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

Single-centre experience with endovascular rotational thrombectomy for single session salvage of thrombosed arteriovenous fistulas and grafts

OBJECTIVES

This paper documents our experience and outcomes of using a relatively new endovascular rotational thrombectomy device for salvage of thrombosed vascular access.

METHODOLOGY

A retrospective study reviewing patients with thrombosed native AVF or AVG who underwent endovascular declotting using a rotational thrombectomy device between November 2018 and May 2020 at a tertiary university hospital in Southeast Asia. We evaluated demographics, procedural data, technical and procedural success, patency rates and complications.

RESULTS

A total of 40 patients underwent single session endovascular declotting of thrombosed vascular access. The mean follow-up period was 21.6 months (range 13.4-31 months). The technical success was 92.5% and clinical success was 80%. About 50% of patients had concomitant thrombolysis for pharmacomechanical thrombectomy. One patient had a myocardial infarction during the post-operative period. There were no other major complications within 30 days. The primary patency was 45.5% at 6 months and 22.7% at 12 months. Assisted primary patency was 68.1% at 6 months and 61.6% at 12 months, which was maintained up to 2 years. The secondary patency was 84.1% at 6 and 12 months.

CONCLUSION

Our study shows that rotational thrombectomy device for single session thrombectomy of thrombosed arteriovenous fistulas and grafts is safe and effective. A high technical and clinical success rate was achieved, with low complication rates and specific advantages compared to other techniques, including reduced length of hospital stay. Our reported mid-term outcomes are reasonable with an assisted primary patency of 62% at 12 and 24 months. The use of newer techniques and novel dedicated thrombectomy devices show promise.

Comparison of Clinical Outcomes in Patients Undergoing a Salvage Procedure for Thrombosed Hemodialysis Arteriovenous Grafts

Background

The major limitation of arteriovenous graft access is the high incidence of thrombotic occlusion. This study investigated the outcomes of our salvage strategy for thrombosed hemodialysis arteriovenous grafts (including surgical thrombectomy with balloon angioplasty) and evaluated the efficacy of intragraft curettage.

Methods

Salvage operations were performed for 290 thrombotic occluded arteriovenous grafts with clinical stenotic lesions from 2010 to 2018. Of these, 117 grafts received surgical thrombectomy and balloon angioplasty from 2010 to 2012 (group A), and 173 grafts received surgical thrombectomy and balloon angioplasty, with an additional salvage procedure using a curette and a graft thrombectomy catheter, from 2013 to 2018 (group B). Outcomes were described in terms of post-intervention primary patency and secondary patency rates.

Results

The post-intervention primary patency rates in groups A and B were 44.2% and 66.1% at 6 months and 23.0% and 38.3% at 12 months, respectively (p=0.003). The post-intervention secondary patency rates were 87.6% and 92.6% at 6 months and 79.7% and 85.0% at 12 months, respectively (p=0.623). Multivariate Cox regression analysis demonstrated that intragraft curettage was a positive predictor of post-intervention primary patency (hazard ratio, 0.700; 95% confidence interval, 0.519-0.943; p=0.019).

Conclusion

Surgical thrombectomy and balloon angioplasty showed acceptable outcomes concerning post-intervention primary and secondary patency rates. Additionally, intragraft curettage may offer better patency to salvage thrombotic occluded arteriovenous grafts with intragraft stenosis.

Noninvasive thrombectomy of graft by nano-magnetic ablating particles

Artificial vascular treatment is an emerging interdisciplinary subject of medicine. Although the use of artificial vessels has led to many successful advancements, blood clotting remains a major challenge, especially in terms of mural clots created along the vessel wall that do not completely block the vessel. The main objective of this study is to present a method for declotting artificial vessels. This research introduces a novel thrombectomy technique in artificial vessels by employing nano-magnetic particles under a rotating magnetic field to remove mural clots in artificial vessels. A mathematical model describes the relationship between process parameters. In vitro tests confirm the feasibility of nano-magnetic thrombectomy in cleaning and declotting artificial vessels. The results show that the clot fragments are nano-sized, which eliminates the risk of distal emboli as a concern of using current atherectomy techniques. Meanwhile, no damage to the artificial vessels is observed. The results show that the frequency of rotating the magnetic field has the greatest effect on clot removal. The conceptual principles stated in this study also have the potential to be used in other vascular depositions, such as the accumulation of lipids, and calcification atherosclerosis.

Hemodialysis access thrombosis

For the over 400,000 patients in the United States dependent on hemodialysis, arteriovenous (AV) access thrombosis may lead to missed dialysis sessions, inpatient admissions and the need for placement of temporary dialysis catheters. It is also the leading cause of permanent access loss. Percutaneous declotting is generally preferred over surgical thrombectomy. Various percutaneous approaches can be employed including the lyse-and-wait technique, thromboaspiration, pulse spray aided pharmacomechanical thrombolysis, and use of mechanical thrombectomy device.

In-center thrombolysis for clotted AV access: a cohort review

Thrombosis is the leading cause of arteriovenous (AV) access failure for hemodialysis patients requiring frequent interventions. We describe a novel approach to the lyse-and-wait technique in thrombosed AV access using nurse-administered thrombolytics in a hospital-based hemodialysis unit. All patients at a single-center, large, urban, tertiary care hospital, who underwent in-center thrombolysis via alteplase instilled directly into a thrombosed AV access by inpatient hemodialysis unit staff between January 1, 2003 and December 31, 2007, were eligible. Included subjects were at least 18 years old and did not have known or suspected infection or trauma to the AV access site. Primary outcome measure was successful thrombolysis defined as hemodialysis performed immediately or after the interventional radiology (IR) procedure. Adverse events related to the procedure were collected. A total of 321 procedures, performed on 145 subjects (77 (53%) male, 68 (47%) female) remained for analysis. Successful instillation occurred in 317 of 321 procedures (98.8%). Successful thrombolysis occurred in 237 of 321 procedures (73.8%). Adverse events (8 major and 10 minor) occurred in 18 procedures, yielding a complication rate of 5.6%. In-center thrombolysis with alteplase administration by hemodialysis unit nursing staff under physician supervision is safe and effective with an adverse outcome rate similar to the literature. Thus, this modified lyse-and-wait protocol can be adopted with appropriate IR and surgical backup in place.

Thrombosed dialysis access grafts: randomized comparison of the Amplatz thrombectomy device and surgical thromboembolectomy

We report the final results of the trial comparing the Amplatz thrombectomy device (ATD) with surgical thromboembolectomy (ST) to declot thrombosed dialysis access grafts (DAG). The study population consisted of 174 DAG, 109 of which were randomized to mechanical thrombectomy using the ATD and 65 of which were randomized to conventional surgical thromboembolectomy. Forty grafts were re-enrolled in the trial when they failed beyond the 90 days follow-up after the initial treatment. Thirty-one were re-enrolled for mechanical thrombectomy and nine were re-enrolled for surgical thrombectomy, resulting in a total of 140 ATD procedures and 74 surgical thromboembolectomy. Immediate thrombectomy success was defined as greater than 90% thrombus removal followed by the ability to dialyze after treatment, and analysis of long term success based on graft patency at 30 and 90 days, with successful dialysis. Immediate thrombectomy success with the ATD procedure was achieved in 79.2% and with ST in 73.4%. Patency of the graft, with successful dialysis, at 30 days with the ATD procedure was 79.2% and with ST was 73.4%. Patency of the graft, with successful dialysis, at 90 days with the ATD procedure was 75.2% and with ST was 67.8%. The data collected in this study provided a prospective comparison of mechanical thrombectomy with the ATD and ST performance in thrombosed DAG. The results of the performance of both methods were comparable. No statistically significant differences were seen.

Management of thrombosed dialysis access: thrombectomy versus thrombolysis

More than 250,000 patients per year with end stage renal disease are maintained on long-term hemodialysis. Because of this large population, hemodialysis access procedures now account for a large percentage of operative interventions in the United States. Prosthetic arteriovenous access thrombosis is a frequent complication that occurs at a rate of 0.5 to 0.8 episodes per year and is a major source of hospital admissions, increasing hospital costs, patient morbidity, and physician frustration. Thrombosed grafts often require rescue procedures to extend the life of the graft and make the most use of the limited available access sites. Such salvage procedures of thrombosed prosthetic dialysis shunts may be performed with either conventional surgical or endovascular techniques. Many techniques for declotting have been used, including open surgical thrombectomy, percutaneous pharmacologic or mechanical thrombectomy, and pharmacomechanical techniques. Despite the various treatment options, no individual declotting modality has proven itself superior. Long-term patencies after a single revascularization procedure are meager, with a median of less than 90 days. This article will review prosthetic hemodialysis access graft declotting mechanisms and supporting literature.

Preliminary experience with a cuffed ePTFE graft for hemodialysis vascular access

The purpose of this study was to determine graft patency and blood flow rates in recipients of a new cuffed ePTFE graft (Venaflo graft) used for hemodialysis access. A pilot study was conducted with 12 (7 men, 5 women) consecutive patients (age range, 36-76 yr; mean, 65 yr). All patients were recipients of a new cuffed PTFE graft placed for hemodialysis access. Seven were high risk because of a prior history of clotted hemodialysis accesses (1-6; mean, 3.3). Blood flow rates were determined by ultrasound dilution technique at 3 month intervals. One year and 2 year overall graft patency rates were 90.9% and 68.2%, respectively. One graft (high risk, six prior grafts) was lost to thrombosis in the first year; two grafts (one high risk, four prior grafts) were lost to thrombosis in the second year of follow-up. No graft thrombosis resulted from stenosis at the graft-vein anastomosis. Blood flow rates ranged from 550 to 2,110 ml/min (mean, 1,086 ml/min; n = 8) when first measured 3 months after graft placement. Similar flow rates were observed at 12 months (mean, 1,043 ml/min; n = 7) and 24 months (mean, 1,014 ml/min; n = 4) in grafts available for comparison. Dialysis flow rates in excess of 350 ml/min were possible with all patent grafts. A cuffed ePTFE graft provided stable blood flow and satisfactory graft patency during 2 years of follow-up, even in high risk patients with a prior history of vascular access thrombosis.

Comparison of the mechanical thrombectomy efficacy of the Amplatz thrombectomy device and the Cragg thrombolytic brush in vitro

RATIONALE AND OBJECTIVES

To determine the efficacy of thrombectomy (without thrombolytic agents) for the Amplatz thrombectomy device (ATD) and the Cragg thrombolytic brush catheter (CBC) in vitro.

METHODS

Thrombectomy was performed with the ATD or CBC (6F) in a flow model. Embolus sizes, weight, remaining thrombus, and activation time were evaluated.

RESULTS

No significant difference in the activation time was found. The CBC produced significantly less embolism (3.3% vs. 0.03% in the 5-mm and 89% vs. 0.5% in the 7-mm model), but also much more thrombus remained in the system than with the ATD (1% vs. 41% in the 5-mm and 0.1% vs. 62% in the 7-mm model).

CONCLUSIONS

The ATD can remove almost all thrombus (99%), whereas the CBC removes only up to 60%, producing fewer emboli than the ATD. This might be due to the lower rotational speed of the CBC compared with the ATD, which is 20 times greater. The soft nylon brush offers less resistance and shear force toward the thrombus than the stainless-steel impeller of the ATD. Because of the large amount of remaining thrombus, the CBC should not be used without lytic agents.

Graft surveillance: venous pressure, access flow, or the combination?

BACKGROUND

Increased venous pressure (VP) and decreased access flow (Qa) are predictors of dialysis access graft thrombosis. VP is easily obtainable. Qa assessment requires a special device and takes more time. The aims of our randomized multicenter studies were to compare outcome in patients with grafts monitored by VP or Qa (study A) or monitored by VP or the combination of VP and Qa (study B).

METHODS

We performed VP measurements consisting of weekly VP at a pump flow of 200 mL/min (VP200) and the ratio of VP0/MAP. Qa was measured every eight weeks with the Transonic HD01 hemodialysis monitor. Threshold levels for referral for angiography were VP200> 150 mm Hg or VP0/MAP> 0.5 (both at 3 consecutive dialysis sessions) or Qa <600 mL/min. Subsequent therapy consisted of either percutaneous transluminal angioplasty (PTA) or surgery.

RESULTS

Total follow-up was 80.5 patient-years for 125 grafts. The vast majority of a total of 131 positive tests was followed by angiography and corrective intervention. In study A, the rate of thromboses not preceded by a positive test was 0.19 and 0.24 per patient-year (P = NS), and in study B, it was 0.32 versus 0.28 per patient-year (P = NS). Survival curves were not significantly different between the subgroups.

CONCLUSIONS

These data demonstrate that standardized monitoring of either VP or Qa or the combination of both and subsequent corrective intervention can reduce thrombosis rate in grafts to below the recommended quality of care standard (that is, 0.5 per patient-year, NKF-DOQI). These surveillance strategies are equally effective in reducing thrombosis rates.

Effectiveness of pharmacomechanical thrombolysis in infants and children

Between March 1995 and February 2000, 10 children with major thromboses were treated with local pharmacomechanical thrombolysis. Clinical improvement was found in 8 patients: follow-up angiography showed complete thrombus resolution in 5 patients and subtotal resolution in 4.

Endovascular versus surgical treatment for thrombosed hemodialysis grafts: A prospective, randomized study

PURPOSE

The objective of this study was to compare clinical outcome and costs for two widely used treatment strategies for hemodialysis graft thrombosis.

METHODS

During a 4-year period, 80 patients with thrombosed dialysis grafts were randomly assigned to surgical thrombectomy with or without graft revision (SURG) or thrombolytic therapy with urokinase with the pulse-spray technique (ENDO), with adjunctive percutaneous transluminal angioplasty as indicated. All the procedures were performed in an endovascular operating suite with fistulography. The clinical and cost data were tabulated, and the outcome was analyzed with the life-table method.

RESULTS

Fifty-six women and 24 men ranged in age from 33 to 90 years (mean, 63.7 years). The patients had undergone a mean of 2.8 prior access procedures in the ipsilateral extremity. All the grafts were upper extremity expanded polytetrafluoroethylene grafts. Lesions that were presumed to be the primary cause of graft thrombosis were identified in 73 of 80 grafts, and 60 of these were at the venous anastomosis. The procedure time averaged 99 minutes for the patients in the SURG group and 113 minutes for the patients in the ENDO group (P =.12). Eleven patients in the ENDO group crossed over to surgical revision as compared with two patients in the SURG group who required adjunctive percutaneous transluminal angioplasty (P =.005). The mean cost of treatment (including room and supply costs but not professional fees) was significantly higher for the ENDO group than for the SURG group ($2945 vs $1512; P <.001). There were no procedure-related complications in either group. At a median follow-up time of 24 months, there was no difference in primary or assisted primary patency between groups, which averaged 6 and 7 months, respectively.

CONCLUSION

Although thrombolytic therapy combined with endovascular treatment can extend the life of dialysis grafts with results similar to surgical revision, there is a high rate of technical failure necessitating surgery and a substantially higher cost for thrombolysis.

Synthetic dialysis shunts: thrombolysis with the Cragg thrombolytic brush catheter

PURPOSE

To evaluate the effectiveness of the Cragg thrombolytic brush catheter for declotting of synthetic arteriovenous dialysis shunts.

MATERIALS AND METHODS

In this randomized controlled trial, 77 patients with synthetic forearm loop shunts that were thrombosed were randomly assigned to undergo pharmacomechanical thrombolysis with a pulsed spray (n = 34) or a thrombolytic brush catheter (n = 43). The following findings were evaluated: declotting time, urokinase dose, procedure time, complications, and shunt patency at the first dialysis session and at 3 months. All data were collected prospectively in an unblinded manner.

RESULTS

The total amount of urokinase used, including secondary interventions, was 243,657 IU with the catheter versus 476,563 IU with the pulsed spray (P = .001). At 15 minutes, clot lysis was successful in 66% of the patients with the catheter versus in 19% with the pulsed spray (P = .001). At 30 minutes, clot lysis was successful in 98% with the catheter versus 47% with the pulsed spray (P = .001). Procedure complication rates and patency at 3 months were similar for the catheter and the pulsed-spray groups.

CONCLUSION

Use of the Cragg catheter with urokinase offered faster and more complete clot lysis than did use of the pulsed spray with urokinase. The amount of urokinase used with the catheter was half that used with the pulsed spray. Shunt patency at 3 months was similar for the two treatment methods.

Ventilation-perfusion scintigraphic evaluation of pulmonary clot burden after percutaneous thrombolysis of clotted hemodialysis access grafts

The objective of this study is to determine, by using rigorous methods, if pulmonary perfusion defects were detectable by ventilation-perfusion scintigraphy after percutaneous thrombolysis of clotted hemodialysis access grafts. Thirteen patients were studied. Four patients underwent pharmacomechanical thrombolysis with urokinase and the remainder had mechanical thrombolysis alone. Pre- and postthrombolysis scintigraphic studies were performed on all patients. Perfusion defects were described as vascular (well-defined borders confined to segmental boundaries) or nonvascular. Vascular defects were graded by severity (0 to 3) and area (0 to 3) for each involved segment. Nonvascular defects were graded by severity (0 to 1) and area (0 to 1). Two experienced readers evaluated the scans blinded to each other's results and all other clinical data, including thrombolysis outcomes. Twelve patients did not have any significant worsening of their perfusion defect scores postthrombolysis. In only one patient did a study show a new nonvascular perfusion defect with a matching ventilation abnormality. The defect was believed to be caused by mucus plugging. The patient had no evidence of pulmonary embolism. Our study suggests emboli that resulted from the pharmacomechanical or mechanical thrombolysis procedure were either small, underwent lysis before impacting the lung, or were below the limit of detection of ventilation-perfusion scintigraphy.

Cerebral embolism after mechanical thrombolysis of a clotted hemodialysis access

Clinically significant embolic complications after thrombolysis of clotted hemodialysis grafts are uncommon. Most of the concern has focused on the risks associated with pulmonary emboli. We report a case of a hemodialysis patient who developed a cerebral embolism after percutaneous graft thrombolysis who was found to have a patent foramen ovale and intermittent right-to-left shunt.

New thrombolytic brush catheter in thrombosed polytetrafluoroethylene dialysis grafts: preclinical animal study

PURPOSE

To assess the safety, efficacy, endothelial changes, and risks of pulmonary embolic events after the use of a new thrombolytic brush catheter in mature thrombosed polytetrafluoroethylene (PTFE) dialysis grafts in an animal model.

MATERIALS AND METHODS

Loop configuration PTFE grafts were implanted in the femoral vessels of 12 canines 4 weeks before mechanical thrombosis was performed. The thrombus was allowed to consolidate for 24 hours in 10 animals, 72 hours in one animal, and 7 days in one animal. Standard percutaneous criss-cross catheter access was performed, and a soft, low-speed, brush (6 mm in diameter), aided by 250,000 U of periprocedural urokinase, was utilized for thrombolysis. The native vessels, just distal to the anastomosis, and lungs were evaluated macro- and microscopically.

RESULTS

Thrombolysis was complete in all grafts with the exception of a small segment between the crossing of the access vascular sheaths. The total thrombolysis time ranged from 8 to 12 minutes; this included 5 minutes of pulse-spray lacing. No difference in thrombolysis time was found with regard to the age or amount of thrombus. Minimal endothelial changes were noted and no evidence of acute pulmonary embolus was found on necropsy or histologic studies.

CONCLUSION

This method offers a simple, safe, and efficient means of recanalization of thrombosed PTFE dialysis grafts in this canine model.

Prospective randomized comparison of surgical versus endovascular management of thrombosed dialysis access grafts

PURPOSE

Salvage of thrombosed prosthetic dialysis shunts can be performed using surgical or endovascular techniques. A prospective randomized trial was designed to compare the efficacy of these two methods in restoring dialysis access function.

METHODS

One hundred fifteen patients with thrombosed dialysis shunts were randomized prospectively to surgical (n = 56) or endovascular (n = 59) therapy. In the surgical group, salvage was attempted with thrombectomy alone in 22% and with thrombectomy plus graft revision in 78%. In the endovascular group, graft function was restored with mechanical (82%) or thrombolytic (18%) graft thrombectomy followed by percutaneous angioplasty.

RESULTS

Stenosis limited to the venous anastomotic area was the cause of shunt thrombosis in 55% of patients, and long-segment venous outflow stenosis or occlusion was the cause in 30%. In 83% of the surgical group and in 72% of the endovascular group, graft function was immediately restored (p = NS). The postoperative graft function rate was significantly better in the surgical group (p < 0.05). Thirty-six percent of grafts managed surgically remained functional at 6 months and 25% at 12 months. In the endovascular group, 11% were functional at 6 months and 9% by 12 months. Patients with long-segment venous outflow stenosis or occlusion had a significantly worse patency rate than those with venous anastomotic stenosis (p < 0.05).

CONCLUSIONS

Neither surgical nor endovascular management resulted in long-term function for the majority of shunts after thrombosis. However, surgical management resulted in significantly longer primary patency in this patient population, supporting its use as the primary method of management in most patients in whom shunt thrombosis develops.

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.

Graft-to-vein fistulas associated with polytetrafluoroethylene dialysis grafts: diagnosis and clinical significance

PURPOSE

To describe the diagnosis and morphology of abnormal fistulas between dialysis grafts and adjacent native veins in five patients and to discuss their clinical significance.

PATIENTS AND METHODS

Five patients with PTFE loop-type forearm dialysis grafts were found to have graft-to-vein fistulas in the presence of venous outflow stenosis or occlusion. Three patients underwent surgical revision and two patients underwent percutaneous angioplasty of the venous obstruction. Only one patient required ligation of the abnormal graft-to-vein fistula. The clinical history, dialysis records, surgical reports, and subsequent radiographs of the fistula were reviewed to determine the clinical significance of these fistulas.

RESULTS

Two patients presented with partial graft thrombosis; the proximal portion of the graft remained patent due to persistent flow through the fistulous communication to an adjacent native vein. Two other patients had a graft-to-vein fistula arising from a pseudoaneurysm, which itself was originating from the graft. After either surgical or percutaneous treatment of the venous obstruction, all five grafts remained functional during the follow-up period.

CONCLUSION

These iatrogenic, small-caliber fistulas are not uncommon but only manifest during periods of elevated graft pressure. Once the graft pressure is normalized, these fistulas have minimal hemodynamic effect and need not be specifically treated.

Improved treatment of thrombosed hemodialysis access sites with thrombolysis and angioplasty

We treated percutaneously 135 expanded polytetrafluoroethylene (PTFE) prosthetic grafts which had thrombosed using thrombolysis with urokinase followed by balloon angioplasty. Functional patency was re-established in 38 of 62 (61%) using single catheter technique, and in 62 of 73 (85%) using crossed catheter technique (P < 0.01). Hemorrhagic complications were reduced from 12.9% in the single catheter technique to 1.4% in the crossed catheter technique (P < 0.01). Median "primary patency after treatment" of the PTFE accesses after successful restoration of function was 98 days. Cumulative "primary patency after treatment" from the time of successful recanalization of the thrombosis for the PTFE grafts was 70.5% at one month, 45.8% at 6 months, and 16.2% at 12 months. Among a smaller group of 26 PTFE patients who were treated with only interventional radiologic procedures (repeat thrombolysis and/or angioplasty), without surgical revision, "secondary patency after treatment" from the time of thrombosis was 92.3% at 1 month, 80.2% at 6 months, 69.4% at 12 months, and 36.5% at 24 months. We conclude that lysis/angioplasty is a valuable means of treating thrombosed hemodialysis access sites. The crossed catheter technique produces superior initial technical success compared with single catheter infusion of the lytic agent. "Primary patency after treatment" after successful recanalization is relatively short, but long-term patency is improved substantially with retreatment of recurrent failure of the access with repeat thrombolysis and/or angioplasty.

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)