Thrombolytic therapy with use of alteplase (rt-PA) in peripheral arterial occlusive disease: review of the clinical literature. The Advisory Panel

Response Surface Methodology to Optimize the Expression Efficiency of Recombinant Reteplase

Background

Over expression of Reteplase enzyme has already been studies in the periplasmic space of Escherichia coli (E. coli). However, the role different factors in its expresssin rate remained to be elucidated.

Objectives

Optical cell density (OD), IPTG concentration, and expression time are highly effective in the protein expression rates. Therefore, we aimed to determine the optimum levels of these factors for reteplase expression using response surface methodology (RSM).

Materials and Methods

The pET21b plasmid was used to sub-clone the designed reteplase gene. Then, the gene was transformed into E. coli BL21 strain. Induction of expression was done by IPTG and analyzed by the SDS page. experiments were designed using the RMS, while the effects of different conditions were evaluated using the Real time-PCR.

Results

Sequence optimization removed all undesirable sequences of the designed gene. Transformation into E. coli BL21 was confirmed with an 1152 bp band on the agarose gel. A 39 kDa expression band on the SDS gel confirmed the gene expression. Performing 20 RSM-designed experiments, the optimum levels for IPTG concentration and OD were determined as 0.34mM and 5.6, respectively. Moreover, the optimum level of expression time was demonstrated to be 11.91 hours. The accuracy of the regression model for reteplase overexpression was confirmed by an F-value equal to 25.31 and a meager probability value [(Prob > F) < 0.0001]. The real-time-PCR results indicated that the performed calculations were highly accurate.

Conclusion

The obtained results indicate that IPTG concentration, OD, and expression time are significantly involved in the augmentation of recombinant reteplase expression. To the best of our knowledge, this is the first study to assess the combined effect of these factors on reteplase expression. Further RSM-based experiments would bring about new insights regarding the best conditions for reteplase expression.

Waist Training Corset: An Unusual Cause of Acute Lower Limb Ischemia

Acute limb ischemia (ALI) can occur due to many causes. This article illustrates a novel case of a very rare presentation and etiology of acute lower extremity ischemia. This case involves a middle-aged female with a history of smoking and obesity who presented with right lower extremity (RLE) pain. The patient had undergone a liposuction procedure a few days prior to her presentation and had been wearing a waist training corset. The patient was found to have multivessel thrombotic occlusive plaques starting from the right common iliac to the right tibial arteries. She was fully worked up and no other etiologies of her presentation was found. Thus, we concluded that her presentation was very likely precipitated by wearing the training corset, leading to right iliac artery thrombosis or perhaps a formal iliac atherosclerotic plaque destabilization and ipsilateral limb showering with athero-thrombi.

Catheter-directed intra-arterial thrombolysis for lower extremity arterial occlusions

Catheter-directed intra-arterial thrombolysis (CDT) is a rational treatment method in patients with acute/subacute and even some chronic occlusions of lower extremity arteries and bypass grafts having salvageable limb ischemia. Immediate vessel patency can be achieved with an acceptable complication rate in many patients, especially those with fresh thrombus or emboli. It can be also an adjuvant treatment modality for endovascular interventions for chronic occlusions. There is no standard method of CDT including thrombolytic agent dose and technique. Selection of treatment strategy should be based on individual judgment based on viability of limb, lesion characteristics, and risks of hemorrhage.

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.

Should Age Limit the Use of Catheter-Directed Thrombolysis: Results of National Survey

OBJECTIVE

To determine whether advanced age should be a contraindication to catheter-directed thrombolysis (CDT) based on hemorrhagic complication rate.

METHODS

A survey was generated via Survey Monkey and sent out to vascular surgeons who were members of the society of vascular surgery (SVS).

RESULTS

Of the responders, 32.7% state they do not have an age limit for tissue plasminogen activator (TPA) infusion, and the remaining 29.2% of the responders use 80 years of age as their limitation. When asked why place limits on age for TPA infusion, 56.6% stated concern for intracranial hemorrhage. Major complications were access site hemorrhage (58.4%) and intracranial hemorrhage (41.6%). Chi-square analysis did not show age as a limiting factor to thrombolysis. Furthermore, when asked in which age-group complications occurred most commonly, 72.4% were less than 80.

CONCLUSION

Among vascular specialist, there seems to be no consensus on age limitations for TPA infusion. Serious complications do not seem to be age related and thus age alone should not be a contraindication for catheter-directed thrombolysis.

Vascular injuries in the upper extremity in athletes

Repetitive, high-stress, or high-impact arm motions can cause upper extremity arterial injuries. The increased functional range of the upper extremity causes increased stresses on the vascular structures. Muscle hypertrophy and fatigue-induced joint translation may incite impingement on critical neurovasculature and can cause vascular damage. A thorough evaluation is essential to establish the diagnosis in a timely fashion as presentation mimics more common musculoskeletal injuries. Conservative treatment includes equipment modification, motion analysis and adjustment, as well as equipment enhancement to limit exposure to blunt trauma or impingement. Surgical options include ligation, primary end-to-end anastomosis for small defects, and grafting.

Outcome and complications after intra-arterial thrombolysis for lower limb ischaemia with or without continuous heparin infusion

Background

Thrombolysis is a common treatment for acute leg ischaemia. The purpose of this study was to evaluate different thrombolytic treatment strategies, and risk factors for complications.

Methods

This was a retrospective analysis of prospective databases from two vascular centres. One centre used a higher dose of heparin and recombinant tissue plasminogen activator (rtPA).

Results

Some 749 procedures in 644 patients of median age 73 years were studied; 353 (47·1 per cent) of the procedures were done in women. The aetiology of ischaemia was graft occlusion in 38·8 per cent, acute arterial thrombosis in 32·2 per cent, embolus in 22·3 per cent and popliteal aneurysm in 6·7 per cent. Concomitant heparin infusion was used in 63·2 per cent. The mean dose of rtPA administered was 21·0 mg, with a mean duration of 25·2 h. Technical success was achieved in 80·2 per cent. Major amputation and death within 30 days occurred in 13·1 and 4·4 per cent respectively. Bleeding complications occurred in 227 treatments (30·3 per cent). Blood transfusion was needed in 104 (13·9 per cent). Three patients (0·4 per cent of procedures) had intracranial bleeding; all were fatal. Amputation-free survival was 83·6 per cent at 30 days at both centres. In multivariable analysis, preoperative severe ischaemia with motor deficit was the only independent risk factor for major bleeding (odds ratio (OR) 2·98; P <0·001). Independent risk factors for fasciotomy were severe ischaemia (OR 2·94) and centre (OR 6·50). Embolic occlusion was protective for major amputation at less than 30 days (OR 0·30; P = 0·003). Independent risk factors for death within 30 days were cerebrovascular disease (OR 3·82) and renal insufficiency (OR 3·86).

Conclusion

Both treatment strategies were successful in achieving revascularization with acceptable complication rates. Continuous heparin infusion during intra-arterial thrombolysis appeared to offer no advantage.

Fibrinogen Level as a Surrogate for the Outcome of Thrombolytic Therapy Using Tissue Plasminogen Activator for Acute Lower Extremity Intravascular Thrombosis

Purpose:

Monitoring of fibrinogen level is used to predict bleeding during lower extremity tissue plasminogen activator (tPA) infusions for peripheral arterial or venous thrombolysis. This practice is not fully addressed in the literature.

Materials and Methods:

We retrospectively reviewed fibrinogen levels and studied bleeding rate from charts of patients who underwent lower extremity tPA infusions at a single hospital from January 2010 to May 2012.

Results:

The rate of thrombolytic success did not correlate with fibrinogen level ( P = .53). The rate of major bleeding was significantly higher for patients with a fibrinogen level at or below 150 mg/dL ( P = .01). Patients whose tPA infusion was terminated within 46 hours had significantly lower rates of major bleeding ( P = .01) and thrombolytic failure ( P < .01). Periprocedural systolic blood pressure above 160 mm Hg was a risk factor for major bleeding ( P = .02). There was no association between concomitant aspirin use ( P = .90, .51) or hourly tPA dose ( P = .71, .62) and thrombolytic success or major bleeding, respectively.

Conclusion:

Fibrinogen level ≤150 mg/dL is associated with increased risk of major bleeding during tPA infusions. We suggest serial fibrinogen measurement as a viable method to monitor bleeding risk during lower extremity tPA infusions.

Acute limb ischemia

Acute limb ischemia is a medical emergency with management options ranging from urgent revascularization to limb amputation. The best patient outcome requires tailoring the treatment to the individual patient. This article describes a step-by-step approach for diagnosis and management of patients presenting with acute limb ischemia.

[Arterial occlusive disease. Catheter-directed thrombolytic therapy]

Local catheter-directed thrombolysis of extremity artery or bypass thromboembolic occlusions is a promising therapeutic option with comparatively low complication rates, if the severity of the ischemia does not require urgent surgical revascularization. This therapeutic decision has to be made by a vascular team taking individual circumstances and contraindications into consideration. Apart from an adequate dosage, a strict intrathrombotic administration of the fibrinolytic agent and careful clinical monitoring including surveillance of the coagulation system is necessary and intensive care unit resources should be used. If necessary the thrombolysis therapy can be combined with mechanical thrombaspiration and balloon dilatation or surgical correction of an underlying lesion.

Acute arterial thrombosis after covered stent exclusion of bleeding mycotic pseudoaneurysm: treatment using catheter-directed thrombolysis

Conventional absolute contraindications to catheter-directed thrombolysis include active or recent hemorrhage and the presence of local vascular infection, both of which increase the risk of procedure-related complications such as bleeding and systemic sepsis. For this reason, lytic therapy of arterial thromboembolism under these circumstances is generally precluded. Herein, we describe a unique case of safe catheter-directed lysis of an acutely thrombosed iliac artery following covered stent placement for treatment of an actively bleeding infected pseudoaneurysm. Our management approach is discussed.

[Medicamentous thrombolysis in acute occlusions of extremity arteries]

Local catheter-directed thrombolysis for thromboembolic extremity artery or bypass occlusions is a promising therapeutic option with comparatively low complication rates if the severity of the ischemia does not require an urgent surgical revascularization. This therapeutic decision has to be made by the vascular team under consideration of individual circumstances and contraindications. Apart from an adequate dosage, a strict intrathrombotic application of the fibrinolytic agent and careful clinical monitoring, including surveillance of the coagulation system is necessary. If needed, the thrombolysis therapy can be combined with interventional thrombaspiration and balloon dilatation or surgical correction of an underlying lesion.

Similar Success Rates with Bivalirudin and Unfractionated Heparin in Bare-Metal Stent Implantation

BACKGROUND

Unfractionated heparin (UFH) is the traditional agent utilized during percutaneous peripheral interventions (PPIs) despite its well-known limitations. Bivalirudin, a thrombin-specific anticoagulant, overcomes many of the limitations of UFH and has consistently demonstrated comparable efficacy with significantly fewer bleeding complications. The purpose of this study was to compare procedural success in patients undergoing bare-metal stent implantation for atherosclerotic blockage of the renal, iliac, and femoral arteries and receiving either bivalirudin (0.75 mg/kg bolus/1.75 mg/kg/hr infusion) or UFH (50-70 U/kg/hr bolus) as the primary anticoagulant.

METHODS

This study was an open-label, nonrandomized retrospective registry with the primary endpoint of procedural success. Secondary endpoints included incidence of: death, myocardial infarction (MI), urgent revascularization, amputation, and major and minor bleeding.

RESULTS

One hundred and five consecutive patients were enrolled (bivalirudin = 53; heparin = 52). Baseline demographics were comparable between groups. Patients were pretreated with clopidogrel (approx. 71%) and aspirin (approx. 79%). Procedural success was achieved in 97% and 96% of patients in the bivalirudin- and heparin-treated groups, respectively. Event rates were low and similar between groups.

CONCLUSION

Bivalirudin maintained an equal rate of procedural success in this cohort without sacrificing patient safety. Results of this study add to the growing body of evidence supporting the safety and efficacy of bivalirudin as a possible substitute for UFH in anticoagulation during peripheral vascular bare-metal stent implantation.

Catheter-directed thrombolysis for acute limb ischemia

Acute limb ischemia is a potentially life-threatening clinical event. Thrombosis in situ, bypass graft thrombosis, and embolic occlusion are the three major precipitating events leading to acute limb ischemia. Management of acute ischemia depends on the clinical status of the affected limb and patient comorbidities. Catheter-directed thrombolysis (CDT) is the treatment of choice for patients with relatively mild acute limb ischemia (Rutherford categories I and IIa) with no contraindications to thrombolytic therapy. Patients with severe acute limb ischemia (Rutherford category IIb) need emergent revascularization. CDT should be considered, nonetheless, if the relative risks compared with primary operation are favorable. CDT is a life- and limb-saving treatment for many patients despite limitations of efficacy and associated complications. This article is a review of the etiology of acute arterial occlusion; clinical triage of patients presenting with acute limb ischemia; catheter guide wire techniques, pharmacological agents, and devices in current use for CDT; as well as the outcomes of CDT.

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.

Thrombolytic Therapies:The Current State of Affairs

Thrombotic occlusive diseases are manifested in several disorders that have significant morbidity and mortality, including acute myocardial infarction, pulmonary embolism, deep venous thrombosis, and cerebrovascular accidents. This review summarizes the recently published literature covering thrombolytic therapies in these diseases, with particular attention to comparisons between the fibrin-specific tissue plasminogen activators (alteplase, reteplase, and tenecteplase) and the nonfibrin-specific activators (streptokinase or urokinase plasminogen activator). These agents act to convert plasminogen to plasmin, which in turn cleaves fibrin as part of the lysis process. Fibrin-specific activators were anticipated to be more efficacious and safer than nonspecific agents in thrombolytic occlusive diseases because of their pathophysiologically restricted mechanism of action. However, the fibrin-specific activators also lyse physiological hemostatic plugs, which can result in costly adverse events. Efficacy of fibrin-specific tissue plasminogen activators has been shown to be generally equivalent, with similar mortality rates compared with nonspecific agents; however, fibrin-specific agents may be associated with an increased incidence of intracerebral hemorrhage and with increased costs. Therefore, it appears that given equivalent efficacy, nonfibrin-specific activators, such as streptokinase or urokinase, may be a safer choice in many thrombotic situations.

Percutaneous treatment of pediatric thrombosis

While rare, thrombosis in the pediatric population can result serious sequelae including death. The best treatment options have not yet been firmly established for this age group. During childhood, there are age-related changes in components of the coagulation system that can affect treatment choices. This review article gives an overview of pediatric coagulation and describes the current state of percutaneous treatment options including local thrombolysis and thrombectomy.

Clinical and economic outcomes in thrombolytic treatment of peripheral arterial occlusive disease and deep venous thrombosis

PURPOSE

Over the past 2 decades the use of thrombolytic therapy in the management of peripheral occlusive diseases, most notably peripheral arterial occlusion (PAO) and deep venous thrombosis (DVT), has become an accepted and potentially preferable alternative to surgery. We examined the period when urokinase was in short supply and subsequently unavailable, to explore potential differences in clinical outcome and economic effect between urokinase and recombinant tissue plasminogen activator (rt-PA).

MATERIAL AND METHODS

Data were obtained from the Premier Perspective Database, a broad clinical database that contains information on inpatient medical practices and resource use. The study population included all patients hospitalized in 1999 and 2000 with a primary or secondary diagnosis of PAO or DVT. Incidence was calculated for common adverse events, including bleeding complications, intracranial hemorrhage, amputation, and death. Cost data were also abstracted from the database, and are expressed as mean +/- SD.

RESULTS

Demographic variables were similar in the urokinase and rt-PA groups. The rate of bleeding complications was similar in the urokinase and rt-PA groups. There were no intracranial hemorrhages in the urokinase group, compared with a rate of 1.5% in the rt-PA PAO group (P = .087) and 1.9% in the rt-PA DVT group (P = .175). The in-hospital mortality rate was lower in the urokinase-treated PAO subgroup (3.6% vs 8.5%; P = .026), but a similar finding in the DVT subgroup did not achieve statistical significance (4% vs 9.8%; P = .069). While pharmacy costs were greater in the urokinase-treated group (US 5472 dollars +/- US 5579 dollars vs US 3644 dollars +/- US 6009 dollars, P < .001; PAO subgroup, US 11,070 dollars +/- US 15,409 dollars vs US 6150 dollars +/- US 12,398 dollars, P = .003), overall hospital costs did not differ significantly between the 2 groups. This finding appears to be explained by a shorter hospital stay and reduced room and board costs in the urokinase-treated group.

CONCLUSION

There were significant differences in outcome in patients with PAO and DVT who received treatment with urokinase and rt-PA. While pharmacy costs were significantly greater when urokinase was used, reduction in length of stay accounted for similar total hospital costs compared with rt-PA. These findings must be considered in the context of the retrospective nature of the analysis and the potential to use dosing regimens that differ from those in this study.

Distributed intraclot thrombolysis: mechanism of accelerated thrombolysis with encapsulated plasminogen activators

BACKGROUND

The delivery of encapsulated plasminogen activators has demonstrated enhanced thrombolysis in vivo in several models. The mechanism of such improvement has not previously been established.

OBJECTIVES

We explored in vitro the mechanism by which microencapsulation of streptokinase in polymeric microparticles accelerates clot digestion and reduces reperfusion times by as much as an order of magnitude in vivo.

METHODS

The efficacy of microencapsulated streptokinase (MESK) was directly compared with identical dosages of unencapsulated streptokinase (FREE SK) at three initial pressure drops using clots formed of plasma or whole blood in 0.2-cm inner diameter glass capillary tubes.

RESULTS

MESK demonstrated accelerated flow restoration compared with FREE SK for each condition in plasma (23.8 +/- 4.5% faster) and whole blood clots (17.2 +/- 9.2% faster). Images collected by light microscopy show sites of thrombolysis internal to the clot only with MESK while the spatial distribution of fluorescently labeled streptokinase by confocal microscopy confirms greater penetration of the encapsulated agent compared with unencapsulated streptokinase. Digestion thus proceeds in three dimensions rather than restricted to a two-dimensional lysis front.

CONCLUSIONS

The improved clot penetration with MESK establishes enhanced transport with encapsulation and the concept of distributed intraclot thrombolysis as a basis for the accelerated dissolution observed with encapsulated plasminogen activators in vivo.

Continuous Tenecteplase Infusion Combined With Peri/Postprocedural Platelet Glycoprotein IIb/IIIa Inhibition in Peripheral Arterial Thrombolysis:Initial Safety and Feasibility Experience

PURPOSE

To evaluate a continuous-infusion protocol for peripheral arterial thrombolysis using tenecteplase (TNK), with regard to the technique, dosing, infusion times, and clinical outcomes.

METHODS

Between November 1999 and July 2002, 48 patients (30 men; mean age 68.5+/-11.9 years) presented with acute limb ischemia (ALI) owing to iliofemoral arterial thrombosis, which was treated with continuous TNK infusion (either 0.50 mg/h [n=22, group A] or 0.25 mg/h [n=26, group B]). All patients received periprocedural heparin (500 U/h) and peri and postprocedural tirofiban for 6 to 12 hours. Follow-up included ankle-brachial index and duplex ultrasound at baseline, 1 month, and 6 months. The variables retrospectively analyzed included total infusion time, total TNK dose, fibrinogen analysis, clinical and thrombolysis outcomes, and complications.

RESULTS

The overall clinical procedural success was 95.8%. Complete (>95%) lysis was observed in 35 (73%) patients; overall mean infusion time was 7.5 hours, and overall mean TNK dose was 4.8 mg. No deaths, intracranial bleeding, or embolic events occurred in either group. Of the 8 (16.7%) complications, 5 (10.4%) were major: 1 femoral repair (group A), 2 >5-cm nonsurgical hematomas (1 in each group), and 2 gastrointestinal hemorrhages (1 in each group). The 3 (6.3%) minor complications were minor hematomas (2 in group A and 1 in group B). The 30-day and 14-month mean limb salvage rates were 95.8% (46/ 48) and 89.6% (43/48), respectively.

CONCLUSIONS

Continuous TNK infusion (0.25-0.50 mg/h) is a safe and feasible treatment for continuous pharmacological thrombolysis in ALI, potentially offering decreased infusion times and bleeding complications, as well as improved outcomes.

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.

Controlled localized thrombolysis with the "turbo" trellis to treat acute arterial occlusions following major surgery

PURPOSE

To present the management of acute arterial ischemia following major abdominal and orthopedic surgery using a percutaneous thrombectomy device and a low dose of thrombolytic agent.

CASE REPORT

A 38-year-old woman with T-8 paraplegia from a traumatic fall developed pelvic osteomyelitis, for which a left hemipelvectomy, hysterectomy, and partial vaginal resection were performed. Twelve hours after the procedure, the patient developed an ischemic left leg. Computed tomographic angiography demonstrated an occlusion of the left external iliac and common femoral arteries. A Turbo Trellis percutaneous thrombectomy device was used to lyse the left external iliac artery thrombosis using 1 mg of tissue plasminogen activator infused between the proximal and distal occluding balloons of the device. Total dispersion time was 5 minutes. There was complete thrombus removal without any significant bleeding complications. At 6 months, the artery remains widely patent.

CONCLUSIONS

Combination therapy with mechanical thrombectomy devices and low dose thrombolytic agents can be used to treat acute arterial occlusions at a single setting. The increased speed of the Turbo Trellis may allow for smaller doses of thrombolytic agents and shorter treatment times.

Reteplase with or without Abciximab for Peripheral Arterial Occlusions: Efficacy and Adverse Events

PURPOSE

To retrospectively evaluate reteplase in thrombolysis of peripheral arterial occlusion (PAO).

MATERIALS AND METHODS

Forty limbs in 36 patients were treated with reteplase (0.5 U/h) with or without abciximab (bolus and 12-hour infusion). Twenty-four occlusions were in bypass grafts and 16 were in native arteries. Nineteen patients were treated with reteplase alone and 21 patients were treated with reteplase and abciximab. Chart review provided data from procedures and follow-up at 30 days and 6 months. Multivariable, analysis of variance, and Student t test comparisons of results and complications were performed.

RESULTS

Reteplase infusions averaged 31 hours in duration (range, 12-72 hours). The technical success rate was 80%. The clinical success rates were: immediate, 80%; 30-day, 65%; and 6-month, 45%. Major bleeding complications occurred in 20% of cases and intracranial hemorrhage occurred in 2.5%. The 6-month amputation-free survival rate was 78%. Major, minor, and lack of complications were statistically associated with mean decreases in fibrinogen levels from baseline of 72%, 46%, and 15%, respectively (P =.000013). Complications were not associated with length of infusion or use of abciximab (P =.77). Patients with grafts accounted for 89% of the major complications (eight of nine; P =.009) and had worse clinical success immediately (71%), at 30 days (50%), and at 6 months (21%; P =.002, P =.003, P =.00001).

CONCLUSIONS

There was significant fibrinogen depletion with use of reteplase for PAO. The percent decrease in fibrinogen level correlates with lack of complications and incidence of minor and major complications. Abciximab use did not increase the complication rate. Thrombolysis of grafts is associated with increased incidence of complications and worse outcomes compared with thrombolysis of native arteries.

Novel simultaneous combination chemical thrombolysis/rheolytic thrombectomy therapy for acute critical limb ischemia: The power-pulse spray technique

The novel power-pulse spray (P-PS) technique maximizes and combines the advantages and minimizes the disadvantages of both chemical thrombolysis (CT) and rheolytic thrombectomy (RT). Forty-nine consecutive patients with iliofemoral thrombotic occlusion were treated via P-PS technique. Using a 6 Fr RT catheter, saline prime was exchanged for thrombolytic solution [group 1, 10-20 mg tenecteplase (TNK)/50 cc saline, n = 25; group 2, 1,000,000 urokinase (UK)/50 cc saline, n = 24]. The outflow port was closed, then the catheter was advanced at 1 mm increments while pulsing lytic agent. After 30-min lysis time, RT and definitive treatment of the underlying stenosis were performed. Procedure success was 23/25 (92%) and 22/24 (91.6%) for group 1 and 2, respectively. The mean total procedure time was 72 and 75 min in group 1 and 2, respectively. Thirty-day limb salvage was 91% in both groups. There were no major surgical complications. The P-PS technique is safe and effective using either UK or TNK, offering several potential advantages over monotherapy, including more rapid revascularization, decreases systemic lytic exposure and bleeding complications while facilitating both CT and RT capacity and efficacy.

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.

[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.

Endovascular techniques in the treatment of acute limb ischemia: thrombolytic agents, trials, and percutaneous mechanical thrombectomy techniques

Acute peripheral arterial occlusion is associated with great risk to the patient's limb and life. Failure to restore adequate arterial flow in a timely fashion can result in the development of irreversible tissue infarction and the opportunity for limb salvage is lost. On the other hand, patients with acute limb ischemia are often elderly and frail, and early invasive open surgical procedures without adequate preoperative stabilization and preparation result in an unacceptably high risk of perioperative cardiopulmonary complications and death. Percutaneous methods designed to remove the intraluminal thrombus offer an alternative to immediate open surgical revascularization. These less invasive techniques constitute an option that is better tolerated in medically compromised patients. The causative lesion can be precisely identified and the patency of outflow vessels can be restored. The lesion can then be addressed on an elective basis in a well-prepared patient, using percutaneous or open surgical techniques to effect a durable long-term solution. The treatment options include primary surgical revascularization, thrombolytic therapy, percutaneous mechanical thrombectomy, or a combination of any of the three. Clinicians who themselves have the skills to perform a wide assortment of interventions ranging from percutaneous therapies through open surgical revascularization are best able to arrive at the most rational option for treating a specific clinical scenario. This article is directed at providing the practicing surgeon with a basic fund of knowledge on the diagnostic and therapeutic strategies useful in treating patients with peripheral arterial occlusion. Only in this manner can we expect to reduce the high rate of morbidity and mortality that remains associated with these events.

Emergency Pedal Artery Bypass Grafting

OBJECTIVES

To determine the value of emergency pedal artery bypass.

MATERIAL AND METHODS

Data were drawn from a prospective vascular database. Inclusion criteria were: acute onset of critical forefoot ischemia, emergency surgery, no pre-operative angiographic imaging of the pedal vasculature and attempted revascularisation of a pedal vessel. Follow-up was obtained from outpatient records. The grafts were considered patent if a pedal pulse was palpable.

RESULTS

Eight out of 208 pedal vascular procedures performed between January 1996 and June 2002 were entered into the study. This cohort consisted of 3 women and 5 men (age 23-85 years, median 71). Operations were performed because of thrombo-embolic occlusion of the tibial vasculature (5 patients), severe tibial embolism following a percutaneous angioplasty of the superficial femoral artery, trash foot following aortic reconstruction and acute occlusion of tibial run-off vessels following a crural reconstruction. Two patients suffered an early graft occlusion, one of them resulting in major amputation. At a median follow up of 17 months (10-52 months) the remaining 6 grafts were patent.

CONCLUSIONS

If catheter directed methods (local lysis, aspiration embolectomy) or surgical procedures (embolectomy, tibial bypass) fail to treat critical foot ischemia, pedal probatorial dissection and pedal bypass is worthwhile.

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 in peripheral artery occlusions: combining reteplase and abciximab

OBJECTIVE

The goal of this study was to assess the safety and efficacy of combination therapy consisting of the third-generation plasminogen activator reteplase and the glycoproteins IIb and IIIa platelet receptor antagonist abciximab for thrombolysis in peripheral artery occlusive disease. This two-center experience focused on immediate thrombolytic success, thrombolysis time, complication rate, and 30-day patency rate.

SUBJECTS AND METHODS

Fifty patients with arterial occlusive disease (age range, 40-96 years; mean age, 69 years) were prospectively enrolled at two centers. Eighteen patients (36%) had native artery thromboses, and 32 patients (64%) had graft thromboses. Catheter-directed intraarterial thrombolytic infusion of reteplase (average dose, 0.51 U/hr; range, 0.25-1 U/hr) was combined with IV infusion of abciximab (bolus, 0.25 mg/kg of body weight; 12-hr infusion, 0.125 microg/kg of body weight per minute). Nontherapeutic heparin (100-400 U/hr) was given intraarterially during the thrombolytic infusion.

RESULTS

Complete thrombolysis was achieved in 89% of the patients with native artery occlusions and 94% of the patients with graft occlusions for an overall rate of 92%. The average thrombolysis time was 20.7 hr (range, 4-41 hr) with a mean reteplase dose of 12.1 U (range, 2-23 U). Major hematoma occurred in 12% of the patients, with an average blood transfusion of 3.1 U of packed RBC (range, 1-11 U), and correlated to increased thrombolysis time and dose. No intracranial hemorrhage occurred. The 30-day primary patency rate was 92%. Two patients (4%) underwent amputation, including one major amputation (2%), within 30 days of thrombolysis.

CONCLUSION

The combination of reteplase and abciximab in catheter-directed arterial thrombolysis is feasible and effective. Results of this combination therapy suggest acceptable thrombolysis times and doses with tolerable complication rates. Which patient group might benefit the most from combination therapy and the long-term results of combination therapy still need to be determined.

The safety, efficacy, and pharmacoeconomics of low-dose alteplase compared with urokinase for catheter-directed thrombolysis of arterial and venous occlusions

PURPOSE

The purpose of this study was to compare the efficacy, complications, and costs associated with low-dose (<2 mg/h) alteplase (tissue plasminogen activator [t-PA]) versus urokinase for the catheter-directed treatment of acute peripheral arterial occlusive disease (PAO) and deep vein thrombosis (DVT).

MATERIALS AND METHODS

A retrospective review was performed during sequential time periods on two groups with involved extremities treated with either t-PA with subtherapeutic heparin (TPA group) or urokinase with full heparin (UK group) at a single center. Treatment group characteristics, success rates, complications, dosages, infusion time, and costs were compared.

RESULTS

Eighty-nine patients with 93 involved limbs underwent treatment (54 with DVT, 39 with PAO). The treatment groups were statistically identical (TPA: 45 limbs; 24 with DVT, 53.3%; 21 with PAO, 46.7%; UK: 48 limbs; 30 with DVT, 62.5%; 18 with PAO, 37.5%). The overall average hourly infused dose, total dose, infusion time, success rates, and cost of thrombolytic agent were as follows (+/- standard deviation): TPA, 0.86 +/- 0.50 mg/h, 21.2 +/- 15.1 mg, 24.6 +/- 11.2 hours, 89.4%, $466 +/- $331; and UK, 13.5 +/- 5.6 (10(4)) U/h, 4.485 +/- 2.394 million U, 33.3 +/- 13.3 hours, 85.7%, $6871 +/- $3667, respectively. Major and minor complication rates were: TPA, 2.2% and 8.9%; and UK, 2.1% and 10.4%, respectively. No statistical differences in success rates or complications were observed; however, t-PA was significantly (P <.05) less expensive and faster than urokinase.

CONCLUSION

Low-dose t-PA combined with subtherapeutic heparin is equally efficacious and safe compared with urokinase. Infusions with t-PA were significantly shorter and less expensive than those with urokinase.

Acute and long-term results after intra-arterial thrombolysis of occluded lower extremity bypass grafts using recombinant tissue plasminogen activator for acute limb-threatening ischemia

Occlusion of lower extremity vascular bypass grafts results in acute limb-threatening ischemia. The underlying cause of graft failure generally is distal anastomosis stenosis, and relief of culprit stenosis is a required to maintain long-term patency. Of the three thrombolytic agents used for prolonged infusion to accomplish fibrinolysis, streptokinase was the first to be used and is limited owing to the antigenicity that precludes repeated use. Urokinase had been the mainstay of thrombolytic therapy until it was withdrawn by the U.S. Food and Drug Administration in 1999 because of the potential of transmission of infectious agents during its manufacturing process. Recombinant tissue plasminogen activator (rt-PA) has not been studied adequately to assess safety and efficacy, and there are no standardized dosing guidelines. We report our experience with six patients presenting with acute limb-threatening ischemia attributable to thrombosis of synthetic lower extremity bypass grafts. After thrombolysis using rt-PA (mean bolus dose, 12.2 +/- 3.6 mg; range, 6-15 mg administered over 5 minutes followed by infusion at 2 mg/h for 15.6 +/- 6.4 hours; total dose, 51 +/- 16 mg), successful thrombolysis was achieved in 84% of the patients. The primary patency rate was 75% and the secondary patency rate 100% at 16 weeks. One patient underwent amputation owing to unsuccessful thrombolysis. No major bleeding or vascular complications occurred. We conclude that intra-arterial thrombolysis using rt-PA is a safe and effective therapy for patients with thrombotic occlusion of synthetic lower extremity bypass grafts presenting with acute limb-threatening ischemia and allows a high rate of secondary patency, avoiding amputation.

Pediatric thrombosis

Although thrombosis is less frequent in children than in adults, it represents a significant source of morbidity and mortality. Multiple factors. both genetic and acquired. contribute to the development of thrombosis in chiidren. Thrombosis in a child warrants investigation of potential underlying prothrombotic conditions. The risk of thrombosis in children with heterozygous deficiencies is not clearly defined, but it appears that children who are heterozygous for more than one risk factor or who have a combination of inherited and acquired defects are at higher risk for thrombosis. Treatment of thrombosis primarily involves a rapidly acting anticoaguiant such as heparin or LMWH to prevent extension, and long-term anticoagulation with warfarin may be instituted to prevent recurrence. Thrombolytic therapy with recombinant tissue plasminogen activator also appears to be safe and effective in children. Prospective and multicenter studies are still needed to clarify the contribution of specific prothrombotic disorders to childhood TE so that evidence-based treatment recommendations can be made.

Thrombolysis of occluded peripheral arteries and veins with tenecteplase: a pilot study

PURPOSE

To prospectively assess the feasibility, risk profile, and effect on fibrinogen levels of tenecteplase in transcatheter thrombolysis for peripheral arterial and venous occlusive disease.

MATERIALS AND METHODS

Between March 2001 and January 2002, 18 consecutive patients (14 men, four women) with arterial (n = 13) or venous (n = 5) occlusive disease were treated with tenecteplase infusions of 0.25 mg/h. Technical success was defined as restoration of antegrade flow and removal of more than 95% of thrombus. Clinical success was defined in arterial cases as immediate limb salvage and relief of ischemic rest pain and in venous cases as resolution or improvement in extremity pain and swelling. Major bleeding was defined as an intracranial bleeding episode, bleeding that resulted in death, or bleeding that required transfusion, surgery, or cessation of thrombolytic therapy.

RESULTS

Technical success was achieved in all 18 patients (100%). Clinical success was achieved in 11 of 13 arterial cases (85%) and in four of five (80%) venous cases. The mean duration of thrombolysis treatment was 21.5 hours +/- 6.2 (range, 7-35 h), with total tenecteplase doses of 7.1 mg +/- 4.3 (range, 1.75-18.75 mg). Major bleeding occurred in one patient (5.5%) because of slow oozing from bilateral femoral groin access sites, which caused a 25% decrease in hematocrit level. There were no deaths, intracranial hemorrhages, remote sites of bleeding, or minor bleeding complications. The serum fibrinogen level dropped to a mean of 77.4% +/- 19.2% of baseline.

CONCLUSION

In this initial study, tenecteplase was shown to be a feasible treatment for peripheral arterial and venous thrombolysis with only moderate effect on fibrinogen levels.

Current status of thrombolysis for peripheral arterial occlusive disease

Acute peripheral arterial occlusion occurs as a result of thrombosis or embolism. A reduction in the prevalence of rheumatic heart disease accounts for a shift in the frequency of embolic to thrombotic occlusions. Also, a dramatic increase in the number of lower extremity arterial bypass graft procedures explains the predominance of graft occlusions in most recent series of patients with acute limb ischemia. While open surgical procedures remain the gold standard in the treatment of peripheral arterial occlusion, thrombolytic agents have been employed as an alternative to primary surgical revascularization in patients with acute limb ischemia. Systemic administration of thrombolytic agents, while effective for small coronary artery clots, fails to achieve dissolution of the large peripheral arterial thrombi. Catheter-directed administration of the agents directly into the occlusive thrombus is the only means of effecting early recanalization. Prior to 1999, urokinase was the sole agent used in North America for peripheral arterial indications, but the loss of the agent from the marketplace forced clinicians to turn to alternate agents, specifically alteplase and reteplase. Interest in the use of platelet glycoprotein inhibitors and mechanical thrombectomy devices also rose, coincident with the loss of urokinase from the marketplace. Most clinicians welcome the predicted return of urokinase to the marketplace. New investigative trials should be organized and executed to answer some of the remaining questions related to thrombolytic treatment of peripheral arterial disease. Foremost in this regard remains the question of which patients are best treated with percutaneous thrombolytic techniques and which are best treated with primary operative intervention. Ultimately, however, the thrombolytic agents are but one tool in the armamentarium of the vascular practitioner. This review is directed at providing the practicing clinician with the basic fund of knowledge necessary when determining the most appropriate intervention in a particular patient with peripheral arterial occlusion, be it thrombolytic therapy, percutaneous mechanical thrombectomy, primary surgical revascularization, or a combination of the three.

Declining-dose study of reteplase treatment for lower extremity arterial occlusions

PURPOSE

To prospectively determine the technical success and complication rates of three different reteplase dosing regimens during catheter-directed arterial thrombolysis.

MATERIALS AND METHODS

Prospective data were obtained from three groups of patients who underwent lower extremity arterial thrombolysis with three different regimens of reteplase: 0.5 U/h, 0.25 U/h, and 0.125 U/h. A total of 101 thrombosed lower extremity arterial occlusions in 87 patients were treated. A subtherapeutic intravenous heparin dose of 400-500 U/h was administered. All limbs were viable at presentation. Thrombolytic success was defined as 95% thrombolysis of the occluded artery or graft with restored distal antegrade flow. Thirty-day mortality and amputation rates were calculated. Bleeding complications and need for transfusions were recorded. Laboratory values recorded included fibrinogen level, platelet count, hematocrit level, hemoglobin level, and prothrombin time.

RESULTS

Thrombolytic success was achieved in 86.7% of patients in the 0.5-U/h dose group, 83.8% of patients in the 0.25-U/h dose group, and 85.3% of patients in the 0.125-U/h dose group. The major bleeding and transfusion rates were 13.3% in the 0.5-U/h dose group, 5.4% in the 0.25-U/h dose group, and 2.9% in the 0.125-U/h dose group. The 30-day amputation-free survival rates were 90% in the 0.5-U/h dose group, 97.3% in the 0.25-U/h dose group, and 94.1% in the 0.125-U/h dose group. Pre- and postprocedural fibrinogen levels and the fibrinogen nadir were not statistically different between the groups. No differences in total infusion times were found between the 0.5-U/h dose and 0.25-U/h dose groups. However, the infusion time in the 0.125-U/h dose group was significantly longer than in the other two groups (42 h vs 30 h; P <.05).

CONCLUSION

All dosing regimens were equally effective in the treatment of acute lower extremity occlusions. The infusion times were longer with the 0.125-U/h dose. Significantly fewer major bleeding complications were encountered with the 0.25-U/h and 0.125-U/h dose regimens than with the 0.5-U/h dose regimen.