Recombinant Tissue Plasminogen Activator Versus Urokinase for Local Thrombolysis of Femoropopliteal Occlusions:A Prospective, Randomized Multicenter Trial

Fibrinolytic agents for peripheral arterial occlusion

BACKGROUND

Peripheral arterial thrombolysis is used in the management of peripheral arterial ischaemia. Streptokinase was originally used but safety concerns led to a search for other agents. Urokinase and recombinant tissue plasminogen activator (rt-PA) have increasingly become established as first line agents for peripheral arterial thrombolysis. Potential advantages of these agents include improved safety, greater efficacy and a more rapid response. Recently drugs such as pro-urokinase, recombinant staphylokinase and alfimperase have been introduced.

OBJECTIVES

To determine which fibrinolytic agents are most effective in peripheral arterial ischaemia.

SEARCH STRATEGY

The Cochrane Peripheral Vascular Diseases Group searched their Specialised Register (last searched October 2009) and the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (last searched 2009, Issue 4) for randomised controlled trials (RCTs) comparing fibrinolytic agents to treat peripheral arterial ischaemia.

SELECTION CRITERIA

RCTs comparing fibrinolytic agents to treat peripheral arterial occlusion.

DATA COLLECTION AND ANALYSIS

Data were analysed for the outcomes vessel patency, time to lysis, limb salvage, amputation, death, complications including major haemorrhage, stroke, and distal embolization.

MAIN RESULTS

Five RCTs involving a total of 687 patients with a range of clinical indications were included. In one three-pronged study, vessel patency was greater with intra-arterial recombinant tissue plasminogen activator (rt-PA) than with intra-arterial streptokinase (P < 0.04) or intravenous rt-PA (P < 0.01). In patients with peripheral arterial occlusion there was no statistically significant difference in limb salvage at 30 days with either urokinase or rt-PA, though this may reflect the small numbers in the studies. Incidences of haemorrhagic complications varied with fibrinolytic regime but there was no statistically significant difference between intra-arterial urokinase and intra-arterial rt-PA. In the three-pronged study intravenous rt-PA and intra-arterial streptokinase were associated with a significantly higher risk of haemorrhagic complications than with intra-arterial rt-PA (P < 0.05).

AUTHORS' CONCLUSIONS

There is some evidence to suggest that intra-arterial rt-PA is more effective than intra-arterial streptokinase or intravenous rt-PA in improving vessel patency in people with peripheral arterial occlusion. There was no evidence that rt-PA was more effective than urokinase for patients with peripheral arterial occlusion and some evidence that initial lysis may be more rapid with rt-PA, depending on the regime. Incidences of haemorrhagic complications were not statistically significantly greater with rt-PA than with other regimes. However, all of the findings come from small studies and a general paucity of results means that it is not possible to draw clear conclusions.

Adjunctive abciximab improves patency and functional outcome in endovascular treatment of femoropopliteal occlusions: initial experience

PURPOSE

To prospectively evaluate the safety and effectiveness of adjunctive administration of abciximab observed within 30 days and at 6 months after randomization in patients undergoing endovascular revascularization of long-segment femoropopliteal occlusions.

MATERIALS AND METHODS

The study was approved by the local ethical committee, and patients gave written informed consent. In a prospective, double-blind, placebo-controlled design, patients undergoing percutaneous treatment for long-segment (>5 cm) femoropopliteal occlusions were randomly assigned to receive abciximab or a placebo; all patients also received standard-dose heparin. Effectiveness and safety analyses were based on an intention-to-treat approach. Patency was calculated according to life-table analysis, and P values were derived from the log-rank statistic. The P values for dichotomous safety end points were calculated with the Fisher exact test. Odds ratios were calculated for subgroup analyses. Logistic regression modeling was used for analysis of the safety bleeding data.

RESULTS

A total of 98 patients (103 limbs) were included: 47 patients received abciximab and 51 received a placebo. Patency with abciximab versus placebo was 95.7% versus 80.4% (relative risk, 0.21; 95% confidence interval: 0.05, 0.96; P = .02) at 30 days and was 61.7% versus 41.2% (relative risk, 0.57; 95% confidence interval: 0.32, 1.01; P = .03), coupled with a better clinical outcome according to the Rutherford score, at the end of follow-up (P = .03). Risk of major bleeding was not significantly increased, while access-site bleeding was significantly higher among patients receiving abciximab (odds ratio, 2.9; 95% confidence interval: 1.04, 8.2; P = .04).

CONCLUSION

The data show that adjunctive administration of abciximab has a favorable effect on patency and clinical outcome in patients undergoing complex femoropopliteal catheter interventions not hampered by serious bleeding. Treatment effect of abciximab observed at 30 days was maintained at 6-month follow-up.

Comparative Safety and Efficacy of Urokinase and Recombinant Tissue Plasminogen Activator for Peripheral Arterial Occlusion: A Meta-Analysis

STUDY OBJECTIVE

To evaluate differences in the efficacy and safety of recombinant tissue plasminogen activator (rt-PA) and urokinase in the treatment of peripheral arterial occlusion.

DESIGN

Systematic review and meta-analysis of prospective comparative trials.

DATA SOURCE

PubMed/MEDLINE database from 1966-October 2004.

MEASUREMENTS AND MAIN RESULTS

The literature was systematically searched to identify prospective comparative trials of urokinase and rt-PA for the treatment of peripheral arterial occlusion. The primary outcome measure was successful complete lysis of the occlusion. Other outcome measures were hemorrhage (major, minor, or combined), intracranial hemorrhage, limb loss, and mortality. Six trials were identified, five of which were randomized. On meta-analysis, the rate of clot lysis was higher with rt-PA than with urokinase (odds ratio [OR] 1.54, 95% confidence interval [CI] 1.12-2.10, p=0.007). However, urokinase was associated with lower rates of minor (OR 0.52, 95% CI 0.28-0.97, p=0.04) and total (OR 0.51, 95% CI 0.29-0.91, p=0.02) bleeding. Rates of major hemorrhage, intracranial hemorrhage, limb loss, and mortality were similar between agents.

CONCLUSION

Urokinase was less effective than rt-PA in successfully lysing acute peripheral arterial occlusion, but it was associated with lower rates of total and minor bleeding. Overall, rt-PA was a reasonable substitute for urokinase, now that urokinase has been removed from the market in the United States. However, judicious monitoring for minor bleeding is necessary.

Thrombolytic Therapy: Current Clinical Practice

Thrombolytic therapy is an essential tool in the array of therapies designed to reopen arteries and veins occluded with thrombus. As the use of thrombolytic agents has entered mainstream practice, their application has expanded to include a wide variety of indications and settings. Thrombolytic agents are used in patients who have thrombosis of coronary arteries, precerebral and cerebral arteries, the aorta, iliac and mesenteric arteries, and peripheral arteries. The use of thrombolysis in venous thrombosis has included deep venous thrombosis of the upper and lower extremities and vena cava, mesenteric veins, cerebral veins, and central access catheters. Guidelines are available from the American College of Cardiology/American Heart Association regarding thrombolysis in myocardial infarction and from the American Stroke Association regarding thrombolysis in acute ischemic stroke.

Management of Peripheral Vascular Disease

The management of patients with peripheral arterial occlusive disease (PAD) has to be planned in the context of natural history, epidemiology, and apparent risk factors that predict deterioration. The ankle-brachial index to date has proved to be the most effective, accurate, and practical method of PAD detection. Given that PAD is a powerful indicator of systemic atherosclerosis and (independent of symptoms) is associated with an increased risk of myocardial infarction and stroke, as well as a six times greater likelihood of death, the prevalence and demographic distribution of measurable PAD becomes particularly relevant. Reliable information on interventions to confer symptom relief is much weaker and reflects discrepancies between published reports from centers of excellence and the experience of patients routinely treated in communities around the world. The impact of newer treatment modalities, such as complex endovascular procedures and therapeutic angiogenesis, has been a subject of recent controversy.

Antiplatelet and anticoagulant drugs for prevention of restenosis/reocclusion following peripheral endovascular treatment

BACKGROUND

Peripheral arterial disease (PAD) is frequently treated by balloon angioplasty. Restenosis/reocclusion of the dilated segments occurs often depending on length of occlusion, lower leg outflow, stage of disease and presence of cardiovascular risk factors. To prevent reocclusion, patients are treated with antithrombotic agents.

OBJECTIVES

To determine whether any antithrombotic drug is more effective in preventing reocclusion after peripheral endovascular treatment, compared to another antithrombotic drug, no treatment, placebo, or other vasoactive drugs.

SEARCH STRATEGY

We searched the Cochrane Peripheral Vascular Diseases Group's trials register (last searched April 2004), the Cochrane Central Register of Controlled trials (CENTRAL Issue 2, 2004), MEDLINE and EMBASE (last searched June 2004).

SELECTION CRITERIA

Randomised trials were categorised as A (double or single blinded) or B (not blinded). Participants included patients with symptomatic PAD treated by endovascular revascularisation of the pelvic or femoropopliteal arteries. Interventions were anticoagulant, antiplatelet or other vasoactive drug therapy compared with no treatment, placebo, or any other vasoactive drug. Clinical endpoints were re-obstruction, amputation, death, myocardial infarction, stroke and major bleeding.

DATA COLLECTION AND ANALYSIS

Details of the number of randomised patients, treatment, study design, study category, allocation concealment and patient characteristics were extracted. Analysis was based on intention-to-treat data. To examine the effects of binary outcomes such as amputation and major bleeding, odds ratios were computed using a fixed effect model. The 95% confidence intervals of the effect sizes were calculated.

MAIN RESULTS

A 60% reduction of recurrent obstruction was found with aspirin (ASA) 330 mg combined with dipyridamol (DIP) as compared to placebo at 12 months follow-up. At six months following endovascular treatment, a positive effect on patency was found with 50 to 100 mg ASA combined with DIP (n = 356). However, this was not significant. ASA/DIP tended towards showing a superior effect on patency after femoropopliteal angioplasty compared with VKA at three, six, and twelve months. Periinterventional treatment with LMWH in femoropopliteal obstructions resulted in significantly lower restenosis/reocclusion rates than with unfractionated heparin.

AUTHORS' CONCLUSIONS

Aspirin 50 to 300 mg started prior to femoropopliteal endovascular treatment appears to be the most effective and is safe. Clopidogrel might be an alternative, but data are lacking. Abciximab might be a useful adjunctive for high risk patients with long segmental femoropopliteal interventions. Low molecular weight heparin seems to be more effective in preventing reocclusion or restenosis than unfractionated heparin.

Catheter-directed Thrombolytic Therapy for Limb Ischemia: Current Status and Controversies

Absence of urokinase from the United States market for the past 4 years has resulted in increasing experience with other plasminogen activators in catheter-directed thrombolytic therapy. The differences in the pharmacologic properties and biologic behavior of these agents may translate into clinical outcomes that are distinct. Some of these manifestations can be predicted based on the existing large clinical trials in the acute myocardial infarction literature. However, because of the fundamental differences in techniques and thrombolytic regimens, extrapolation of the coronary data may not always predict the performance of these agents in peripheral catheter-directed fibrinolysis. In this article, the current status of the available lytic agents in the treatment of limb ischemia is reviewed.

Catheter-directed Thrombolytic Therapy for Limb Ischemia: Current Status and Controversies

Absence of urokinase from the United States market for the past 4 years has resulted in increasing experience with other plasminogen activators in catheter-directed thrombolytic therapy. The differences in the pharmacologic properties and biologic behavior of these agents may translate into clinical outcomes that are distinct. Some of these manifestations can be predicted based on the existing large clinical trials in the acute myocardial infarction literature. However, because of the fundamental differences in techniques and thrombolytic regimens, extrapolation of the coronary data may not always predict the performance of these agents in peripheral catheter-directed fibrinolysis. In this article, the current status of the available lytic agents in the treatment of limb ischemia is reviewed.

Adjunctive techniques in percutaneous mechanical thrombectomy

Percutaneous mechanical thrombectomy is an established method in interventional radiology and refers to the removal of acute embolic or thrombotic occlusive material in arteries, veins, or vascular grafts using percutaneous transluminal methods. However, initial complete removal of occlusive material can be achieved only in a minority of patients. The amount of removed material varies with the age and composition of the occlusive material. To achieve sufficient revascularization, adjunctive use of a variety of percutaneous endovascular recanalization techniques is necessitated. Additional treatment with local intra-arterial fibrinolysis, balloon angioplasty, stent implantation, endoluminal atherectomy, and other measures results in primary technical success rates of 70% to 100% for revascularization of acutely occluded vessels. The above-mentioned different techniques should not be viewed as competitive treatment modalities, rather a synergistic approach should be offered. The aim of this report is to review different adjunctive techniques in percutaneous mechanical thrombectomy with emphasis on techniques, mechanisms of action, experimental and clinical results, potential complications, and their potential role in view of clinical pathways to treat acute limb ischemia.