Two urokinase dose regimens in native arterial and graft occlusions: initial results of a prospective, randomized clinical trial

Study Protocol of a Prospective Multicenter Observational Study Evaluating Acute Lower Limb Ischemia

INTRODUCTION

Acute lower limb ischemia (ALI) is a limb- and potentially life-threatening condition which requires urgent evaluation and treatment. Contemporary data on optimal therapy and prognosis of ALI are lacking, while surgical, hybrid, and foremost endovascular techniques have rapidly evolved over the past decades. Available clinical guidelines are not based on high-level evidence and do not fully reflect day-do-day practice. Contemporary data on etiology, procedural strategies as well as patient outcomes in ALI are urgently needed to improve care and prevent limb loss. The current study was initiated by the European Vascular Research Collaborative (EVRC), established by young European vascular specialists, and aims to provide insight into contemporary treatment strategies in ALI and its clinical results within Europe. In this manuscript we report the rationale and a detailed study protocol.

MATERIAL AND METHODS

The proposed study is a prospective, international, multicenter, observational study on ALI (PROMOTE-ALI) (ClinicalTrials.gov - NCT05138679). Patients with ALI (Rutherford classification grade I -III) of one or both lower extremities will be included in the study. The primary endpoint of the study is amputation-free survival (AFS) at 30 d. Secondary endpoints are freedom from target limb reintervention, freedom from complications, clinical outcome of the index leg, and limb salvage and survival at 30 and 90 d after diagnosis of ALI.

CONCLUSIONS

ALI remains a challenging condition and due to the heterogeneous etiology, clinical presentation and treatment strategies, a large multicenter study on this topic is needed to gain contemporary data on clinical outcomes and prognosis, especially for modern endovascular techniques. PROMOTE-ALI is expected to provide these data and set a benchmark for future randomized controlled trials (RCTs).

Infusion techniques for peripheral arterial thrombolysis

BACKGROUND

Acute limb ischaemia usually is caused by a blood clot blocking an artery or a bypass graft. Severe acute ischaemia will lead to irreversible damage to muscles and nerves if blood flow is not restored in a few hours. Once irreversible damage occurs, amputation will be necessary and the condition can be life-threatening. Infusion of clot-busting drugs (thrombolysis) is a useful tool in the management of acute limb ischaemia. Fibrinolytic drugs are used to disperse blood clots (thrombi) to clear arterial occlusion and restore blood flow. Thrombolysis is less invasive than surgery. A variety of techniques are used to deliver fibrinolytic agents. This is an update of a review first published in 2004.

OBJECTIVES

To compare the effects of infusion techniques during peripheral arterial thrombolysis for treatment of patients with acute limb ischaemia.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, CENTRAL, MEDLINE, Embase, and CINAHL databases and World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registries to 20 October 2020. We undertook reference checking to identify additional studies.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) comparing infusion techniques for fibrinolytic agents in the treatment of acute limb ischaemia.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures as recommended by Cochrane. We assessed the risk of bias in included trials using the Cochrane 'Risk of bias' tool. We evaluated certainty of evidence using GRADE. For dichotomous outcomes, we calculated the odds ratio (OR) with the corresponding 95% confidence interval (CI). We were not able to carry out meta-analyses due to clinical heterogeneity, so we have reported the results and performed the comparisons narratively. The main outcomes of interest were amputation-free survival or limb salvage, amputation, mortality, vessel patency, duration of thrombolysis, and complications such as cerebrovascular accident and major and minor bleeding.

MAIN RESULTS

Nine studies with a total of 671 participants are included in this update. Trials covered a variety of infusion techniques, dosage regimens, and adjunctive agents. We grouped trials according to types of techniques assessed (e.g. intravenous and intra-arterial delivery of the agent, 'high-' and 'low-dose' regimens of the agent, continuous infusion and 'forced infusion' of the agent, use of adjunctive antiplatelet agents). We assessed the certainty of evidence as very low to low due to the limited power of individual studies to deliver clinically relevant results, small and heterogeneous study populations, use of different inclusion criteria by each study in terms of severity and duration of ischaemia, considerably different outcome measures between trials, and use of different fibrinolytic agents. This heterogeneity prevented pooling of data in meta-analyses. No regimen has been shown to confer benefit in terms of amputation-free survival (at 30 days), amputation, or death. For vessel patency, complete success was more likely with intra-arterial (IA) than with intravenous (IV) infusion (odds ratio (OR) 13.22, 95% confidence interval (CI) 2.79 to 62.67; 1 study, 40 participants; low-certainty evidence); radiological failure may be more likely with IV infusion (OR 0.02, 95% CI 0.00 to 0.38; 1 study, 40 participants; low-certainty evidence). Due to the small numbers involved in each arm and design differences between arms, it is not possible to conclude whether any technique offered any advantage over another. None of the treatment strategies clearly affected complications such as cerebrovascular accident or major bleeding requiring surgery or blood transfusion. Minor bleeding complications were more frequent in systemic (intravenous) therapy compared to intra-arterial infusion (OR 0.03, 95% CI 0.00 to 0.56; 1 study, 40 participants), and in high-dose compared to low-dose therapy (OR 0.11, 95% CI 0.01 to 0.96; 1 study, 63 participants). Limited evidence from individual trials appears to indicate that high-dose and forced-infusion regimens reduce the duration of thrombolysis. In one trial, the median duration of infusion was 4 hours (range 0.25 to 46) for the high-dose group and 20 hours (range 2 to 46) for the low-dose group. In a second trial, treatment using pulse spray was continued for a median of 120 minutes (range 40 to 310) compared with low-dose infusion for a median of 25 hours (range 2 to 60). In a third trial, the median duration of therapy was reduced with pulse spray at 195 minutes (range 90 to 1260 minutes) compared to continuous infusion at 1390 minutes (range 300 to 2400 minutes). However, none of the studies individually showed improvement in limb salvage at 30 days nor benefit for the amputation rate related to the technique of drug delivery. Similarly, no studies reported a clear difference in occurrence of cerebrovascular accident or major bleeding. Although 'high-dose' and 'forced-infusion' techniques achieved vessel patency in less time than 'low-dose' infusion, more minor bleeding complications may be associated (OR 0.11, 95% CI 0.01 to 0.96; 1 study, 72 participants; and OR 0.48, 95% CI 0.17 to 1.32; 1 study, 121 participants, respectively). Use of adjunctive platelet glycoprotein IIb/IIIa antagonists did not improve outcomes, and results were limited by inclusion of participants with non-limb-threatening ischaemia.

AUTHORS' CONCLUSIONS

There is insufficient evidence to show that any thrombolytic regimen provides a benefit over any other in terms of amputation-free survival, amputation, or 30-day mortality. The rate of CVA or major bleeding requiring surgery or blood transfusion did not clearly differ between regimens but may occur more frequently in high dose and IV regimens. This evidence was limited and of very low certainty. Minor bleeding may be more common with high-dose and IV regimens. In this context, thrombolysis may be an acceptable therapy for patients with marginally threatened limbs (Rutherford grade IIa) compared with surgery. Caution is advised for patients who do not have limb-threatening ischaemia (Rutherford grade I) because of risks of major haemorrhage, cerebrovascular accident, and death from thrombolysis.

Heterogeneity in Standard Operating Procedures for Catheter Directed Thrombolysis for Peripheral Arterial Occlusions in The Netherlands: A Nationwide Overview

OBJECTIVE

Catheter directed thrombolysis (CDT) for acute arterial occlusions of the lower extremities is associated with a risk of major bleeding complications. Strict monitoring of vital functions is advised for timely adjustment or discontinuation of thrombolytic treatment. Nevertheless, current evidence on the optimal application of CDT and use of monitoring during CDT is limited. In this study the different standard operating procedures (SOPs) for CDT in Dutch hospitals were compared against a national guideline in a nationwide analysis.

METHODS

SOPs, landmark studies, and national and international guidelines for CDT for acute lower extremity arterial occlusions were compared. The protocols of 34 Dutch medical centres where CDT is performed were assessed. Parameters included contraindications to CDT, co-administration of heparin, thrombolytic agent administration, angiographic control, and patient monitoring.

RESULTS

Thirty-four SOPs were included, covering 94% of medical centres performing CDT in the Netherlands. None of the SOPs had identical contraindications and a strong divergence in relative and absolute grading was found. Heparin and urokinase dosages differed by a factor of five. In 18% of the SOPs heparin co-administration was not mentioned. Angiographic control varied between once every 6 h to once every 24 h. In 76% of the SOPs plasma fibrinogen levels were used for CDT dose adjustments. However, plasma fibrinogen level threshold values for treatment adjustments varied between 2.0 g/L and 0.5 g/L.

CONCLUSION

The SOPs for CDT for acute arterial occlusions of the lower extremities differ greatly on five major operating aspects among medical centres in the Netherlands. None of the SOPs exactly conforms to current national or international guidelines. This study provides direction on how to increase homogeneity in guideline recommendations and to improve guideline adherence in CDT.

Early Thrombosuction and Tirofiban Use in Knee and Below-Knee Arterial Thrombosis

BACKGROUND Acute limb ischemia (ALI) is a clinical entity with a high rate of morbidity and mortality. Despite advances and variety of its management, there is still no criterion standard treatment. The goal of this study was to evaluate the effect of tirofiban use on the early and 6-month prognosis of patients with knee and below-knee arterial thrombosis who were treated with percutaneous thrombosuction (PT) within 24 h. MATERIAL AND METHODS Data of consecutive ALI patients who were diagnosed with popliteal and infra-popliteal arterial thrombosis and underwent PT procedure within 24 h between January 2010 and September 2015 were evaluated retrospectively. Patients were separated into 2 groups according to tirofiban usage. RESULTS A total of 105 patients (mean age 67±16; 53% men) were included in the study. Atrial fibrillation (n 64, 61%) and hypertension (n 60, 57%) were the most frequent comorbidities in patients with thromboembolic events. A significantly higher rate of distal embolization (6% vs. 16%; p=0.01) and slow-flow (17% vs. 30%; p<0.01) developed in patients who were not treated with tirofiban after the PT procedure. Although major and minor bleeding were more frequent in the tirofiban group, only the rate minor bleeding was statistically significant (29% vs. 9%, p=0.001). Reverse embolic event ratio was similar in both groups. Although there was a higher rate of amputation in patients not treated with tirofiban, the difference was not significant. CONCLUSIONS Adding tirofiban to PT reduces angiographic thromboembolic complications. Usage of tirofiban in patients prone to thromboembolic events may be useful for improving success of the PT procedure, with a reasonable bleeding ratio.

Endovascular treatment of acute limb ischemia due to thrombotic occlusion of the suprainguinal artery

Acute limb ischemia (ALI) is a serious condition requiring prompt intervention due to a sudden decrease in limb perfusion threatening limb viability. Treatment of ALI depends on the clinical status of the affected limb and patient comorbidities. Surgical therapy has been the historical standard of care for restoring limb perfusion; however, percutaneous endovascular intervention has been shown to be a promising treatment option in selected patients of ALI at high surgical risk. We report on a case of a 75-year-old man with ALI caused by thrombotic occlusion of the suprainguinal artery, successfully treated with endovascular therapy including stent insertion and thrombus aspiration and catheter-directed urokinase infusion in view of the clinical findings and imaging studies.

Low-dose thrombolysis for thromboembolic lower extremity arterial occlusions is effective without major hemorrhagic complications

OBJECTIVE

To evaluate the efficacy and bleeding complications associated with a low-dose thrombolysis protocol for thromboembolic lower extremity arterial occlusions.

DESIGN

A retrospective cohort study.

MATERIALS AND METHODS

A retrospective analysis was performed using data from all consecutive patients who underwent catheter-directed, intra-arterial thrombolysis for thromboembolic lower extremity arterial occlusions between January 2004 and May 2013. All patients were treated on a standard surgical ward. Endpoints were incidence of bleeding complications, duration of thrombolysis, angiographic patency rate, 30-day mortality rate, and amputation-free rate at 6 months.

RESULTS

Of the 171 cases analyzed, 129 cases underwent low-dose thrombolysis and 42 underwent high-dose thrombolysis. No major bleeding complications occurred in the low-dose group versus 5% in the high-dose group (p = .01). The median duration of thrombolysis was 67 hours (4-304 hours) in the low-dose and 49 hours (2-171 hours) in the high-dose group (p = .027). Angiographic patency was restored in 67% of the cases in the low-dose group versus 79% of the high-dose group (p = .17). The 30-day mortality rates were 1% in the low-dose versus 5% in the high-dose group (p = .09). However, this higher mortality rate was not related to bleeding complications. Major amputation-free rates at 6 months were 81% in the low-dose group and 88% in the high-dose group (p = .22).

CONCLUSIONS

Based on this data series, low-dose thrombolysis for thromboembolic lower extremity arterial occlusions is as effective as high-dose thrombolysis; however, the risk of major bleeding complications is substantially lower when using low-dose thrombolysis.

Quality improvement guidelines for percutaneous catheter-directed intra-arterial thrombolysis and mechanical thrombectomy for acute lower-limb ischemia

Percutaneous catheter-directed intra-arterial thrombolysis is a safe and effective method of treating acute and subacute lower limb ischemia, as long as accurate patient selection and procedural monitoring are ensured. Although larger, controlled trials are needed to establish the role of PTDs in ALI, mechanical thrombectomy could currently be applied combined with lytic infusion in selected cases where rapid recanalization is required or as a stand-alone therapy when the administration of thrombolytic agents is contraindicated.

Differentiating pharmacologic agents used in catheter-directed thrombolysis

The use of catheter-directed thrombolysis is a proven treatment for arterial ischemia, deep vein thrombosis, and severe pulmonary embolism. For arterial ischemia, thrombolysis has resulted in improved amputation-free survival and fewer subsequent surgeries to reestablish blood flow to the ischemic limb. The management of patients with thromboembolic diseases is complex, and the multiple thrombolytic drugs available to choose from compound this complexity. Although some believe the available thrombolytic agents are interchangeable, real biochemical differences exist that may prove otherwise. This article describes these pharmacologic differences and how they may affect the clinical practice of catheter-directed thrombolysis.

Do randomized trials of thrombolysis versus open revascularization still apply to current management: what has changed?

Several randomized trials of catheter-directed thrombolysis versus operative revascularization in patients with acute lower extremity ischemia were performed in the mid-1990 s. Although the outcomes of these trials were not definitive, they did provide insight into potential uses and techniques of catheter-directed thrombolysis and lytic agents. This article reviews the outcomes of these randomized trials and describes advances in thrombolytic techniques and technology, including percutaneous mechanical thrombectomy devices and innovative catheter designs that accelerate lysis and the development of direct-acting lytic agents.

Intracoronary Fibrin-Specific Thrombolytic Infusion Facilitates Percutaneous Recanalization of Chronic Total Occlusion

OBJECTIVES

We sought to investigate the benefit, predictors of procedural success, and safety of pre-procedural intra-coronary fibrin-specific lytic infusion (ICL) in patients with failed prior percutaneous coronary intervention (PCI) for chronic total occlusions (CTO).

BACKGROUND

Percutaneous coronary intervention for CTO remains a challenge with a high incidence of procedural failure secondary to inability to cross the occlusion with the guidewire.

METHODS

Eighty-five patients who underwent unsuccessful PCI procedures of CTO (more than three months' duration) had a repeat attempt of recanalization with the use of pre-procedural ICL. Patients received a weight-adjusted dose of either alteplase (tPA) (2 to 5 mg/h) or tenecteplase (TNK) (0.5 mg/h) for a total of 8 h. The total dose of ICL therapy was infused split between the guiding catheter and an intracoronary infusion catheter. A step-down multivariate logistic regression analysis was completed to determine the best predictors of procedural success. In-hospital major adverse cardiac events (MACE) including myocardial infarction, acute reocclusion, stroke, and death, as well as bleeding complications, were also examined.

RESULTS

The procedure was successful in 46 of 85 cases (54%). Four of 85 (5%) contained dissections that did not result in perforations, tamponade, or MACE. The incidence of groin complications was 7 of 85 (8%) and of bleeding complications requiring transfusions was 3 of 85 (3.5%). On multivariate analysis, predictors of success were tapering morphology (odds ratio, 15.5; 95% confidence interval, 3.73 to 63; p = 0.0002) and lack of bridging collaterals (odds ratio, 5.08; 95% confidence interval, 1.53 to 17; p = 0.008).

CONCLUSIONS

Intracoronary infusion of fibrin-specific thrombolytic therapy may provide a valuable and safe option for facilitating percutaneous revascularization of CTO.

Current trends in thrombolysis: implications for diagnostic and interventional radiology

Current trends in thrombolysis are of relevance to both diagnostic and interventional radiologists. In addition to the traditional use of thrombolytic therapy in conditions such as peripheral arterial thrombosis, venous thrombosis and pulmonary embolic disease, more recent interest has focused on the potential use of thrombolysis in acute stroke. There will be significant implications for the provision of radiological services if current trials show a favourable outcome for thrombolysis in stroke. This article looks at a range of conditions in which thrombolysis may be useful, on the strength of currently available evidence. Future trends will depend on the outcomes of the current trials.

Safety of Thrombolytic Therapy with Urokinase or Recombinant Tissue Plasminogen Activator for Peripheral Arterial Occlusion:A Comprehensive Compilation of Published Work

PURPOSE

To report a comprehensive literature review focused on comparing the risk of complications with urokinase versus recombinant tissue plasminogen activator (rtPA) for thrombolytic treatment of peripheral arterial occlusions.

METHODS

The English-language literature between 1985 and 2002 was searched for studies that used tissue-derived urokinase or rtPA in the treatment of peripheral arterial occlusions. Forty-eight studies (22 urokinase, 22 rtPA, and 4 that included both treatments) were identified, encompassing 2226 urokinase-treated patients and 1927 rtPA-treated patients. The safety of each thrombolytic agent was assessed based on the incidence of major hemorrhage, intracerebral hemorrhage, major limb amputation, transfusions, and mortality.

RESULTS

The review revealed a wide range of study protocols, patient conditions, ages of occlusions, dosages/delivery methods of lytic agents, and criteria for reporting complications. The incidence of major hemorrhage varied widely, but the overall rate was lower among urokinase-treated patients (6.2%) than for patients treated with rtPA (8.4%, p=0.007). The overall incidence of intracerebral hemorrhage was also significantly lower for urokinase (0.4% versus 1.1% for rtPA, p=0.020). The major amputation rate was similar for both treatments (urokinase 7.9%, rtPA 7.2%), but the mortality rate was significantly lower for urokinase (3.0% versus 5.6% for rtPA, p<0.001). The need for transfusions was less frequent with urokinase (11.1% versus 16.1%, p=0.002).

CONCLUSIONS

These results from a large body of published literature suggest that urokinase may be associated with a lower incidence of complications than rtPA in the treatment of peripheral arterial occlusions.

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.

Infusion techniques for peripheral arterial thrombolysis

BACKGROUND

Thrombolytic therapy is a useful tool in the management of acute peripheral arterial ischaemia. Fibrinolytic drugs are used to disperse blood clot to clear arterial occlusion. A variety of techniques are used to deliver these agents.

OBJECTIVES

To determine the optimal technique for infusion of fibrinolytic drugs in peripheral arterial ischaemia.

SEARCH STRATEGY

The Cochrane Library (issue 3, 2003) and the Specialised Trials Register of the Cochrane Review Group on Peripheral Vascular Diseases (July 2003) were searched. Proceedings from meetings of British, European and North American Vascular Surgical and Radiological Societies, plus reference lists of identified studies were also searched for relevant trials. Major pharmaceutical firms and trialists were asked about unpublished trials.

SELECTION CRITERIA

Two reviewers independently selected randomised controlled trials comparing infusion techniques of fibrinolytic agents in the treatment of acute peripheral arterial ischaemia. Trials with poor quality methodology were excluded.

DATA COLLECTION AND ANALYSIS

Data from included trials were collated and analysed for the following outcomes: limb salvage, amputation, death, vessel patency, time to achieve thrombolysis, and reduction in the need for surgical intervention. Complication rates were compared for: major haemorrhage, cerebrovascular accident and distal embolization.

MAIN RESULTS

Intra-arterial delivery of thrombolytic agents appeared to be more effective than intravenous administration. Thrombolysis was more effective when the angiographic catheter was placed within the thrombus. Although 'high dose' and 'forced infusion' techniques achieved vessel patency in less time than 'low dose infusion', there were more bleeding complications, and no increase in patency rates or improvement in limb salvage at 30 days.

REVIEWER'S CONCLUSIONS

Implications for practice Thrombolysis should be reserved for patients with limb threatening ischaemia, due to the high risk of haemorrhage or death. Greater benefit is seen when the thrombolytic agent is delivered into the thrombus. Systemic intravenous thrombolysis is less effective than intra-arterial thrombolysis and is associated with an increase in bleeding complications. 'High dose' and 'forced infusion' techniques, or adjunctive agents such as platelet glycoprotein IIb/IIIa inhibitors may speed up thrombolysis, but these are not accompanied by lower amputation rates or a decreased need for adjunctive endovascular or surgical procedures. 'Low dose continuous infusion', following initial lacing of the thrombus with a high dose of the thrombolytic agent, is the least labour intensive technique. Implications for research Only large multicentre trials with carefully controlled inclusion criteria will be sufficiently powerful to demonstrate genuine benefit for a particular thrombolytic regime.

[Radiological diagnosis and treatment of acute limb ischemia]

Acute limb ischemia is associated with significant morbidity and mortality, despite diagnostic and therapeutic advances. Threatened limbs require immediate imaging in order to determine the subsequent therapeutic procedures. Conventional angiography in the DSA technique still has advantages over CT and MR angiography. In acute arterial occlusions below the femoral bifurcation, endovascular treatment with intra-arterial local thrombolysis or percutaneous thrombectomy is an alternative to open vascular surgical procedures. The following article describes diagnostic and therapeutic strategies for acute limb threat induced by arterial occlusion.

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.

Weight-based rt-PA thrombolysis protocol for acute native arterial and bypass graft occlusions

PURPOSE

To determine technical success and complications with weight-adjusted dosing of recombinant tissue plasminogen activator (rt-PA) for arterial and bypass graft occlusions.

MATERIALS AND METHODS

During an 8-month period, prospective data were collected on patients undergoing catheter-directed thrombolysis. Retrospective review of all medical charts and blood bank data were performed for confirmation. All patients underwent a standard weight-adjusted protocol for catheter-directed thrombolysis. Thrombolytic therapy with rt-PA (0.2 mg/mL) was defined as low-dose when 0.02 mg/kg/h rt-PA was used and high-dose when 0.04 mg/kg/h of rt-PA was used. Low-dose heparin therapy was used. Total infusion time, total dose, and hourly rate of dose were calculated. Technical success, defined as complete removal of all clot without surgical intervention, complications, and frequency of transfusions were tabulated.

RESULTS

A total of 35 patients underwent catheter-directed thrombolysis with rt-PA, including a total of 21 bypass grafts (60%) and 14 native arteries (40%). Mean age was 57 years (+/- 22.5; range, 3 mo to 83 y). Average rate of heparin infusion was 472.8 U/h (+/- 227). Success rates for graft thrombolysis were 90% (18 of 21). Success rates for native vessels were 79% (11 of 14). In patients who underwent only a low-dose protocol, the transfusion rate was 15% and major complications were 10%. In patients with a combined low-dose/high-dose administration, the transfusion rate was 46% and major complications were 13%. Overall success rate and major complication rates were 86% (30 of 35) and 11% (four of 35), respectively. Frequency of transfusions was 37% (13 of 35; mean, 2.8 U).

CONCLUSION

Although weight-adjusted dosing for rt-PA provides a high efficacy of relieving ischemia, the rate of complications, especially bleeding, seems excessive in comparison to historical experience with urokinase. Administration of short-term high doses of rt-PA did not appear to have any beneficial effect. Further investigation with lower dosing and concentration should be considered.

Augmented pulse-spray thrombolysis with tPA by early pulsed intrathrombic plasminogen enrichment

PURPOSE

This study was designed to evaluate the efficacy of plasminogen enrichment of subacute thrombus in further accelerating pulse-spray pharmacomechanical thrombolysis (PSPMT) with urokinase (UK) or tissue plasminogen activator (tPA) in a rabbit model.

MATERIALS AND METHODS

With use of a subacute rabbit inferior vena cava (IVC) thrombosis model, 78 rabbits were divided into eight groups according to the agents used for thrombolysis: (i) controls (IVC thrombosis, no lysis performed), (ii) pulse-spray thrombolysis with saline only, (iii) PSPMT with UK, (iv) PSPMT with UK, plus interim pulse-spray plasminogen enrichment after 14 minutes, (v) pulse-spray plasminogen enrichment, followed at 10 minutes by PSPMT with UK, (vi) PSPMT with tPA, (vii) PSPMT with tPA, plus interim plasminogen enrichment, and (viii) pulse-spray plasminogen enrichment, followed at 10 minutes by PSPMT with tPA.

RESULTS

Intrathrombic pulsed injection of glu-plasminogen after 14 minutes of tPA PSPMT demonstrated significant augmentation of lysis (approximately 31% decrease in residual thrombus) compared with tPA alone (P = .006). Lysis was not augmented significantly when plasminogen was sprayed into thrombus before tPA, or before or after UK.

CONCLUSION

Plasminogen enrichment of thrombus after onset of PSPMT with tPA significantly accelerated thrombolysis in a subacute in vivo rabbit model. A clinical trial of this method may be warranted.

Intraarterial urokinase for acute native arterial occlusion of the limbs

Since 1988, 49 limbs of 47 patients underwent intraarterial urokinase infusion for acute native artery occlusion. The time from the onset of ischemic symptoms ranged from 1 to 45 days (mean = 17.5). The arterial sectors involved were femoropopliteal in 32 cases, followed by aortoiliac in 13 cases, distal in three cases, and subclavian in one case. Treatment consisted of placing a catheter in the clot and the infusion of 4400 U/kg in 20', followed by a series of 4400 U/kg weight/hour during 6 hours. Clinical evaluation, hemodynamic and coagulation parameters, and angiographical changes were assessed periodically. Infusion time ranged from 6 to 24 hours (mean = 13.2 hours). Improvement of ischemic was achieved in 43 (87.75%) patients. In five patients (12.25%) there was no improvement. Total immediate lysis was achieved in 35 cases (71.5%), and among them, 13 patients (26%) required no associated treatment, 16 (48%) underwent PTA, and four (12%) had surgery of underlying peripheral aneurysms revealed after thrombolysis. Partial lysis was achieved in 13 cases (26.5%), that was enough in four of them, but the remaining nine required further treatment (four PTA, and five arterial surgery). In one case no lysis was achieved, and arterial surgery was carried out. No mortality was recorded, and major complications included one upper gastrointestinal bleeding, and one cerebral hematoma. Late follow-up of successfully treated patients who did not require further surgery shows a cumulative patency rate of 81% at 24 months.

Comparison of streptokinase and urokinase in local thrombolysis of peripheral arterial occlusions for lower limb salvage

PURPOSE

To compare the efficacy and safety of streptokinase (SK) and urokinase (UK) in the treatment of local thrombolysis.

PATIENTS AND METHODS

Over a 24-month period, 40 patients with 45 lower limb arterial occlusions of less than 45 days duration underwent intraarterial fibrinolysis. Twenty occlusions were treated with recombinant UK and tissue culture-derived UK, and 25 occlusions were treated with SK. The study was retrospective, but the two groups were very homogeneous in terms of vascular surgical history, medical risk factors, and occlusion characteristics.

RESULTS

Complete lysis (95% or more) was achieved in 84% of SK infusions and 89% of UK infusions. Endoluminal and surgical interventions as well as clinical outcomes of SK and UK treatment were comparable. However, infusion time was significantly longer for SK treatment: 28.5 hours versus 19.1 hours for UK treatment (P = .035). Complication rates were not statistically significantly different. Average length of stay in the intensive care unit was identical (2.2 days) for both groups, and the difference in hospital stay was not statistically significant (7.7 days for SK vs 8.7 days for UK).

CONCLUSION

At the concentrations and doses used, the efficacy and safety of SK and UK were comparable, despite longer SK infusion time.

Prospective, randomized trial of prolonged intracoronary urokinase infusion for chronic total occlusions in native coronary arteries

OBJECTIVES

The purpose of this study was to determine the safety and efficacy of three dosing regimens of intracoronary urokinase for facilitated angioplasty of chronic total native coronary artery occlusions.

BACKGROUND

Percutaneous transluminal coronary angioplasty of chronically occluded (>3 months) native coronary arteries is associated with low initial success secondary to an inability to pass the guide wire beyond the occlusion.

METHODS

Patients were enrolled if a chronic total occlusion >3 months old could not be crossed with standard angioplasty equipment. Of the 101 patients enrolled, 41 had successful guide wire passage and were excluded from urokinase treatment. The remaining 60 patients were randomized to receive one of three intracoronary dosing regimens of urokinase over 8 h (group A = 0.8 million U; group B = 1.6 million U; group C = 3.2 million U), and angioplasty was again attempted after completion of the urokinase infusion in 58 patients.

RESULTS

Coronary angioplasty was successful in 32 patients (53%) (group A 52%, group B 50%, group C 59%, p = 0.86). This study had a 90% power to detect at least a 50% difference between dosing groups at alpha 0.05. Bleeding complications requiring blood transfusion did not differ significantly among the dosing groups (A 0%, B 15%, C 6%, p = 0.14), although major bleeding episodes were less common in group A (p < 0.05). There were no major procedural or in-hospital complications. Angiographic follow-up in 69% of the patients with successful angioplasty revealed target vessel patency in 91% but an angiographic restenosis rate of 59%.

CONCLUSIONS

A prolonged supraselective intracoronary infusion of urokinase can be safely administered and may facilitate angioplasty of chronic total occlusions. Lower doses of urokinase are equally effective and result in fewer bleeding complications than do higher dosage regimens. Vessel patency is frequently maintained, but restenosis remains a problem.

In vitro model to evaluate the relative efficacy of catheter-directed thrombolytic strategies

RATIONALE AND OBJECTIVES

Catheter-directed thrombolytic therapy has become an accepted treatment for many vascular occlusions. However, the relative rates of lysis of the different methods of drug administration have not been quantified. We developed an in vitro model to simulate and quantify local lytic therapy of a thrombotic vascular occlusion and tested it by evaluating three catheter-directed lytic strategies.

METHODS

Seven-centimeter-long segments of 125I-fibrinogen-labeled thrombus made from recently expired human blood from a blood bank were formed in plastic tubes and were placed in a flowing stream of saline. Using multisidehole catheters, the clots were "treated" with intrathrombic saline or urokinase administered by drip infusion or forced injection using identical total doses of drug and volumes of fluid. Using endhole catheters, saline or urokinase was drip infused into the leading edge of the thrombus using the same protocol. A collimated scintillation detector was used to quantify the amount of activity remaining in the thrombus during each experiment, and the resultant time-activity curves for the different trials were compared.

RESULTS

Forced-injection administration of urokinase using a multisidehole catheter produced the fastest lysis, resulting in a half-life of 42 min. The other infusion methods were slower, with half-lives of 153 min for multisidehole urokinase drip infusion, 365 min for endhole urokinase drip infusion, and more than 1,000 min for multisidehole catheter forced injection of saline and multisidehole and endhole saline drip infusion. The differences among these groups were reproducible and statistically significant.

CONCLUSION

Results suggest that a simple and inexpensive in vitro model simulating lysis of a vascular occlusion can produce reproducible quantitative data. The data demonstrate that forced injection of lytic agents with a multisidehole catheter enhances the rate of thrombolysis and that the enhancement is not primarily attributable to the mechanical effect of this mode of administration.

The case for better research standards in peripheral thrombolysis: poor quality of randomized trials during the past decade

RATIONALE AND OBJECTIVES

We assessed how well published randomized controlled trials (RCTs) of peripheral thrombolysis have been designed and how they adjusted for patient characteristics that may influence responses to therapy.

METHODS

RCT studies published between 1984 and 1994 were reviewed to determine whether they included nine crucial elements: sample size calculations, description of unenrolled eligible participants, homogeneous samples, balanced experimental groups, equal potency therapies, equal follow-up of outcomes, appropriate statistical inference, multivariable or subgroup analyses, and anonymous review of subjective endpoints.

RESULTS

The nine RCTs complied with a median of three of nine standards (range = 2-6). Each report exhibited serious flaws that may affect generalizability and external validity. None adequately adjusted for sample heterogeneity or sought to identify characteristics that may affect responses to therapy.

CONCLUSION

Failure to address prognostic or confounding variables restricts the utility of peripheral thrombolysis RCTs and helps explain why contentious debates about this therapy persist. A model for future thrombolysis trials is proposed.

Technical determinants of success in catheter-directed thrombolysis for peripheral arterial occlusions

Local intraarterial thrombolytic therapy restores blood flow to the ischemic limb by dissolving the occlusive thrombus and identifies culprit lesions for treatment by means of surgical and/or percutaneous procedures. The techniques used for administration of the thrombolytic agent, the drug used, and the criteria for termination of the therapy are all factors that can influence both technical success and speed of lysis. This article discusses these factors and their influence on thrombolytic success.

Drug variables in thrombolytic therapy

Fibrinolytic therapy has become an accepted treatment modality for recent peripheral arterial and bypass graft occlusions and, in some cases, for chronic arterial occlusions. Streptokinase, urokinase, and tissue plasminogen activator have all been used for intraarterial infusion with varying protocols and results. This review focuses on dosing variables and clinical results for the various thrombolytic agents in peripheral arterial and bypass graft occlusions. Also discussed are new thrombolytic agents and the effects of concomitant use of other drugs as part of the treatment regimen.

Failure of thrombolytic therapy to improve long-term vascular patency

PURPOSE

Few data are available on long-term follow-up of arterial segments subjected to thrombolysis. We reviewed all cases of vascular occlusion treated with urokinase to identify early success and determine the influence of postlysis intervention and the nature of the thrombosed segment (i.e., artery vs graft) on long-term patency.

METHODS

Data on 134 cases (58 arteries, 76 grafts) treated with high-dose urokinase infusion in the lower limbs over a 7-year period were analyzed. Limbs were divided into five groups on the basis of therapy after lytic infusion to determine long-term efficacy: group I, success with no additional therapy; group II, percutaneous angioplasty alone; group III, limited surgical procedure (operative angioplasty, jump graft); group IV, extensive procedure (new bypass); and group V, revascularization after lytic failure. Long-term results were assessed by life-table analysis and groups compared by log-rank test (Mantel-Haenszel).

RESULTS

Initial patency was established in 87 (64.9%) of 134 cases with 5 deaths (3.7%), 11 amputations (8.2%), and 16 complications (11.9%). Follow-up was available in 68.6% of cases for a mean of 10.9 months. No difference was seen between grafts and native arteries. Patency was analyzed at 6, 12, 18, and 24 months. The 24-month patency rate after lysis alone (group I-25.9%) was inferior (p < 0.05) to results after lysis and any subsequent intervention (groups II, III, and IV). The type of intervention did not influence subsequent patency. Twenty-four-month patency of procedures performed after failed thrombolysis (group V, 41.4%) was not different from those after successful lysis (groups I to IV). Twenty-four-month patency in groups II and III (minor interventions, 62.9%) was not significantly different from that of groups IV and V (major interventions, 53.2%) (p > 0.25).

CONCLUSIONS

Operative intervention is required to produce long-term arterial patency, even after successful thrombolysis. No statistically significant benefit of thrombolysis on vascular patency was seen in our series.

Percutaneous intraarterial thrombolysis: analysis of factors affecting outcome

PURPOSE

The authors report results of high-dose thrombolytic therapy in native arteries and vein grafts and discuss the various factors affecting outcome.

PATIENTS AND METHODS

In a retrospective study, the outcome of 82 high-dose urokinase infusions in 76 patients was examined. Comorbid risk factors as they relate to outcome were studied extensively with log-linear analysis. Positive thrombolytic outcome (PTO) is defined as complete thrombolysis of a previously occluded segment with restoration of antegrade flow augmented by angioplasty or operative intervention to clear symptoms for 30 days.

RESULTS

The procedure resulted in a PTO in 63 of 82 instances (77%). The treatment was with urokinase alone in 39 cases (47%) and urokinase followed by surgery in 34 (41%), by angioplasty in four (5%), and by angioplasty in the proximal artery and peripheral vein grafting in five (6%). All stenoses associated with grafts were treated surgically. None of the following affected thrombolytic outcome: age of occlusion, heparin dose, catheter type, length or location of graft, or artery versus graft occlusion. The 30-day mortality was 6.1%, with a procedure-related mortality rate of 2.4%. Overall amputation rate was 18% (74% for patients in whom lysis failed by 30 days).

CONCLUSION

The presence of at least one runoff vessel was the most important factor affecting outcome (PTO, 95%; P = .00001, chi 2). The most important comorbid risk factor for failed thrombolysis was coronary artery disease (P = .03, chi 2).

Transcatheter therapy of severe acute lower extremity ischemia

PURPOSE

Transcatheter methods of revascularization were performed in 11 patients with severe acute lower extremity ischemia and extensive vascular occlusions in whom surgical revascularization was not possible (10 patients) or was not preferred (one patient).

PATIENTS AND METHODS

The acute ischemia was considered category 2 in nine patients and category 3 in two. Vascular occlusions were located in the superficial femoral artery in four patients, popliteal artery in 10, all three crural arteries in 10, and two crural arteries in one. Transcatheter methods included accelerated thrombolysis with 325,000 to 1.75 million U of urokinase, adjunct angioplasty, use of intraarterial vasodilators, and creation of pedal arterial flow loops.

RESULTS

Initial success was 100% in the nine patients with category 2 ischemia. Eight limbs were saved; one occlusion at 10 days necessitated below-knee amputation. For the two patients with category 3 ischemia, one procedure failed and the other reduced the level of amputation.

CONCLUSION

In patients with severe acute ischemia, transcatheter revascularization is a viable treatment option when strategies for reperfusion establish both inflow and microcirculatory outflow.

Thrombolysis of the occluded prosthetic graft with tissue-type plasminogen activator--technique, results and problems in 23 patients

Over a 12 month period all patients but one presenting to our hospital with occluded prosthetic grafts were treated by thrombolysis using local pulsed administration of tissue-type plasminogen activator (t-PA). There were 30 interventions in 23 patients but in one patient no thrombolytic was given after aspiration of pus from the graft. Thrombolysis was attempted in the remaining 29 procedures. 22/29 (76%) of these procedures were performed by direct puncture and catheterization of the occluded graft and in a further six (21%) access was from a non-occluded femoral artery or graft. In one case the graft was accessed surgically. Supplementary angioplasties were performed in 15 cases (52%). Complications requiring surgery occurred in four (14%) with a further seven minor complications. There were no deaths. A lower rate of complications occurred in the grafts entered by direct puncture. Thrombolysis was achieved in all but one case taking an average of only 2.5 h but was only maintained beyond the end of the procedure in 21/29 (72%). An underlying cause for occlusion was identified and treated where possible, e.g. haematological or clotting abnormalities or inflow or outflow stenoses. There was a high rate of reocclusion but with repeat procedures when necessary patency was maintained in 10/22 patients (45%) on follow-up at 1 to 12 months. The best results were obtained with lysis of occluded femoro-femoral crossover grafts.

Low-dose urokinase regimen for the treatment of lower extremity arterial and graft occlusions: experience in 132 cases

In a retrospective review, a low-dose urokinase (UK) infusion regimen (mean, 87,000 U of UK per hour and 100 U of heparin per hour) was evaluated for lower extremity arterial and graft occlusions. Results of 132 infusions in 111 patients were analyzed to determine efficacy, limb salvage, and complications. Angiographic success was achieved with 126 infusions (95%), and amelioration of presenting signs and symptoms was achieved after 116 infusions (88%). Patients who underwent additional percutaneous procedures were more likely to have a successful outcome. There was no significant difference in success rates for patients receiving low-dose heparin through the arterial sheath (n = 101) versus those receiving concomitant systemic heparinization (n = 29), (P = .08) [corrected]. Of 88 threatened extremities (with rest pain, cold, ulcers, or gangrene), nine were amputated (limb salvage = 90%), accounting for 82% (nine of 11) of amputations in the overall study. Patients with zero- or one-vessel runoff before infusion were more likely to require limb amputation compared with the group with two- or three-vessel runoff before infusion (P less than .01). Major periprocedural complications occurred in nine of 132 (7%) infusions, five of which necessitated specific surgery and/or transfusion for bleeding. Pericatheter thrombosis was not encountered in either subgroup. This standard local low-dose infusion represents a safe and effective treatment for lower extremity arterial and graft occlusions.

Superior mesenteric artery embolism: treatment with intraarterial urokinase

Four patients with a superior mesenteric artery (SMA) embolism were successfully treated with intraarterial urokinase. Angiography showed partial SMA occlusion by intraluminal thrombus in two cases and almost total occlusion in two cases. Laparotomy was performed in the latter two cases, one of which required resection of infarcted bowel. Several additional reports of partially occluding SMA emboli treated successfully with streptokinase were found in the literature. The use of intraarterial thrombolytic drugs is an important addition to the treatment of mesenteric embolism that, in some cases, can eliminate or simplify surgical management.

Urokinase thrombolysis using a multiple side hole multilumen infusion catheter

A multilumen, multiple side hole infusion catheter was used for urokinase thrombolysis in 13 patients with thromboembolic occlusions of peripheral arteries and grafts. Balloon angioplasty was performed following urokinase infusion in 6 patients and atherectomy in 1 patient. There was one hemorrhagic complication. The major advantage of the multiple sidehole infusion catheter was the elimination of the need to reposition the catheter during the infusion and the reduction of the time burden on the angiographic facility. The success rate for the thrombolysis (77%) was comparable to results recorded in the literature. The total duration of infusion was not reduced compared to other series.