Femoro-popliteal artery thrombolysis with intra-arterial infusion of recombinant tissue-type plasminogen activator--report of a pilot trial

Outcomes of accelerated catheter-directed thrombolysis in patients with acute arterial thrombosis

Current intra-arterial catheter-directed thrombolysis (CDT) protocols recommend treatment with small doses of a thrombolytic agent, which excludes patients in need of urgent revascularization. We evaluated the effects of accelerated thrombolysis utilizing increased recombinant tissue plasminogen activator (rt-PA) doses. Forty-one patients with acute, thrombotic limb ischemia (ALI) were treated using accelerated CDT. The treatment consisted of an initial dose of 10 mg rt-PA for 30 minutes followed by a 3-hour course of a continuous intra-arterial 10 mg/hour rt-PA infusion. Simultaneously, intravenous unfractionated heparin (500 IU/hour) was administered. No deaths occurred. Satisfactory lysis was achieved in 37 of the 41 patients (90.2%). All significant underlying lesions were corrected (89.2%). Complications developed in nine patients (22%); the most frequent complication (four patients, 9.8%) was puncture site hematoma. The reintervention rate was 2.6% and 15.4% at the 1 and 6-month follow-ups, respectively. The major amputation rate was 10.3% and 12.8% at the 1 and 6-month follow-ups, respectively. Outflow compromise was adversely related to successful outcome at the 6-month follow-up ( p=0.01). In conclusion, this study confirms the effectiveness and safety of the accelerated CDT regimen for treatment of thrombotic ALI at a single center, but requires confirmation in further studies.

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.

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.

Comparison of Urokinase, Alteplase, and Reteplase for Catheter-directed Thrombolysis of Deep Venous Thrombosis

PURPOSE

To compare the efficacy, safety, and costs associated with catheter-directed thrombolysis with urokinase (UK) and the recombinant agents alteplase (tissue plasminogen activator [TPA]) and reteplase (recombinant plasminogen activator [RPA]) in the treatment of symptomatic deep vein thrombosis (DVT).

MATERIALS AND METHODS

The authors conducted a retrospective analysis on 74 patients (82 limbs) who underwent treatment for DVT. Thrombosed extremities were treated with either urokinase with therapeutic heparin dosing (UK group; 38 limbs), alteplase with subtherapeutic heparin dosing (TPA group; 32 limbs), or reteplase with subtherapeutic heparin dosing (RPA group; 12 limbs). Infusion times, dosages, drug costs, success rates, and complications were compared among the groups.

RESULTS

Gender, age, disease location, duration of symptoms, and use of additional interventional therapies did not differ statistically among the three cohorts. Median hourly infused doses, total doses, infusion times, drug costs, and success rates per limb were: UK, 11.3 (10(4)) U/hour, 4.361 million U, 40.6 hours, US dollars 6577, 97.4%; TPA, 0.57 mg/hour, 21.6 mg, 30.8 hours, US dollars 488, 96.9%; RPA, 0.74 U/hour, 21.4 U, 24.3 hours, US dollars 1787, 100.0%. Major and overall complication rates were: UK, 5.3% and 10.5%; TPA, 3.1% and 12.5%; RPA, 8.3% and 16.7%. Infusion times, success rates, and complications were not statistically different among the three groups. Alteplase and reteplase were significantly less expensive than urokinase (P <.001 and P <.01, respectively).

CONCLUSION

Catheter-directed thrombolysis for the treatment of DVT is safe and effective, regardless of the agent used. However, the new recombinant agents are significantly less expensive than urokinase.

Thrombolysis in the Management of Lower Limb Peripheral Arterial Occlusion—A Consensus Document

The aim of this paper is to develop an intercontinental consensus on the use of thrombolytic therapy in occlusive peripheral arterial disease affecting lower limbs. A working party of self-designated angiologists, hematologists, interventional radiologists, and vascular surgeons of Europe and North America convened at 4 closed meetings. All published data known to any of the participants was entered into discussion. The working party discussed the topics outlined in this paper and a first draft was prepared in segments by members of the working party, discussed, and further revised into an interim report. It was then circulated to a number of Societies for their input. A final meeting of the Working Party together with delegates of the Societies collaborated on the definitive version of the text. The Party appreciates that in many areas the scientific evidence is not yet available. Nevertheless, it was felt that enough practical and scientific data were available to establish recommendations for clinical practice as well as for reporting results of thrombolytic therapy, which could be updated as later evidence became available. The guidelines apply only to drugs currently available for clinical use. The data are also considered to be sufficiently cogent that regulatory agencies should move to approve thrombolytic agents for intra-arterial therapy of acute lower extremity ischemia.

Recombinant tissue plasminogen activator versus urokinase for local thrombolysis of femoropopliteal occlusions: a prospective, randomized multicenter trial

PURPOSE

To report the outcome of a prospective, randomized, open multicenter trial comparing (1) the effects of local thrombolysis with recombinant tissue plasminogen activator (rtPA) or urokinase (UK) and (2) 2 administration techniques.

METHODS

Two hundred thirty-four patients with thromboembolic occlusions in 223 native femoral or popliteal arteries (95%) and 11 bypass grafts (5%) were randomized to rtPA (n = 124) or UK (n = 110) administered either through an endhole catheter (Hess technique) in 81 patients or a microporous balloon catheter (Schneider technique) in 153 patients. When lysis was incomplete, additional catheter interventions were applied to achieve patency. Results were analyzed by fluoroscopy during intervention and by angiography evaluated by independent experts blinded to the methods applied.

RESULTS

The only significant difference between rtPA and UK was found at the end of lysis using the Hess technique. Complete reperfusion (TIMI grade 3) was produced in 60% of patients by rtPA versus 37% by UK (p = 0.045). By both techniques TIMI grade 3 was achieved in 62% with rtPA and in 50% with UK (p = 0.18). Independent of delivery technique, thrombolytic agent, or additional catheter interventions, TIMI grade 3 was achieved in 81% and angiographic patency in 88%. Primary patency at 6 months was 66%, which was increased by secondary interventions to 75%. Major amputations were performed in 6%, all in patients with initial Fontaine stage III/IV ischemia.

CONCLUSIONS

With local thrombolysis alone, rtPA appears to be more effective than UK; however, additional catheter interventions further improved patency, abolishing the difference between the lytic agents.

Safety and efficacy of limited-dose tissue plasminogen activator in acute vascular occlusion

OBJECTIVE

The purposes of this study were to evaluate the safety and efficacy of limited-dose tissue plasminogen activator (t-PA) in patients with acute vascular occlusion and to compare these results with those obtained in equivalent patients receiving urokinase.

METHODS

We compared the results of 60 patients receiving catheter-directed urokinase from November 1997 to November 1998 (240,000 units/h x 4 h, 120,000 units/h thereafter for a maximum of 48 h) with those of 45 patients receiving catheter-directed t-PA from November 1998 to August 2000 (2 mg/h, total dose < or =100 mg) for acute arterial occlusion (AAO) and acute venous occlusion (AVO). Interventional approaches such as cross-catheter and coaxial techniques were used to reduce the dose of lytic agent needed to achieve pre-lysis-treatment goals (eg, complete lysis of all thrombus/unmasking graft stenosis or establishing outflow target). Statistical analysis was performed using Student t test and Fisher exact test.

RESULTS

The urokinase and t-PA groups were comparable with regard to age, comorbidities (coronary artery disease, hypertension, diabetes, renal insufficiency, smoking), duration of ischemic or occlusive symptoms, location of occlusive process, pretreatment with warfarin, and thrombotic versus embolic and native versus graft occlusion in patients with AAO. In patients with AAO and in those with AVO, t-PA was equivalent to or better than urokinase with regard to percent of clot lysis, incidence of major bleeding complications, limb salvage, and mortality. Achievement of pretreatment goals (arterial patients only) was 50% for urokinase patients and 76% for t-PA patients (P =.02). Analysis of success in individual pretreatment-goal achievement showed urokinase and t-PA to be equivalent in unmasking stenoses (85% and 84%, respectively; P = NS), whereas t-PA was superior to urokinase in the more critical task of establishing run-off (39% versus 81% for urokinase and t-PA, respectively; P =.001). Additional interventions, either endovascular or surgical, were required in 60% and 51% (P = NS) of patients receiving urokinase and t-PA, respectively, for AAO, and in 54% and 62% (P = NS) of patients receiving urokinase and t-PA, respectively, for AVO.

CONCLUSIONS

Limited-dose t-PA is a safe and effective therapy for AAO and AVO when administered by experienced teams using innovative but well-established interventional techniques.

Alteplase and tenecteplase: applications in the peripheral circulation

Alteplase (t-PA), a recombinant analogue of human tissue plasminogen activator, became the first genetically engineered thrombolytic approved by the Food and Drug Administration in 1987 for acute myocardial infarction (AMI). In addition to AMI, alteplase is currently approved for the treatment of acute ischemic stroke and pulmonary embolism, and we anticipate approval for catheter clearance in late 2001 in a 2-mg vial configuration. With the withdrawal of human neonatal kidney cell-derived urokinase, alteplase has become an alternative agent in peripheral vascular applications. Because few interventionalists had prior experience with the handling and dosage of alteplase, the Advisory Panel to the Society of Cardiovascular and Interventional Radiology established practice guidelines for use in noncoronary applications. Emerging clinical experience with contemporary dosing regimens shows a safety and efficacy profile similar to urokinase but with significantly reduced drug costs. Tenecteplase (TNK) is a genetically modified version of alteplase. TNK is the only plasminogen activator available that has shown a significantly enhanced safety profile versus alteplase in AMI. Approved for a 5-second, single-bolus injection in AMI, TNK possesses a longer half-life, increased resistance to plasminogen activator inhibitor, and improved fibrin specificity compared with alteplase. Because of its enhanced safety profile, TNK may be a desirable agent for peripheral vascular applications. Initial clinical studies with TNK in acute arterial and venous disease are ongoing. This article outlines the Advisory Panel guidelines for using alteplase and highlights features of tenecteplase.

Transcatheter intraarterial infusion of rt-PA for acute lower limb ischemia: results and complications

PURPOSE

To determine the success and complication rates of intraarterial recombinant tissue-type plasminogen activator (rt-PA) infusion for the treatment of acute lower extremity artery and bypass graft occlusions.

MATERIALS AND METHODS

The results of 74 limbs in 70 patients (mean age, 66 y) treated with catheter-directed rt-PA infusion for the treatment of acute lower extremity ischemia were retrospectively evaluated. The group included 42 bypass grafts and 32 native arteries. All limbs were viable at presentation. The mean duration of symptoms was 11.9 days. rt-PA was infused for a mean of 27.9 hours for a mean total dose of 38.7 mg. Initial infusion rates of 3-6 mg/h were lowered to a preferred rate of 1.5 mg/h. Thrombolytic success was defined as 95% thrombolysis of an occluded segment with return of antegrade flow. Major bleeding complications were defined as any hemorrhagic event leading to surgery, extended or unexpected hospitalization, transfusion, death, intracranial hemorrhage, or a decrease in hemoglobin of 5 g/dL or in hematocrit of 15%. Thirty-day mortality and amputation rates were calculated. Patient characteristics and infusion parameters were evaluated as to whether they contributed to thrombolytic success or major bleeding events.

RESULTS

Thrombolytic success was achieved in 64 limbs (86%). Major bleeding complications occurred in 33 (47%) patients. In 22 of these patients, bleeding occurred at a vascular puncture site, whereas remote bleeding occurred in seven patients. Remote bleeding complications included two retroperitoneal hematomas, two rectus sheath hematomas, one lower gastrointestinal hemorrhage, one episode of hemoptysis, and one dehiscence of a femoral-popliteal bypass graft revision. No parameters were found to be predictive of thrombolytic success, whereas a negative history of smoking, increasing duration of infusion, and a low preprocedural ankle-brachial index (ABI) were found to be associated with major hemorrhagic events. Four patients (6%) underwent amputation and one patient (1%) died, resulting in a 30-day amputation-free survival rate of 93%.

CONCLUSION

Catheter-directed rt-PA infusion is effective in achieving thrombolysis. Despite a significant number of bleeding complications, 30-day mortality and amputation rates were favorable. Nonetheless, complication rates related to bleeding were not trivial and further evaluation with use of variable dosing regimens is indicated.

Percutaneous catheter thrombus aspiration for acute or subacute arterial occlusion of the legs: how much thrombolysis is needed?

OBJECTIVE

To evaluate the role of a combined percutaneous endovascular approach including thrombus aspiration, catheter thrombolysis, and percutaneous transluminal angioplasty (PTA) to treat acute and subacute occlusions of native leg arteries.

MATERIALS AND METHODS

Retrospective evaluation of the effectiveness and safety of this catheter therapy in 89 consecutive patients (93 legs) in a single centre.

RESULTS

Treatment was initially successful in 90% of legs. Mortality at 30 days was 8%, and at 12 months 19%. Amputation-free survival at 12 months was 78%. Aspiration alone was sufficient in 31% of cases, urokinase (mean dose 112 500+/-55 900 IU) was used in 22%, PTA was added in 69%. There was no major bleeding except for one false aneurysm treated by ultrasound-guided compression. Secondary interventions within 12 months were required in 30% of cases (14 endovascular, 16 open surgical procedures).

CONCLUSIONS

Catheter thrombus aspiration in combination with thrombolysis and/or PTA is highly effective. Only in a minority of patients are thrombolytics in modest doses necessary, and serious bleeding complications are rare. We recommend this procedure as first-line treatment for acute or subacute infrainguinal arterial occlusions.

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

PURPOSE

The clinical literature describing the use of alteplase in the treatment of peripheral arterial occlusive (PAO) disease is reviewed.

MATERIALS AND METHODS

The literature database was acquired by a MEDLINE search using the Boolean keyword string: tissue plasminogen activator and/or rt-PA and peripheral not animal. A review was performed to identify the dose range of alteplase, technique of infusion, use of anticoagulation, clinical success rates, and risk of complications.

RESULTS

Forty-six clinical studies were identified. There are few prospective, randomized clinical trials and a lack of standardized protocols and endpoints. Use of catheter-directed infusions of recombinant tissue plasminogen activator (rt-PA) may be beneficial versus surgery in the initial management of acute limb ischemia (< 14 days) and in reducing the magnitude of subsequent surgical or percutaneous revascularization. For patients with chronic limb ischemia (> 14 days), irreversible acute limb ischemia, or advanced diabetic arteriopathy, catheter-directed infusion of rt-PA or other plasminogen activators may be unsuitable. The risk of adverse bleeding appears related to the overall dose and duration of infusion. These risks appear similar to those of urokinase. The role of heparin in increasing adverse bleeding during rt-PA therapy is unclear.

CONCLUSIONS

There is no generally accepted dose or technique for administering catheter-directed thrombolysis using alteplase; however, several studies have demonstrated its clinical safety and efficacy. Formal studies will be required to determine the optimal dose, technique of infusion, the role of anticoagulation, and complication rates when alteplase is used for PAO disease.

Clinical applications of thrombolytic therapy for arterial and graft occlusion

Catheter-directed thrombolysis and intraoperative intra-arterial thrombolysis are important adjuncts to how we care for patients with acute arterial and bypass graft occlusions. Of importance is that intra-arterial thrombolysis not to be thought of as a competitor to operative revascularization, but rather as an adjunct to what can be accomplished, which enables the responsible physician to offer the best care for these patients.

Pulsed transthrombotic fibrinolysis: technique and results in the management of occluded lower limb bypass grafts

Between March 1987 and March 1993 we used pulsed transthrombotic fibrinolysis to treat 58 symptomatic thrombotic occlusions of lower limb bypass grafts in 45 patients. There were 17 suprainguinal grafts and 28 infrainguinal grafts. Treatment consisted of pulsed infusion of fibrinolytic agents into the thrombus followed by continuous infusion using an electric pump. Minor percutaneous or surgical procedures were often associated. The mean delay to treatment was 7 days. The mean duration of treatment was 150 +/- 66 minutes. Immediate patency was achieved in 88% of cases with no significant difference between suprainguinal and infrainguinal grafts. The clinical success rate was 55%. Actuarial patency at 1 year was 54% +/- 11% for suprainguinal grafts and 26% +/- 7% for infrainguinal grafts. The probability of patency was much lower in patients whose grafts had been implanted within 3 months before occlusion and in patients in whom an adjuvant procedure had not been performed. This study demonstrates that, in cases not requiring immediate surgery, pulsed transthrombotic fibrinolysis can achieve durable patency by treating both the bypass and distal arterial network. This technique allows identification of lesions causing thrombosis and adaptation of treatment specifically to these lesions.

Peripheral arterial occlusions: local low-dose thrombolytic therapy with recombinant tissue-type plasminogen activator (rt-PA)

OBJECTIVE

To study the efficacy and risks of local thrombolytic therapy of peripheral arterial occlusions using rt-PA.

DESIGN

This open study was performed in one clinic in Munich, Germany.

METHODS

288 patients suffering from occlusions of the lower limb arteries were subjected to 336 treatments performed with a permanently controlled technique. In a short pilot study 10mg rt-PA/h were administered for 5 h but in the majority of the cases only 2.5mg/h were administered for a maximum of 5 h. The average total dose of rt-PA was 2.97mg and the average time for lysis was 78 min.

RESULTS

43 (84.3%) out of 51 embolic occlusions and 168 (71.5%) out of 235 thrombotic occlusions were recanalised with a cumulative patency of 95% and 79.7% respectively after 2 years. One systemic bleeding occurred in the pilot study with 10mg rt-PA/h whereas with the 2.5mg/h dosage no systemic bleeding or embolism occurred in the 315 treatments. There were no deaths during hospitalisation. Six major and two forefoot amputations were necessary. Thirteen patients required a bypass operation and one an embolectomy. The advantages of our controlled technique are: short duration of treatment, small doses of activating agent, an accurately directed pathway with the possibility of dilating stenoses during the same session, no danger of systemic bleeding or embolism and, therefore, good prospects of success with minimal risk.

CONCLUSION

The use of rt-PA for local lysis substitutes the inadequate tissue activator available for effective spontaneous lysis and is, therefore, almost physiological. The effect of a very low dose of rt-PA was as good as that of higher doses.

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.

Recombinant tissue plasminogen activator for the treatment of lower extremity peripheral vascular occlusive disease

PURPOSE

Regional thrombolysis in the recanalization of peripheral vascular occlusive disease is an increasingly accepted therapeutic modality. Efficacy and complication rate are major issues in thrombolytic therapy. This prospective study was undertaken to determine if locally delivered recombinant tissue plasminogen activator (r-TPA) is safe and effective in clot lysis at non-weight-adjusted doses.

PATIENTS AND METHODS

Twenty patients (undergoing 21 infusions) from two centers underwent fibrinolytic therapy with use of r-TPA, at a dose rate of 2 mg/h. The mean duration of arterial occlusion was 27.2 days (range, 1-117 days). Concomitant intravenous heparin anticoagulation was administered to all patients. A coaxial infusion delivery system was employed. Hematologic parameters and angiographic follow-up were evaluated at 4-hour intervals during thrombolytic infusion. The chosen maximum r-TPA dose of 40 mg could be extended at investigator discretion.

RESULTS

Complete clot lysis was achieved in 18 of 21 (85.7%) infusions at a mean total dose of 38.9 mg (range, 8-84 mg). The mean infusion duration was 19.7 hours. In 16 of 19 (84.2%) infusions, in which the nadir fibrinogen level was recorded, it remained greater than 65% of baseline. Three of 21 (14.3%) infusions resulted in three major bleeding complications, one of which resulted in death.

CONCLUSION

In this two-center trial, catheter-directed r-TPA infusion at 2 mg/h is effective for clot lysis. When combined with concomitant heparin administration, this treatment may result in an unacceptably high frequency of bleeding complications.

Thrombolysis with tissue-plasminogen activator: results with a high-dose transthrombus technique

PURPOSE

Low-dose intraarterial tissue plasminogen activator (t-PA) is effective in peripheral thrombolysis but treatment time is prolonged. The aim of this study was to determine whether a transthrombus bolus of t-PA before low-dose infusion shortens lysis time.

METHODS

Twenty-three patients with peripheral arterial or bypass graft occlusion were treated with an initial bolus of 20 mg t-PA followed by a continuous infusion of 1 mg/hr.

RESULTS

Angiographic lysis was achieved in 16 patients (70%) with a mean time to complete lysis of 14.4 +/- 7.9 hours. Two patients had reocclusion on days 1 and 3, respectively. There were three deaths within the first week of treatment, one from cerebral hemorrhage and two from myocardial infarction. A clinically successful outcome was achieved in 11 patients (48%). Those patients with patency at 1 week maintained this response at a mean follow-up of 11.7 +/- 9.1 months. Thrombolysis was unsuccessful in seven instances. In three of these cases the infusion had to be discontinued prematurely because of serious hemorrhage. Of the seven unsuccessful cases, three patients subsequently underwent a femorodistal bypass, two were left with tolerable ischemic symptoms, and two required a major amputation. There were eight major bleeding complications (35%), four at or adjacent to the catheter entry site and four at a distance, including two cases of cerebral hemorrhage, one of which was fatal.

CONCLUSIONS

Transthrombus bolus delivery of tissue plasminogen activator followed by a low-dose infusion shortens lysis time, but this technique appears to be associated with an increased risk of serious hemorrhage.

Thrombolysis in acute lower limb ischaemia

For the past three decades balloon embolectomy has been the treatment of choice for acute lower limb occlusion. However, although usually successful in emboli, results are often disappointing in thrombotic atherosclerotic vessels. Attempted dissolution of the clot is accordingly attractive, and has theoretically been possible since the introduction of streptokinase in 1933. This was initially used intravenously, with variable success rates, although intraarterial administration is currently the method of choice. Later thrombolytic drugs such as tissue plasminogen activator, urokinase and anistreplase have been introduced. Lysis time has also been increased by using pharmaco-mechanical methods of administration such as pulsed spray catheters, which could increase the usefulness of thrombolysis in patients with rapidly progressive neurological signs where currently surgical embolectomy would be advocated. Several newer drugs with theoretical advantages over older drugs such as single-chain urokinase-type plasminogen activator or K1K2PU are currently undergoing trials. The role of thrombolysis as an adjunct to surgical embolectomy is also promising, though again requires further trials. There is still no consensus as to which patients are best suited to thrombolysis, nor an optimum drug or method of administration. However, there seems no doubt that thrombolysis will be increasingly used in the management of peripheral limb ischaemia, though requiring a team approach between surgeons, radiologists and haematologists.

Long-term results of a single protocol for thrombolysis in acute lower-limb ischaemia

In a prospective study, 78 of 157 patients with acute lower-limb ischaemia were considered suitable for thrombolysis. The immediate and 4-year results of 52 patients managed by a single protocol are reported. Of 34 patients alive at 4 years, 23 had limb salvage. Initial treatment produced effective lysis in 38 patients (73 per cent) with significant benefit in 35 (67 per cent); that benefit was sustained for a minimum of 4 years in 30 patients (58 per cent). Seven of the 18 deaths by 4 years occurred within 30 days. Amputation was carried out in six patients within 30 days and in five during the next 4 years. Delayed amputation followed persistent distal occlusion or progression of distal disease. No death or amputation was caused by complication of treatment. In selected patients the risks of thrombolysis can be reduced to an acceptable level by personal supervision and a strict protocol. In survivors, limb salvage is generally sustained for at least 4 years.

Options for percutaneous coronary and peripheral revascularization

Angioplasty has become an established treatment for both coronary and peripheral atherosclerosis, and a number of new techniques and devices promise to improve the results of percutaneous intervention during the coming decades. It is likely that balloon angioplasty will remain the percutaneous treatment of choice for both coronary and peripheral intervention; however, we look with hope toward the development of new devices that will expand the role of percutaneous angioplasty and improve the long-term success of these procedures. As technical expertise grows with the new procedures, prospective randomized trials comparing them with standard PTCA will be required to enable physicians to judge their clinical utility.

Tissue plasminogen activator cerebrovascular thrombolysis in rabbits is dependent on the rate and route of administration

BACKGROUND AND PURPOSE

The main aim of our study was to assess the cerebrovascular thrombolytic efficacy of different tissue plasminogen activator treatment protocols with Doppler ultrasound.

METHODS

We occluded one internal carotid artery in 48 New Zealand White rabbits with whole blood emboli. Five minutes later the rabbits were assigned to receive one of the following tissue plasminogen activator protocols: 1) intravenous square-wave infusion in a total dose of 10 mg/kg, 2) intravenous constant infusion in a total dose of 10 mg/kg, 3) intravenous square-wave infusion in a total dose of 3 mg/kg, or 4) regional intra-arterial square-wave infusion in a total dose of 3 mg/kg. Blood flow velocities in the internal carotid arteries were continuously monitored during the study with Doppler ultrasound.

RESULTS

In all 12 animals treated with a 10-mg/kg square-wave intravenous tissue plasminogen infusion, internal carotid artery blood flow was reestablished within 2 hours (57.9 +/- 33.3 minutes) after the initiation of treatment, whereas this was the case for only six (50%) of the 12 animals treated with a constant 10-mg/kg intravenous tissue plasminogen activator infusion (p less than 0.05, Fisher's exact test). Internal carotid artery blood flow was restored within 2 hours (33.5 +/- 40.4 minutes) in all animals treated with a regional intra-arterial tissue plasminogen infusion in a total dose of 3 mg/kg and in only three (50%) of the six animals treated with the same dosage intravenously (p less than 0.05, signed rank test).

CONCLUSIONS

The thrombolytic efficacy of tissue plasminogen activator in the rabbit cerebral vasculature was superior when the same intravenous dose was given as a square-wave rather than a constant infusion and when the drug was given as a regional intra-arterial infusion rather than intravenously.

Surgical treatment versus thrombolysis in acute arterial occlusion: a randomised controlled study

Thrombolytic treatment has been tried in various forms for acute limb ischaemia with varying degrees of success but is also often accompanied by bleeding problems. The present investigation compares the effect of surgical thrombectomy (TE) and thrombolysis (TL) using recombinant tissue plasminogen activator (rt-PA). Twenty patients with a need for intervention owing to ischaemia lasting more than 24 h but less than 14 days were included. Patients randomised to TE were operated under epidural anaesthesia and patients in the TL group received 30 mg rt-PA during a 3 h period through a catheter placed into the thrombus and advanced as lysis was achieved. Thrombectomy resulted in an immediate restitution of blood flow in six out of nine cases, in three cases a bypass procedure was performed, and one of these failed with a resultant amputation. Thrombolysis gave a good primary result in six cases which lasted in four of them. Three had a subsequent percutaneous transluminal angioplasty. Partial lysis was seen in two cases and a further two failed. Five went to surgery with three bypass and two fogarty procedures being necessary. There was no hospital mortality and there were no bleeding complications due to the rt-PA treatment in this series. In 19 out of 20 patients the circulation was re-established. Appropriate handling of acute ischaemic conditions implies the use of both thrombolysis and appropriate surgical procedures, including distal bypass grafts.

Recombinant tissue-type plasminogen activator is superior to streptokinase for local intra-arterial thrombolysis

The results of local intra-arterial thrombolysis in 98 patients treated with streptokinase and 69 patients treated with recombinant tissue plasminogen activator (rtPA) have been compared. The two groups of patients were well matched and their treatment protocols were identical except with regard to the thrombolytic agent used. Strict criteria for defining successful thrombolysis were used. Successful lysis was achieved in 40 of 98 patients (41 per cent) receiving streptokinase and 40 of 69 patients (58 per cent) receiving rtPA (P less than 0.05). The time to lysis was significantly shorter with rtPA, median time 22 h, than with streptokinase, median time 40 h (P less than 0.002). There was no difference in the incidence of haemorrhagic complications. These results suggest that rtPA is superior to streptokinase for local intra-arterial thrombolysis.

Segmentally enclosed thrombolysis in percutaneous transluminal angioplasty for femoropopliteal occlusions: a report from a pilot study

Segmentally enclosed thrombolysis (SET) was performed immediately following 34 percutaneous transluminal angioplasties (PTAs) for femoropopliteal occlusions. The dilated segment was sealed off with a double balloon catheter, and recombinant tissue plasminogen activator (rt-PA) 1 mg/ml and heparin 200 IU/ml were injected between the balloons. The catheter was removed after 30 min and heparin treatment was continued for 24 h. Alpha-2-antiplasmin was initially reduced by 13% and normalized 2 h after SET, indicating that only small amounts of free plasmin were liberated during thrombolysis. No clinically relevant changes in plasma fibrinogen occurred. Two puncture site hemorrhages did not coincide with the coagulopathy induced by SET. One-year patency was 80%. Early rethrombosis occurred in 9% versus 41% in our previous series on standard PTA for femoropopliteal occlusions (p less than 0.001). Therefore, SET is considered beneficial in reducing the incidence of early rethrombosis.

Randomized trial of intra-arterial recombinant tissue plasminogen activator, intravenous recombinant tissue plasminogen activator and intra-arterial streptokinase in peripheral arterial thrombolysis

Sixty patients were recruited into a randomized parallel group comparison of three thrombolytic regimens for acute or subacute peripheral arterial thrombosis. There were no significant differences in age, duration of history, length of occlusion or presence of neurosensory deficit between the groups. Initially successful lysis was significantly greater with intra-arterial (IA) recombinant tissue plasminogen activator (rt-PA) than with either streptokinase (Sk) (P less than 0.04) or intravenous (IV) rt-PA (P less than 0.01). The duration of therapy varied from a median of 35 h with IA rt-PA to 40 h with Sk (P greater than 0.5). The median (confidence interval) increase in ankle:brachial pressure index following IA rt-PA of 0.57 (0.33-0.82) was significantly higher than for either Sk of 0.24 (0-0.57) or for IV rt-PA of 0.18 (0-0.41). Limb salvage at 30 days was achieved in 80, 60 and 45 per cent respectively for IA rt-PA, Sk and IV rt-PA. Haemorrhagic complications occurred in six patients following Sk and in 13 following IV rt-PA; only one minor haemorrhage occurred following a catheter perforation in a patient who received IA rt-PA (P less than 0.05). IA rt-PA provides a more effective, safer fibrinolytic regimen than conventional therapy with Sk. IV rt-PA has not been as successful and carries a significantly higher risk of haemorrhagic complications.

Thrombolytic therapy for noncoronary diseases

Thrombolytic therapy has been used fairly extensively in the management of acute proximal deep-vein thrombophlebitis of the extremities, acute pulmonary embolism, and acute peripheral arterial thrombosis and embolism in addition to acute thrombotic coronary events. In the presence of acceptable indications and a favorable benefit to risk ratio, this form of therapy, when successful, has served as a useful adjunct in the management of these disorders. In deep-vein thrombophlebitis, lysis of the thrombus before permanent pathological changes (eg, organization, scarring) have occurred can prevent venous valvular dysfunction and postural venous hypertension and its complications, especially the postphlebitic syndrome. In the more severe forms of acute pulmonary embolism, thrombolytic therapy, when applied early after symptom onset, decreases morbidity and is likely to prevent a chronic increase in pulmonary vascular resistance and persistent pulmonary hypertension. In peripheral arterial thrombo-occlusive events, early restoration of flow through thrombolysis has been shown to limit ischemic damage and serve as a useful supplement to angioplasty or surgery. Thrombolytic therapy has been used less extensively in acute strokes. Here the danger of reperfusion causing bleeding into a softened area of brain undergoing infarction has slowed its evaluation for this disorder; its application to stroke remains experimental.

Thrombolytic therapy in the management of acute limb ischaemia

Acute limb ischaemia poses a threat to both the limb and life of a patient. Until recently, attempted revascularization by thromboembolectomy or vascular reconstruction held the best chance of limb salvage. Thrombolytic techniques afford an alternative method of management for this condition and are effective in selected patients. Low-dose intra-arterial streptokinase is the most established method of thrombolysis, although the recently developed tissue plasminogen activator offers a promising alternative. Intra-arterial thrombolysis is not an easy option, being labour intensive and requiring close co-operation between surgeon and radiologist. Thrombolytic and surgical techniques are not mutually exclusive but are best used to complement each other. Ideally patients with acute limb ischaemia should be managed by surgeons with knowledge of, and access to, optimal current surgical and non-surgical techniques.

Tissue plasminogen activator in peripheral arterial thrombolysis

Thirty acute peripheral arterial thromboses in 28 patients were treated with local low-dose intra-arterial recombinant tissue plasminogen activator (t-PA). All patients received 0.5 mg h-1 t-PA and 15 also received 250 units h-1 of intra-arterial heparin. Overall limb salvage at 30 days was 83 per cent (25 out of 30 limbs). Mean(s.d.) ankle/brachial index was increased by 0.53(0.26) and there was no significant difference between the group receiving t-PA alone and that receiving t-PA and heparin. No strokes or major haemorrhages occurred but there were four (13 per cent) minor haematomas associated with the catheter entry site. There were four (13 per cent) deaths from myocardial infarction occurring between 5 and 21 days after treatment. Rethrombosis occurred in four cases (13 per cent). In two patients following t-PA alone, rethrombosis occurred after 2 and 11 days. Limb salvage was achieved with a successful repeat thrombolysis and a femoropopliteal graft respectively. Rethrombosis after t-PA and heparin occurred after 30 days in two patients due to poor run-off and extensive proximal atheromatous disease respectively. t-PA is a safe, effective thrombolytic agent when given as a low-dose intra-arterial infusion. The addition of low-dose heparin does not produce any significant benefit.

Local low dose intra-arterial thrombolytic therapy: the risk of stroke or major haemorrhage

The use of local low dose thrombolysis is gradually increasing. Most experience is with streptokinase, although newer agents such as recombinant tissue plasminogen activator (rTPA) may offer more effective lysis with reduced complications. We have reviewed the experience documented in 19 prospective series published between 1974 and 1988 in an attempt to define the incidence of stroke, major haemorrhage and minor haemorrhage. The overall risk of stroke was 1.0 per cent of patients (14 cases). Major haemorrhage occurred in 5.1 per cent of patients (71 cases) and minor haemorrhage occurred in 14.8 per cent (92 out of 620 cases). There was little difference between the two thrombolytic agents, although the experience with lower doses of rTPA suggests it may offer a reduced risk of haemorrhagic complications. It is essential that all studies concerning thrombolysis should give their exclusion and inclusion criteria in full to allow an accurate appraisal of haemorrhagic complications, with the hope of improved patient selection and reduced morbidity in the future.

Differential effects of low-dose tissue plasminogen activator and streptokinase on platelet aggregation

Despite increasing success with low-dose intra-arterial thrombolysis, early rethrombosis still occurs. Platelet aggregation is thought to play a major part in this process. We have therefore investigated the effects of recombinant tissue plasminogen activator (rt-PA) and streptokinase on platelet function at doses currently used for peripheral arterial thrombolysis. Platelet-rich plasma was stirred at 37 degrees C, with either streptokinase (100, 300 or 1000 units ml-1) or rt-PA (10 (T10), 30 (T30) and 100 (T100) mg l-1), with immediate addition of an agonist for platelet aggregation (thrombin, collagen, adenosine diphosphate (ADP) or adrenaline) at a predetermined threshold dose. Significant inhibition of collagen-induced and adrenaline-induced platelet aggregation was produced with rt-PA at all doses used (P less than 0.05). With adrenaline as the agonist, T100 produced disaggregation to a mean (s.d.) level of 26 per cent. Thrombin-stimulated platelet aggregation was significantly reduced by T100 (P less than 0.001) and T30 (P less than 0.01) only, disaggregation being dose-dependent and complete with T100. Using ADP as the agonist, T100 produced a significant reduction in maximum platelet aggregation (P less than 0.01), and disaggregation was achieved to a mean (s.d.) level of 48(13) per cent. Streptokinase did not produce any significant changes in any parameter of aggregation.