الفهرس 
Introduction
IntroductionOnly 14 pages are availabe for public view
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Abstract
Vascular access is one of the most important cornerstones of chronic hemodialysis therapy, and patients’ security and well being. Therefore, every effort should be made to assure timely construction, maintenance, and salvage of thrombosed or malfunctioned vascular access, being at least equally important.111
Despite nearly universal agreement that AVFs should be the hemodialysis access of first choice, AVGs continue to play an important role in the creation of permanent hemodialysis access circuits.112The natural history of AVG is the gradual development of neointimal hyperplastic stenosis most commonly at the venous anastomosis with subsequent reduction of blood flow and thereby decrease in the performance of the vascular access. If left untreated, this will eventually lead to thrombosis of the graft.113
Surgical thrombectomy, using Fogarty catheter, has been the traditional treatment of thrombosed AVGs. However, in the last several years, endovascular procedures, including pharmacological/pharmacomechanical thrombolysis, thromboaspiration, and/or mechanical thrombectomy devices, have progressively changed the approach and management of thrombosed AVGs.114
A debate still exists regarding which treatment modality is most effective in restoring and maintaining access function.114 There are no randomised trials comparing surgery versus endovascular therapy for thrombosed AVFs.107 On the other hand, there are two meta-analyses of randomised trials of surgical versus endovascular procedures for thrombosed AVGs. An earlier meta-analysis clearly supported surgical thrombectomy over endovascular therapy.106 However, a more recent meta-analysis concluded that surgical thrombectomy and endovascular therapy had comparable results.107 Therefore, KDOQI clinical practice guidelines of the NKF recommend either method for treatment of thrombosed AVGs based upon expediency and physician expertise.108
In the past, surgical revision of the underlying venous anastomotic lesion, by means of patch angioplasty, reanastomosis or jump graft, was the only option.114Nowadays, however, percutaneous balloon angioplasty is endorsed by KDOQI guidelines as the first-line treatment of hemodialysis-related access stenosis.108
However, balloon angioplasty constitutes a barotraumatic event that damages the vascular wall and incites a reparative process, the development of neointimal hyperplasia at the site of vascular injury.113 In addition, a large proportion of these patients are in a naturally vasculopathic state as a result of underlying uremia, diabetes, hypertension, and hyperlipidemia.115
Therefore, despite improvements in angioplasty balloon technology, including the advent the of high-pressure balloons capable of delivering inflation pressures greater than 20 atm to mechanically disrupt the dense fibrous tissue at the stenotic segments, the mid- and long-term results of angioplasty remain dismal.116,117
Multiple devices and approaches have been developed to broaden the armamentarium of the physician to treat venous anastomotic lesions, including cutting balloons, brachytherapy, cryoplasty, bare metal stents, stent grafts, and paclitaxel-coated balloons.113,118,119
However, concerns remain about their cost-effectiveness, and the real value in preventing graft thrombosis. Moreover, their respective indication, and whether any of them will become the new standard of care remain unclear in the literature. Thus, their use for treatment of venous anastomotic stenosis is reserved for complicated cases.120
We do believe that, despite advances in endovascular techniques, there remains a role for the relatively low cost, high speed, mini-incisional surgical thrombectomy of thrombosed AVGs, and a hybrid treatment modality combining surgical thrombectomy and adjuvant high pressure balloon angioplasty of the underlying venous anastomtic stenosis would enlarge the possibilities to save a thrombosed AVGs.
The technical and clinical success of salvage of thrombosed AVGs was achieved in 90.9%, and 87.3% of cases, respectively. This is in accordance with the KDOQI guidelines that suggest a clinical success rate of at least 85% as a reasonable goal after either surgical or percutaneous thrombectomy of AVGs.108
The intention-to-treat population of 148 patients had a postintervention primary patency rate of 52.4%, and 44.2% at 6, and 12 months, respectively, that compares favorably with the KDOQI guidelines reasonable goal of 50% 6-month, and 40% 12-month primary unassisted patency after surgical thrombectomy.108 We attribute this to the thorough use of angiography to identify and subsequently treat the underlying stenotic lesions. There are no recommendations, however, on the minimum goals of the hybrid approach of surgical thrombectomy of the graft plus balloon angioplasty of the venous anastomotic stenosis.121
During the study period, 33 AVGs (60%) required further interventions either to maintain or restore patency. This was highly successful in increasing significantly the assisted primary patency to 66.8% (log-rank test, P = .0004), and secondary patency to 78.6% (log-rank test, P < .0001) at 12 months. This highlights the importance of aggressive monitoring and surveillance of hemodialysis accesses to extend their lifespan.
The SIR Quality Improvement Guidelines for hemodialysis-related interventions specify various threshold complication rates, including 2-4% for vascular perforation or rupture.122 In the present study, there were three device-related venous injuries, a complication rate of 5.5%. This is only slightly higher than the SIR threshold values. All these complications were successfully managed at the time of the initial procedure, and these patients subsequently underwent successful hemodialysis treatment. Therefore, they were considered minor complications according to SIR criteria.110
Multivariate analysis did not identify any of demographics, graft, or lesion characteristics as a predictor of postintervention primary patency. Others have identified that patient age, diabetes, graft age, thrombus age, repeated intervention, and/or untreatable central venous stenosis as predictors of future graft patency.123,124
Hybrid treatment of thrombosed AVGs was previously reported by many authors who combined surgical thrombectomy with a variety of procedures including conventional angioplasty balloons, bare metal stents, stent grafts, both pharmacomechanical thrombolysis and balloon angioplasty, or stent grafts and high pressure balloons.104,105,121,125,126However, given the different techniques, the limited number of cases, and the design of studies, it is very difficult to compare our results with those of other reports.
Limitations of this study are being a single-center, single-arm study with relatively small number of patients, and short follow-up period.
Conclusion
Hybrid salvage of thrombosed hemodialysis access grafts using high pressure balloon angioplasty of the venous anastomotic stenosis following surgical thrombectomy by Fogarty catheter is a highly successful and safe procedure, with acceptable short-term primary patency. The need for repeated interventions demonstrates the necessity of continuous graft monitoring and surveillance to improve both assisted primary, and secondary patency rates.