Prevention of arterial thromboembolism with acetylsalicylic acid. A controlled clinical study in patients with aortic ball valves

American Society of Hematology 2020 guidelines for management of venous thromboembolism: treatment of deep vein thrombosis and pulmonary embolism

BACKGROUND

Venous thromboembolism (VTE), which includes deep vein thrombosis (DVT) and pulmonary embolism (PE), occurs in ∼1 to 2 individuals per 1000 each year, corresponding to ∼300 000 to 600 000 events in the United States annually.

OBJECTIVE

These evidence-based guidelines from the American Society of Hematology (ASH) intend to support patients, clinicians, and others in decisions about treatment of VTE.

METHODS

ASH formed a multidisciplinary guideline panel balanced to minimize potential bias from conflicts of interest. The McMaster University GRADE Centre supported the guideline development process, including updating or performing systematic evidence reviews. The panel prioritized clinical questions and outcomes according to their importance for clinicians and adult patients. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to assess evidence and make recommendations, which were subject to public comment.

RESULTS

The panel agreed on 28 recommendations for the initial management of VTE, primary treatment, secondary prevention, and treatment of recurrent VTE events.

CONCLUSIONS

Strong recommendations include the use of thrombolytic therapy for patients with PE and hemodynamic compromise, use of an international normalized ratio (INR) range of 2.0 to 3.0 over a lower INR range for patients with VTE who use a vitamin K antagonist (VKA) for secondary prevention, and use of indefinite anticoagulation for patients with recurrent unprovoked VTE. Conditional recommendations include the preference for home treatment over hospital-based treatment for uncomplicated DVT and PE at low risk for complications and a preference for direct oral anticoagulants over VKA for primary treatment of VTE.

Anticoagulation and antiplatelet therapy in patients with prosthetic heart valves

BACKGROUND

The choice of antithrombotic therapy, anticoagulants or antiplatelets, after prosthetic heart valve replacement or repair, remains a disputed topic in the literature. Antithrombotic therapies are used after heart valve intervention to reduce the rates of thromboembolic events, therefore improving patient outcomes. Different interventions may require different therapeutic regimens to achieve the most efficacious clinical outcome for patients.

METHODS AND DISCUSSION

This review aims to summarize and critique the available literature concerning therapeutic agents used for bioprosthetic and mechanical valves as well as for valve repair, so as to assist clinicians and researchers in making decisions with regard to their patients and research endeavors.

Diagnosis of Coronary Embolism: A Review1

Coronary embolism is an uncommon but distinct clinical entity. It can be diagnosed clinically, and should be suspected when acute myocardial infarction occurs in association with an underlying condition which predisposes to embolism. The most common are valvular heart disease, a prosthetic heart valve, infective endocarditis, cardiomyopathy with mural thrombus and arrhythmia. The diagnosis may be obscured by atypical symptoms and transient ECG changes. The diagnosis is supported by the demonstration of normal coronary arteries by selective coronary arteriography. Treatment with long-term anticoagulants may prevent further emboli. Additional antiplatelet drugs are also necessary in patients with prosthetic heart valves.

Primary prophylaxis for venous thromboembolism in patients undergoing cardiac or thoracic surgery

BACKGROUND

Cardiac and thoracic surgery are associated with an increased risk of venous thromboembolism (VTE). The safety and efficacy of primary thromboprophylaxis in patients undergoing these types of surgery is uncertain.

OBJECTIVES

To assess the effects of primary thromboprophylaxis on the incidence of symptomatic VTE and major bleeding in patients undergoing cardiac or thoracic surgery.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched May 2014) and CENTRAL (2014, Issue 4). The authors searched the reference lists of relevant studies, conference proceedings, and clinical trial registries.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs comparing any oral or parenteral anticoagulant or mechanical intervention to no intervention or placebo, or comparing two different anticoagulants.

DATA COLLECTION AND ANALYSIS

We extracted data on methodological quality, participant characteristics, interventions, and outcomes including symptomatic VTE and major bleeding as the primary effectiveness and safety outcomes, respectively.

MAIN RESULTS

We identified 12 RCTs and one quasi-RCT (6923 participants), six for cardiac surgery (3359 participants) and seven for thoracic surgery (3564 participants). No study evaluated fondaparinux, the new oral direct thrombin, direct factor Xa inhibitors, or caval filters. All studies had major study design flaws and most lacked a placebo or no treatment control group. We typically graded the quality of the overall body of evidence for the various outcomes and comparisons as low, due to imprecise estimates of effect and risk of bias. We could not pool data because of the different comparisons and the lack of data. In cardiac surgery, 71 symptomatic VTEs occurred in 3040 participants from four studies. In a study of 2551 participants, representing 85% of the review population in cardiac surgery, the combination of unfractionated heparin with pneumatic compression stockings was associated with a 61% reduction of symptomatic VTE compared to unfractionated heparin alone (1.5% versus 4.0%; risk ratio (RR) 0.39; 95% confidence interval (CI) 0.23 to 0.64). Major bleeding was only reported in one study, which found a higher incidence with vitamin K antagonists compared to platelet inhibitors (11.3% versus 1.6%, RR 7.06; 95% CI 1.64 to 30.40). In thoracic surgery, 15 symptomatic VTEs occurred in 2890 participants from six studies. In the largest study evaluating unfractionated heparin versus an inactive control the rates of symptomatic VTE were 0.7% versus 0%, respectively, giving a RR of 6.71 (95% CI 0.40 to 112.65). There was insufficient evidence to determine if there was a difference in the risk of major bleeding from two studies evaluating fixed-dose versus weight-adjusted low molecular weight heparin (2.7% versus 8.1%, RR 0.33; 95% CI 0.07 to 1.60) and unfractionated heparin versus low molecular weight heparin (6% and 4%, RR 1.50; 95% CI 0.26 to 8.60).

AUTHORS' CONCLUSIONS

The evidence regarding the efficacy and safety of thromboprophylaxis in cardiac and thoracic surgery is limited. Data for important outcomes such as pulmonary embolism or major bleeding were often lacking. Given the uncertainties around the benefit-to-risk balance, no conclusions can be drawn and a case-by-case risk evaluation of VTE and bleeding remains preferable.

Antiplatelet and anticoagulation for patients with prosthetic heart valves

BACKGROUND

Patients with prosthetic heart valves are at increased risk for valve thrombosis and arterial thromboembolism. Oral anticoagulation alone, or the addition of antiplatelet drugs, has been used to minimise this risk. An important issue is the effectiveness and safety of the latter strategy.

OBJECTIVES

This is an update of our previous review; the goal was to create a valid synthesis of all available, methodologically sound data to further assess the safety and efficacy of combined oral anticoagulant and antiplatelet therapy versus oral anticoagulant monotherapy in patients with prosthetic heart valves.

SEARCH METHODS

We updated the previous searches from 2003 and 2010 on 16 January 2013 and searched the Cochrane Central Register of Controlled Trials (CENTRAL) on The Cochrane Library (2012, Issue 12), MEDLINE (OVID, 1946 to January Week 1 2013), and EMBASE (OVID, 1980 to 2013 Week 02). We have also looked at reference lists of individual reports, review articles, meta-analyses, and consensus statements. We included reports published in any language or in abstract form.

SELECTION CRITERIA

All reports of randomised controlled trials comparing standard-dose oral anticoagulation to standard-dose oral anticoagulation and antiplatelet therapy in patients with one or more prosthetic heart valves.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed the search strategy, assessed trials for inclusion and study quality, and extracted data. We collected adverse effects information from the trials.

MAIN RESULTS

One new study has been identified and included in this update. In total, 13 studies involving 4122 participants were included in this review update. Years of publication ranged from 1971 to 2011. Compared with anticoagulation alone, the addition of an antiplatelet agent reduced the risk of thromboembolic events (odds ratio (OR) 0.43, 95% confidence interval (CI) 0.32 to 0.59; P < 0.00001) and total mortality (OR 0.57, 95% CI 0.42 to 0.78; P = 0.0004). Aspirin and dipyridamole reduced these events similarly. The risk of major bleeding was increased when antiplatelet agents were added to oral anticoagulants (OR 1.58, 95% CI 1.14 to 2.18; P = 0.006).For major bleeding, there was no evidence of heterogeneity between aspirin and dipyridamole and in the comparison of trials performed before and after 1990, around the time when anticoagulation standardisation with the international normalised ratio was being implemented. A lower daily dose of aspirin (< 100 mg) may be associated with a lower major bleeding risk than higher doses.

AUTHORS' CONCLUSIONS

Adding antiplatelet therapy, either dipyridamole or low-dose aspirin, to oral anticoagulation decreases the risk of systemic embolism or death among patients with prosthetic heart valves. The risk of major bleeding is increased with antiplatelet therapy. These results apply to patients with mechanical prosthetic valves or those with biological valves and indicators of high risk such as atrial fibrillation or prior thromboembolic events. The effectiveness and safety of low-dose aspirin (100 mg daily) appears to be similar to higher-dose aspirin and dipyridamole. In general, the quality of the included trials tended to be low, possibly reflecting the era when the majority of the trials were conducted (1970s and 1980s when trial methodology was less advanced).

Aspirin and clopidogrel for prevention of ischemic stroke

This review examines the role of platelets in ischemic stroke, platelet activation mechanisms, aspirin's rise as an antithrombotic agent, clopidogrel's appearance on the stage, a possible role for combination therapy, antiplatelet resistance, practical considerations, and future directions. Reviewed in this chapter are issues central to optimal antiplatelet therapy: efficacy, safety, resistance, and biochemical/laboratory testing. Current guidelines do not recommend combination aspirin and clopidogrel use, however recent research indicates dual antiplatelet therapy with combined aspirin and clopidogrel may have specific roles in secondary prevention of ischemic stroke. A cautious and analytical interpretation of the literature is advised before application of this knowledge to clinical practice. The best recommendation at this time is to follow the published guidelines for secondary prevention of ischemic stroke.

Plasminogen activators and ischemic stroke: conditions for acute delivery

Appropriate acute treatment with plasminogen activators (PAs) can significantly increase the probability of minimal or no disability in selected ischemic stroke patients. There is a great deal of evidence showing that intravenous recombinant tissue PAs (rt-PA) infusion accomplishes this goal, recanalization with other PAs has also been demonstrated in the development of this treatment. Recanalization of symptomatic, documented carotid or vertebrobasilar arterial territory occlusions have also been achieved by local intra-arterial PA delivery, although only a single prospective double-blinded randomized placebo-controlled study has been reported. The increase in intracerebral hemorrhage with these agents by either delivery approach underscores the need for careful patient selection, dose-appropriate safety and efficacy, proper clinical trial design, and an understanding of the evolution of cerebral tissue injury due to focal ischemia. Principles underlying the evolution of focal ischemia have been expanded by experience with acute PA intervention. Several questions remain open that concern the manner in which PAs can be applied acutely in ischemic stroke and how injury development can be limited.

Antiplatelet drugs: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

The article describes the mechanisms of action, pharmacokinetics, and pharmacodynamics of aspirin, dipyridamole, cilostazol, the thienopyridines, and the glycoprotein IIb/IIIa antagonists. The relationships among dose, efficacy, and safety are discussed along with a mechanistic overview of results of randomized clinical trials. The article does not provide specific management recommendations but highlights important practical aspects of antiplatelet therapy, including optimal dosing, the variable balance between benefits and risks when antiplatelet therapies are used alone or in combination with other antiplatelet drugs in different clinical settings, and the implications of persistently high platelet reactivity despite such treatment.

Guidelines for the prevention of stroke in patients with stroke or transient ischemic attack: a guideline for healthcare professionals from the american heart association/american stroke association

The aim of this updated statement is to provide comprehensive and timely evidence-based recommendations on the prevention of ischemic stroke among survivors of ischemic stroke or transient ischemic attack. Evidence-based recommendations are included for the control of risk factors, interventional approaches for atherosclerotic disease, antithrombotic treatments for cardioembolism, and the use of antiplatelet agents for noncardioembolic stroke. Further recommendations are provided for the prevention of recurrent stroke in a variety of other specific circumstances, including arterial dissections; patent foramen ovale; hyperhomocysteinemia; hypercoagulable states; sickle cell disease; cerebral venous sinus thrombosis; stroke among women, particularly with regard to pregnancy and the use of postmenopausal hormones; the use of anticoagulation after cerebral hemorrhage; and special approaches to the implementation of guidelines and their use in high-risk populations.

Update on antithrombotic therapy for stroke prevention in atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia in the elderly, affecting 1 in 20 adults over the age of 70 years. Stroke is a major yet highly preventable complication of AF, and the strokes related to AF often are disabling and fatal. Warfarin is the treatment of choice in high-risk patients with AF, and its superior efficacy over aspirin for preventing stroke in these patients is widely recognized. However, several eligible patients with AF are not being treated with warfarin or are being treated inadequately, largely because of concerns regarding the attendant strict monitoring, drug interactions, and risk of major bleeding. As such, alternative antithrombotic therapies that can rival or exceed the efficacy of warfarin, yet compare favorably with its administration and side effect profile, are being sought. One such strategy, the use of a combination antiplatelet regimen, for stroke prevention in high-risk patients with nonvalvular AF was investigated recently in two clinical trials. This article reviews the role of combination antiplatelet regimens in stroke prevention for patients with AF. Other therapies discussed include oral anticoagulation, single antiplatelet therapies, oral anticoagulation plus antiplatelet treatment, direct thrombin inhibitors, and factor Xa inhibitors.

Clinical trials in heart valve disease

PURPOSE OF REVIEW

To summarize evidence from clinical trials of heart valve disease and identify areas where further trials are needed.

RECENT FINDINGS

Recent randomized studies suggest that statins do not influence progression of aortic stenosis. Other medical therapies with the potential to reduce progression of valve disease or decrease myocardial dysfunction include vasodilators in aortic regurgitation, angiotensin II receptor antagonists or beta-blockers in mitral regurgitation and angiotensin-converting enzyme inhibitors in aortic stenosis. However, these treatments have not been evaluated or have been evaluated only in small studies. Meta-analysis of randomized studies of antithrombotic strategies in patients with mechanical valves suggests overall risk is lower with the combination of warfarin with a lower target international normalized ratio and an antiplatelet drug. Novel anticoagulants have the potential to replace warfarin but have not yet been evaluated for this indication. Clinical trials are also needed to reliably evaluate different surgical strategies and novel percutaneous technology.

SUMMARY

Clinical trials in heart valve disease have important limitations, including the small number of trials undertaken and the small size of most studies. Many trials were undertaken more than 10-20 years ago in patients with earlier generation valve prostheses. To improve outcomes for patients with heart valve disease more clinical trials of contemporary approaches are needed.

Can acetylsalicylic acid alone prevent arterial thromboembolism? A pilot study in patients with aortic ball valve prostheses

Encouraged by the effective prevention of arterial thromboembolism with a combination of ASA and anticoagulants (9), the present study was done in 77 patients with a single Starr-Edwards aortic ball valve. They received one gm. of ASA daily, then the dose of anticoagulants was reduced gradually and the drug discontinued on average five weeks later. Six arterial embolic episodes occurred in five patients, the incidence being 14.5 complications per 100 patients per year. Five emboli were cerebral, none of them serious, and one was removed from a femoral artery. Four of the embolic episodes occurred in three of the 11 patients with continuous arrhythmia, probably from venus thrombi that developed in the left atrium. The occurrence of only two embolic complications in the 66 patients with sinus rhythm suggests some prevention of arterial thrombus formation on the prosthetic valves. The results indicate that ASA is inferior to anticoagulants in patients with arrhythmia, while it may represent an alternative to anticoagulation in individuals with sinus rhythm. We prefer, however, the combined therapy in patients with aortic valve prostheses because of the strong anti-thrombotic effect achieved by this treatment.

Antiplatelet drugs: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This article about currently available antiplatelet drugs is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). It describes the mechanism of action, pharmacokinetics, and pharmacodynamics of aspirin, reversible cyclooxygenase inhibitors, thienopyridines, and integrin alphaIIbbeta3 receptor antagonists. The relationships among dose, efficacy, and safety are thoroughly discussed, with a mechanistic overview of randomized clinical trials. The article does not provide specific management recommendations; however, it does highlight important practical aspects related to antiplatelet therapy, including the optimal dose of aspirin, the variable balance of benefits and hazards in different clinical settings, and the issue of interindividual variability in response to antiplatelet drugs.

Aspirin: Promise and Resistance in the New Millennium

Although conceived at the end of the 19th century, aspirin remains the gold standard of antiplatelet therapy. Approximately 100 randomized clinical trials have established its efficacy and safety in the prevention of myocardial infarction, ischemic stroke, and vascular death among high-risk patients treated for a few weeks, at one end of the spectrum, and in low-risk subjects treated up to 10 years at the other. Despite this wealth of data, several issues continue to be debated concerning the use of aspirin as an antiplatelet agent, and novel opportunities appear on the horizon for this 110-year-old drug. These issues include: (1) the optimal dose for cardiovascular prophylaxis; (2) the uncertain threshold of cardiovascular risk for its use in primary prevention; (3) the apparent gender-related difference in its cardioprotective effects; (4) the increasingly popular theme of aspirin “resistance”; (5) the opportunities of chemoprevention in colorectal cancer; and (6) the renewed interest in aspirin as an analgesic agent in osteoarthritic patients at high cardiovascular risk. The aim of this review is to address these issues by integrating our current understanding of the molecular mechanism of action of the drug with the results of clinical trials and epidemiological studies of aspirin as an antiplatelet drug.

Guidelines for Prevention of Stroke in Patients With Ischemic Stroke or Transient Ischemic Attack

The aim of this new statement is to provide comprehensive and timely evidence-based recommendations on the prevention of ischemic stroke among survivors of ischemic stroke or transient ischemic attack. Evidence-based recommendations are included for the control of risk factors, interventional approaches for atherosclerotic disease, antithrombotic treatments for cardioembolism, and the use of antiplatelet agents for noncardioembolic stroke. Further recommendations are provided for the prevention of recurrent stroke in a variety of other specific circumstances, including arterial dissections; patent foramen ovale; hyperhomocysteinemia; hypercoagulable states; sickle cell disease; cerebral venous sinus thrombosis; stroke among women, particularly with regard to pregnancy and the use of postmenopausal hormones; the use of anticoagulation after cerebral hemorrhage; and special approaches for the implementation of guidelines and their use in high-risk populations.

Hemorrhagic Complications of Anticoagulant Treatment

This chapter about hemorrhagic complications of anticoagulant treatment is part of the seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Bleeding is the major complication of anticoagulant therapy. The criteria for defining the severity of bleeding varies considerably between studies, accounting in part for the variation in the rates of bleeding reported. The major determinants of vitamin K antagonist-induced bleeding are the intensity of the anticoagulant effect, underlying patient characteristics, and the length of therapy. There is good evidence that vitamin K antagonist therapy, targeted international normalized ratio (INR) of 2.5 (range, 2.0 to 3.0), is associated with a lower risk of bleeding than therapy targeted at an INR > 3.0. The risk of bleeding associated with IV unfractionated heparin (UFH) in patients with acute venous thromboembolism (VTE) is < 3% in recent trials. This bleeding risk may increase with increasing heparin dosages and age (> 70 years). Low molecular weight heparin (LMWH) is associated with less major bleeding compared with UFH in acute VTE. UFH and LMWH are not associated with an increase in major bleeding in ischemic coronary syndromes, but are associated with an increase in major bleeding in ischemic stroke. Information on bleeding associated with the newer generation of antithrombotic agents has begun to emerge. In terms of treatment decision making for anticoagulant therapy, bleeding risk cannot be considered alone, ie, the potential decrease in thromboembolism must be balanced against the potential increased bleeding risk.

Platelet-Active Drugs: The Relationships Among Dose, Effectiveness, and Side Effects

This article discusses platelet active drugs as part of the Seventh American College of Chest Physicians Conference on Antithrombotic and Thrombolytic Therapy: Evidence-Based Guidelines. New data on antiplatelet agents include the following: (1) the role of aspirin in primary prevention has been the subject of recommendations based on the assessment of cardiovascular risk; (2) an increasing number of reports suggest a substantial interindividual variability in the response to antiplatelet agents, and various phenomena of "resistance" to the antiplatelet effects of aspirin and clopidogrel; (3) the benefit/risk profile of currently available glycoprotein IIb/IIIa antagonists is substantially uncertain for patients with acute coronary syndromes who are not routinely scheduled for early revascularization; (4) there is an expanding role for the combination of aspirin and clopidogrel in the long-term management of high-risk patients; and (5) the cardiovascular effects of selective and nonselective cyclooxygenase-2 inhibitors have been the subject of increasing attention.

Antithrombotic Therapy in Valvular Heart Disease—Native and Prosthetic

This chapter about antithrombotic therapy in native and prosthetic valvular heart disease is part of the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Grade 1 recommendations are strong and indicate that the benefits do, or do not, outweigh risks, burden, and costs. Grade 2 suggests that individual patients' values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this chapter are the following: For patients with rheumatic mitral valve disease and atrial fibrillation (AF), or a history of previous systemic embolism, we recommend long-term oral anticoagulant (OAC) therapy (target international normalized ratio [INR], 2.5; range, 2.0 to 3.0) [Grade 1C+]. For patients with rheumatic mitral valve disease with AF or a history of systemic embolism who suffer systemic embolism while receiving OACs at a therapeutic INR, we recommend adding aspirin, 75 to 100 mg/d (Grade 1C). For those patients unable to take aspirin, we recommend adding dipyridamole, 400 mg/d, or clopidogrel (Grade 1C). In people with mitral valve prolapse (MVP) without history of systemic embolism, unexplained transient ischemic attacks (TIAs), or AF, we recommended against any antithrombotic therapy (Grade 1C). In patients with MVP and documented but unexplained TIAs, we recommend long-term aspirin therapy, 50 to 162 mg/d (Grade 1A). For all patients with mechanical prosthetic heart valves, we recommend vitamin K antagonists (Grade 1C+). For patients with a St. Jude Medical (St. Paul, MN) bileaflet valve in the aortic position, we recommend a target INR of 2.5 (range, 2.0 to 3.0) [Grade 1A]. For patients with tilting disk valves and bileaflet mechanical valves in the mitral position, we recommend a target INR of 3.0 (range, 2.5 to 3.5) [Grade 1C+]. For patients with caged ball or caged disk valves, we suggest a target INR of 3.0 (range, 2.5 to 3.5) in combination with aspirin, 75 to 100 mg/d (Grade 2A). For patients with bioprosthetic valves, we recommend vitamin K antagonists with a target INR of 2.5 (range, 2.0 to 3.0) for the first 3 months after valve insertion in the mitral position (Grade 1C+) and in the aortic position (Grade 2C). For patients with bioprosthetic valves who are in sinus rhythm and do not have AF, we recommend long-term (> 3 months) therapy with aspirin, 75 to 100 mg/d (Grade 1C+).

Should aspirin be continued in patients started on warfarin?

BACKGROUND AND OBJECTIVE

Clinicians frequently face the decision of whether to continue aspirin when starting patients on warfarin. We performed a meta-analysis to characterize the tradeoffs involved in this common clinical dilemma.

DATA SOURCES

Multiple computerized databases (1966 to 2003), reference lists of relevant articles, conference proceedings, and queries of primary authors.

STUDY SELECTION

Randomized trials comparing warfarin plus aspirin versus warfarin alone. Studies with target international normalized ratios (INRs) <2 were excluded.

DATA EXTRACTION

Two reviewers independently extracted baseline data and major outcomes: rates of thromboembolism, hemorrhage, and all-cause mortality.

DATA SYNTHESIS

Nine studies met the inclusion criteria. Of the five that enrolled patients with mechanical heart valves, four used the same target INR in both groups, while one used a reduced target INR for the warfarin plus aspirin group. Pooling the results of the first four studies demonstrated that combination of warfarin plus aspirin significantly decreased thromboembolic events (relative risk [RR], 0.33; 95% confidence interval [CI], 0.19 to 0.58), increased major bleeding (RR, 1.58; 95% CI, 1.02 to 2.44), and decreased all-cause mortality (RR, 0.43; 95% CI, 0.23 to 0.81) compared to warfarin alone. The one valve trial using a reduced INR in the warfarin plus aspirin group reported no difference in thromboembolic outcomes but found decreased major bleeding and a significant mortality benefit with combination therapy. Of the remaining trials, three evaluated a warfarin indication not routinely used in the United States (post-myocardial infarction), and the only trial that considered atrial fibrillation was terminated early due to inadequate enrollment.

CONCLUSIONS

For mechanical heart valve patients, the benefits of continuing aspirin when starting warfarin therapy are clear. For other routine warfarin indications, there are not adequate data to guide this common clinical decision.

Antiplatelet and anticoagulation for patients with prosthetic heart valves

BACKGROUND

Patients with prosthetic heart valves are at increased risk for valve thrombosis and arterial thromboembolism. Oral anticoagulation alone, or the addition of antiplatelet drugs, has been used to minimize this risk. An important issue is the effectiveness and safety of the latter strategy.

OBJECTIVES

To compare the effectiveness and safety of adding antiplatelet therapy to standard oral anticoagulation among patients with prosthetic heart valves.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (Cochrane Library Issue 2, 2003), MEDLINE (January 1966 to August 2002), EMBASE (January 1988 to July 2001) and reference lists of individual reports, review articles, meta-analyses, and consensus statements.

SELECTION CRITERIA

All reports of randomised controlled trials comparing standard dose oral anticoagulation to standard dose oral anticoagulation and antiplatelet therapy in patients with one or more prosthetic heart valves. We included reports published in any language or in abstract form.

DATA COLLECTION AND ANALYSIS

Two reviewers independently performed the search strategy, assessed trials for inclusion criteria, study quality, and extracted data. Adverse effects information was collected from the trials.

MAIN RESULTS

Eleven studies involving 2,428 subjects met the inclusion criteria. Year of publication ranged from 1971 to 2000. Compared with anticoagulation alone, the addition of an antiplatelet agent reduced the risk of thromboembolic events (odds ratio 0.39 (95% confidence interval 0.28 to 0.56; p<0.00001)) and total mortality (odds ratio 0.55 (95% confidence interval 0.40 to 0.77; p=0.0003)). Aspirin and dipyridamole reduced these events similarly. The risk of major bleeding was increased when antiplatelet agents were added to oral anticoagulants (odds ratio 1.66 (95% confidence interval 1.18 to 2.34; p=0.003)). For major bleeding, there was no evidence of heterogeneity between aspirin and dipyridamole and in the comparison of trials performed before and after 1990, around the time when anticoagulation standardization with the international normalized ratio was being implemented.

REVIEWER'S CONCLUSIONS

Adding antiplatelet therapy, either dipyridamole or low-dose aspirin, to oral anticoagulation decreases the risk of systemic embolism or death among patients with prosthetic heart valves. The risk of major bleeding is increased with antiplatelet therapy. These results apply to patients with mechanical prosthetic valves or those with biological valves and indicators of high risk such as atrial fibrillation or prior thromboembolic events. The effectiveness and safety of low dose aspirin (100 mg daily) appears to be similar to higher dose aspirin and dipyridamole.

Risks and benefits of adding anti-platelet therapy to warfarin among patients with prosthetic heart valves: a meta-analysis

OBJECTIVES

The objective of this study was to compare the effectiveness and safety of adding dipyridamole or aspirin to warfarin among patients with prosthetic heart valves using meta-analytic techniques.

BACKGROUND

Patients with prosthetic heart valves are at increased risk for valve thrombosis and arterial thromboembolism. Oral anticoagulation alone, or the addition of antiplatelet drugs, has been used to minimize this risk. An important issue is the effectiveness and safety of the latter strategy.

METHODS

A combined MEDLINE and manual search was made for relevant articles from 1966 to November 1999. Standard meta-analysis techniques were used.

RESULTS

Ten studies involving 2,199 subjects met the inclusion criteria. Compared with anticoagulation alone, the addition of an antiplatelet agent reduced the risk of thromboembolic events (odds ratio [OR]: 0.41, p < 0.001) and total mortality (OR: 0.49, p < 0.001). The risk of major bleeding was increased when antiplatelet agents were added (OR: 1.50, p = 0.033). For major bleeding, the comparison of trials performed before and after 1990 (OR: 2.23 and 0.88, respectively) showed that the chi-square test for heterogeneity was significant (p = 0.025). The latter trials used low-dose aspirin, suggesting that the risk of bleeding may be lower with contemporary low-dose (100 mg daily) aspirin.

CONCLUSIONS

Adding antiplatelet therapy, especially low-dose aspirin, to warfarin decreases the risk of systemic embolism or death among patients with prosthetic heart valves. The risk of major bleeding is slightly increased with antiplatelet therapy. Nonetheless, the risk of bleeding appears to have diminished with the lower doses of aspirin used in the more recent trials, resulting in a favorable risk-to-benefit profile.

Hemorrhagic complications of anticoagulant treatment

Bleeding is the major complication of anticoagulant therapy. The criteria for defining the severity of bleeding varied considerably between studies, accounting in part for the variation in the rates of bleeding reported. Since the last review, there have been several meta-analyses published on the rates of major bleeding in trials of anticoagulants for atrial fibrillation and ischemic heart disease. The major determinants of oral anticoagulant-induced bleeding are the intensity of the anticoagulant effect, underlying patient characteristics, and the length of therapy. There is good evidence that low-intensity oral anticoagulant therapy (targeted INR of 2.5; range, 2.0 to 3.0) is associated with a lower risk of bleeding than therapy targeted at a higher intensity. Lower-intensity regimens (INR < 2.0) are associated with an even smaller increase in major bleeding. In terms of treatment decision making for anticoagulant therapy, bleeding risk cannot be considered alone, ie, the potential decrease in thromboembolism must be balanced against the potential increased bleeding risk. The risk of bleeding associated with IV heparin in patients with acute venous thromboembolism is < 3% in recent trials. There is some evidence to suggest that this bleeding risk increases with the heparin dosage and age (> 70 years). LMW heparin is not associated with increased major bleeding compared with standard heparin in acute venous thromboembolism. Standard heparin and LMW heparin are not associated with an increase in major bleeding in ischemic coronary syndromes, but are associated with an increase in major bleeding in ischemic stroke.

Effect of aortic valve replacement on plasma soluble P-selectin, von Willebrand factor, and fibrinogen

We measured indexes of platelet activation (soluble P-selectin), endothelial dysfunction (von Willebrand factor), and fibrinogen in 54 patients who underwent aortic valve replacement (AVR): after mechanical AVR implantation, there was a significant increase in plasma levels of soluble P-selectin and von Willebrand factor levels 3 months after surgery, with no change in mean plasma fibrinogen levels. No significant changes in measured indexes were noted in patients undergoing biologic AVR, suggesting that mechanical AVR results in abnormal endothelial damage and/or dysfunction and platelet activation, which is not apparent among patients undergoing this procedure.

Clinical scoring systems for determining the prognosis of gastrointestinal bleeding

The prognosis of GI bleeding depends upon many factors. Patients should be evaluated carefully for risk factors. To avoid complications from GI bleeding, triage should be performed promptly after patient presentation. The history and physical examination should emphasize analysis of risk factors for severe GI bleeding and mortality. Factors that increase the morbidity and mortality include: age greater than 60 years; underlying comorbidity such as pulmonary diseases, liver diseases, renal diseases, encephalopathy, or cancer; physiologic stress from major surgery, trauma, or sepsis; coexisting disease in three organ systems; low hematocrit; melena or hematochezia; and prolonged prothrombin time. Hospitalized patients who require more than five units of packed erythrocytes transfusion or who develop hypotension or hypovolemic shock are more likely to need surgery. Patients with a high APACHE II score, the presence of esophageal varices, active bleeding, or other endoscopic stigmata of recent hemorrhage are more likely to rebleed and undergo surgery. The proliferation of multivariable prognostic scales, as described herein, provides ample evidence that the goal of developing a single comprehensive multivariable scale to accurately assess severity of disease and to determine prognosis of GI bleeding is still not achieved. Yet significant progress has occurred in this field, leading to the hope of developing a universally applicable multivariable scale.

Early and long-term (one-year) effects of the association of aspirin and oral anticoagulant on thrombi and morbidity after replacement of the mitral valve with the St. Jude medical prosthesis: a clinical and transesophageal echocardiographic study

OBJECTIVES

The aim of the study was to test the value of low dose aspirin associated with standard oral anticoagulants (OAC) after mechanical mitral valve replacement (MMRV) to reduce strands, thrombi and thromboembolic events.

BACKGROUND

Strands and thrombi are thought to increase the risk of embolic events after MMVR, particularly in the immediate postoperative period.

METHODS

Two hundred twenty-nine patients were prospectively recruited: 109 patients (group A+) were randomly assigned to aspirin (200 mg per day) with OAC and 120 patients (group A-) to OAC alone (international normalized ratio 2.5 to 3.5). All patients were subjected to multiplane transesophageal echocardiography at nine days and five months and were followed up for one year.

RESULTS

At nine days and five months, there was a high and comparable incidence of strands in the two groups (group A+: 44%, 58%; group A-: 49%, 63%). However, the incidence of nonobstructive periprosthetic valve thrombi was significantly lower in group A+ at 9 days: 5% versus 13%, p = 0.03. Total thromboembolic events were reduced in group A+ (9% vs. 25%, p = 0.004) although there was an increased incidence of gastrointestinal hemorrhage (7% vs. 0%). Overall mortality was 9% in group A+ and 4% in group A-. Valve-related events were similar in both groups. Early thrombi, but not strands, were associated with higher morbidity, especially thromboembolic events (30% vs. 13%, p = 0.003).

CONCLUSIONS

One year after MMVR, the association of aspirin with OAC reduced thrombi and thromboembolic events, but not morbidity, due to an increase in hemorrhagic complications.

Controversies in Antithrombotic Therapy in Cardiovascular Diseases

Antithrombotic treatment became an important point in human medical treatment. Dicoumarols, heparin, aspi rin, and more recently, direct antithrombins and platelet glyco protein IIb/IIIa receptor blockers are the most frequent medi cations used as antithrombotics. The role of these drugs in the treatment of cardiovascular diseases remains controversial. Low-dose aspirin (80-100 mg/day) should be used for second ary prevention in patients with a history of coronary disease. Primary prevention in patients with no risk factors is not rec ommended. Studies using oral anticoagulant therapy indicated that long-term therapy achieves substantial benefit in arterial complications in patient survivors of myocardial infarction. Combined therapy of aspirin and a higher dose of oral antico agulant than that used in the CARS trial seem necessary after myocardial infarction, and further studies should be under taken. In the treatment of unstable angina, the combined use of aspirin and unfractioned heparin (UFH) is widely accepted. Low molecular weight heparin (LMWH) was also proposed for the treatment of these patients, but the beneficial effect of LMWH over UFH is a matter of discussion, and more prospec tive studies with different LMWHs should be undertaken be fore reaching a definitive answer. The use of hirudin needs additional studies because its superiority over heparin is un- proved. The initial clinical experience with blockers/inhibitors of platelet glycoprotein IIb/IIIa receptors has been promising, although some increase of bleeding was reported. According to published trials on the use of antiplatelet drugs and antithrom botic therapy in the prevention of acute closure after PTCA or after stent implantation, antithrombotic therapy decreased the incidence of abrupt closure or reocclusion at 30 days postan gioplasty, but neither antiplatelet agents nor other pharmaco logical agents have been shown to reduce significantly the rate of restenosis. Finally, oral anticoagulant in a target INR of 2.0 to 3.0 together with aspirin 100 mg/day provide good protec tion from thromboembolism and diminish the rate of minor bleeding complications in patients with cardiac valve replace ment.

Low-intensity oral anticoagulation plus low-dose aspirin versus high-intensity oral anticoagulation alone: a randomized trial in patients with mechanical prosthetic heart valves

BACKGROUND

Mechanical heart valve replacement requires lifelong anticoagulant treatment. Aspirin has proved useful in further reducing thromboembolic events when added to oral anticoagulants. However, increased (gastrointestinal) bleeding was observed at the doses previously tested for this combination in heart valve prostheses.

METHODS

We performed a prospective randomized trial to compare the combination of low-intensity oral anticoagulants (international normalized ratio 2.5 to 3.5) plus aspirin (100 mg/day) (arm A) versus high-intensity oral anticoagulants alone (arm B) (international normalized ratio 3.5 to 4.5). Arm A included 258 patients and arm B 245 patients. The two groups were comparable for all baseline characteristics.

RESULTS

The outcomes of the study were embolism, valve thrombosis, and major hemorrhage. The median follow-up was 23 months. The two treatments offered similar antithrombotic protection. The incidence of embolic episodes was 1.32 per 100 patient-years (95% confidence interval 0.53 to 2.7) for arm A and 1.48 per 100 patient-years (95% confidence interval 0.59 to 3.03) for arm B. Major hemorrhage occurred in 1.13 per 100 patient-years (95% confidence interval 0.41 to 2.45) for arm A and 2.33 per 100 patient-years (95% confidence interval 1.17 to 4.14) for arm B. Gastrointestinal bleeding was not increased by this combined reduced dose of aspirin and coumarin.

Safer anticoagulant therapy after heart valve replacement. Recommendations for less intense regimens

The use of anticoagulants in patients who undergo heart valve replacement greatly reduces the rate of thromboembolism but increases the risk of bleeding. A number of studies have been done to determine the efficacy of anticoagulation regimens that are less intense than those considered standard. Dr Turpie reviews these and lists the current recommendations of the American College of Chest Physicians.

Prevalence of Anemia and Occult Blood Losses in the Long-Term Follow-Up of Cardiac Mechanic Valve Patients Treated with a Combination of Low-Dose Aspirin Plus Low-Intensity Acenocoumarin

Mechanic replacement of cardiac prostheses requires lifelong and high-intensity oral anticoagulant treatment. The addition of aspirin to coumarin treatment has resulted in more effective thromboembolic prevention, though it also led to increased (digestive) bleeding. Aspiriri enhanced the risk of apparent or occult gastrointestinal bleeding in a dose-dependent fashion. The combined use of low-dose aspirin/low-intensity coumarins might offer a safer approach. We prospectively evaluated the prevalence of anemia markers in 127 prosthesic valve patients, receiving two treatment modalities: Group A comprised 62 patients who received 100 mg acetylsalicylic acid (ASA) added to acenocoumarin [international normatized ratio (INR) 2.5-3.5]. Group B comprised 65 patients receiving acenocoumarin alone (INR, 3.5-4.5). We found no significant differences in the mean values for the blood markers of anemia or for the presence of blood losses in urine and feces. The addition of low-dose ASA to less intense chronic anticoagulation does not increase the risk of developing anemia. Key Words: Anticoagulants—Aspirin—Coumarins—Gastrointestinal hemorrhage—Heart valve prosthesis.