When do vascular surgeons prescribe antiplatelet therapy? Current attitudes

Prescribing patterns of antiplatelet agents are highly variable after lower extremity endovascular procedures

BACKGROUND

The use of antiplatelet and antithrombotic agents after peripheral vascular interventions is a common clinical practice despite a lack of clear convincing evidence or accepted practice guidelines. The goal of this study was to assess surgeons' prescribing practices after endovascular procedures for lower extremity arterial occlusive disease.

METHODS

Attendees at a national vascular meeting were asked to complete a voluntary survey indicating their prescribing practices of antiplatelet/antithrombotic agents for the following procedures: iliac bare-metal stent, iliac covered stent, infrainguinal balloon angioplasty, infrainguinal bare-metal stent, infrainguinal covered stent, infrainguinal atherectomy, and lower extremity cryoplasty. The respondents were given choices of aspirin (ASA) alone, clopidogrel alone, ASA/clopidogrel combined, warfarin alone, or ASA/clopidogrel/warfarin combined. They were also asked to indicate their preferred length of treatment for each medication or combination of medications for each procedure: 1, 3, 6, or 12 months.

RESULTS

There were 51 respondents (48 vascular surgeons and 3 vascular fellows) with an average of 11 ± 6.4 years of experience and practicing in a university hospital (48%), community hospital (44%), or combined university/Veterans A hospital (6%) setting. The majority of respondents (98%) prescribe an antiplatelet agent for patients with peripheral arterial disease using 81 mg of ASA preferentially. Most surgeons do not obtain genetic testing (i.e., cytochrome P450, polypeptide 19 [CYP2C19] polymorphism) for antiplatelet effectiveness. The most common antiplatelet/antithrombotic medication of choice after lower extremity endoluminal therapy was a combination of ASA/clopidogrel. However, the duration of medical treatment was variable, with a 1- to 3-month course being the most common. The use of the ASA/clopidogrel combination increased with further distal endovascular treatment and the placement of stents versus angioplasty. In the vast majority of ASA-only responses, ASA was administered for at least 12 months if not recommended for life. Although the majority of surgeons would recommend dual antiplatelet therapy (52-77%), there was no consensus regarding the duration of treatment.

CONCLUSIONS

The antiplatelet/antithrombotic prescribing practices of vascular surgeons after lower extremity endovascular procedures are highly variable. Multicenter randomized controlled trials are needed to define optimal treatment efficacy and define the much-needed practice guidelines.

Antithrombotic agents after peripheral transluminal angioplasty: a review of the studies, methods and evidence for their use

OBJECTIVE

to review published studies and assess the strength of the evidence for the use of antithrombotic agents for the prevention of re-occlusion after peripheral angioplasty.

METHODS

a literature search was performed. All randomised comparative studies with patency assessments or clinical endpoints were included. The methods and results of the studies were compared and evaluated.

RESULTS

eleven randomised trials were identified, six of them were double blind. The majority of patients included were those with femoropopliteal lesions. A significant benefit of aspirin in one placebo-controlled study is balanced by no apparent benefit in another study. No dose-dependent effect of aspirin in the range 50-1000 mg/day has been shown in any of the four studies investigating such an effect. None of the three studies comparing platelet inhibitors and oral anticoagulants have shown any differences in outcome and no other well-designed studies of anticoagulants have been reported.

CONCLUSIONS

evidence for a reduction in the likelihood of re-occlusion or restenosis after peripheral transluminal angioplasty with platelet inhibitors remains equivocal. Evidence for the efficacy of any other agent in this indication is also lacking.

The long-term outcome of infrainguinal vein graft surveillance

OBJECTIVES

Vein graft surveillance is of proven benefit in improving graft patency at least in the first year after arterial bypass surgery. The aim of this study was to look at the longer term outcome of a vein graft surveillance programme on graft patency.

METHODS

One hundred and twelve consecutive vein grafts in 106 patients were prospectively entered into a vein graft surveillance programme. The median (range) follow up was 34 (1-76) months.

RESULTS

There were 23 (21%) early (less than 1 month) failures and a further 15 grafts occluded during follow up. The primary, primary assisted and secondary patencies at 4 years were 27%, 59% and 67% respectively. Thirty-eight grafts (34%) developed at least one stenosis at a median interval of 5 months after the operation. Eight (21%) of these stenoses occurred more than 12 months after surgery and would have been missed had surveillance been curtailed after 1 year.

CONCLUSIONS

The benefits of graft surveillance extend beyond one year and surveillance should therefore continue indefinitely.

Pharmacological prophylaxis against postoperative graft occlusion after peripheral vascular surgery: a world-wide survey

OBJECTIVES

To define current practice regarding the use of pharmacological prophylaxis to prevent postoperative graft occlusion.

DESIGN

Prospective open questionnaire.

MATERIALS AND METHODS

Questionnaires regarding this subject were sent to vascular surgeons throughout the world to analyse current practice.

RESULTS

651 questionnaires were returned with a response rate of 62% and form the basis for this report. Data from 100,334 vascular reconstructions were reported in this survey. Prophylaxis against postoperative graft occlusions was common. Treatment periods were usually greater than 1 year. Among carotid surgery patients, 82% received prophylaxis, consisting mainly of low-dose acetysalicylic acid (ASA). In Mid-Europe the use of oral anticoagulation was more common than in other regions (p < 0.001). Among aneurysm surgery patients, 38% received prophylaxis. For infrainguinal bypass, ASA in low dose was the most commonly used agent worldwide. However, oral anticoagulation was more frequent in Mid-Europe, in contrast to South America where the combination of ASA and dipyridamole was most common. Considerable geographical differences regarding patient selection, the frequency of specific procedures and operative techniques existed.

CONCLUSIONS

Important world-wide differences exist regarding prophylaxis for postoperative graft occlusion.

Epidural anaesthesia prolonged into the postoperative period prevents stress response and platelet hyperaggregability after peripheral vascular surgery

The occlusion rate of peripheral vascular grafts depends on technical as well as endogenous factors. Platelets play an integral part in graft failure and it has been suggested that anaesthesia may influence platelet function. In order to evaluate the influence of anaesthesia on stress response and platelet function in peripheral vascular surgery, patients (n = 18) were allocated to either general anaesthesia (GA; n = 9) followed by alleviation of postoperative pain with intramuscular analgesics or to lumbar epidural anaesthesia (EPI; n = 9) which was continued for 24 hours postoperatively. Before, during, as well as after vascular surgery of the lower extremity plasma levels of cortisol, glucose, serotonin (p-5HT), and urinary 5-hydroxyindole-3-acetic acid (5-HIAA) were analysed and platelet aggregability was determined. In the GA group surgery was accompanied by a significant stress response while in the EPI group this stress response was almost completely abolished. Platelet aggregability was reduced intraoperatively in both groups but in the postoperative period there was a marked hyperaggregability only in the GA group. P-5HT was increased preoperatively in both groups but was not affected by surgery. It is concluded that epidural anaesthesia, due to its effects on platelet aggregability, may be advantageous for peripheral vascular surgery.

Role of the leucocyte in the pathogenesis of vascular disease

The leucocyte plays a key role in the local and systemic tissue injury that results from peripheral arterial disease and chronic venous insufficiency. Despite the apparent dissimilarities between limb ischaemia and chronic venous ulceration, in both diseases macrovascular abnormalities lead to microvascular leucocyte trapping and activation. Activated leucocytes adhere to and damage adjacent endothelium by expressing adhesion molecules and releasing harmful moieties such as proteases and free radicals. Subsequent loss of endothelial integrity and the migration of activated leucocytes outwith the circulation leads to destruction of surrounding tissue. Leucocytes and their products are also involved in the systemic manifestations of ischaemia such as multiple organ failure and coagulopathy. An overview of leucocyte biology as it pertains to peripheral arterial and venous disease is presented. The opportunities for novel therapeutic interventions based on a better understanding of this biology are also discussed.