Combination therapy with warfarin plus clopidogrel improves outcomes in femoropopliteal bypass surgery patients

Therapeutic anticoagulation after index peripheral endovascular intervention in patients with claudication

OBJECTIVE

Antiplatelet agents are commonly used after peripheral endovascular intervention (PVI). However, the effect of full-dose anticoagulation on outcomes after PVI is not well-established. We sought to investigate whether full-dose anticoagulation after PVI is associated with adverse events.

METHODS

We utilized the Vascular Quality Initiative to study patients undergoing index PVI for claudication (2010-2019), stratified by the presence or absence of an anticoagulant on discharge. The primary outcomes were 2-year patency, major adverse limb events (MALE), and mortality. We built a propensity score adjusting for comorbidities and employed inverse probability weighting to estimate the association of anticoagulation with outcomes.

RESULTS

We identified 26,240 patients; 9.1% were discharged on an anticoagulant. Patients receiving any anticoagulation had a significantly higher risk of mortality (adjusted hazard ratio [aHR], 1.61; 95% confidence interval [CI], 1.35-1.92), but not MALE, or patency loss. Patients receiving a vitamin K antagonist had a significantly higher risk of patency loss (aHR, 1.32; 95% CI, 1.09-1.60), MALE (aHR, 1.33; 95% CI, 1.13-1.57), and mortality (aHR, 1.46; 95% CI, 1.27-1.69). Patients on an oral Factor Xa inhibitors had a significantly lower risk of patency loss (aHR, 0.61; 95% CI, 0.41-0.93) but increased mortality (aHR, 1.51; 95% CI, 1.19-1.92).

CONCLUSIONS

Therapeutic anticoagulation after PVI is associated with higher risk of all-cause mortality. Although oral Factor Xa inhibitors are associated with decreased risk of patency loss, vitamin K antagonists are associated with higher risk of patency loss, MALE, and death. Further prospective studies are necessary to study the safety and efficacy of full-dose anticoagulation after PVI.

Antithrombotic Therapy for Symptomatic Peripheral Arterial Disease: A Systematic Review and Network Meta-Analysis

BACKGROUND

High-quality evidence from trials directly comparing single antiplatelet therapies in symptomatic peripheral arterial disease (PAD) to dual antiplatelet therapies or acetylsalicylic acid (ASA) plus low-dose rivaroxaban is lacking. Therefore, we conducted a network meta-analysis on the effectiveness of all antithrombotic regimens studied in PAD.

METHODS

A systematic search was conducted to identify randomized controlled trials. The primary endpoints were major adverse cardiovascular events (MACE) and major bleedings. Secondary endpoints were major adverse limb events (MALE) and acute limb ischaemia (ALI). For each outcome, a frequentist network meta-analysis was used to compare relative risks (RRs) between medication and ASA. ASA was the universal comparator since a majority of studies used ASA as in the reference group.

RESULTS

Twenty-four randomized controlled trials were identified including 48,759 patients. With regard to reducing MACE, clopidogrel [RR 0.78, 95% confidence interval (CI) 0.66-0.93], ticagrelor (RR 0.79, 95% CI 0.65-0.97), ASA plus ticagrelor (RR 0.79, 95% CI 0.64-0.97), and ASA plus low-dose rivaroxaban (RR 0.84, 95% CI 0.76-0.93) were more effective than ASA, and equally effective to one another. As compared to ASA, major bleedings occurred more frequently with vitamin K antagonists, rivaroxaban, ASA plus vitamin K antagonists, and ASA plus low-dose rivaroxaban. All regimens were similar to ASA concerning MALE, while ASA plus low-dose rivaroxaban was more effective in preventing ALI (RR 0.67, 95% CI 0.55-0.80). Subgroup analysis in patients undergoing peripheral revascularization revealed that ≥ 3 months after intervention, evidence of benefit regarding clopidogrel, ticagrelor, and ASA plus ticagrelor was lacking, while ASA plus low-dose rivaroxaban was more effective in preventing MACE (RR 0.87, 95% CI 0.78-0.97) and MALE (RR 0.89, 95% CI 0.81-0.97) compared to ASA. ASA plus clopidogrel was not superior to ASA in preventing MACE ≥ 3 months after revascularization. Evidence regarding antithrombotic treatment strategies within 3 months after a peripheral intervention was lacking.

CONCLUSION

Clopidogrel, ticagrelor, ASA plus ticagrelor, and ASA plus low-dose rivaroxaban are superior to ASA monotherapy and equally effective to one another in preventing MACE in PAD. Of these four therapies, only ASA plus low-dose rivaroxaban provides a higher risk of major bleedings. More than 3 months after peripheral vascular intervention, ASA plus low-dose rivaroxaban is superior in preventing MACE and MALE compared to ASA but again at the cost of a higher risk of bleeding, while other treatment regimens show non-superiority. Based on the current evidence, clopidogrel may be considered the antithrombotic therapy of choice for most PAD patients, while in patients who underwent a peripheral vascular intervention, ASA plus low-dose rivaroxaban could be considered for the long-term (> 3 months) prevention of MACE and MALE.

Effect of Direct Oral Anticoagulants versus Warfarin on Patency in High-Risk Bypass Patients

OBJECTIVES

The use of warfarin for anticoagulation in thromboembolic disease has been the mainstay of treatment. Direct oral anticoagulants (DOACs) have demonstrated equivalent anticoagulant effects, without increased bleeding risks or need for frequent monitoring. However, the role of DOACs remains unclear in the setting of replacing warfarin for high-risk peripheral artery disease (PAD) interventions. The purpose of this study is to evaluate the efficacy of DOACs compared to warfarin during the postoperative period in patients that underwent a lower extremity high risk bypass (HRB).

METHODS

The study is a single institution, retrospective review of all lower extremity HRBs be-tween January 2012 and June 2021, who were previously placed on or started on anticoagulation with a DOAC or warfarin. The HRB group included all patients undergoing femoral to above or below knee bypass with an adjunct procedure, or below knee bypass with synthetic or composite vein conduit. All demographics, preoperative factors, and complications were evaluated with respect to DOAC versus warfarin.

RESULTS

A total of 44 patients (28 males; average age 68.8 ± 10.9) underwent a HRB during the study period. There were no significant differences in demographics and preoperative characteristics between the two groups. Among patient comorbidities, coronary artery disease was found to be significantly higher in patients on DOACs (p=0.03). The 12-month primary patency rate was 83.3% vs 57.1%, for DOAC vs warfarin respectively (p=0.03). Multivariate analyses revealed that <30-day reinterventions contribute to 12-month patency (p=0.02).

CONCLUSION

Patients who underwent lower extremity HRB with postoperative DOAC appeared to exhibit higher graft patency rates than those who were placed on warfarin. Due to their low incidence of undesirable side effects and the lack of frequent monitoring, DOACs could be considered a safe alternative to warfarin in the postoperative period for patients with HRB.

Canadian Cardiovascular Society 2022 Guidelines for Peripheral Arterial Disease

Patients with widespread atherosclerosis such as peripheral artery disease (PAD) have a high risk of cardiovascular and limb symptoms and complications, which affects their quality of life and longevity. Over the past 2 decades there have been substantial advances in diagnostics, pharmacotherapy, and interventions including endovascular and open surgical to aid in the management of PAD patients. To summarize the evidence regarding approaches to diagnosis, risk stratification, medical and intervention treatments for patients with PAD, guided by the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) framework, evidence was synthesized, and assessed for quality, and recommendations provided-categorized as weak or strong for each prespecified research question. Fifty-six recommendations were made, with 27% (15/56) graded as strong recommendations with high-quality evidence, 14% (8/56) were designated as strong recommendations with moderate-quality evidence, and 20% (11/56) were strong recommendations with low quality of evidence. Conversely 39% (22/56) were classified as weak recommendations. For PAD patients, strong recommendations on the basis of high-quality evidence, include smoking cessation interventions, structured exercise programs for claudication, lipid-modifying therapy, antithrombotic therapy with a single antiplatelet agent or dual pathway inhibition with low-dose rivaroxaban and aspirin; treatment of hypertension with an angiotensin converting enzyme or angiotensin receptor blocker; and for those with diabetes, a sodium-glucose cotransporter 2 inhibitor should be considered. Furthermore, autogenous grafts are more effective than prosthetic grafts for surgical bypasses for claudication or chronic limb-threatening ischemia involving the popliteal or distal arteries. Other recommendations indicated that new endovascular techniques and hybrid procedures be considered in patients with favourable anatomy and patient factors, and finally, the evidence for perioperative risk stratification for PAD patients who undergo surgery remains weak.

A Review of Antithrombotic Therapies for Patients with Chronic Peripheral Arterial Disease and after Revascularization

Peripheral arterial disease (PAD) represents a major health issue that significantly impacts patient's survival and quality of life. In addition to limb-related events, patients with PAD have an increased risk of myocardial infarction, stroke, and death. However, compared with coronary and cerebrovascular disease, studies addressing optimal risk reduction modalities including antithrombotic therapies in patients with PAD have been underrepresented in the literature. This publication serves as a narrative review of existing evidence on the effectiveness of antithrombotic therapy in patients with PAD. In patients with chronic stable PAD or post-revascularization, antithrombotic therapies including single or dual antiplatelet agents, anticoagulation, or a combination of these treatments have been shown to reduce cardiovascular and limb events. This narrative review provides a summary of the available literature on the management of patients with PAD, categorized into treatment strategies for chronic, post-endovascular treatment, and post-open surgical revascularization and to discuss the antithrombotic protocol utilized at our institution while providing a rational for our treatment algorithm.

Antithrombotic Therapy in Peripheral Artery Disease: Stepping in the Right Direction

We reviewed the various antithrombotic therapies available to treat peripheral artery disease (PAD). A literature review using the PubMed and MEDLINE databases used the following keywords: antithrombotic therapy, anticoagulation, peripheral artery disease, and peripheral vascular disease. Randomized studies written in English that assessed the use of antithrombotic therapy in patients with PAD were evaluated. PAD is a worldwide condition that limits blood flow in the lower extremities, leading to a risk of major adverse cardiovascular events and major adverse limb events. Antithrombotic therapy is necessary to prevent these complications, and the choice of therapy depends upon the stage of disease progression. For symptomatic patients in the beginning stage, single antiplatelet therapy (SAPT) is the preferred therapy, specifically, aspirin. For patients undergoing endovascular revascularization, the preferred therapy is dual antiplatelet therapy using aspirin and clopidogrel combined for at least the first month followed by long-term SAPT. For patients undergoing surgical revascularization, the preferred choice of therapy depends upon the type of graft used, with better results obtained with antiplatelet therapy for prosthetic grafts and anticoagulation for venous grafts. New studies have shown that therapy using both antiplatelets and anticoagulation in the form of aspirin plus low-dose rivaroxaban can reduce complications in all three patient populations, which has paved the way for future studies featuring direct oral anticoagulants with the potential to change current guideline recommendations.

Efficacy and Safety of Antiplatelet Therapies in Symptomatic Peripheral Artery Disease: A Systematic Review and Network Meta-Analysis

BACKGROUND

Clopidogrel monotherapy is guideline-recommended in symptomatic peripheral artery disease (PAD). The advent of new antithrombotic strategies prompts an updated analysis of available evidence on antiplatelet therapy for PAD.

METHODS

We searched MEDLINE, Embase and CENTRAL through January 2019 for randomised controlled trials and observational studies comparing antiplatelet therapies as monotherapy, dual therapy, or combination with anticoagulants. Efficacy (major adverse cardiovascular events, acute or chronic limb ischaemia, vascular amputation, peripheral revascularisation) and safety (all-cause mortality and overall bleeding) outcomes were evaluated via Bayesian network meta-analyses.

RESULTS

We analysed 26 randomised controlled trials. Clopidogrel (hazard ratio, HR, 0.78; 95% credible interval [CrI] 0.65-0.93) and ticagrelor (HR 0.80; 95% CrI 0.65-0.98) significantly reduced major adverse cardiovascular events risk compared with aspirin. No significant difference was observed for dual antiplatelet therapy with clopidogrel and aspirin. Vorapaxar significantly reduced limb ischaemia and revascularisation compared with placebo, while dual antiplatelet therapy with clopidogrel and aspirin showed a trend for reduced risk of amputation compared with aspirin (risk ratio 0.68; 95% CrI 0.43-1.04). For all-cause mortality, picotamide, vorapaxar, dipyridamole with aspirin, and ticlopidine showed a significantly lower risk of all-cause mortality vs aspirin. Clopidogrel and ticagrelor showed similar overall bleeding risk vs aspirin, while dual antiplatelet therapy with clopidogrel and aspirin significantly increased bleeding risk.

CONCLUSION

This updated network meta-analysis confirms that clopidogrel significantly decreases the risk of major adverse cardiovascular events compared with aspirin, without increasing bleeding risk. Clopidogrel should remain a mainstay of PAD treatment, at least in patients at higher bleeding risk.

Antithrombotic therapy for postinterventional management of peripheral arterial disease

PURPOSE

Evidence on the use of antithrombotic pharmacotherapy in patients undergoing revascularization of lower extremities for symptomatic peripheral arterial disease (PAD) is reviewed.

SUMMARY

Individuals with PAD can experience leg pain, intermittent claudication, critical limb ischemia, and acute limb ischemia. In such patients, revascularization may be indicated to improve the quality of life and to prevent amputations. Antithrombotic therapy is often intensified in the postrevascularization period to prevent restenosis of the index artery and to counteract the prothrombotic state induced by the intervention. Therapeutic modalities include dual antiplatelet therapy (DAPT), anticoagulation, a combination of antiplatelet and anticoagulation therapy, and addition of cilostazol to single antiplatelet therapy. Subgroup analyses of data from randomized clinical trials provided low-quality evidence for the use of DAPT in patients with a below-knee prosthetic bypass graft and anticoagulation for those with a venous bypass graft. Cilostazol, when added to aspirin therapy, has been shown to prevent index vessel reocclusion after an endovascular intervention in patients at low risk for thrombosis in several small randomized trials.

CONCLUSION

There is a considerable paucity of high-quality evidence on the optimal antithrombotic regimen for patients undergoing lower extremity revascularization, with no particular therapy shown to consistently improve patient outcomes. The decision to initiate intensified antithrombotic therapy should include a close examination of its risk-benefit profile. The demonstrated benefit of such treatment is restricted to the prevention of index artery reocclusion, while an increased risk of bleeding may lead to significant morbidity and mortality.

Design, synthesis, and biological evaluation of 4-methoxy-3-arylamido-N-(substitutedphenyl)benzamide derivatives as potential antiplatelet agents

A series of 4-methoxy-3-arylamido-N-(substitutedphenyl)benzamides 6a-u were designed according to the splicing principle of structural design in the medicinal chemistry theory and were synthesized in five steps: nitration, acylation, ammoniation, reduction, and secondary ammoniation. The structures of the target compounds were characterized and verified by infrared, ¹ H nuclear magnetic resonance (NMR), ¹³ C NMR, and electron spray ionization spectroscopy. Their in vitro antiplatelet aggregation activities induced by adenosine diphosphate (ADP) or arachidonic acid (AA) were assessed by Born's method. The biological evaluation revealed that all compounds exhibited certain levels of activities in both of the antiplatelet aggregation assays; compounds 6c (IC₅₀  = 3.84 μM) and 6f (IC₅₀  = 3.12 μM) displayed the strongest antiplatelet aggregation activities in the ADP-induced and AA-induced assay, separately. Moreover, compounds that had stronger activities were chosen for cell toxicity testing via the cell counting kit-8 assay. The results indicated that none of the compounds had obvious cell toxicity against L929 cells at the doses of 10 and 20 μM. It is worth pointing out that compound 6c showed the highest antiplatelet activity and the lowest cell toxicity. In general, 4-methoxy-3-arylamido-N-(substitutedphenyl)benzamides have the potential to become a kind of safer and more effective antiplatelet agents.

[Therapeutic aspects of the choice of antithrombotic therapy in patients with multifocal lesions of peripheral arteries]

The article discusses the features of the development and course of the atherosclerotic process in various vascular basins. Variability of factors such as local hemodynamics, differences in the structure of the arteries can influence the formation of atherosclerotic plaque and the progression of the atherosclerotic process. A better understanding of the nature and causes of these differences can help improve the tactics of treatment and prevention of vascular complications. Analysis of the results of the COMPASS study (cardiovascular outomes for people using anticoagulation stategies - evaluation of cardiovascular outcomes in patients receiving anticoagulant therapy) showed for the first time the effectiveness of combination therapy using rivaroxaban direct anticoagulant at a dose of 2.5 mg 2 times a day in combination with acetylsalicylic acid at a dose of 100 mg per day. It was shown that, against the background of combination therapy, patients with coronary heart disease or atherosclerotic peripheral artery disease showed a significant decrease in the incidence of events of the primary end point of efficacy: a reduced risk of stroke, cardiovascular mortality and myocardial infarction, and also a reduction in the risk of major lower amputations extremities and total mortality in patients with stable forms of atherosclerosis. The emergence of combination therapy can help to achieve both an improvement in the overall prognosis and the prognosis of limb preservation in patients with multifocal arterial lesion.

Critical evaluation on proper antithrombotic treatment in different groups of patients undergoing vascular surgery

Antithrombotic treatment including anticoagulants and antiplatelets has evolved during the last decades, and several recommendations have been included in the latest guidelines regarding the proper management of patients undergoing vascular surgery. However, there are significant differences compared to older recommendations, and indications vary among patients with peripheral artery disease, carotid disease, and abdominal aortic aneurysm. In this mini review, we critically evaluate all these data to produce useful conclusions for everyday clinical practice.

Comparative effectiveness of anticoagulation on midterm infrainguinal bypass graft patency

OBJECTIVE

Therapeutic anticoagulation (AC) is used clinically for prolongation of infrainguinal bypass patency, but evidence for the efficacy of this practice is conflicting. The objective of our study was to determine the association of AC with bypass graft primary patency.

METHODS

Clinical and comorbid data of patients undergoing infrainguinal bypass grafts to a below-knee target with at least 1 year of follow-up performed from 2003 to 2015 were obtained from the Society for Vascular Surgery Vascular Quality Initiative. Inverse propensity of treatment-weighted Cox regression was used to assess the effect of AC on patency in the total cohort while adjusting for clinical, operative, and comorbid differences between treatment groups. Subgroup analyses of distal targets and conduit type were performed. Perioperative complications were analyzed using propensity-weighted logistic regression.

RESULTS

We identified 7612 bypass grafts with intact 1-year follow-up information from 2003 to 2015. The mean age was 67.5 ± 11.2 years; 30.5% (n = 2320) were female, and 28.6% (n = 2165) were discharged on therapeutic AC. The anticoagulated group had a higher rate of tibial, ankle, and pedal targets (52.1% [n = 1127] vs 47.6% [n = 2269]; P < .001), had a greater use of non-single-segment vein conduits (44.3% [n = 951] vs 26.5% [n = 1426]; P < .001), and was more likely to have had a previous ipsilateral bypass (27.2% [n = 589] vs 14.7% [n = 794]; P < .001) or stent (25.4% [n = 550] vs 20.9% [n = 1130]; P < .001). Estimated unadjusted primary patency was 70.8% ± 0.6% at 1 year and lower for anticoagulated bypasses (66.9% ± 1.2% vs 72.4% ± 0.7%; P < .001). Propensity-weighted analysis showed no significant association of AC with primary patency in the overall cohort (hazard ratio [HR], 0.98; 95% confidence interval [CI], 0.86-1.11; P = .8) but demonstrated a trend toward improvement of primary patency in those with a non-single-segment vein conduit to a below-knee popliteal target (HR, 0.85; 95% CI, 0.80-1.02; P = .09). AC was associated with significantly improved secondary patency in those with prosthetic bypass grafts (HR, 0.77; 95% CI, 0.62-0.96; P = .02) or prosthetic bypasses to an infrapopliteal target (HR, 0.72; 95% CI, 0.54-0.97; P = .02). Odds of postoperative wound complications were significantly higher in those receiving AC (odds ratio, 1.33; 95% CI, 1.11-1.61; P = .002).

CONCLUSIONS

This study does not demonstrate a significant impact of therapeutic AC on primary patency for infrainguinal bypass grafts. Treatment with AC may benefit secondary patency in those with a prosthetic bypass, especially to an infrapopliteal target, but at an increased risk of postoperative wound complications.

Synthesis and in Vitro and in Vivo Anticoagulant and Antiplatelet Activities of Amidino- and Non-Amidinobenzamides

Three amidino- and ten non-amidinobenzamides were synthesized as 3-aminobenzoic acid scaffold-based anticoagulant and antiplatelet compounds. The anticoagulant activities of thirteen synthesized compounds 1-13, and 2b and 3b as prodrugs were preliminary evaluated by screening the prolongation of activated partial thromboplastin time (aPTT) and prothrombin time (PT) in vitro. From the aPTT results obtained, two amidinobenzamides, N-(3'-amidinophenyl)-3-(thiophen-2''-ylcarbonylamino) benzamide (1, 33.2 ± 0.7 s) and N-(4'-amidinophenyl)-3-(thiophen-2''-ylcarbonylamino) benzamide (2, 43.5 ± 0.6 s) were selected to investigate the further anticoagulant and antiplatelet activities. The aPTT results of 1 (33.2 ± 0.7 s) and 2 (43.5 ± 0.6 s) were compared with heparin (62.5 ± 0.8 s) in vitro at 30 μM. We investigated the effect of 1 and 2 on blood anticoagulant activity (ex vivo) and on tail bleeding time (in vivo) on mice. A tail cutting/bleeding time assay revealed that both 1 and 2 prolonged bleeding time in mice at a dose of 24.1 g/mouse and above. Compounds 1 and 2 dose-dependently inhibited thrombin-catalyzed fibrin polymerization and platelet aggregation. In addition, 1 and 2 were evaluated on the inhibitory activities of thrombin and FXa as well as the generation of thrombin and FXa in human umbilical vein endothelial cells (HUVECs). Collectively, 1 and 2 possess some antiplatelet and anticoagulant activities and offer a basis for development of a novel antithrombotic product.

Vein graft failure: from pathophysiology to clinical outcomes

Occlusive arterial disease is a leading cause of morbidity and mortality worldwide. Aside from balloon angioplasty, bypass graft surgery is the most commonly performed revascularization technique for occlusive arterial disease. Coronary artery bypass graft surgery is performed in patients with left main coronary artery disease and three-vessel coronary disease, whereas peripheral artery bypass graft surgery is used to treat patients with late-stage peripheral artery occlusive disease. The great saphenous veins are commonly used conduits for surgical revascularization; however, they are associated with a high failure rate. Therefore, preservation of vein graft patency is essential for long-term surgical success. With the exception of 'no-touch' techniques and lipid-lowering and antiplatelet (aspirin) therapy, no intervention has hitherto unequivocally proven to be clinically effective in preventing vein graft failure. In this Review, we describe both preclinical and clinical studies evaluating the pathophysiology underlying vein graft failure, and the latest therapeutic options to improve patency for both coronary and peripheral grafts.

Role of Vitamin K Antagonists in the Prevention of Thrombotic Bypass Occlusion After Infrainguinal Venous Bypass

CLINICAL VIGNETTE

Despite being the most common antithrombotic strategy in trials comparing venous with prosthetic grafts, the use of vitamin K antagonists (VKAs) to improve the outcome of venous bypass remains the subject of debate. In this systematic review, evidence supporting the use of VKAs for improving venous patency following infrainguinal venous bypass is provided.

CLINICAL QUESTION

A 67 year old man with lifestyle limiting claudication underwent a successful infrainguinal venous bypass. Can VKAs help preserve patency after venous bypass surgery?

METHODS

A systematic review of electronic databases, including MEDLINE and Embase, was conducted. Only randomized controlled studies comparing VKAs with aspirin (ASA) were included. The main outcome was bypass patency.

RESULTS

Four studies using different intensities of anticoagulation ± ASA were identified. All but one showed a benefit of VKAs over ASA with respect to primary patency. However, this benefit was also accompanied by an increased risk of bleeding. The Dutch Bypass Oral Anticoagulants, or ASA, study was the largest included and showed that VKAs (without concomitant ASA) were superior to ASA alone for the prevention of graft occlusion (hazard ratio 0.69, 95% confidence interval 0.54-0.88).

CONCLUSION

Current evidence suggests that VKAs are superior to ASA for the prevention of infrainguinal autologous venous graft thrombosis.

Antiplatelet agents for preventing thrombosis after peripheral arterial bypass surgery

BACKGROUND

Peripheral arterial disease (PAD) may cause occlusions (blockages) in the main arteries of lower limbs. One treatment option is bypass surgery using autologous (the patient's own tissue) vein graft or prosthetic (artificial) graft. A number of factors influence occlusion rates in these patients, including the material used. To prevent graft occlusion patients are usually treated with antiplatelet, antithrombotic drugs, or a combination of both.

OBJECTIVES

To determine the effects of antiplatelet agents for the prevention of thrombosis in people with lower limb atherosclerosis who were undergoing femoropopliteal or femorodistal bypass grafting. Outcomes included the overall success of therapy (graft patency and limb salvage rates) and complications of treatment.

SEARCH METHODS

For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched June 2014) and the Cochrane Central Register of Controlled Trials (CENTRAL) (2014, Issue 5). We sought additional trials through screening the reference lists of relevant papers.

SELECTION CRITERIA

Two review authors, RB and AL, independently reviewed studies found in the search and evaluated them based on the inclusion and exclusion criteria, resolving disagreements through discussion.

DATA COLLECTION AND ANALYSIS

RB and AL independently extracted details of the selected studies for the update. We compared the treatment and control groups for important prognostic factors and differences described. If any data were unavailable, we sought further information from study authors. We synthesised data by comparing group results. We addressed unit of analysis issues by subgroup analysis.

MAIN RESULTS

We include 16 studies with 5683 randomised participants. Nine different treatment groups were evaluated: aspirin (ASA) or aspirin and dipyridamole (ASA/DIP) versus placebo or nothing (six studies); ASA or ASA/DIP versus pentoxifylline (two studies); ASA/DIP versus indobufen (one study); ASA or ASA/DIP versus vitamin K antagonists (two studies); ASA/DIP versus low molecular weight heparin (one study); ticlopidine versus placebo (one study); ASA versus prostaglandin E1 (one study); ASA versus naftidrofuryl (one study); and clopidogrel and ASA versus ASA alone (one study). The treatment comparisons were evaluated separately, and, where possible, we performed subgroup analysis for venous grafts and prosthetic grafts and at different follow-up time points. The quality of evidence was low to moderate as many of the treatment comparisons had very few studies to contribute data, several of the included studies had unit of analysis issues, the treatment dosages varied between studies, and data for many outcomes important to this review were not given in any of the studies, or differed greatly between studies. Overall study quality was moderate, with the largest problem being that the majority of studies did not describe their methods of randomisation, allocation concealment or blinding of outcome assessors, leading to risk ratings of 'unclear'. The other main issue with study quality was studies not blinding participants or personnel.The treatment comparison with the most number of included studies, which allowed for robust conclusions, was that of aspirin (ASA) or ASA and dipyridamole (ASA/DIP) versus placebo or nothing, covered by six studies. For this treatment group, there was improved graft patency in the ASA or ASA/DIP treatment group, odds ratio (OR) 0.42 (95% confidence interval (CI) 0.22 to 0.83; P = 0.01; 952 participants). This effect was not seen for venous grafts alone at any of the time points, but was observed for all time points in prosthetic grafts, including the final time point of 12 months (OR 0.19, 95% CI 0.10 to 0.36; P < 0.00001; 222 participants). Only a single study evaluated secondary patency, for which there was no difference between treatment groups. For the comparison ASA or ASA/DIP versus placebo or nothing there was no difference for any of the side effects, including general, gastrointestinal, bleeding and wound/graft infection. Amputations, cardiovascular events and mortality were also similar between the treatment groups. The comparison of ASA or ASA/DIP versus vitamin K antagonists included two studies, one of which was very large, with over 2000 participants. There were no differences between treatment for primary graft patency at three, six, 12 or 24 months, and there was also no evidence of a difference for limb amputation, cardiovascular events or mortality. One large study (851 participants) evaluated clopidogrel and ASA versus ASA alone, and for all grafts there was no evidence of a difference of primary patency at 24 months. There was evidence of increased total bleeding in the clopidogrel and ASA group (OR 2.65, 95% CI 1.69 to 4.15) from an increase in mild (OR 2.34, 95% CI 1.37 to 4.00), and moderate bleeding (OR 4.13, 95% CI 1.37 to 12.45), but no difference in severe or fatal bleeding. There was no difference between the treatment groups for limb amputation or mortality. For the remaining treatment comparisons there is not currently enough evidence to draw any robust conclusions about the efficacy or safety of the treatment on graft patency after peripheral bypass.

AUTHORS' CONCLUSIONS

Antiplatelet therapy with aspirin or with aspirin plus dipyridamole had a beneficial effect on primary patency of peripheral bypass grafts compared to placebo or no treatment. This effect was not evident when evaluating venous grafts alone, but antiplatelet therapy did have a beneficial effect on patency in those who had prosthetic grafts. There was no evidence of differences in side effects (including general, gastrointestinal, bleeding or infection), amputation, cardiovascular events or mortality between the treatment groups. However, the number of participants included in this analysis might be too small to detect a statistically significant effect for side effects, amputation, cardiovascular morbidity or mortality. We found no difference in primary graft patency when aspirin or aspirin with dipyridamole was compared to a vitamin K antagonist or when clopidogrel with aspirin was compared to aspirin alone. However, there was evidence of increase bleeding in the clopidogrel with aspirin group for the latter comparison. The remaining six treatment comparisons did not include enough data to draw any robust conclusions about their efficacy or safety at this time.

Antithrombotic therapy after infrainguinal bypass

OBJECTIVE

Bypass surgery is regularly performed for the treatment of critical limb ischemia, but the risk of occlusion remains significant. Antiplatelet therapy in patients with arterial disease is useful for secondary cardiovascular and bypass occlusion prevention. However, despite the common use of an antiplatelet agent, especially aspirin, which became the standard of care, the risk of graft occlusion persists. The best antithrombotic treatment for bypass patency therefore remains a matter of debate.

METHODS

We conducted a systematic literature search to identify studies and consensus reporting the use of antithrombotic treatment to prevent bypass occlusion. We excluded case reports and clinical trials with a placebo arm.

RESULTS

Aspirin remains the mainstay of treatment to improve infrainguinal bypass patency; however, the effect differs according to the bypass material used. The greatest beneficial effect of antiplatelet agents was observed with prosthetic bypasses. In such cases, the addition of clopidogrel to aspirin, for at least 1 year, in patients who benefited from a below-knee bypass graft significantly improved bypass patency (occlusion 32% vs 47% for aspirin alone; P = .02) and the amputation rate (9.4% vs 19.2% for aspirin alone; P = .03), without increasing the incidence of major hemorrhage. In contrast, antiplatelet regimens were less efficacious for autologous vein bypasses. The addition of a vitamin K antagonist (VKA) is not routinely proposed because of the increased incidence of associated major hemorrhage. The use of VKA alone, instead of aspirin, should probably be discussed in selected patients, and a combination of VKA and antiplatelet agents should be discussed in patients with venous infrainguinal bypasses considered to be at a high risk for occlusion.

CONCLUSIONS

Although aspirin remains the first-line treatment to prevent infrainguinal bypass occlusion, future studies are needed to define stronger recommendations.