Pulsed-spray pharmacomechanical thrombolysis: preliminary clinical results

Local intraarterial thrombolysis: in vitro comparison between automatic and manual pulse-spray infusion

PURPOSE

Manual and automatic pulse-spray infusion techniques are compared in vitro to evaluate the efficacy of thrombolysis and the distribution of urokinase and saline solution within thrombus using a pulse-spray catheter.

METHODS

A pulse-spray catheter was introduced into a human thrombus within a stenotic flow model. Automatic and manual pulsed infusion of urokinase and automatic pulsed infusion of saline solution were compared. To quantify the efficacy of thrombolysis, pressure gradients were recorded proximal and distal to the thrombus and during the course of infusion. Distribution of infused urokinase was assessed radiographically.

RESULTS

The fastest and most homogeneous dissolution of the thrombus was achieved with automatic pulsed infusion of urokinase, shown by decreasing transthrombotic pressure gradients (p < 0.001, Wilcoxon, matched pairs). Manual pulsed infusion of urokinase or saline solution resulted in inhomogeneous thrombus dissolution and delayed thrombolysis.

CONCLUSION

Application of automatic pulse-spray injectors seems beneficial for more effective and homogeneous intraarterial pulse-spray thrombolysis when compared with conventional manual pulsed technique.

Catheter-delivered ultrasound potentiates in vitro thrombolysis

PURPOSE

To develop a catheter-directed method to enhance urokinase- mediated thrombolysis with use of ultrasound.

MATERIALS AND METHODS

A prototype catheter was constructed by using a 9-F piezoelectric crystal capable of producing 640-kHz pulsed ultrasound energy. Clots formed in vitro from whole blood were trace-labeled with iodine-125 fibrinogen, and the release of radiolabeled fibrin degradation products was measured in the presence of urokinase, ultrasound, or a combination of urokinase and ultrasound.

RESULTS

By 30 minutes, clot lysis was more complete with urokinase plus ultrasound (78.7% +/- 5.3 [mean +/- SD]) than with ultrasound alone (19.3% +/- 10.0) or urokinase alone (47.9% +/- 10.0) (P < .001 for ultrasound and urokinase vs either alone). The time to 50% clot lysis was shortened by 46% on average with the application of urokinase and ultrasound compared with urokinase alone (P < .03).

CONCLUSIONS

Catheter-based ultrasound enhances enzymatic thrombolysis in vitro and may be a practical means to reduce the dose of enzyme and the time needed to achieve clot lysis in vivo.

Induced thrombosis in the pig inferior vena cava: a model of deep venous thrombosis

PURPOSE

To establish a new animal model of deep venous thrombosis.

MATERIALS AND METHODS

Fifteen young pigs underwent temporary interruption of the inferior vena cava (IVC) below the entry of the right renal vein by means of either a silicone band (surgical technique, n = 6) or an intraluminal balloon catheter (endovascular technique, n = 9), followed by injection of absolute ethanol. Lumbar veins within 3 cm below the obstruction were ligated or occluded interventionally. The iatrogenic caval obstruction was relieved after 2 days.

RESULTS

Procedure-related mortality was 33% (n = 2) and 11% (n = 1) for the surgical and endovascular groups, respectively. An adherent, occlusive thrombus was found in all four of the remaining surgically treated animals and in six of eight animals treated percutaneously. The IVC remained patent in two animals in whom balloon migration occurred. Severe caval stenosis invariably occurred after surgical banding.

CONCLUSION

IVC thrombi suitable for the study of various recanalization therapies can be reliably created with this pig model.

Admixture of heparin with urokinase to decrease thrombolysis time and urokinase dose in polytetrafluoroethylene dialysis graft recanalization

PURPOSE

To determine whether the addition of heparin to urokinase during dialysis graft thrombolysis can lower urokinase dose and shorten procedure time.

PATIENTS AND METHODS

Patients who underwent dialysis graft thrombolysis during an 18-month period were studied retrospectively. Twenty patients were treated with urokinase alone, and 19 patients were treated with urokinase and heparin. Thrombolysis was performed in the angiography suite by using a crossed-catheter technique. Urokinase was administered directly into the thrombus. In patients receiving heparin, 5,000 IU was added directly to the initial urokinase solution.

RESULTS

In patients who received urokinase alone, an average of 750,000 U of urokinase was used, and the average procedure time was 2 hours 42 minutes. When heparin was added, an average of 435,000 U of urokinase was used, and the average procedure time was 2 hours.

CONCLUSION

The addition of heparin to urokinase can decrease both urokinase dose and thrombolysis time in the recanalization of dialysis grafts.

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.

Pulmonary embolism following hemodialysis access thrombolysis/thrombectomy

PURPOSE

The increased use of thrombectomy with deliberate pulmonary embolization of thrombus following initial thrombolysis for occluded hemodialysis fistulas prompted the authors to measure the prevalence of pulmonary embolism (PE) due to the procedure.

PATIENTS AND METHODS

Thirty-one patients with 43 acutely thrombosed polytetrafluoroethylene hemodialysis fistulas were treated with thrombolysis/thrombectomy. Perfusion lung scans were obtained in 22 patients. Patients were also continuously monitored for clinical signs or symptoms of PE.

RESULTS

Perfusion scans were interpreted as consistent with PE in 59% of those studied, but no clinical signs or symptoms were present in 41 of the 43 cases (95%). However, two patients developed both signs and symptoms of acute PE in the postprocedural period and died. One had underlying pulmonary disease and had undergone thrombectomy before. The other had chronic heart disease.

CONCLUSION

Thrombolysis/thrombectomy is usually safe and effective, even though many patients develop subclinical PE. The authors urge extreme caution in patients who have underlying pulmonary or cardiac disease and/or have undergone the procedure before.

Thrombolytic therapy compared with mechanical recanalization in non-acute peripheral arterial occlusions: a randomized trial

PURPOSE

To evaluate whether thrombolytic therapy followed by angioplasty has any added benefit compared with angioplasty alone for the treatment of chronic peripheral arterial occlusions.

PATIENTS AND METHODS

Twenty patients with claudication or limb-threatening ischemia of at least 3 weeks duration due to iliac or femoropopliteal artery occlusions were randomized either to thrombolytic therapy with recombinant tissue-type plasminogen activator for up to 4 hours (n = 11) followed by angioplasty or to angioplasty alone (n = 9). Clinical follow-up was obtained for 1 year.

RESULTS

Life-table analysis revealed a significant improvement in the cumulative primary patency rate for patients with claudication treated initially with thrombolysis followed by angioplasty (n = 7; 86% at 6 months; 51% at 1 year) compared with angioplasty alone (n = 9; 11% at 6 months and 1 year) (P < .02). All four patients with limb-threatening ischemia were randomized to thrombolytic therapy, and none exhibited continued patency at 1 year. The most common complication in the thrombolysis group was peripheral embolization; three of these four patients were among those who had limb-threatening ischemia as the indication for entry into this study. There was no increased incidence of bleeding with thrombolytic therapy.

CONCLUSIONS

A short course of thrombolytic therapy prior to angioplasty appears to improve the 1-year patency rate for claudication due to iliac or femoropopliteal occlusions. However, patients with limb-threatening ischemia have a high prevalence of peripheral embolization and dismal patency rates with this form of therapy. A larger scale study is necessary to confirm these findings.

Prospective randomised comparative study of pulse spray and conventional local thrombolysis

OBJECTIVES

To compare the time required to achieve lysis with the pulse spray technique and the conventional slow continuous infusion technique.

DESIGN

Prospective randomised open Study.

METHODS

Eighteen patients suitable for intra-arterial thrombolytic therapy with conventional and pulse spray technique were randomised 1:1 to receive either pulse spray thrombolysis with 0.33 mg/ml rt-PA injected as a bolus of 0.2 ml or conventional thrombolysis with 0.05 mg/ml rt-PA infused at a rate of 10 ml/h.

RESULTS

The age, duration of symptoms, length of occlusion and prethrombolysis ankle brachial pressure index were comparable in the two groups. The median duration of thrombolytic therapy in the pulse spray group was 195 min (range 90-1260) compared to 1390 min (range 300-2400) in the Conventional group. The difference between the two groups was significant, p < 0.002 (Mann-Whitney test).

CONCLUSIONS

Significantly shorter time is required to achieve local thrombolysis with pulse spray compared to the conventional infusion method.

Lower limb intra-arterial thrombolysis

In the UK, approximately 5000 patients present annually with acute lower limb ischaemia. The aetiology is usually thromboembolic disease, other causes include aortic dissection and arterial trauma. Over the past two decades thrombosis has replaced embolism as the principal cause of acute ischaemia, and now accounts for approximately 59% of cases. As a consequence, intra-arterial thrombolysis is being increasingly used as first-line treatment for this condition.

Pharmacomechanical thrombolysis of experimental pulmonary emboli. Rapid low-dose intraembolic therapy

We utilized low-dose intraembolic urokinase (UK) infusions in a canine model of experimental pulmonary embolism (PE) and compared the arteriographic extent of thrombolysis with three other treatment regimens. Group 1 animals (n = 16) received the intraembolic UK infused directly into the PE offering the mechanical effect of the infusion combined with pharmacologic thrombolysis. In the group 2 animals (n = 5), UK was delivered via a guide catheter placed proximal to the clot. Group 3 animals (n = 6) were treated with a direct intraembolic saline solution infusion. Group 4 (n = 7) received only intravenous heparin. The arteriographic extent of thrombolysis was graded 1+ to 3+. The extent of thrombolysis was 2.88+ in the group 1 animals and was significantly greater than in groups 2, 3, or 4 (p = 0.003, 0.0005, and 0.0001, respectively). Fibrinogen levels did not significantly decrease with intraembolic treatment (p = 0.07). Delivery of UK directly into emboli in an experimental canine PE model appears to elicit a combined mechanical and pharmacologic effect resulting in extensive thrombolysis.

Recurrent thrombosis of polytetrafluoroethylene dialysis fistulas after recent surgical thrombectomy: salvage by means of thrombolysis and angioplasty

PURPOSE

To test the hypothesis that thrombolysis followed by angioplasty for salvage of thrombosed polytetrafluoroethylene (PTFE) dialysis fistulas is safe and effective even after recent surgical thrombectomy.

MATERIALS AND METHODS

Thrombolysis and balloon angioplasty were performed on 12 fistulas in which thrombosis had recurred within 30 days after thrombectomy (n = 10) or thrombectomy/revision (n = 2). All patients underwent pulse-spray pharmacomechanical thrombolysis with urokinase and use of a crossed-catheter technique. A total of 250,000-1,000,000 IU of urokinase and 2,500 IU of heparin were injected throughout the clot in 17-33 minutes. A bolus of 2,500 IU of heparin was simultaneously administered intravenously.

RESULTS

Thrombolysis was successful in restoring flow in all grafts, but thrombosis recurred in three grafts before they could be used for dialysis. The clinical success rate was thus 75%. There were no major complications. Mean primary patency after thrombolysis in this small select group of patients was 94 days (median, 68.5 days), comparing favorably with the mean patency of 44 days (median, 23 days) achieved by the prior 23 surgical revisions in the same grafts.

CONCLUSION

Percutaneous fistula salvage appears to be a safe and effective means of treating recurrent thrombosis in PTFE dialysis fistulas when recent surgical thrombectomy has failed.

The treatment of vascular access graft dysfunction: a nephrologist's view and experience

Chronic hemodialysis, as it is practiced today, is heavily dependent on the use of the expanded polytetrafluoroethylene graft for vascular access, although it is prone to the problem of venous stenosis and its sequela, thrombosis. The natural history of untreated venous stenosis is to decrease the efficiency of dialysis and to limit the life expectancy of the graft. Prospective treatment of venous stenosis has been advocated and percutaneous transluminal angioplasty (PTA) has been shown to be safe and reasonably effective for this purpose. Because there is no optimum screening test for venous stenosis, patient selection for PTA is particularly important. The use of a group of clinical indicators that serve to indicate a significant degree of graft dysfunction has been recommended for this purpose. Long-term patency may be better when venous stenosis is surgically revised; however, PTA has a number of advantages, especially the preservation of potential vascular access sites. Endovascular metallic stents have been used to preserve patency following PTA with disappointing results except in selected cases with central lesions. Three types of percutaneous thrombolysis have been studied for the treatment of thrombosed access grafts. The technique of pharmacological thrombolysis in which a lytic enzyme is infused into the clotted graft has proven to be unsatisfactory. The more recently developed technique of pharmacomechanical thrombolysis (PMT) has proven to be practical for use in the dialysis patient. This procedure consists of two components, a pharmacological phase in which lytic enzyme is administered and a mechanical phase in which the residual clot is macerated and removed to restore flow. This technique offers the benefits of being quick, effective, and safe. Additionally, it combines angiographic evaluation of the access, thrombolysis, and angioplasty of stenotic lesions. Mechanical thrombolysis, performed in a manner identical to PMT except that saline is used in place of the lytic enzyme, has been shown to be equally effective and safe.

Mechanical versus pharmacomechanical thrombolysis for the treatment of thrombosed dialysis access grafts

Pharmacomechanical thrombolysis offers the first practical approach for non-surgical therapy of thrombosed dialysis access grafts. This technique involves both lysis using a fibrinolytic enzyme and mechanical maceration of the clot. The technique can be accomplished in a short period of time, has a high degree of success and has a low level of complications. To evaluate the effectiveness of the mechanical aspects of this technique used alone without the lytic enzyme, a study was designed in which 103 cases of thrombosed PTFE grafts were randomly assigned to either a mechanical (M) group consisting of 55 cases or a pharmacomechanical (PM) group consisting of 48 cases. Both groups were treated in an identical manner using crossed pulse-spray catheters, except that in the M group heparinized saline was used as the pulsing agent while in the PM group concentrated urokinase was used. The two groups were completely comparable in all other respects. The combined procedure of thrombolysis and angioplasty was successful in restoring flow in 92.8% of the M group and 93.8% of the PM group. Life table analysis revealed 74%, 65%, 58% and 37% function in the M group at 15, 30, 60 and 90 days, respectively. The rates for the PM group at the same time intervals were 77%, 72%, 62% and 46%. In none of these parameters was there any significant difference between the two groups. The mean time required for the procedure in the M group was shorter because of the time delay between pulses of enzyme in the PM group built into the technique which was used.(ABSTRACT TRUNCATED AT 250 WORDS)

Recent development of rigors during infusion of urokinase: is it related to an endotoxin?

PURPOSE

This study was undertaken to determine the prevalence of rigors associated with the use of urokinase (UK) and to assay for the presence of an endotoxin in the UK solution.

PATIENTS AND METHODS

Records of 75 patients who underwent 86 UK infusions between January 1988 and July 1992 were reviewed to evaluate for the development of UK-associated rigors. A modified chromogenic limulus amebocyte lysate (LAL) test was performed to determine the presence of endotoxin in four samples of UK from lots associated with rigors, one sample of UK not associated with rigors, sterile water, nonionic contrast medium, and ionic contrast medium.

RESULTS

Between January 1, 1988, and July 10, 1990, 43 patients underwent 46 UK treatments (group 1) with no documented rigors (0% prevalence). In 45 of these 46 treatments, a standard, non-pulse-spray bolus of 75,000-500,000 IU of UK (mean dose, 182,222 IU) was used. Between July 11, 1990, and July 6, 1992, 38 patients underwent 40 UK treatments (group 2). In 33 of these 40 treatments, a standard bolus was given. Five patients received a pulse-spray bolus. The mean bolus was 213,768 IU (range, 100,000-500,000 IU). Eleven group 2 patients developed rigors (28% prevalence; P = .0005 vs group 1). The chromogenic LAL tests demonstrated no endotoxin in sterile water, nonionic contrast media, or ionic contrast media. Endotoxin was detected in small concentrations in the four samples of UK associated with rigors and in the UK sample not associated with rigors.

CONCLUSION

The increase in the prevalence of rigors associated with the use of UK does not appear to be related to an endotoxin in UK, since the concentration of endotoxin detected is well below the threshold pyrogenic dose in humans.

Percutaneous intraarterial thrombolysis: analysis of factors affecting outcome

PURPOSE

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSION

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

Pulse-spray thrombolysis of inferior vena cava thrombosis complicating filter placement

Inferior vena cava thrombosis is an uncommon but potentially serious complication of caval filter placement. A 34-year-old man with symptomatic caval thrombosis, which occurred 6 weeks after filter placement, was successfully treated with a combination of pulse-spray and local infusion of urokinase.

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.

Acute limb deterioration during intra-arterial thrombolysis

Approximately 12 per cent of limbs undergoing intra-arterial thrombolysis (IAT) develop distal embolism or extension of thrombus during the procedure. These are usually of little clinical consequence and can be treated by increasing the rate of administration of the lytic agent. However, in some patients the clinical condition of the limb deteriorates rapidly. In an attempt to define the incidence of acute limb deterioration during IAT, information was collected from five centres in the UK with experience of the technique. A total of 866 treatments were recorded, with 20 limbs (2.3 per cent) undergoing acute deterioration. This complication was more common during the treatment of thrombosed popliteal aneurysm than during that of emboli or thrombosed atheromatous arteries or grafts (P < 0.001). The amputation rate associated with the complication was high, and operative intervention provided better results than continuation of lysis.

Pulse-spray pharmacomechanical thrombolysis for treatment of thrombosed dialysis access grafts

The results of pulse-spray pharmacomechanical thrombolysis (PSPMT) of 209 thrombosed hemodialysis grafts were reviewed. In PSPMT, concentrated urokinase is injected forcefully through catheters with multiple tiny sideholes or sideslits. Catheters placed in a crisscross fashion cover the entire clot simultaneously. This therapy was successful in treating patients with thrombosed grafts. Of the 200 grafts with complete therapy, 197 grafts (99%) were patent at the end of the procedure. Mean time for pulsed-spray lysis was 40 minutes. Etiologies for graft thrombosis were anastomotic venous outflow stenosis, stenosis of the venous outflow away from the anastomosis, arterial stenosis, intragraft stenosis, pseudoaneurysms, and no identifiable cause in a small percentage. There were 16 complications, 8 of which required additional therapy or potentially compromised the graft. These results suggest that pharmacomechanical thrombolysis and angioplasty provide rapid, consistent, and safe recanalization of thrombosed hemodialysis grafts and represent an additional therapeutic approach to graft management.

Transcatheter therapy of severe acute lower extremity ischemia

PURPOSE

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSION

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

Percutaneous thrombectomy of the acutely thrombosed dialysis graft: in vitro evaluation of four devices

Percutaneous recanalization of completely thrombosed hemodialysis grafts was simulated in a flow model. Thrombus removal was performed by 1) a Trac-Wright catheter; 2) an ultrasound-driven, oscillating probe aspiration thrombectomy (US-OAT) device; 3) an electric motor-driven oscillating probe aspiration thrombectomy (EM-OAT) device; and 4) a rotating spiral aspiration thrombectomy (RAT) device. All devices were able to restore a continuous lumen of the shunt model within 1-5 min, but residual layers of wall-adherent thrombi remained attached, particularly to the inner curvature of the shunt loop. Clot removal rate was 95% for the Trac-Wright catheter, 73% for the US-OAT device, 68% for the EM-OAT device (straight tip catheter), 88% for the EM-OAT device (angulated tip catheter), and 51% for the RAT device. Effluent particle rates for particles > 100 microns were 3.6% for the Trac-Wright catheter, 0.6% for US-OAT, and less than 0.1% for the other devices. Compared with the Trac-Wright catheter, the balance of clot-removing efficiency and creation of effluent particles favored the electric oscillating device with the angulated tip catheter, which had a slightly reduced, but still efficient, clot-removing capability and produced almost no effluent particles.

The use of tissue plasminogen activator to declot arteriovenous accesses in hemodialysis patients

Thrombosis is the most common complication of arteriovenous (A-V) access, resulting in malfunction or total failure. We describe the first use of the thrombolytic agent tissue plasminogen activator (t-PA) to declot the A-V access in 15 hemodialysis patients (14 A-V grafts and one fistula). The t-PA was infused directly into the A-V access in 10-mg doses, at 2-hour intervals, to a maximum of 30 mg. As determined by angiography, t-PA infusion resulted in a dramatic decrease in clot volume in all cases and complete lysis, with return of bruit and thrill, in 10 patients. Eight of the 10 were able to be treated with hemodialysis via the A-V access the following day. In these patients, angiography demonstrated stenosis at the venous end of the A-V access in eight of nine A-V grafts (the one fistula did not have a venous stenosis). Three patients reclotted within 24 hours, and one had bleeding 5 days later after dialysis requiring compression of the A-V access, which resulted in reclotting. Five patients had functioning A-V grafts 1 to 15 months after t-PA treatment (with angioplasty of the venous stenosis required in three of these), and one patient was lost to follow-up. All five patients in whom t-PA infusion was only partially successful had venous stenosis. One patient died before surgery (unrelated to t-PA). Thus, venous stenosis was present in 13 of 15 A-V accesses studied, the highest incidence reported to date.(ABSTRACT TRUNCATED AT 250 WORDS)

Choice of agent for peripheral thrombolysis

Evidence has been accumulating that tissue plasminogen activator (tPA) is a more rapid and effective agent than streptokinase for peripheral thrombolysis. Twenty-three patients with acute limb-threatening ischaemia treated with tPA (0.5 mg h-1) over 15 months were compared with 20 consecutive patients previously receiving streptokinase (5000-10,000 units h-1). There were no major differences between the rates of complete and partial lysis (61 per cent for tPA versus 65 per cent for streptokinase) or limb salvage (65 versus 55 per cent respectively). Complication rates were also similar. It was not possible to show that tPA, an agent ten times more expensive than streptokinase, was superior for peripheral thrombolysis.

Effect of ultrasound on tissue-type plasminogen activator-induced thrombolysis

BACKGROUND

The efficacy of fibrinolytic therapy is limited by the small surface area of the clot that is available for the binding of the thrombolytic agent, such as tissue-type plasminogen activator (t-PA). We hypothesized that exposure of the clot to ultrasound during thrombolytic treatment could enhance lysis through perturbation of the thrombus, which would expose additional fibrin binding sites for t-PA.

METHODS AND RESULTS

Whole human blood clots containing radiolabeled fibrinogen were incubated in vitro for 200 minutes with Tris-albumin buffer containing t-PA at concentrations ranging from 3 to 3,000 IU/ml. In paired experiments, one of the clots also was exposed to intermittent ultrasound (1 MHz, 1.75 W/cm2) throughout the experiment. The ultrasound was delivered as a 2-second exposure followed by a 2-second rest interval. The overall difference in mean clot lysis between thrombi receiving ultrasound and those receiving no ultrasound was significant (p less than 0.001) at all concentrations of t-PA. For clots incubated with t-PA at a concentration of 300 IU/ml, ultrasound increased the percent lysis at 200 minutes from 42 +/- 5% (mean +/- SEM) to 64 +/- 10%. In six paired experiments in a rabbit jugular vein thrombosis model, rabbits received 1 mg t-PA alone or t-PA and intermittent ultrasound (1 MHz, 1.75 W/cm2) for 200 minutes. For rabbits receiving ultrasound and t-PA, lysis was 55 +/- 11% at 100 minutes compared with 30 +/- 12% for rabbits receiving only t-PA. Lysis was 6 +/- 10% for rabbits (n = 4) receiving ultrasound alone. No evidence for tissue damage was noted in rabbits exposed to intermittent ultrasound.

CONCLUSIONS

Exposure of whole blood clots in vitro to intermittent ultrasound combined with t-PA caused a significant enhancement of thrombolysis compared with t-PA alone. Intermittent ultrasound also showed a trend toward enhancement of t-PA-induced clot lysis in an animal thrombosis model. These data suggest that noninvasive intermittent ultrasound may be a useful adjunct to thrombolytic therapy.

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

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

Superior mesenteric artery embolism: treatment with intraarterial urokinase

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

Pulse-spray pharmacomechanical thrombolysis

The synergistic potential of combining pharmacologic and mechanical methods of thrombolysis has recently been recognized. Pulse-spray pharmacomechanical thrombolysis is one such method, which in our experience has markedly increased the efficiency and acceptability of thrombolysis. With this technique, dialysis grafts usually require only 20-35 min for thrombolysis; bypass grafts or native arteries usually require 60-150 min. The entire procedure is accomplished in one session within the angiography suite, including the supplemental transluminal angioplasty, atherectomy, or stenting that is usually also necessary. Clear understanding of the principle of the method and meticulous attention to technical details is essential for maximal speed, safety, and efficacy.

Enhancement of fibrinolysis with ultrasound energy

The effect of ultrasound energy on fibrinolysis of artificial thrombus in vitro was investigated. Thrombi produced by the Chandler loop method were exposed to low-energy ultrasound (5,000-6,000 Pa) in an ultrasound bath (48 kHz) for 60 seconds. Fibrinolysis with urokinase was enhanced from 40.6% +/- 1.8% to 59.2% +/- 2.6% (mean +/- standard deviation) with ultrasound exposure after a 60-minute incubation. Ultrasound alone without urokinase resulted in no fibrinolysis. In a second experiment, a newly developed miniature ultrasound-emitting ceramic element (2 x 1 x 5 mm) was attached to the tip of a catheter. Ultrasound exposure (225 kHz) from this device markedly enhanced fibrinolysis with urokinase from 8.9% +/- 1.5% to 37.3% +/- 0.8% (total ultrasound exposure 60 seconds, intensity 30 mW/cm2) after a 30-minute incubation. After a 120-minute incubation, fibrinolysis with ultrasound exposure was 61.1% +/- 1.8% versus 46.7% +/- 0.5% for the unexposed group. Ultrasound enhancement of fibrinolysis was less pronounced with longer incubation time (60 or 120 minutes). Ultrasound energy enhanced fibrinolysis with urokinase, especially in the early phase of lysis. This new device may shorten the time needed to complete fibrinolysis and reduce total drug dosage needed for treatment of thromboembolic diseases.

Ultrarapid urokinase in hemodialysis access occlusion

Over a 3-month period, 14 consecutive hemodialysis access occlusions were treated with 1-1.25 million IU of urokinase (UK) delivered at a rate of 20,000 IU/min. After systemic heparin administration, lytic infusion via the crossed-catheter technique was performed with use of pediatric microdrip pumps, with determination of success within 1 hour. Patency was established radiographically in 11 of 14 occlusions, for a 79% immediate success rate. At 285-day mean follow-up, 9% (one of 11) remained patent without further radiologic or surgical intervention; graft survival was 64% (seven of 11). No significant complications occurred with use of ultrarapid UK. The 1-hour outpatient procedure safely allowed for rapid triage between surgical and radiologic intervention, minimal catheter manipulation or physician dependency, shorter duration compression of any bleeding venipuncture sites during UK administration, and greater patient comfort because of shortened procedure times.

Guide wire traversal test: retrospective study of results with fibrinolytic therapy

The validity of the guide wire traversal test as a predictor of the outcome of selective fibrinolytic infusion therapy was investigated. A retrospective analysis of 51 consecutive urokinase infusions at the authors' institution revealed that the initial attempt at guide wire traversal of clotted vessels was successful in 36 patients and unsuccessful in 15. In those 15 patients in whom the initial guide wire traversal was unsuccessful, urokinase was infused proximal to the occlusion for 2-8 hours. In 10 of these 15 vessels, either guide wire traversal (n = 7) or complete lysis with only proximal infusion (n = 3) was then achieved. Final results for this group of 15 patients were similar to those found in the group of 36 patients in whom initial attempts at guide wire traversal were successful (chi 2 contingency analysis, P greater than .8). There were no statistically significant differences between these two groups with regard to ages of the grafts, duration of vessel occlusion prior to treatment, infusion times, or patient gender composition. These data indicate that failure to traverse a clotted vessel with a guide wire does not preclude successful urokinase fibrinolytic therapy in a substantial percentage of patients.

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.

Urokinase infusion: feasibility of monitoring for complications in a non-intensive care setting

In an effort to more effectively use critical care facilities and to reduce costs, during a 2 1/2-year period, the condition of 32 patients who received 37 local intraarterial urokinase (UK) infusions was monitored in a non-intensive care unit (ICU) setting. Techniques of infusion, mean total dose of lytic agent used (1.7 million IU), and mean duration of infusion (22 hours) were similar to those reported previously in series of patients monitored in the ICU. Complete lysis (no angiographically detectable residual clot within the treated segment) was achieved in 28 of 37 infusions (76%). Major complications occurred during two infusions (5.4%). In 33 of the 37 cases, systemic heparin was administered during UK infusion. No cases of pericatheter thrombosis were encountered. At the authors' institution, patients can be safely monitored during local UK infusion in a non-ICU setting without compromising effectiveness of therapy. This approach has resulted in enhanced cost-effectiveness of thrombolytic therapy and more effective use of critical care facilities.

Multilevel infusion catheter for use with thrombolytic agents

A new multilevel infusion catheter for administration of thrombolytic agents is described that provides near equal flow distribution through each of four infusion ports. Advantages of the catheter include fluoroscopically visible infusion length markers, small size (4.7 F), and secure positioning of the catheter within the occluded segment of graft or vessel. This catheter was used for infusion of urokinase in the treatment of 20 peripheral vascular occlusions. Complete or near complete thrombolysis was achieved in all cases.

Symptomatic native arterial occlusions: early experience with "over-the-wire" thrombolysis

"Over-the-wire" thrombolysis was successfully accomplished in eight patients with symptomatic lower-extremity ischemia. The authors used a 5-F catheter with multiple side holes designed to pulse-spray urokinase directly over the guidance of a 0.035-inch guide wire. The mean occlusion length was 11.5 cm (range, 5-27 cm). Complete thrombolysis was achieved after delivery of a mean of 480,000 IU of urokinase in a mean infusion time of 48 minutes. One embolic complication was successfully treated with the catheter-wire system. No bleeding complications occurred. Over-the-wire thrombolysis is an alternative method of administering urokinase for the treatment of arterial occlusions.