Low Molecular Weight Heparin (Enoxaparin) versus Dextran in the Prevention of Early Occlusion Following Arterial Bypass Surgery Distal to the Groin

The Impact of Antithrombotic Regimens on Clinical Outcomes After Endovascular Intervention and Bypass Surgery for Infrapopliteal Artery Disease

Endovascular intervention and bypass surgery are the main options of treatments for infrapopliteal artery disease. Although post-intervention treatment with antiplatelet (AP) and/or anticoagulant (AC) drugs has reduced morbidity and mortality rates from cardiovascular complications; the ideal antithrombotic treatment regimen is unknown. The aim of this review was to compare the efficacy and safety of various anticoagulation and/or AP therapy regimens in patients undergoing below-knee endovascular treatment for infrapopliteal artery disease. We reviewed published literature in PubMed and Google Scholar, and Cochrane, evaluating efficacy and safety outcomes after antithrombotic treatment following endovascular intervention or bypass surgery in patients with infrapopliteal artery disease. We extracted relevant efficacy and safety data with related statistics from each study. We found that AP treatment should be administered to patients receiving endovascular therapy or bypass. We did not find superior effects for dual AP treatment (DAPT) over mono-AP therapy (MAPT) for endovascular intervention or bypass surgery with venous graft, suggesting that MAPT suffices for these groups. Also, aspirin + clopidogrel was effective over aspirin alone for prosthetic, but not venous graft, albeit higher non-severe bleeding incidences, suggesting a potential benefit of this regime for below-knee prosthetic graft. AP + AC yielded superior results compared to AP following endovascular procedure and bypass surgery, suggesting the potential benefit of this regime in the absence of contraindications. More prospective studies with large number of patients are warranted to identify the best treatment for infrapopliteal artery diseases.

MCA-to-MCA Bypass with Interposition Graft for Ruptured Mycotic Middle Cerebral Artery Aneurysm

Mycotic aneurysm, also referred to as infected aneurysm, is a rare entity that may result from the bacterial infection or infective endocarditis.^1-3 The treatment options include conservative medication and endovascular or direct microsurgical intervention.^1,4,5 However, the optimal strategy remains unknown and cerebral revascularization may be required in some rare cases.⁶ In this surgical video, we demonstrate a distal middle cerebral artery (MCA) mycotic aneurysm that we treated by intracranial-intracranial bypass with an interpositional graft. Our patient is a 53-year-old male who presented with a 6-day history of severe headache. He was subsequently admitted to our institution. Preoperative computed tomography angiography showed a left temporal hematoma (>30 mL) and an opercular segment of the MCA (M3) aneurysm, which was highly suspicious for mycotic origin. A standard frontotemporal craniotomy was carried out with preservation of superficial temporal artery (STA). Following the sylvian fissure dissection, the aneurysm was exposed with the characteristics of a thick wall and an undefinable neck, which made direct clip application difficult. The aneurysm was resected initially, and 2 cut ends were reconnected by an STA graft. Following arterial reconstruction, intraoperative Doppler revealed a patent status of the interpositional graft vessel. Postoperatively, no neurologic deficit was observed and computed tomography angiography demonstrated total elimination of the aneurysm without stenosis of the graft vessel. Low-molecular dextran was prescribed rather than aspirin, as there was concern for hemorrhage. Antibiotic treatment was used for at least 4 weeks, and the patient was transferred to the inpatient cardiology team for management of endocarditis. A 4-month follow-up angiogram showed a patent STA and excellent left distal MCA blood flow (Video 1). The favorable outcome of this case revealed that MCA-to-MCA bypass with interpositional graft is a safe, effective method for the unclippable cerebral aneurysm. As other authors have asserted, a full dose of long-term antibiotic therapy remains essential following intervention.⁷ Meanwhile, dextran has proved to be a viable alternative for anticoagulation during perioperative management of bypass surgery.^8,9.

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.

Effects of Three Months of Low Molecular Weight Heparin (dalteparin) Treatment After Bypass Surgery for Lower Limb Ischemia—A Randomised Placebo-controlled Double Blind Multicentre Trial

OBJECTIVES

To test the hypothesis that long-term postoperative dalteparin (Fragmin), Pharmacia Corp) treatment improves primary patency of peripheral arterial bypass grafts (PABG) in lower limb ischemia patients on acetylsalicylic acid (ASA) treatment.

DESIGN

Prospective randomised double blind multicenter study.

MATERIALS AND METHODS

Using a computer algorithm 284 patients with lower limb ischemia, most with pre-operative ischemic ulceration or partial gangrene, from 12 hospitals were randomised, after PABG, to 5000 IU dalteparin or placebo injections once daily for 3 months. All patients received 75 mg of ASA daily for 12 months. Graft patency was assessed at 1, 3 and 12 months.

RESULTS

At 1 year, 42 patients had died or were lost to follow-up. Compliance with the injection schedule was 80%. Primary patency rate, in the dalteparin versus the control group, respectively, was 83 versus 80% (n.s.) at 3 months and 59% for both groups at 12 months. Major complication rates and cardiovascular morbidity were not different between the two groups.

CONCLUSIONS

In patients on ASA treatment, long-term postoperative dalteparin treatment did not improve patency after peripheral artery bypass grafting. Therefore, low molecular weight heparin treatment cannot be recommended for routine use after bypass surgery for critical lower limb ischemia.

Low molecular weight heparin and atherosclerosis

Low molecular weight heparin (LMWH) has dramatically impacted the treatment of venous thromboembolic disease and acute coronary syndromes. Recent studies help define the role of these agents for patients undergoing percutaneous coronary interventions and for patients treated with thrombolytic agents for ST-segment elevation myocardial infarction. Recent studies also suggest potential usefulness of LMWH for patients with peripheral vascular disease and its limits of utility in stroke. This review summarizes the evidence about the use of LMWH in these clinical situations.

Scientific surgery

The BJS is committed to the practice of surgery based on scientific evidence. Each month we will publish a list of randomized trials and meta-analyses collated from English-language publications. A collection of all these papers will be available in the Scientific Surgery Archive which will be held on the BJS website together with links to free Medline sites where the full papers can be accessed (see below for details). If you have published a recent randomized trial which has not been featured in Scientific Surgery, the Editors would be pleased to receive a reprint and consider its inclusion.