Thrombolysis in the treatment of lower extremity occlusive disease

Acute Limb Ischemia

Acute limb ischemia is a vascular event presenting with sudden decrease in limb perfusion (of <14 days' duration) that threatens limb viability. Acute thrombosis of the native artery or graft makes up the bulk of etiopathogenesis. Prompt revascularization is the cornerstone of management of acute limb ischemia in limbs that have not undergone irreversible tissue and nerve damage. Amputation is performed in patients with irreversible tissue and nerve damage.

The role of thrombolysis in acute infrainguinal bypass occlusion: a prospective nonrandomized controlled study

Current treatment of acute infrainguinal bypass occlusion consists of either surgical revascularization or catheter-guided intra-arterial thrombolysis with adjunctive correction of the underlying flow-limiting lesion. In maintaining long-term patency, improving the number of outflow vessels could be of utmost importance. To compare the efficiency of both thrombolysis and primary surgical revascularization and to study the effect of thrombolysis on the number of patent outflow vessels, a prospective nonrandomized study was performed. Between February 2002 and August 2003, 54 patients with 56 occluded bypasses were included. Thirty bypasses were treated with thrombolysis, 26 primarily with surgery. Thrombolysis was successful in 80% of cases, with restoration of patency of the bypass but also with doubling of the amount of patent outflow vessels; surgery was successful in 85.71% of cases. However, in only 60% of the successfully lysed bypasses no adjunctive major surgery was needed. Amputation-free survival was 87.5% 1 year after surgery and 82.6% 1 year after thrombolysis. One year after thrombolysis without adjunctive major surgery, the amputation-free survival was only 39.7%. Therefore, a strategy could be to start with thrombolysis to improve outflow followed by a new bypass, whatever the underlying causative lesions are.

A phase I trial of alfimeprase for peripheral arterial thrombolysis

PURPOSE

To evaluate the safety profile, pharmacokinetics, and thrombolytic activity of alfimeprase, a novel direct-acting thrombolytic agent, in patients with chronic peripheral arterial occlusion (PAO).

MATERIALS AND METHODS

In this multicenter, open-label, single-dose, dose-escalation study, 20 patients with worsening symptoms of lower extremity ischemia within 6 months of enrollment were treated with alfimeprase in five escalating dose cohorts (0.025 mg/kg, 0.05 mg/kg, 0.1 mg/kg, 0.3 mg/kg, and 0.5 mg/kg) by means of intraarterial and sometimes intrathrombic pulsed infusion. The primary endpoint was safety assessed by adverse event rates. Additional safety assessments included vital sign monitoring, serum chemistry testing, hematologic testing, and coagulation testing for 28 days after the procedure, as well as alpha2-macroglobulin and antialfimeprase antibody testing for as long as 3 months after treatment. Pharmacokinetic parameters were evaluated with use of an assay that measures free and alpha2-macroglobulin-bound (ie, total) alfimeprase.

RESULTS

No patient experienced a hemorrhagic adverse event. Mean plasminogen and fibrinogen concentrations were not substantially altered by treatment. Three transient treatment-related adverse events were reported in the same patient: one incidence each of increased blood fibrinogen level, skin rash, and headache. All three adverse events were graded as mild. The pharmacokinetic profile of alfimeprase suggested that the half-life for total alfimeprase ranges from 11 to 54 minutes (median, 25 min) in patients with PAO. The serum alpha2-macroglobulin concentrations decreased transiently in a dose response-like manner between 12 and 24 hours and returned to within normal limits approximately 14 days after alfimeprase exposure.

CONCLUSIONS

Alfimeprase in doses as high as 0.5 mg/kg was generally well-tolerated in patients with chronic PAO. No bleeding complications were noted. The stable fibrinogen concentrations suggest that the activity of alfimeprase may be limited to the target thrombus. Alfimeprase holds the potential to achieve dissolution of thrombus with a diminished risk of hemorrhage.

Thrombolysis and mechanical thrombectomy for arterial disease

Thrombolytic therapy has been around for close to 30 years now,but its exact role in the treatment of acute and chronic arterial occlusive disease continues to be debated. Studies have produced varying and contradictory results. We are still not sure if thrombolysis has any true advantages over surgical thromboembolectomy,or which lytic agent is the best. Nonetheless, the technique still plays an important role in the treatment of arterial occlusions.

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.

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.

Comparison of thrombolytic therapy of lower-extremity acute, subacute, and chronic arterial occlusions

Our purpose was to study the effectiveness of thrombolytic therapy in treating acute, subacute, and chronic arterial occlusions in a multicenter retrospective study. Intraarterial urokinase infusion was performed in 235 patients for occluded native arteries. There were 70 (30%) with acute and 26 (5%) with subacute occlusions, and 141 (59%) with chronic symptoms for longer than 3 mo. Complete thrombolysis was achieved in 60 (86%) of the acute, 20 (77%) of the subacute, and 106 (75%) of the chronic occlusions. Adjunctive interventional procedures were performed as needed. Long-term follow-up revealed a primary patency of 87%, 85%, and 76% for the acute, subacute, and chronic occlusion groups, respectively. We conclude that the rate of complete thrombolysis of chronic occlusions proved slightly more efficient for acute and virtually the same for subacute occlusions. Long-term follow-up demonstrated a higher failure rate with chronic than with acute occlusions, probably due to worsened peripheral vascular runoff.

Quantitative evaluation of selective thrombolysis techniques: influence of catheter characteristics and delivery parameters

Here, we evaluate in vitro the site-specific delivery ability of thrombolysis catheters and compare continuous infusion (CI) and periodic injection (PI) protocols with reference to this parameter. Thrombotic occlusion was simulated by placing a porcine blood clot proximal to an eccentric stenosis in a flow phantom. Iodinated contrast agent was used as the marker. Part I-Evaluation of thrombolysis catheters: four CI and three PI catheters were tested. The marker was delivered as an infusion at 1 ml/min for 1 min (CI), or as two 0.25 ml boluses 30 sec apart (PI). Iodine content of the clot was then estimated with x-ray fluorescence spectrometry. This value as a ratio of the delivered dose was defined as the targeting efficiency. Part II-Evaluation of thrombolysis protocols: CI and PI were compared. The marker was delivered for 3 or 5 min using one of seven protocols. The iodine content of both clot and effluent were estimated. Among PI catheters, the Jet-Lysis catheter proved to be the best (P = 0.02). The EDM catheter had the lowest targeting efficiency in the CI group (P = 0.01). With CI, median iodine recovery dropped from 0.21 (95% confidence interval: 0.08, 0.25) for 1 min to 0.13 (0.05, 0.16) for 3 min and 0.07 (0.03, 0.10) for 5 min; for PI the values remained unchanged. The fraction lost in the effluent increased with the duration of regimen with both CI (P = 0.014) and PI (P = 0.004). Reducing the rate of infusion or the bolus frequency resulted in major improvements with respect to this parameter (P = 0.005). For CI, the targeting efficiency increased as well (P = 0.03). We conclude that currently used thrombolysis protocols do not fully exploit the delivery advantage offered by CI or PI. Fortunately, simple modifications offer the possibility of overcoming these drawbacks.