Clopidogrel hydrogen sulphate for atrial fibrillation

INTRODUCTION: Atrial fibrillation is a common cardiac rhythm abnormality with a considerable cardiovascular disease burden worldwide. It is an independent major risk factor for stroke. Stroke prevention with anticoagulation or antiplatelet agents has been an important area of clinical research. Warfarin is the most widely used antithrombotic therapy for stroke prophylaxis for last several years, and now dabigatran (150 mg b.i.d.) is more effective than warfarin in stroke prevention in individuals at increased of stroke. In addition, several studies have evaluated the efficacy of clopidogrel for stroke prophylaxis either alone or in combination with aspirin. AREAS COVERED: This review summarizes the key findings of the trials looking at the efficacy of clopidogrel in stroke prevention. A literature search was performed using PubMed and Google Scholar. The trials that evaluated the efficacy of clopidogrel in preventing atherothrombotic events or stroke were also included. EXPERT OPINION: Clopidogrel prevents more vascular events, including stroke, in patients with a recent myocardial infarction, stroke or peripheral vascular disease than aspirin. Combination of clopidogrel and aspirin provides a greater reduction of stroke than aspirin or clopidogrel monotherapy, but at an increased risk of bleeding. Dual antiplatelet therapy (clopidogrel and aspirin) is inferior to warfarin in primary stroke prevention for patient with atrial fibrillation and thus should be considered for stroke prophylaxis only in patients ineligible for warfarin. However, with the advent of newer agents, like direct thrombin inhibitors and Factor Xa inhibitors, the role of antiplatelet therapy for stroke prevention in atrial fibrillation remains unclear.     

Role of Emerging Antithrombotic Therapy in the Prevention of Cardioembolic Complications in Patients with Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and is an independent risk factor of potentially catastrophic cardioembolic strokes. AF patients are categorized into high-, intermediate-, and low-risk for thromboembolic complications using the CHADS₂ or CHA₂DS₂-VASc scoring system. Oral anticoagulation using warfarin has been the standard therapy for stroke prevention in intermediate- to high-risk AF patients. However, warfarin use has been limited by several factors such as narrow therapeutic windows, drug-drug and drug-food interactions, and hemorrhagic complications. Rigorous research evaluated dual antiplatelet therapy of clopidogrel and aspirin (acetylsalicylic acid) as a potential alternative to warfarin in the ACTIVE W trial. Dual antiplatelet therapy of clopidogrel and aspirin was found to be inferior to warfarin in preventing stroke and systemic embolism with increased bleeding risk. Other extensive research has led to the development of new antithrombotic agents. Recently, dabigatran etexilate 150 mg twice daily, a direct thrombin inhibitor, was approved by the US FDA for stroke prevention in patients with non-valvular AF after it was found to be superior to warfarin in preventing thromboembolic events and associated with less bleeding in the RE-LY trial. It was also cost effective when compared with warfarin. Dabigatran can be considered in high-risk AF patients who are unable or unwilling to comply with the frequent laboratory and clinic visits that are required when receiving treatment with warfarin. Factor Xa inhibitors are another class of new anticoagulants that have been developed. Oral rivaroxaban was non-inferior to warfarin in thromboprophylaxis and with similar bleeding in the ROCKET-AF trial (HR 0.88; p=0.117). Apixaban, another factor Xa inhibitor, was superior to aspirin in reducing stroke and systemic embolism in patients with AF in the AVERROES trial (HR 0.45; p<0.001). The results of the ARISTOTLE trial, which is evaluating apixaban against warfarin in ～18 000 patients with AF, are expected to be available later this year. Edoxaban, another oral factor Xa inhibitor, is currently being evaluated against warfarin in the ENGAGE AF-TIMI 48 trial in ～20 000 patients with AF. With these new developments, there is a necessity for the clinical practitioner to become familiar with these new and upcoming therapies and guidelines. This review provides an overview of the available data regarding the clinical usefulness of these agents.     

Clopidogrel hydrogen sulphate for atrial fibrillation

Introduction: Atrial fibrillation is a common cardiac rhythm abnormality with a considerable cardiovascular disease burden worldwide. It is an independent major risk factor for stroke. Stroke prevention with anticoagulation or antiplatelet agents has been an important area of clinical research. Warfarin is the most widely used antithrombotic therapy for stroke prophylaxis for last several years, and now dabigatran (150 mg b.i.d.) is more effective than warfarin in stroke prevention in individuals at increased of stroke. In addition, several studies have evaluated the efficacy of clopidogrel for stroke prophylaxis either alone or in combination with aspirin.

Areas covered: This review summarizes the key findings of the trials looking at the efficacy of clopidogrel in stroke prevention. A literature search was performed using PubMed and Google Scholar. The trials that evaluated the efficacy of clopidogrel in preventing atherothrombotic events or stroke were also included.

Expert opinion: Clopidogrel prevents more vascular events, including stroke, in patients with a recent myocardial infarction, stroke or peripheral vascular disease than aspirin. Combination of clopidogrel and aspirin provides a greater reduction of stroke than aspirin or clopidogrel monotherapy, but at an increased risk of bleeding. Dual antiplatelet therapy (clopidogrel and aspirin) is inferior to warfarin in primary stroke prevention for patient with atrial fibrillation and thus should be considered for stroke prophylaxis only in patients ineligible for warfarin. However, with the advent of newer agents, like direct thrombin inhibitors and Factor Xa inhibitors, the role of antiplatelet therapy for stroke prevention in atrial fibrillation remains unclear.     

Indobufen: an updated review of its use in the management of atherothrombosis

Indobufen inhibits platelet aggregation by reversibly inhibiting the platelet cyclooxygenase enzyme thereby suppressing thromboxane synthesis. Clinical trials have evaluated the efficacy of oral indobufen in the secondary prevention of thromboembolic complications in patients with or without atrial fibrillation, in the prevention of graft occlusion after coronary artery bypass graft (CABG) surgery and in the treatment of intermittent claudication. In the secondary prevention of thromboembolic events indobufen 200 mg once or twice daily was significantly more effective than no treatment although not as effective as ticlopidine 250 mg once or twice daily, during 1-year nonblind clinical trials. Compared with placebo, indobufen 100 mg twice daily significantly reduced the risk of stroke in a small 28-month trial of patients at increased risk of systemic embolism (50% had atrial fibrillation). Furthermore, in patients with nonrheumatic atrial fibrillation and a recent cerebrovascular event enrolled in the 1-year Studio Italiano Fibrillazione Atriale (SIFA) trial, indobufen 100 or 200 mg twice daily was as effective as warfarin (titrated to produce an international normalised ratio of 2.0 to 3.5) in the secondary prevention of thromboembolic events; the incidences of the composite end-point of major vascular events (10.6 vs 9.0%) and recurrent stroke (5 vs 4%) were similar between treatments. In 2 large 12-month trials, the Studio Indobufene nel Bypass Aortocoronarico (SINBA) and the UK study, indobufen 200 mg twice daily was as effective as aspirin (acetylsalicylic acid) 300 or 325 mg plus dipyridamole 75 mg 3 times daily in the prevention of early and late occlusion of saphenous grafts in patients after CABG surgery. Indobufen 200 mg twice daily for 6 months significantly improved walking capacity compared with placebo, and caused a more pronounced improvement in both pain-free and total walking distance than either pentoxifylline 300 mg or aspirin 500 mg twice daily in separate 6- and 12-month studies of patients with intermittent claudication. Oral indobufen up to 200 mg twice daily was generally well tolerated in >5000 patients with atherosclerotic disease. Adverse events (predominantly gastrointestinal), reported by 3.9% of patients, rarely required withdrawal from treatment. In the SINBA and UK studies, fewer adverse events and less gastrointestinal bleeding were seen with indobufen than with aspirin plus dipyridamole treatment, while in the SIFA trial, noncerebral bleeding events occurred significantly less frequently in indobufen than warfarin recipients (0.6 vs 5.1%) and major bleeding events occurred only in the warfarin group. Conclusion: Indobufen is as effective as warfarin in the prophylaxis of thromboembolic events in at risk patients with nonrheumatic atrial fibrillation, as aspirin plus dipyridamole in the prevention of CABG occlusion and may be more effective than aspirin or pentoxifylline in improving walking capacity in patients with intermittent claudication. The improved tolerability profile of indobufen (favourable gastric tolerance and reduced haemorrhagic complications) compared with aspirin 300 to 325 mg 3 times daily or warfarin, in addition to a similar antiplatelet effect, suggests indobufen can be considered a drug with a definite role in the management of atherothrombotic events. In particular, indobufen may be an effective alternative for at risk patients with nonrheumatic atrial fibrillation in whom anticoagulant therapy is contraindicated or who are at higher risk of bleeding.     

More light at the end of the tunnel - apixaban in atrial fibrillation

INTRODUCTION: Subjects with atrial fibrillation are at risk of thromboembolic events. The vitamin K antagonists (e.g., warfarin) are useful at preventing coagulation in atrial fibrillation, but are difficult to use. One of the FXa inhibitors, oral apixaban, has been tested as an anticoagulant in atrial fibrillation. AREAS COVERED: In ARISTOTLE (Apixaban for reduction in stroke and other thromboembolic events in atrial fibrillation) apixaban was compared to warfarin in subjects with atrial fibrillation, and shown to cause a lower rate of stroke or systemic embolism and of major bleeding, than warfarin. In the AVERROES (Apixaban versus acetylsalicylic acid [ASA] to prevent stroke in atrial fibrillations patients who have failed or are unsuitable for vitamin K antagonist treatment) trial, stroke or systemic embolism occurred less often with apixaban than aspirin, whereas the occurrence of major bleeding was similar in the groups. EXPERT OPINION: Apixaban is much easier for subjects with atrial fibrillation to use than warfarin, as it does not require regular monitoring by a health professional, with dosage adjustment. In addition to replacing warfarin in subjects with atrial fibrillation who are unable or not prepared to use warfarin, apixaban has the potential to replace warfarin more widely in the prevention of thromboembolism in subjects with atrial fibrillation.     

Ximelagatran

Despite the significant advances over the last 50 years with regard to anticoagulant therapy, warfarin remains the definitive standard for the long-term prevention of thromboembolic events in at-risk patients, except those with acute coronary syndromes, in which antiplatelets are preferred. Ximelagatran, a prodrug of melagatran, is an orally administered direct thrombin inhibitor whose therapeutic potential has been investigated in venous thromboembolism, acute coronary syndromes and prevention of stroke in atrial fibrillation. Clinical studies have demonstrated ximelagatran to be comparable in efficacy to the oral vitamin K antagonist warfarin and low molecular weight heparin for prophylaxis of venous thromboembolism, comparable to warfarin for stroke prevention in the setting of atrial fibrillation, and, when combined with aspirin, more effective than aspirin alone at preventing major adverse cardiovascular events in patients with a recent myocardial infarction. Double-blind trials have also revealed the efficacy of ximelagatran in the secondary prevention of venous thromboembolism and shown the agent to be as effective as enoxaparin/warfarin in treating patients with acute deep vein thrombosis. Adverse effects with ximelagatran include elevations in alanine transaminase (ALT), which may require monitoring, and bleeding complications. Bleeding complications appear to be less than or at least comparable to those occurring with standard anticoagulant treatments like warfarin or low molecular weight heparin. In addition to its favorable efficacy and safety profile in comparison with standard anticoagulant therapy, the convenience of its oral, fixed-dose administration without the need for anticoagulation monitoring might help encourage a wider use of appropriate anticoagulation using ximelagatran across the population at risk, reducing the incidence of thromboembolic events.     

The immediate future for the medical treatment of atrial fibrillation

Atrial fibrillation is the most commonly sustained cardiac arrhythmia and a common reason for mortality and morbidity. Atrial fibrillation causes disease for three reasons: i) the ventricular rate is often high, which leads to symptoms ranging from discomfort to life threatening heart failure; ii) the rhythm causes loss of atrioventricular synchrony, which reduces diastolic filling and may lead to heart failure; and iii) atrial contraction is lost leading to stagnant blood that again may lead to atrial thrombi and peripheral embolism. Thus, the treatment of atrial fibrillation is focused on the maintenance of sinus rhythm, rate control and prevention of embolism. For the maintenance of sinus rhythm, all drugs under current development are potassium channel blockers; the so-called class III anti-arrhythmic drugs. Those which have been further investigated appear to be valuable for maintenance of sinus rhythm but all carry a significant risk of pro-arrhythmia, in particular Torsade de Pointe ventricular tachycardia. Rate control has been a focus of treatment for many years and several very old drugs, including digoxin, are used for this. There is, to the author's knowledge, no current effort for evaluating new drugs for this indication. Prevention of embolism has for many years been obtained with vitamin K antagonists for which the clinical evidence is overwhelming. Previous attempts to replace vitamin K antagonists with aspirin have not been fruitful. A large number of newer anticoagulation regimes are in development, but to the author's knowledge only a single thrombin inhibitor is actively being developed for atrial fibrillation.     

Guidelines for stroke prevention in patients with atrial fibrillation

Atrial fibrillation (AF) is a major independent risk factor for stroke. AF is most commonly associated with nonvalvular cardiovascular disease and is especially frequent among the elderly. The annual risk for stroke in patients with AF is approximately 5% with a wide range depending on the presence of additional risk factors. For patients who cannot successfully be converted and maintained in normal sinus rhythm (NSR), antithrombotic therapy is an effective method for preventing stroke. The 2 drugs which are indicated for stroke prophylaxis in patients with AF are warfarin and aspirin. For primary prevention, warfarin reduces the risk of stroke approximately 68%. Aspirin therapy is less effective, resulting in a 20 to 30% risk reduction. Combination therapy with aspirin and low intensity warfarin adjusted to an International Normalised Ratio (INR) of 1.2 to 1.5 has not been shown to be superior to standard intensity warfarin with a target INR of 2.0 to 3.0. In patients with AF and a prior history of stroke or transient ischaemic attack (TIA), the absolute risk reduction with warfarin is even greater because of the high risk of stroke in this population. In contrast, aspirin has not been shown to significantly reduce the risk of stroke in patients with AF when used for secondary prevention. When appropriately managed, warfarin is associated with a low risk of major bleeding. In controlled trials of highly selected patients, the annual rate of intracranial haemorrhage (ICH) with warfarin was approximately 0.3%. Studies have shown that specialty anticoagulation clinics can achieve similar low rates of major bleeding. However, these results cannot be extrapolated to the general population. Factors which have been identified as predictors of bleeding include advanced age, number of medications and most importantly, the intensity of anticoagulation. INR values above 4.0 have been associated with an increased risk of major bleeding while values below 2.0 have been associated with thrombosis. Slow careful dosage titration, regular laboratory monitoring and patient education can substantially reduce the risk of complications. In patients with AF, antithrombotic therapy has been shown to be cost effective. For high risk patients, warfarin is the most cost-effective therapy, provided the risks for bleeding are minimised. In contrast, aspirin is the most cost-effective agent for low risk patients. Current practice guidelines for stroke prophylaxis recommend warfarin (target INR 2.5: range 2.0 to 3.0) for AF patients at high risk for stroke including those over 75 years of age or younger patients with additional risk factors. Aspirin should be reserved for low risk patients or those unable to take warfarin. Although these recommendations are strongly supported by the clinical trial evidence, studies show that many patients are not receiving appropriate antithrombotic therapy. In particular, warfarin is underutilised in high risk elderly patients. Additional studies are needed to identify barriers that prevent implementation of the clinical trial findings into clinical practice.     

新型口服抗凝药物的安全性

新型抗凝药物主要包括直接凝血酶抑制剂和Xa因子抑制剂。其中,直接凝血酶抑制剂达比加群酯口服制剂、直接Xa因子抑制剂利伐沙班和阿哌沙班口服制剂已在我国上市;另外一种直接Xa因子抑制剂贝曲沙班口服制剂也正在进行Ⅲ期临床研究;而直接Xa因子抑制剂爱多沙班口服制剂已在日本上市。达比加群酯致颅内出血发生风险低于华法林,但该药可能增加急性冠状动脉综合征患者严重出血和具有临床意义轻度出血的发生率,以及心肌梗死或急性冠状动脉综合征的发生风险。利伐沙班在预防非瓣膜性心房颤动所致脑卒中和栓塞方面优于华法林,预防骨科术后血栓效果优于依诺肝素,大出血事件发生风险与两药相似,而颅内出血发生风险低于华法林。阿哌沙班在降低心房颤动患者脑卒中或全身性栓塞发生率及病死率方面优于华法林,颅内出血发生率低于华法林,大出血发生率与华法林相似或降低;阿哌沙班的安全性与用药剂量相关。爱多沙班的主要不良反应为出血,用于心房颤动患者的有效性及安全性均优于华法林。贝曲沙班用于全膝关节置换术后预防血栓效果与依诺肝素相似,出血发生率低于依诺肝素。     

The immediate future for the medical treatment of atrial fibrillation

Atrial fibrillation is the most commonly sustained cardiac arrhythmia and a common reason for mortality and morbidity. Atrial fibrillation causes disease for three reasons: i) the ventricular rate is often high, which leads to symptoms ranging from discomfort to life threatening heart failure; ii) the rhythm causes loss of atrioventricular synchrony, which reduces diastolic filling and may lead to heart failure; and iii) atrial contraction is lost leading to stagnant blood that again may lead to atrial thrombi and peripheral embolism. Thus, the treatment of atrial fibrillation is focused on the maintenance of sinus rhythm, rate control and prevention of embolism. For the maintenance of sinus rhythm, all drugs under current development are potassium channel blockers; the so-called class III anti-arrhythmic drugs. Those which have been further investigated appear to be valuable for maintenance of sinus rhythm but all carry a significant risk of pro-arrhythmia, in particular Torsade de Pointe ventricular tachycardia. Rate control has been a focus of treatment for many years and several very old drugs, including digoxin, are used for this. There is, to the author’s knowledge, no current effort for evaluating new drugs for this indication. Prevention of embolism has for many years been obtained with vitamin K antagonists for which the clinical evidence is overwhelming. Previous attempts to replace vitamin K antagonists with aspirin have not been fruitful. A large number of newer anticoagulation regimes are in development, but to the author’s knowledge only a single thrombin inhibitor is actively being developed for atrial fibrillation.     

Antiplatelet drugs in cardiovascular prevention: stroke: acute phase and secondary prevention

(1) In the acute phase of ischaemic stroke in patients free of thrombogenic heart disease, combined treatment with aspirin + moderate-dose unfractionated heparin reduces the risk of relapse and death. Unfractionated heparin at higher anticoagulant doses has an unfavourable risk-benefit ratio. Treatment is controversial in patients with events associated with atrial fibrillation. (2) After ischaemic stroke in patients free of thrombogenic heart disease, aspirin reduces the risk of relapse and death. Other antiplatelet drugs, the aspirin + dipyridamole combination, ticlopidine and clopidogrel have similar efficacy to aspirin. (3) The risk-benefit ratio of oral anticoagulant is favourable after ischaemic stroke associated with atrial fibrillation; but it is unfavourable after stroke without thrombogenic heart disease.     

新型口服抗凝药在伴有慢性肾脏疾病的非瓣膜性房颤患者中抗凝的研究进展

心房颤动是常见的心律失常疾病,持续48 h即可形成血栓,血栓脱落可导致动脉栓塞,其中90%是缺血性脑卒中,而慢性肾脏疾病可进一步增加房颤患者的卒中和出血风险。因此,在伴有慢性肾脏疾病的非瓣膜性房颤患者中的抗凝尤为重要。华法林用于肾功能不全的房颤患者虽可减少血栓栓塞的发生率,但是随着肾功能的恶化,华法林可增加出血的风险,且维持国际标准化比值（INR）在目标范围的时间非常困难。与华法林相比,新型口服抗凝药物能显著地降低卒中、颅内出血和死亡风险。然而新型口服抗凝药物在轻度、中度、重度,甚至血液透析房颤患者的应用仍存在争议。     

More light at the end of the tunnel – apixaban in atrial fibrillation

Introduction: Subjects with atrial fibrillation are at risk of thromboembolic events. The vitamin K antagonists (e.g., warfarin) are useful at preventing coagulation in atrial fibrillation, but are difficult to use. One of the FXa inhibitors, oral apixaban, has been tested as an anticoagulant in atrial fibrillation.

Areas covered: In ARISTOTLE (Apixaban for reduction in stroke and other thromboembolic events in atrial fibrillation) apixaban was compared to warfarin in subjects with atrial fibrillation, and shown to cause a lower rate of stroke or systemic embolism and of major bleeding, than warfarin. In the AVERROES (Apixaban versus acetylsalicylic acid [ASA] to prevent stroke in atrial fibrillations patients who have failed or are unsuitable for vitamin K antagonist treatment) trial, stroke or systemic embolism occurred less often with apixaban than aspirin, whereas the occurrence of major bleeding was similar in the groups.

Expert opinion: Apixaban is much easier for subjects with atrial fibrillation to use than warfarin, as it does not require regular monitoring by a health professional, with dosage adjustment. In addition to replacing warfarin in subjects with atrial fibrillation who are unable or not prepared to use warfarin, apixaban has the potential to replace warfarin more widely in the prevention of thromboembolism in subjects with atrial fibrillation.     

观察华法林及阿司匹林分别对非瓣膜性心房颤动患者血栓栓塞的影响

目的观察华法林及阿司匹林对非瓣膜性心房颤动患者血栓栓塞事件的影响。方法80例非瓣膜性心房颤动患者分为华法林组及阿司匹林组,阿司匹林组每天服用阿司匹林100 mg,华法林组根据国际标准化比值(INR)调整华法林用量,随访时间为2 a。结果阿司匹林组死亡2例,1例为缺血性卒中,另1例为心力衰竭;华法林组1例为猝死。阿司匹林组发生栓塞事件共8例,出血并发症3例;华法林组发生栓塞事件共3例,出血并发症7例。结论华法林可明显降低非瓣膜性房颤患者血栓栓塞事件,但出血并发症稍增多,关键是要严密随访INR。     

Atrial fibrillation in the elderly: facts and management

Although atrial fibrillation is not widely known by the general public, in developed countries it is the most common arrhythmia. The incidence increases markedly with advancing age. Thus, with the growing proportion of elderly individuals, atrial fibrillation will come to represent a significant medical and socioeconomic problem. The consequences of atrial fibrillation have the greatest impact. The risk of thromboembolism is well known; other outcomes of atrial fibrillation are less well recognised, such as its relationship with dementia, depression and death. Such consequences are responsible for diminished quality of life and considerable economic cost. Atrial fibrillation is characterised by rapid and disorganised atrial activity, with a frequency between 300 and 600 beats/minute. The ventricles react irregularly, and may contract rapidly or slowly depending on the health of the conduction system. Clinical symptoms are varied, including palpitations, syncope, dizziness or embolic events. Atrial fibrillation may be paroxysmal, persistent or chronic, and a number of attacks are asymptomatic. Suspicion or confirmation of atrial fibrillation necessitates investigation and, as far as possible, appropriate treatment of underlying causes such as hypertension, diabetes mellitus, hypoxia, hyperthyroidism and congestive heart failure. In the evaluation of atrial fibrillation, cardiac exploration is invaluable, including electrocardiogram (ECG) and echocardiography, with the aim of detecting cardiac abnormalities and directing management. In elderly patients (arbitrarily defined as aged >75 years), the management of atrial fibrillation varies; it requires an individual approach, which largely depends on comorbid conditions, underlying cardiac disease, and patient and physician preferences. This management is essentially based on pharmacological treatment, but there are also nonpharmacological options. Two alternatives are possible: restoration and maintenance of sinus rhythm, or control of ventricular rate, leaving the atria in arrhythmia. Pharmacological options include antiarrhythmic drugs, such as class III agents, beta-blockers and class IC agents. These drugs have some adverse effects, and careful monitoring is necessary. The nonpharmacological approach to atrial fibrillation includes external or internal direct-current cardioversion and new methods, such as catheter ablation of specific foci, an evolving science that has been shown to be successful in a very select group of atrial fibrillation patients. Another serious challenge in the management of chronic atrial fibrillation in older individuals is the prevention of stroke, its primary outcome, by choosing an appropriate antithrombotic treatment (aspirin or warfarin). Several risk-stratification schemes have been validated and may be helpful to determine the best antithrombotic choice in individual patients.     

阿哌沙班预防心房颤动患者的卒中

阿哌沙班是激活Ⅹ因子(Ⅹa)抑制剂,具有快速吸收、线性药代动力学、较少药物相互作用的特点。在不适合接受华法林治疗的心房颤动人群中所进行的随机对照试验证实,阿哌沙班在减少卒中和系统栓塞方面的疗效优于阿司匹林,安全性相似;在至少有1个危险因素的心房颤动人群中进行的与华法林的对照试验中,阿哌沙班可减少卒中和栓塞事件,主要是减少出血性卒中,同时减少重要出血和全因死亡。     

Antiplatelet drugs in cardiovascular prevention: stroke prevention in patients with thrombogenic heart disease

(1) In patients with atrial fibrillation and a moderate embolic risk, aspirin reduces the risk of stroke and has a comparable risk-benefit ratio to oral anticoagulants. (2) Oral anticoagulants are superior to aspirin in patients with atrial fibrillation and a history of stroke. (3) In patients with a mechanical valve prosthesis and a high embolic risk, the oral anticoagulant + aspirin combination has a better risk-benefit ratio than oral anticoagulant alone.     

华法林在低栓塞风险的心房颤动患者射频消融术后的应用

目的探讨消融治疗获得成功的持续性心房颤动患者,特别是栓塞风险低的个体,术后是否需要继续应用华法林抗凝治疗。方法入选低危栓塞风险的持续性心房颤动患者107例,射频消融术后随机分为华法林治疗组(55例)和非华法林组(52例),华法林治疗组患者术后服用华法林治疗至少3个月,抗凝治疗强度为INR2.0～3.0;非华法林组只服用阿司匹林,每日100mg。所有患者术后均进行随访,观察比较两组患者血栓栓塞和出血事件发生率的差异。结果所有患者均成功完成射频消融术,即刻成功率为100%。两组患者术中均未发生栓塞或出血事件。随访6～18个月,华法林组发生血栓栓塞事件2例(3.6%),非华法林组发生2例(3.7%),两组患者栓塞发生率无统计学差异,P>0.1。华法林组有3例(5.5%)出血事件,非华法林组无出血事件发生。结论对于射频消融取得成功的低危心房颤动患者,可以考虑不应用华法林抗凝,而只服用阿司匹林。     

Secondary prevention of stroke in patients with nonvalvular atrial fibrillation: optimal intensity of anticoagulation

Nonvalvular atrial fibrillation (NVAF) is frequently seen in elderly people and has become a main cause of cardioembolic stroke. The efficacy of anticoagulation for primary prevention of stroke or transient ischaemic attacks (TIAs) in patients with NVAF has been established by prospective, randomised and controlled trials. Warfarin decreased the frequency of all strokes by 68% and the rate of the combined outcome of stroke, systemic embolism or death by 48%. Anticoagulation with warfarin using international normalised ratios (INRs) ranging from 2.0 to 3.0 is recommended for patients with NVAF, who have any of the risk factors identified by the Atrial Fibrillation Investigators (AFI) [previous stroke or TIA, history of hypertension, diabetes mellitus, advanced age (> or = 65 years old), congestive heart failure and coronary artery disease], the American College of Chest Physicians (ACCP) [increased age (> 75 years old), prior stroke, hypertension and heart failure], or the Stroke Prevention in Atrial Fibrillation (SPAF) investigators [women > 75 years old, prior stroke, systolic blood pressure > 160mm Hg, recent heart failure, and fractional shortening < 25% on echocardiography]. For the secondary prevention of stroke, the efficacy of adjusted-dose warfarin therapy has been demonstrated by 2 major randomised trials. SPAF III (INR 2.0 to 3.0) demonstrated a lower incidence of ischaemic stroke or systemic embolism (3.4 %/year) compared with low fixed-dose warfarin plus aspirin (acetylsalicylic acid) [11.9%]. The European Atrial Fibrillation Trial [EAFT] (INR 2.5 to 4.0) showed a lower incidence of all stroke (4.0 %/year) with adjusted-dose warfarin compared with placebo (12.0 %/year). The incidence of major bleeding in the adjusted-dose warfarin group in SPAF III and EAFT was 2.4 and 2.8 %/year, respectively. EAFT incidence rates for the occurrence of a first ischaemic or haemorrhagic complication analysed by INR range indicated that the rate was lowest at INRs of 2.0 to 2.9, and higher with INRs of 3.0 to 3.9. Therefore, the optimal intensity of anticoagulation for prevention of recurrent stroke seems to be an INR of between 2.0 and 3.0, as for primary prevention. Retrospective and prospective studies from Japan reported that in the elderly, haemorrhagic complications occur frequently with INRs above 2.6 and major ischaemic events cannot be prevented at INRs below 1.6. Therefore, an INR target between 1.6 and 2.6 may be an alternative for secondary prevention of stroke in elderly patients with NVAF who have a potential risk of bleeding, to avoid both major ischaemic and haemorrhagic events. Antiplatelets may be administered in patients who are unable to manage taking warfarin properly or who have a high risk of falling and subsequently sustaining a head injury, although the efficacy of antiplatelets for secondary prevention of stroke in NVAF has not yet been established.