blood–brain barrier is disturbed after stroke which may result in a higher intracerebral bleeding risk. Several small randomized trials indicated that the combination of aspirin and clopidogrel might be superior to antiplatelet monotherapy in the acute and early post-ischaemic phase. There is an ongoing debate about antiplatelet resistance. Decreasing response to aspirin is correlated independently with an increased risk of cardiovascular events. However, there is still no evidence from randomized trials linking aspirin resistance and recurrent ischaemic events. Similarly, randomized trials have not demonstrated a clinical significantly decreased antiplatelet effect by the concomitant use of clopidogrel and proton pump inhibitors. Nevertheless, a routine use of this drug combination is not recommended.