Antithrombotic agents for preventing thrombosis after infrainguinal arterial bypass surgery

Graft type for femoro-popliteal bypass surgery

BACKGROUND

Femoro-popliteal bypass is implemented to save limbs that might otherwise require amputation, in patients with ischaemic rest pain or tissue loss; and to improve walking distance in patients with severe life-limiting claudication. Contemporary practice involves grafts using autologous vein, polytetrafluoroethylene (PTFE) or Dacron as a bypass conduit. This is the second update of a Cochrane review first published in 1999 and last updated in 2010.

OBJECTIVES

To assess the effects of bypass graft type in the treatment of stenosis or occlusion of the femoro-popliteal arterial segment, for above- and below-knee femoro-popliteal bypass grafts.

SEARCH METHODS

For this update, the Cochrane Vascular Information Specialist searched the Vascular Specialised Register (13 March 2017) and CENTRAL (2017, Issue 2). Trial registries were also searched.

SELECTION CRITERIA

We included randomised trials comparing at least two different types of femoro-popliteal grafts for arterial reconstruction in patients with femoro-popliteal ischaemia. Randomised controlled trials comparing bypass grafting to angioplasty or to other interventions were not included.

DATA COLLECTION AND ANALYSIS

Both review authors (GKA and CPT) independently screened studies, extracted data, assessed trials for risk of bias and graded the quality of the evidence using GRADE criteria.

MAIN RESULTS

We included nineteen randomised controlled trials, with a total of 3123 patients (2547 above-knee, 576 below-knee bypass surgery). In total, nine graft types were compared (autologous vein, polytetrafluoroethylene (PTFE) with and without vein cuff, human umbilical vein (HUV), polyurethane (PUR), Dacron and heparin bonded Dacron (HBD); FUSION BIOLINE and Dacron with external support). Studies differed in which graft types they compared and follow-up ranged from six months to 10 years.Above-knee bypassFor above-knee bypass, there was moderate-quality evidence that autologous vein grafts improve primary patency compared to prosthetic grafts by 60 months (Peto odds ratio (OR) 0.47, 95% confidence interval (CI) 0.28 to 0.80; 3 studies, 269 limbs; P = 0.005). We found low-quality evidence to suggest that this benefit translated to improved secondary patency by 60 months (Peto OR 0.41, 95% CI 0.22 to 0.74; 2 studies, 176 limbs; P = 0.003).We found no clear difference between Dacron and PTFE graft types for primary patency by 60 months (Peto OR 1.67, 95% CI 0.96 to 2.90; 2 studies, 247 limbs; low-quality evidence). We found low-quality evidence that Dacron grafts improved secondary patency over PTFE by 24 months (Peto OR 1.54, 95% CI 1.04 to 2.28; 2 studies, 528 limbs; P = 0.03), an effect which continued to 60 months in the single trial reporting this timepoint (Peto OR 2.43, 95% CI 1.31 to 4.53; 167 limbs; P = 0.005).Externally supported prosthetic grafts had inferior primary patency at 24 months when compared to unsupported prosthetic grafts (Peto OR 2.08, 95% CI 1.29 to 3.35; 2 studies, 270 limbs; P = 0.003). Secondary patency was similarly affected in the single trial reporting this outcome (Peto OR 2.25, 95% CI 1.24 to 4.07; 236 limbs; P = 0.008). No data were available for 60 months follow-up.HUV showed benefits in primary patency over PTFE at 24 months (Peto OR 4.80, 95% CI 1.76 to 13.06; 82 limbs; P = 0.002). This benefit was still seen at 60 months (Peto OR 3.75, 95% CI 1.46 to 9.62; 69 limbs; P = 0.006), but this was only compared in one trial. Results were similar for secondary patency at 24 months (Peto OR 4.01, 95% CI 1.44 to 11.17; 93 limbs) and at 60 months (Peto OR 3.87, 95% CI 1.65 to 9.05; 93 limbs).We found HBD to be superior to PTFE for primary patency at 60 months for above-knee bypass, but these results were based on a single trial (Peto OR 0.38, 95% CI 0.20 to 0.72; 146 limbs; very low-quality evidence). There was no difference in primary patency between HBD and HUV for above-knee bypass in the one small study which reported this outcome.We found only one small trial studying PUR and it showed very poor primary and secondary patency rates which were inferior to Dacron at all time points.Below-knee bypassFor bypass below the knee, we found no graft type to be superior to any other in terms of primary patency, though one trial showed improved secondary patency of HUV over PTFE at all time points to 24 months (Peto OR 3.40, 95% CI 1.45 to 7.97; 88 limbs; P = 0.005).One study compared PTFE alone to PTFE with vein cuff; very low-quality evidence indicates no effect to either primary or secondary patency at 24 months (Peto OR 1.08, 95% CI 0.58 to 2.01; 182 limbs; 2 studies; P = 0.80 and Peto OR 1.22, 95% CI 0.67 to 2.23; 181 limbs; 2 studies; P = 0.51 respectively)Limited data were available for limb survival, and those studies reporting on this outcome showed no clear difference between graft types for this outcome. Antiplatelet and anticoagulant protocols varied extensively between trials, and in some cases within trials.The overall quality of the evidence ranged from very low to moderate. Issues which affected the quality of the evidence included differences in the design of the trials, and differences in the types of grafts they compared. These differences meant we were often only able to combine and analyse small numbers of participants and this resulted in uncertainty over the true effects of the graft type used.

AUTHORS' CONCLUSIONS

There was moderate-quality evidence of improved long-term (60 months) primary patency for autologous vein grafts when compared to prosthetic materials for above-knee bypasses. In the long term (two to five years) there was low-quality evidence that Dacron confers a small secondary patency benefit over PTFE for above-knee bypass. Only very low-quality data exist on below-knee bypasses, so we are uncertain which graft type is best. Further randomised data are needed to ascertain whether this information translates into an improvement in limb survival.

Clopidogrel plus aspirin versus aspirin alone for preventing cardiovascular events

BACKGROUND

Aspirin is the prophylactic antiplatelet drug of choice for people with cardiovascular disease. Adding a second antiplatelet drug to aspirin may produce additional benefit for people at high risk and people with established cardiovascular disease. This is an update to a previously published review from 2011.

OBJECTIVES

To review the benefit and harm of adding clopidogrel to aspirin therapy for preventing cardiovascular events in people who have coronary disease, ischaemic cerebrovascular disease, peripheral arterial disease, or were at high risk of atherothrombotic disease, but did not have a coronary stent.

SEARCH METHODS

We updated the searches of CENTRAL (2017, Issue 6), MEDLINE (Ovid, 1946 to 4 July 2017) and Embase (Ovid, 1947 to 3 July 2017) on 4 July 2017. We also searched ClinicalTrials.gov and the WHO ICTRP portal, and handsearched reference lists. We applied no language restrictions.

SELECTION CRITERIA

We included all randomised controlled trials comparing over 30 days use of aspirin plus clopidogrel with aspirin plus placebo or aspirin alone in people with coronary disease, ischaemic cerebrovascular disease, peripheral arterial disease, or at high risk of atherothrombotic disease. We excluded studies including only people with coronary drug-eluting stent (DES) or non-DES, or both.

DATA COLLECTION AND ANALYSIS

We collected data on mortality from cardiovascular causes, all-cause mortality, fatal and non-fatal myocardial infarction, fatal and non-fatal ischaemic stroke, major and minor bleeding. The overall treatment effect was estimated by the pooled risk ratio (RR) with 95% confidence interval (CI), using a fixed-effect model (Mantel-Haenszel); we used a random-effects model in cases of moderate or severe heterogeneity (I2 ≥ 30%). We assessed the quality of the evidence using the GRADE approach. We used GRADE profiler (GRADE Pro) to import data from Review Manager to create a 'Summary of findings' table.

MAIN RESULTS

The search identified 13 studies in addition to the two studies in the previous version of our systematic review. Overall, we included data from 15 trials with 33,970 people. We completed a 'Risk of bias' assessment for all studies. The risk of bias was low in four trials because they were at low risk of bias for all key domains (random sequence generation, allocation concealment, blinding, selective outcome reporting and incomplete outcome data), even if some of them were funded by the pharmaceutical industry.Analysis showed no difference in the effectiveness of aspirin plus clopidogrel in preventing cardiovascular mortality (RR 0.98, 95% CI 0.88 to 1.10; participants = 31,903; studies = 7; moderate quality evidence), and no evidence of a difference in all-cause mortality (RR 1.05, 95% CI 0.87 to 1.25; participants = 32,908; studies = 9; low quality evidence).There was a lower risk of fatal and non-fatal myocardial infarction with clopidogrel plus aspirin compared with aspirin plus placebo or aspirin alone (RR 0.78, 95% CI 0.69 to 0.90; participants = 16,175; studies = 6; moderate quality evidence). There was a reduction in the risk of fatal and non-fatal ischaemic stroke (RR 0.73, 95% CI 0.59 to 0.91; participants = 4006; studies = 5; moderate quality evidence).However, there was a higher risk of major bleeding with clopidogrel plus aspirin compared with aspirin plus placebo or aspirin alone (RR 1.44, 95% CI 1.25 to 1.64; participants = 33,300; studies = 10; moderate quality evidence) and of minor bleeding (RR 2.03, 95% CI 1.75 to 2.36; participants = 14,731; studies = 8; moderate quality evidence).Overall, we would expect 13 myocardial infarctions and 23 ischaemic strokes be prevented for every 1000 patients treated with the combination in a median follow-up period of 12 months, but 9 major bleeds and 33 minor bleeds would be caused during a median follow-up period of 10.5 and 6 months, respectively.

AUTHORS' CONCLUSIONS

The available evidence demonstrates that the use of clopidogrel plus aspirin in people at high risk of cardiovascular disease and people with established cardiovascular disease without a coronary stent is associated with a reduction in the risk of myocardial infarction and ischaemic stroke, and an increased risk of major and minor bleeding compared with aspirin alone. According to GRADE criteria, the quality of evidence was moderate for all outcomes except all-cause mortality (low quality evidence) and adverse events (very low quality evidence).

Axillobifemoral bypass: a brief surgical and historical review

Peripheral artery disease (PAD) occurs when plaque accumulates in the arterial system and obstructs blood flow. Narrowing of the abdominal aorta and the common iliac arteries due to atherosclerotic plaques restricts blood supply to the lower limbs. Clinically, the lower limb symptoms of PAD are intermittent claudication, discoloration of the toes, and skin ulcers, all due to arterial insufficiency. Surgical revascularization is the primary mode of treatment for patients with severe limb ischemia. The objective of the surgical procedure is to bypass a blockage in an occluded major vessel by constructing an alternate route for blood flow using an artificial graft. This article presents information on aortoiliac reconstruction, with an emphasis on axillobifemoral bypass grafting.

Comparison of graft patency, limb salvage, and antithrombotic therapy between prosthetic and autogenous below-knee bypass for critical limb ischemia

BACKGROUND

The autogenous vein is the preferred conduit in below-knee vascular reconstructions. However, many argue that prosthetic grafts can perform well in crural bypass with adjunctive antithrombotic therapy. We therefore compared outcomes of below-knee prosthetic versus autologous vein bypass grafts for critical limb ischemia and the use of adjunctive antithrombotic therapy in both settings.

METHODS

Utilizing the registry of the Vascular Study Group of New England (2003-2009), we studied 1227 patients who underwent below-knee bypass for critical limb ischemia, 223 of whom received a prosthetic graft to the below-knee popliteal artery (70%) or more distal target (30%). We used propensity matching to identify a patient cohort receiving single-segment saphenous vein yet had remained similar to the prosthetic cohort in terms of characteristics, graft origin/target, and antithrombotic regimen. Main outcome measures were graft patency and major limb amputation within 1 year. Secondary outcomes were bleeding complications (reoperation or transfusion) and mortality. We performed comparisons by conduit type and by antithrombotic therapy.

RESULTS

Patients receiving prosthetic conduit were more likely to be treated with warfarin than those with greater saphenous vein (57% vs. 24%, P<0.001). After propensity score matching, we found no significant difference in primary graft patency (72% vs. 73%, P=0.81) or major amputation rates (17% vs. 13%, P=0.31) between prosthetic and single-segment saphenous vein grafts. In a subanalysis of grafts to tibial versus popliteal targets, we noted equivalent primary patency and amputation rates between prosthetic and venous conduits. Whereas overall 1-year prosthetic graft patency rates varied from 51% (aspirin+clopidogrel) to 78% (aspirin+warfarin), no significant differences were seen in primary patency or major amputation rates by antithrombotic therapy (P=0.32 and 0.17, respectively). Further, the incidence of bleeding complications and 1-year mortality did not differ by conduit type or antithrombotic regimen in the propensity-matched analysis.

CONCLUSIONS

Although limited in size, our study demonstrates that, with appropriate patient selection and antithrombotic therapy, 1-year outcomes for below-knee prosthetic bypass grafting can be comparable to those for greater saphenous vein conduit.

Therapeutic angiogenesis in critical limb ischemia

Critical limb ischemia (CLI) is a severe form of peripheral artery disease associated with high morbidity and mortality. The primary therapeutic goals in treating CLI are to reduce the risk of adverse cardiovascular events, relieve ischemic pain, heal ulcers, prevent major amputation, and improve quality of life (QoL) and survival. These goals may be achieved by medical therapy, endovascular intervention, open surgery, or amputation and require a multidisciplinary approach including pain management, wound care, risk factors reduction, and treatment of comorbidities. No-option patients are potential candidates for the novel angiogenic therapies. The application of genetic, molecular, and cellular-based modalities, the so-called therapeutic angiogenesis, in the treatment of arterial obstructive diseases has not shown consistent efficacy. This article summarizes the current status related to the management of patients with CLI and discusses the current findings of the emerging modalities for therapeutic angiogenesis.

Current approach to the diagnosis and treatment of femoral-popliteal arterial disease. A systematic review

Peripheral arterial disease (PAD) is a common manifestation of atherosclerosis affecting 5 million adults in the United States, with an age-adjusted prevalence of 4% to 15% and increasing up to 30% with age and the presence of cardiovascular risk factors. In this article we focus on lower extremity PAD and specifically on the superficial femoral and proximal popliteal artery (SFPA), which are the most common anatomic locations of lower extremity atherosclerosis. We summarize current evidence and perform a systematic review on the diagnostic evaluation as well as the medical, endovascular and surgical management of SFPA disease.

Antithrombotic agents for preventing thrombosis after infrainguinal arterial bypass surgery

BACKGROUND

Peripheral arterial disease (PAD) is frequently treated by either an infrainguinal autologous (using the patient's own veins) or synthetic graft bypass. The rate of occlusion of the graft after one year is between 12% and 60%. To prevent occlusion, patients are treated with an antiplatelet or antithrombotic drug, or a combination of both. Little is known about which drug is optimal to prevent infrainguinal graft occlusion. This is an update of a Cochrane review first published in 2003.

OBJECTIVES

To evaluate whether antithrombotic treatment improves graft patency, limb salvage and survival in patients with chronic PAD undergoing infrainguinal bypass surgery.

SEARCH STRATEGY

The Cochrane Peripheral Vascular Diseases Group searched their Specialised Register (last searched August 2010) and the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, Issue 3).

SELECTION CRITERIA

Randomised, controlled trials; two review authors independently assessed the methodological quality of each trial using a standardised checklist.

DATA COLLECTION AND ANALYSIS

Data collected included patient details, inclusion and exclusion criteria, type of graft, antithrombotic therapy, outcomes, and side effects.

MAIN RESULTS

A total of 14 trials were included in this review; 4970 patient results were analysed. Four trials evaluating vitamin K antagonists (VKA) versus no VKA suggested that oral anticoagulation may favour autologous venous, but not artificial, graft patency as well as limb salvage and survival. Two other studies comparing VKA with aspirin (ASA) or aspirin and dipyridamole provided evidence to support a positive effect of VKA on the patency of venous but not artificial grafts. Three trials comparing low molecular weight heparin (LMWH) to unfractionated heparin (UFH) failed to demonstrate a significant difference on patency. One trial comparing LMWH with placebo found no significant improvement in graft patency over the first postoperative year in a population receiving aspirin. One trial showed an advantage for LMWH versus aspirin and dipyridamol at one year for patients undergoing limb salvage procedures. Perioperative administration of ancrod showed no greater benefit when compared to unfractionated heparin. Dextran 70 showed similar graft patency rates to LMWH but a significantly higher proportion of patients developed heart failure with dextran.

AUTHORS' CONCLUSIONS

Patients undergoing infrainguinal venous graft are more likely to benefit from treatment with VKA than platelet inhibitors. Patients receiving an artificial graft benefit from platelet inhibitors (aspirin). However, the evidence is not conclusive. Randomised controlled trials with larger patient numbers are needed in the future to compare antithrombotic therapies with either placebo or antiplatelet therapies.

Clopidogrel plus aspirin versus aspirin alone for preventing cardiovascular disease

BACKGROUND

Aspirin is the prophylactic antiplatelet drug of choice for people with cardiovascular disease. Adding a second antiplatelet drug to aspirin may produce additional benefit for those at high risk and those with established cardiovascular disease.

OBJECTIVES

To quantify the benefit and harm of adding clopidogrel to standard long-term aspirin therapy for preventing cardiovascular events in people at high risk of cardiovascular disease and those with established cardiovascular disease.

SEARCH STRATEGY

The searches have been updated: CENTRAL (Issue 3 2009), MEDLINE (2002 to September 2009) and EMBASE (2002 to September 2009).

SELECTION CRITERIA

All randomized controlled trials comparing long term use of aspirin plus clopidogrel with aspirin plus placebo or aspirin alone in patients with coronary disease, ischemic cerebrovascular disease, peripheral arterial disease, or at high risk of atherothrombotic disease were included.

DATA COLLECTION AND ANALYSIS

Data on mortality, non-fatal myocardial infarction, non-fatal stroke, unstable angina, heart failure, revascularizations, major and minor bleeding, and all adverse events were collected. The overall treatment effect was estimated by the pooled odds ratio (OR) with 95% confidence interval (CI) using a fixed-effect model (Mantel-Haenszel).

MAIN RESULTS

No new studies were identified from the updated searches. A total of two RCTs were found: the CHARISMA and the CURE study. The CURE study enrolled only patients with a recent non-ST segment elevation acute coronary syndrome. The use of clopidogrel plus aspirin, compared with placebo plus aspirin, was associated with a lower risk of cardiovascular events (OR: 0.87, 95% CI 0.81 to 0.94; P<0.01) and a higher risk of major bleeding (OR 1.34, 95% CI 1.14 to 1.57; P<0.01). Overall, we would expect 13 cardiovascular events to be prevented for every 1000 patients treated with the combination, but 6 major bleeds would be caused. In the CURE trial, for every 1000 people treated, 23 events would be avoided and 10 major bleeds would be caused. In the CHARISMA trial, for every 1000 people treated, 5 cardiovascular events would be avoided and 3 major bleeds would be caused.

AUTHORS' CONCLUSIONS

The available evidence demonstrates that the use of clopidogrel plus aspirin is associated with a reduction in the risk of cardiovascular events and an increased risk of bleeding compared with aspirin alone. Only in patients with acute non-ST coronary syndrome benefits outweigh harms.

Graft type for femoro-popliteal bypass surgery

BACKGROUND

Femoro-popliteal bypass is implemented to save limbs that might otherwise require amputation, in patients with ischaemic rest pain or tissue loss; and to improve walking distance in patients with severe life-limiting claudication. Contemporary practice involves using autologous vein, polyterafluoroethylene (PTFE) or Dacron as a bypass conduit.This is an update of a Cochrane review first published in 1999 and previously updated in 2002.

OBJECTIVES

The objective of this review was to determine the most effective type of graft for femoro-popliteal bypass surgery.

SEARCH STRATEGY

The Cochrane Peripheral Vascular Diseases Group searched their Specialised Register (last searched January 2010) and the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, Issue 1 for last search). The authors searched reference lists of relevant articles, and handsearched conference proceedings from the British and European Vascular Surgical Societies.

SELECTION CRITERIA

Randomised trials comparing femoro-popliteal grafts.

DATA COLLECTION AND ANALYSIS

Two authors (CT and ADM) screened studies, extracted data and assessed trials.

MAIN RESULTS

Thirteen randomised control trials were included with a total of 2313 patients (1955 above knee, 358 below knee bypass surgery). Seven graft types were compared (reversed and in situ autologous vein, PTFE with and without vein cuff, human umbilical vein (HUV), Dacron and heparin bonded Dacron (HBD).Above the knee, there was a benefit in primary patency for autologous vein over PTFE (P = 0.0001) and HUV (P = 0.0003) by 60 months. Dacron showed primary patency benefit over PTFE by 24 months (P = 0.02), continuing to 60 months (P = 0.02). HUV also showed benefit over PTFE by 24 months (P = 0.0003) in one trial. Below the knee, in the one trial there was a significant benefit in primary patency for PTFE with a vein cuff when compared to PTFE alone at all time intervals to 24 months (P = 0.03).Limited data were available for limb survival. Antiplatelet and anticoagulant protocols varied extensively between trials, and in some cases within trials.

AUTHORS' CONCLUSIONS

There was a clear primary patency benefit for autologous vein when compared to synthetic materials for above knee bypasses. In the long term (five years) Dacron confers a small primary patency benefit over PTFE for above knee bypass. PTFE with a vein cuff improved primary patency when compared to PTFE alone for below knee bypasses. Further randomised data is needed to ascertain whether this information translates into improvement in limb survival.

Female gender and oral anticoagulants are associated with wound complications in lower extremity vein bypass: an analysis of 1404 operations for critical limb ischemia

BACKGROUND

Infrainguinal bypass (IB) surgery is an effective means of improving arterial circulation to the lower extremity for patients with critical limb ischemia (CLI). However, wound complications (WC) of the surgical incision following IB can impart significant morbidity.

METHODS

A retrospective analysis of WC from the 1404 patients enrolled in a multicenter clinical trial of vein bypass grafting for CLI was performed. Univariate and multivariable regression models were used to determine WC predictors and associated outcomes, including graft patency, limb salvage, quality of life (QoL), resource utilization (RU), and mortality.

RESULTS

A total of 543 (39%) patients developed a reported WC within 30 days of surgery, with infections (284, 52%) and hematoma/hemorrhage (121, 22%) being the most common type. Postoperative anticoagulation (odds ratio [OR], 1.554; 95% confidence interval [CI] 1.202 to 2.009; P = .0008) and female gender (OR, 1.376; 95% CI, 1.076 to 1.757; P = .0108) were independent factors associated with WC. Primary, primary-assisted, and secondary graft patency rates were not influenced by the presence of WC; though, patients with WC were at increased risk for limb loss (hazard ratio [HR], 1.511; 95% CI 1.096 to 2.079; P = .0116) and higher mortality (HR, 1.449; 95% CI 1.098 to 1.912; P = .0089). WC was not significantly associated with lower QoL at 3 months (4.67 vs 4.79, P = .1947) and 12 months (5.02 vs 5.13, P = .2806). However, the subset of patients with serious WC (SWC) demonstrated significantly lower QoL at 3 months compared with patients without WC, (4.43 vs 4.79, respectively, P = .0166), though this difference was not seen at 12 months (4.94 vs 5.13, P = .2411). Patients with WC had higher RU than patients who did not have WC. Mean index length of hospital stay (LOS) was 2.3 days longer, mean cumulative 1-year LOS was 8.1 days longer, and mean number of hospitalizations was 0.5 occurrences greater for patients with WC compared with patients without WC (all P < .0001).

CONCLUSIONS

WC is a frequent complication of IB for CLI, associated with increased risk for major amputation, mortality, and greater RU. Further detailed investigation into the link between female gender and oral anticoagulation use with WC may help identify causes of WC and perhaps prevent or lessen their occurrence.