Prosthetic Bypass Research Articles

Dialysis Access: Percutaneous Endovascular Interventions under Sonographic Guidance Alone

Purpose: Prosthetic shunts or native arteriovenous fistulas (AVFs) often require surgical or percutaneous endovascular interventions to correct stenosis or remove thrombosis. Catheterizations usually require radiation and iodinated contrast medium. Sonography and color-Doppler provide reliable images and measurement of dialysis access anatomy and volume flow, and have therefore a great potential to allow dialysis access percutaneous interventions in simple examination rooms without any contrast medium and any radiation, sparing time and human resources. Methods: From September 2011 to June 2016, all patients with dialysis access requiring percutaneous angioplasty, stenting, or thrombectomy were included in this cohort study and treated under sonography guidance alone. Patients with target lesion in central vessels were excluded. Efficacy outcomes were defined as improvement in volume flow and peak systolic velocity (PSV) of the stenosis. Results: Sixty-six procedures were performed in 31 patients (21 (66.7%) males; 65.5 ± 15.1 years old). There was no adverse event except moderate pain during balloon angioplasty. Primary success of the procedure was 97.0%. The volume flow rose from 449 ± 241 mL/min to 786 ± 262 mL/min and the PSV decrease from 6.1 ± 0.9 to 3.1 ± 1.1 m/s. The median time to next intervention was 10.9 months with 82.9% of re-interventions performed under sonography guidance again. Conclusions: Sonographic guidance alone is efficient and safe, for the majority of percutaneous interventions on prosthetic or native access. This approach is much simpler and cheaper, does not expose the patient and physician to radiations, and does not require contrast medium.

Ultrasound-Accelerated Thrombolysis has Higher Success and Limb Salvage Rates and Similar Costs Compared to Catheter-Directed Thrombolysis for Acute Limb Ischemia

gdfh: Ultrasound-accelerated thrombolysis (UAT) has become an alternative to catheter-directed thrombolysis (CDT) for the treatment of acute limb ischemia. The purpose of this study was to compare outcomes and hospital costs for these two treatments. Methods: The records of all patients treated with UAT (using the EkoSonic Endovascular System, EKOS Corp, Bothell, Washington) and CDT (standard side-hole catheter) at a single institution from January 2007 through December 2010 were reviewed. Patient demographics, treatment times, procedural outcomes, complications, lengths of stay, and hospital economic data were analyzed. Results: A total of 85 patients were treated; 43 underwent UAT and 42 had CDT. Both treatment groups had similar comorbidities and prior vascular procedures. Overall, 85.9% had a previous vascular procedure with 52 prosthetic bypass grafts. UAT was successful in 41/43 patients (95.3%), whereas CDT was successful in 28/42 (66.7%, P=.0019). Median total treatment time for the UAT group was 21.29 hours versus 56.53 hours for the CDT group (P=.000). Length of stay was also less for the UAT group (5.65 vs 8.26 days, P=.027). 30-d amputation rate was significantly higher in the CDT group (42.9% vs 18.6%, P<.01). There was a significantly higher bleeding rate in the CDT (23.8% vs 4.7%, P<.01). Total procedural costs were similar for both groups ($18,270 for UAT vs $16,650 for CDT, P=.366), as were total admission direct costs ($19,556 for UAT vs $18,520 for CDT, P=.685). Conclusion: UAT has higher success rates, shorter treatment times, higher limb salvage, less bleeding complications, and shorter lengths of stay than patients undergoing CDT. Despite the favorable clinical outcome for UAT, total procedural costs and total admission direct costs remain similar. Our institution has chosen to employ standardized techniques using UAT in order to improve outcomes and decrease complications in the future.Objectives: Ultrasound-accelerated thrombolysis (UAT) has become an alternative to catheter-directed thrombolysis (CDT) for the treatment of acute limb ischemia. The purpose of this study was to compare outcomes and hospital costs for these two treatments. Methods: The records of all patients treated with UAT (using the EkoSonic Endovascular System, EKOS Corp, Bothell, Washington) and CDT (standard side-hole catheter) at a single institution from January 2007 through December 2010 were reviewed. Patient demographics, treatment times, procedural outcomes, complications, lengths of stay, and hospital economic data were analyzed. Results: A total of 85 patients were treated; 43 underwent UAT and 42 had CDT. Both treatment groups had similar comorbidities and prior vascular procedures. Overall, 85.9% had a previous vascular procedure with 52 prosthetic bypass grafts. UAT was successful in 41/43 patients (95.3%), whereas CDT was successful in 28/42 (66.7%, P=.0019). Median total treatment time for the UAT group was 21.29 hours versus 56.53 hours for the CDT group (P=.000). Length of stay was also less for the UAT group (5.65 vs 8.26 days, P=.027). 30-d amputation rate was significantly higher in the CDT group (42.9% vs 18.6%, P<.01). There was a significantly higher bleeding rate in the CDT (23.8% vs 4.7%, P<.01). Total procedural costs were similar for both groups ($18,270 for UAT vs $16,650 for CDT, P=.366), as were total admission direct costs ($19,556 for UAT vs $18,520 for CDT, P=.685). Conclusion: UAT has higher success rates, shorter treatment times, higher limb salvage, less bleeding complications, and shorter lengths of stay than patients undergoing CDT. Despite the favorable clinical outcome for UAT, total procedural costs and total admission direct costs remain similar. Our institution has chosen to employ standardized techniques using UAT in order to improve outcomes and decrease complications in the future.

Initial in vitro and in vivo evaluation of a self-monitoring prosthetic bypass graft

ObjectiveProsthetic grafts used for lower extremity revascularization and dialysis access fail because of hyperplastic stenosis and thrombosis. Graft surveillance is advocated to monitor function; however, graft failure can occur between episodic examinations. An innovative sensor with wireless, microchip technology allows automated surveillance with assessment of graft function using a “cloud”-based algorithm. We performed proof-of-concept experiments with in vitro and in vivo models to assess the feasibility such a real-time graft surveillance system. MethodsA self-monitoring graft system was evaluated consisting of a prosthetic conduit of expanded polytetrafluoroethylene and a sensor unit, and a microsensor, microelectronics, battery, and remote processor with a monitor. The sensor unit was integrated on the extraluminal surface of expanded polytetrafluoroethylene grafts without compromise to the lumen of the conduit. The grafts were tested in vitro in a pulsatile, recirculating flow system under physiologic flow parameters. The hemodynamic parameters were varied to assess the ability to obtain wireless signal acquisition reflecting real-time flow properties in vitro. Segments of custom tubing with reduced diameters were inserted into the model to mimic stenosis proximal and distal to the grafts. After characterization of the initial data, the self-monitoring grafts were implanted in an ovine carotid model to assess proof of concept in vivo with 30-day follow-up of signal acquisition as well as arteriographic and histologic analysis. ResultsIn vitro flow data demonstrated the device was able to determine factors related to prosthetic graft function under varied hemodynamic flow conditions. Wireless signal acquisition using Bluetooth technology (Bluetooth SIG, Inc, Kirkland, Wash) allowed remote data analysis reflecting graft flow parameters through changes in microsensor voltage and frequency. Waveform analysis was applied to construct an algorithm using proprietary software and determine a parameter for graft flow characteristics. This algorithm allowed determination of the degree of stenosis and location of stenosis location (proximal or distal) for display on a remote monitor in real time. Subsequent in vivo experiments confirmed the ability of the system to generate signal acquisition through skin and soft tissue under biologic conditions with no arteriographic stenosis and a favorable healing response at 30-day harvest. ConclusionsInitial in vitro and in vivo experiments demonstrate the ability for a self-monitoring graft system to remotely monitor hemodynamic parameters reflecting graft function using wireless data transmission. This automated system shows promise to deliver real-time data that can be analyzed by cloud-based algorithms alerting the clinician of a change in graft function or development of stenosis for further diagnostic study or intervention before graft failure.

Predictive factors for better bypass patency and limb salvage after prosthetic above-knee bypass reconstruction

Peripheral arterial disease (PAD) is one of the most underestimated diseases because of its high prevalence and unfavorable prognosis. Many PAD patients without suitable autologous veins or options for endovascular treatment receive prosthetic above-knee femoropopliteal bypass (PAKB). Until now predictors of prosthetic bypass failure and of increased amputation risk remain indistinct. This study aimed to identify predictive factors associated with better bypass patency and limb salvage to achieve a more favorable outcome after PAKB reconstruction. Pre-, intra-, and postoperative data of 244 PAKB procedures performed at a German university medical center were collected and analyzed using univariate and multivariate methods. To our knowledge this 12-year experience is the largest retrospective study to identify predictors for patency and limb salvage after PAKB reconstruction. Of the PAD patients 94% (229/244) were followed for an average of 34.9months. Patient cohorts characteristics were: mean age, 66.1years, 181 men (74%), claudication (64%), rest pain (16%), ischemic lesions (20%), arterial hypertension (92%), smoking (79%), hyperlipidemia (65%) and type 2 diabetes (43%). Cumulative primary 1- and 3-year graft patency rates were 60.8% and 50.7%, respectively, and cumulative 1- and 3-year limb salvage rates were 89.3% and 86.1%, respectively. One hundred seven bypasses (43.9%) failed, 26 patients (10.7%) required a major and seven patients (2.9%) required a minor amputation. Overall survival rates of PAD patients after 1- and 3-years were 94.4% and 82.9%, respectively. Subjective symptom improvement was found to be the most important prognostic follow-up factor for graft patency and limb salvage. Patients with recurrent symptoms in the follow-up had an increased risk of emerging bypass failure compared with patients with subjective symptom improvement (patency at 1year: 40.8% vs 100% and at 3years: 26% vs 100%; P< .001). No patient with subjective improvement in symptoms during follow-up underwent an amputation (limb salvage at 1year: 100% vs 79% and at 3years: 100% vs 72.8%; P< .001). Therefore, subjective symptom improvement should be the decisive criterion to determine follow-up intervals of PAD patients. In univariate analysis further significant factors associated with better graft patency and limb salvage rates were: claudication compared with critical ischemia, larger graft diameter (>6mm), pre- and postoperative antiplatelet therapy, statin therapy independent from lipid values after PAKB revascularization, and an experienced vascular surgeon. In our study, we determined the subjective improvement in symptoms as the most important prognostic factor for bypass function and limb salvage after PAKB. Furthermore, disease stage of critical ischemia, graft diameter, preoperative aspirin use, and postoperative statin medication were independent predictive factors. Therefore, PAD patients should be treated with aspirin pre- and postoperatively as well as with a statin postoperatively. In case of PAKB reconstruction only prostheses with a large diameter (>6mm) should be used and the procedure should be performed by an experienced surgeon. Considering these results with regard to the predictive factors for better graft patency and limb salvage rates a significant more favorable outcome during the follow-up and an increased 5-year patency rate for PAKB reconstructions can be expected.

Impact of Staphylococcus aureus protein A (spa) genetic typing in cases of prosthetic shunt graft infections.

IntroductionIn January 2014 an internal audit was performed at the department of surgery, division of vascular surgery of the Medical University Graz, Austria, to assess the short and long-term outcomes of prosthetic shunt graft implantations performed between December 1998 and December 2013. A 10.8 % explantation rate due to graft infection was detected. The majority of the cases were associated with Staphylococcus aureus. The aim of this study was to clarify whether this constitutes a nosocomial problem.Patients and methodsBetween December 1998 and December 2014 a total of 490 prosthetic shunt grafts were implanted. After exclusion of 54 cases, 436 shunts remained for statistical analysis. Genetic analysis (spa typing) was acquired from three new cases with involvement of S. aureus in 2014. The impact of several factors (e.g. sex, institute for dialysis, age, type of prosthesis, implantation surgeon and position of shunt) on the shunt graft infection rate was statistically analyzed.ResultsOf the prostheses 14.0 % (61 out of 436) had to be explanted of which 12.4 % (54/436) were due to infection. In 77.8 % (42/54) bacteria were found in blood and/or wound cultures. Staphylococcus aureus was present in 76.2 % (32/42) of the cases with detected bacteria and in all cases was sensitive to methicillin. The infection rate was not significantly dependent on any of the investigated factors; however, the factor “institute for dialysis” had a remarkable p‑value of 0.060 with the infection rate ranging from 8.5 % to 18.2 % depending on the institution. Three different S. aureus protein A (spa) types were found: t015, t359, t6265. The detection of three different spa types means that these patients had different sources of S. aureus so that a nosocomial problem is very unlikely.ConclusionGenetic typing of spa is a suitable technique for distinguishing between nosocomial and community acquired sources of prosthetic shunt graft infections.

Intercondylar Route of Prosthetic Infragenicular Femoropopliteal Bypass Has Better Primary, Assisted, and Secondary Patency but Not Limb Salvage Rate Compared to the Medial Route.

Aim. To compare the differences between medial and intercondylar infragenicular femoropopliteal prosthetic bypasses in terms of their midterm patency and limb salvage rates. Methods. Ninety-three consecutive patients with peripheral arterial disease who underwent a simple distal femoropopliteal bypass using a reinforced polytetrafluorethylene graft were included in this retrospective study. The bypass was constructed in the intercondylar route in 52 of the patients (group A) and in 41 in the medial route (group B). Results. Median observation time of the patients was 12.7 (IQR 4.6–18.5) months. There were 22 and 24 interventional or surgical procedures (angioplasty, stenting, thrombolysis, thrombectomy, or correction of the anastomosis) performed to restore patency of the reconstruction in groups A and B, respectively (p = 0.14). The 20-month primary, assisted, and secondary patency rates and limb salvage rates were 57%, 57%, 81%, and 80% in group A compared to 21%, 23%, 55%, and 82% in group B (p = 0.0012, 0.0052, 0.022, and 0.44, resp.). Conclusion. Despite better primary, assisted, and secondary patency rates in patients with a prosthetic infragenicular femoropopliteal bypass embedded in the intercondylar fossa compared to patients with the medial approach, there is no benefit in terms of the limb salvage rate and the number of interventions required to maintain patency of the reconstruction.

Randomized Study of Noninferiority Comparing Prosthetic and Autologous Vein Above-Knee Femoropopliteal Bypasses

The main aim of this study was to compare the 5 years rates of secondary patency of above-knee femoropopliteal revascularizations with autologous veins or prosthetic grafts. The secondary objectives were to compare the rates of primary patency, limb salvage, morbidity, and mortality between the 2 groups. This was a single-blind randomized study of noninferiority (ratio 1:1), carried out in 11 centers of vascular surgery with 2 parallel groups between July 2002 and November 2005. Follow-up finished in May 2011. The monitoring protocol included a clinical examination and an ultrasound control at 1 month, 3 and 6 months, then annually. One hundred patients were included and randomized in the study, 52 in the prosthetic group and 48 in the autologous vein group. Four patients randomized in the vein group received a prosthetic graft. No patient was excluded from the analysis. In the in intent-to-treat analysis, the 5 years secondary patency was 84.6% in the prosthetic group (IC 95%, 71.9-93.1) and 70.8% in the autologous vein group (IC 95%: 55.9-83.1), and the difference in secondary patency between the prosthetic and the autologous vein groups was 13.8% (IC 95%, -4.4 to 32.0). In the under treatment analysis, the 5 years secondary patency was 96.2% among patients receiving a prosthesis (IC 95%, 80.4-99.9) and 90.5% among patients receiving an autologous vein (IC 95%, 66.9-98.9), and the difference in the rate of patency between prostheses and veins was 5.7% (IC 95%, -13.2 to 24.6). Although there was no significant difference at 5 years, the death rate and the rate of amputation were higher in the prosthetic group. Although it is impossible to conclude definitely to the noninferiority of prosthetic bypass compared with venous bypass because of the insufficient number of inclusions, this randomized study nevertheless showed at 5 years the satisfactory results obtained with prostheses compared with autologous vein for above-knee femoropopliteal bypasses.

Long-Term Outcomes of Catheter-Directed Thrombolysis for Acute Lower Extremity Occlusions of Native Arteries and Prosthetic Bypass Grafts

Catheter-directed thrombolysis is a well-accepted treatment for acute lower extremity occlusions of native arteries and bypass grafts. Several variables that affect outcomes of thrombolysis have been identified. The hypothesis of this study was that the long-term outcome after catheter-directed thrombolysis would be better for acute lower extremity occlusions of native arteries compared with prosthetic bypass grafts. This observational study retrospectively analyzed 159 consecutive patients (114 men),median age, 65years (range 57-73years), with 89 native artery (56%), and 70 prosthetic bypass graft (44%) occlusions of the lower extremity. All patients were treated with catheter-directed thrombolysis between 2006 and 2009 in 2 vascular referral centers in the Netherlands. The severity of ischemia was Rutherford class I (52%), class IIa (27%), class IIb (12%) and unknown (9%) in native arteries and class I (64%), class IIa (19%), class IIb (1%), and unknown (16%) in bypass grafts. Median (range) duration of symptoms before the start of thrombolysis was 3.5 (1-14) days in native arteries and 3 (1-9) days in bypass grafts. All patients were treated with a continuous dosage of urokinase (100,000 IU/h). Amputation-free survival was estimated by conduit type using the Kaplan-Meier method and compared using the log-rank test. Univariate and multivariate analyses were performed using a Cox proportional hazards model. Complete (>95%) lysis was achieved in 69% of native arteries and bypass grafts (P=1.00). Major hemorrhagic complications occurred in 12% (4% hemorrhagic strokes, of which 2% were fatal) of native arteries and in 7% (0% hemorrhagic stroke) of bypass grafts (P=0.28). The 30-day mortality rate was 6% in native arteries and 1% in bypass grafts (P=0.17), and the 30-day amputation rate was 10% in native arteries and 13% in bypass grafts (P=0.45). Mean follow-up was 27±19months. Amputation-free survival at 1year was 76% for native arteries and 78% for bypass grafts and at 5years was 65% for native arteries and 51% for bypass grafts (P=0.32). Multivariate analysis showed 2 negative predictors for amputation-free survival: age >65years and cerebrovascular disease. Conduit type was not an independent predictor for amputation-free survival (P=0.78). Despite initial promising results, long-term follow-up of catheter-directed thrombolysis for acute lower extremity occlusions showed a disappointing amputation-free survival. In multivariate analysis, no significant differences in amputation-free survival between native arteries and prosthetic bypass grafts were determined.

Implantable Multi-Modal Sensor to Improve Outcomes in Hydrocephalus Management

Hydrocephalus is the single most common pediatric neurosurgical problem worldwide. Current treatment of this life-threatening disorder involves diverting excess fluid from the ventricles of the brain via a prosthetic shunt. While many hydrocephalus sufferers rely heavily on their ventriculo-distal shunt to maintain a healthy intracranial pressure, shunts carry a high risk of failure. Current methods of assessing shunt patency are performed within the hospital, and many patients and their families feel bound to remaining within close proximity of a hospital in order to receive timely medical intervention in the event of a shunt failure. There is a need for a system which can detect shunt malfunction, simply and reliably. We present a novel method of obtaining flow measurements from a piezoresistive pressure transducer. This builds on an earlier development of obtaining simultaneous temperature and pressure measurement from the single ultra-miniature solid-state transducer. The flow measurement system is capable of measurements in the range 0-35 ml/h, typical of the fluid flow rates through a hydrocephalus shunt. Within the flow range 0–14 ml/hour the resolution is 2 ml/hour. For flow rates greater than 16 ml/hour the resolution is 5 ml/hour. Employing a thermal flow sensing technique, the maximum heating of the local fluid is 0.65 ± 0.02 °C. The flow signal is independent of ambient temperature. The sensor would be implanted in the shunt to allow the detection of the flow rate of fluid through it, enabling the clinician to measure the patency of a shunt in real time.

Effect of a rapid clinical protocol to the conversion from central venous hemodialysis catheter to arteriovenous access.

Evaluation of the rapid conversion protocol that includes an ambulatory dialysis access center (DAC), and a three-step clinical pathway, to the conversion rate from central venous hemodialysis (HD) catheter to functioning arteriovenous (AV) access. Prospective data were collected on 97 consecutive catheter-dependent HD patients. DAC is defined as an ambulatory unit, able to accommodate clinic visits, ultrasound examinations, surgical, interventional and hybrid procedures. Step I: initial evaluation, vein mapping and creation of AV access. Step II: clinical evaluation in two weeks and if failure identified, secondary procedure to restore function. Step III: evaluation in four weeks after creation, and additional procedure to promote maturation if indicated. The success rate, time to conversion and time to catheter removal were recorded. From the 97 consecutive referred patients, eight patients were excluded. From the remaining 89 patients, 99% were successfully converted to AV access. Seventy-three percent of the patients were converted to native arteriovenous fistulae and 27% of the patients to prosthetic arteriovenous shunts. The median time from creation to HD catheter removal was 63 (SD 41) days. Fifty-two percent of the patients required at least one additional secondary procedure to accomplish successful conversion. High rates of timely conversion from catheter to AV access, primarily AV fistulae, can be accomplished within the context of the rapid conversion protocol.

Medical adjuvant treatment to increase patency of arteriovenous fistulae and grafts.

End-stage renal disease (ESRD) patients often require either the formation of an arteriovenous (AV) fistula or an AV interposition prosthetic shunt for haemodialysis. These access sites should ideally have a long life and a low rate of complications (for example thrombosis, infection, stenosis, aneurysm formation and distal limb ischaemia). Although some of the complications may be unavoidable, any adjuvant technique or medical treatment aimed at decreasing complications would be welcome. This is the second update of the review first published in 2004. To assess the effects of adjuvant drug treatment in ESRD patients on haemodialysis via autologous AV fistulae or prosthetic interposition AV shunts. For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched March 2015) and CENTRAL (2015, Issue 2). Randomised controlled trials (RCTs) of active drug versus placebo in people with ESRD undergoing haemodialysis via an AV fistula or prosthetic interposition AV graft. For this update, the two review authors (NCT, ADS) independently assessed trial quality and one review author (NCT) extracted data. Information on adverse events was collected from the trials. The primary outcome was the long-term fistula or graft patency rate. Secondary outcomes included duration of hospital stay, complications and number of related surgical interventions. For this update, an additional six studies were deemed suitable for inclusion, making a total of 15 trials with 2230 participants. Overall the quality of the evidence was low due to short follow-up periods, heterogeneity between trials and moderate methodological quality of the studies due to incomplete reporting. Medical adjuvant treatments used in the trials were aspirin, ticlopidine, dipyridamole, dipyridamole plus aspirin, warfarin, fish oil, clopidogrel, sulphinpyrazone, and human type I pancreatic elastase (PRT-201). Where possible, the included studies were pooled into similar medical adjuvant groups for meta-analyses.All included studies reported on graft patency by measuring graft thrombosis. There was insufficient evidence to determine if there was a difference in graft patency in studies comparing aspirin versus placebo (three RCTs, 175 participants) (odds ratio (OR) 0.40, 95% confidence interval (CI) 0.07 to 2.25; P = 0.30). The meta-analysis for graft patency comparing ticlopidine versus placebo (three RCTs, 339 participants) favoured ticlopidine (OR 0.45, 95% CI 0.25 to 0.82; P = 0.009). There was insufficient evidence to determine if there was a difference in graft patency in studies comparing fish oil versus placebo (two RCTs, 220 participants; OR 0.24, 95% CI 0.03 to 1.95; P = 0.18); and studies comparing clopidogrel and placebo (two RCTs, 959 participants; OR 0.40, 95% CI 0.13 to 1.19; P = 0.10). Similarly, there was insufficient evidence to determine if there was a difference in graft patency in three studies (306 participants) comparing PRT-201 versus placebo (OR 0.75, 95% CI 0.42 to 1.32; P = 0.31); in one trial comparing the effect of dipyridamole versus placebo (42 participants; OR 0.46, 95% CI 0.11 to 1.94, P = 0.29) and dipyridamole plus aspirin versus placebo (41 participants; OR 0.64, CI 0.16 to 2.56, P = 0.52); in one trial comparing low-dose warfarin with placebo (107 participants; OR 1.76, 95% CI 0.78 to 3.99, P = 0.17); and one trial (16 participants) comparing sulphinpyrazone versus placebo (OR 0.43, 95% CI 0.03 to 5.98, P = 0.53). The single trial evaluating warfarin was terminated early because of major bleeding events in the warfarin group. Only two studies published data on the secondary outcome of related interventions (surgical or radiological); there was insufficient evidence to determine if there was a difference in related interventions between placebo and treatment groups. No studies reported on the length of hospital stay and data reporting on complications was limited and varied between studies. The meta-analyses of three studies for ticlopidine (an anti-platelet treatment), which all used the same dose of treatment but with a short follow-up of only one month, suggest ticlopidine may have a beneficial effect as an adjuvant treatment to increase the patency of AV fistulae and grafts in the short term. There was insufficient evidence to determine if there was a difference in graft patency between placebo and other treatments such as aspirin, fish oil, clopidogrel, PRT-201, dipyridamole, dipyridamole plus aspirin, warfarin, and sulphinpyrazone. However, the quality of the evidence was low due to short follow-up periods, the small number of studies for each comparison, heterogeneity between trials and moderate methodological quality of the studies due to incomplete reporting. It, therefore, appears reasonable to suggest further prospective studies be undertaken to assess the use of these anti-platelet drugs in renal patients with an arteriovenous fistula or graft.

Matrix metalloproteinases and risk stratification in patients undergoing surgical revascularisation for critical limb ischaemia.

Critical limb ischaemia (CLI) is the most advanced form of peripheral artery disease (PAD) and it is often associated with foot gangrene, which may lead to major amputation of lower limbs, and also with a higher risk of death due to fatal cardiovascular events. Matrix metalloproteinases (MMPs) seem to be involved in atherosclerosis, PAD and CLI. Aim of this study was to evaluate variations in MMP serum levels in patients affected by CLI, before and after lower limb surgical revascularisation through prosthetic or venous bypass. A total of 29 patients (7 females and 22 males, mean age 73·4 years, range 65-83 years) suffering from CLI and submitted to lower extremity bypass (LEB) in our Institution were recruited. Seven patients (group I) underwent LEB using synthetic polytetrafluoroethylene (PTFE) graft material and 22 patients (group II) underwent LEB using autogenous veins. Moreover, 30 healthy age-sex-matched subjects were also enrolled as controls (group III). We documented significantly higher serum MMPs levels (P < 0·01) in patients with CLI (groups I and II) with respect to control group (group III). Finally, five patients with CLI (17·2%) showed poor outcomes (major amputations or death), and enzyme-linked immunosorbent assay (ELISA) test showed very high levels of MMP-1 and MMP-8. MMP serum levels seem to be able to predict the clinical outcomes of patients with CLI.

Aggressive Costoclavicular Junction Decompression in Patients with Threatened AV Access

A substantial number of patients with threatened arteriovenous (AV) access are found to have stenoses at the costoclavicular junction (CCJ), which frequently are resistant to angioplasty and stenting. We believe that stenoses in this location will not resolve unless bony decompression is performed to relieve the extrinsic compression on the vein. This article describes our short- to medium-term results following such decompression in patients with failing fistulae. We reviewed a prospectively maintained database to identify all patients with threatened AV access operated on for stenoses at the CCJ. Pre- and postoperative course along with long-term follow-up were analyzed. Between July 2012 and December 2013, 24 patients with threatened access were operated on for CCJ stenoses at our institution. Fifteen had highly dysfunctional AV fistulae otherwise felt to need ligation, 10 had significant arm and/or head swelling, and 3 required access but had no contralateral options. In 6 patients, the subclavian vein was occluded and 18 stenotic; 5 of these had stents in place through the CCJ. Decompression was performed via claviculectomy in 3 patients, 2 of whom underwent reconstruction (one jugular vein, one prosthetic bypass) and 1 was stented. The other 21 patients underwent first rib resection, 20 via an infraclavicular exposure and 1 via a supraclavicular rib resection. A variety of interventions were performed in the arm, including aneurysm plication, cephalic to deep bypass, one prophylactic distal revascularization interval ligation, and several primary fistulae. 30-Day mortality was minimal: there was one significant hematoma and one hemothorax in a patient who underwent on-table thrombolysis and there were no deaths or cardiac, neurologic, or other significant morbidity. Median length of stay was 2 days. At follow-up up to 20 (median 10) months, 4 patients died of unrelated causes and 1 patient undergoing central reconstruction with prosthetic bypass required excision of this for infection and ligation of his fistula. Two other fistulae failed. One-year assisted primary patency of the fistula was 85%, and of the central bypass, 89%. At last follow-up, the index arm continued to be used for access in 85% of patients, and overall survival was 68%. Virtually all patients experienced dramatic symptom relief. In this group of high-risk patients whose access was judged otherwise nonsalvageable, excellent symptom relief and long-term fistula and ipsilateral arm use can be achieved with aggressive decompression of the bony CCJ followed by endovascular intervention as needed.

Ruptured peroneal aneurysm after infrapopliteal prosthetic bypass with Taylor patch

IntroductionA 45-year-old mailman underwent an implantation of a femoro-peroneal polytetrafluoroethylene (PTFE) bypass with a distal Taylor patch six years prior to admission after two failed autologous reconstructions and extensive fasciotomy. The initial pathology was an acute ischemia due to popliteal entrapment with subsequent popliteal thrombectomy.ReportThe patient was examined because of pain, reduction of walking distance and development of a palpable mass at the medial fasciotomy site. A 6-cm pseudoaneurysm with complete disruption of the suture line of the vein patch was discovered and resected. Arterial continuity with a vein interposition graft was established using non-reversed cephalic vein.ConclusionThe etiology of the aneurysm is not entirely clear. One may argue that the fourth revascularization could have been performed with an arm vein instead of a prosthetic graft with the probability of a better long term patency in a young patient. 15 months after the procedure the bypass is patent and the patient is without any symptoms. This complication of a Taylor patch has not been reported before.

Development of a Composite Electrospun Polyethylene Terephthalate‐Polyglycolic Acid Material: Potential Use as a Drug‐Eluting Vascular Graft

Intimal hyperplasia (IH), an excessive wound healing response of an injured vessel wall after bypass grafting, typically leads to prosthetic bypass graft failure. In an approach to ameliorate IH, nondegradable poly(ethylene terephthalate) or PET, which has been used in prosthetic vascular grafts for over 60 years, and biodegradable poly(glycolic acid) or PGA were electrospun using different techniques to generate a material that may serve as permanent scaffold and as a drug/biologic delivery device. PET and PGA polymers were electrospun from either a single‐blended solution (ePET/ePGA‐s) or two separate polymer solutions (ePET/ePGA‐d). ePET/ePGA‐d material revealed two distinct fibers and was significantly stronger than the single fiber ePET/ePGA‐s material. After 21 days of incubation in PBS, ePET‐PGA‐s showed fiber strand breaks likely due to the degradation of the PGA within the ePET‐ePGA‐s fiber, while the ePET/ePGA‐d material showed intact ePET fibers even after ePGA fiber degradation. The ePET/ePGA‐ material was able to release red fluorescent dye for at least 14 days. Attachment of human aortic smooth muscle cells (AoSMCs) was similar to both materials. ePET/ePGA‐d materials maybe a step towards bypass graft materials that can be custom‐designed to promote cellular attachment while serving as a drug delivery platform for IH prevention.

Outcome of the FUSION vascular graft for above-knee femoropopliteal bypass

Although endovascular procedures have become popular for the treatment of patients with femoropopliteal occlusive disease, open surgical bypass is still required in a significant proportion of patients. Saphenous vein is the conduit of choice, but prosthetic bypass grafts are often necessary. The Peripheral Bypass Grafting: Prospective Evaluation of FUSION Vascular Graft for Above Knee Targets (PERFECTION) trial was performed to assess the clinical outcome of the FUSION vascular graft (Maquet Cardiovascular, Wayne, NJ), a novel bilayer prosthetic graft with an external expanded polytetrafluoroethylene inner layer and an outer knit polyester layer. Eligible study patients included those requiring prosthetic femoral-to-above-knee popliteal bypass for claudication, rest pain, or localized tissue loss without wet gangrene. During a 30-month period ending in March 2012, 117 patients were enrolled in the PERFECTION trial and underwent bypass with FUSION vascular grafts at 10 European investigational sites. Patients were followed up with duplex ultrasound imaging and ankle-brachial indices performed at 30 days, 6 months, and 12 months. The primary efficacy end point was 12-month primary patency of the study graft, assessable in 102 patients. Safety end points included all-cause mortality, major adverse events, amputation, and graft reinterventions. The 67 male (57.3%) and 50 female (42.7%) patients averaged 67.8 ± 8.9 years in age and were implanted with 6-mm (25 [21.4%]), 7-mm (26 [22.2%]), or 8-mm (66 [56.4%]) FUSION grafts. The 30-day primary graft patency was 95.3%, with five graft occlusions in the perioperative period. The 12-month primary rate was 85.6%, and the secondary patency rate was 93.2%. Ankle-brachial indices increased from a mean of 0.53 ± 0.20 preoperatively to 0.97 ± 0.16 at 30 days and 0.91 ± 0.22 at 12 months. There were no major amputations through 12 months of follow-up, 15 patients (12.8%) had graft reinterventions, one patient (0.9%) developed a graft infection, and five patients (4.3%) died of unrelated causes. The findings of the prospective, multicenter PERFECTION study confirm clinical utility of the FUSION vascular graft through 12 months of follow-up. Patency rates equal or exceed those reported with other nonbioactive vascular grafts. These observations suggest that the FUSION graft is a useful alterative to standard expanded polytetrafluoroethylene grafts and should be considered as an option in patients requiring prosthetic femoral-to-above-knee popliteal arterial reconstruction.

Resultados del bypass infrainguinal protésico en isquemia crítica: factores asociados a permeabilidad y salvamento de la extremidad

ObjectivesTo assess the outcomes of prosthetic bypass grafts in critical limb ischemia, as well as to determine the predictors of patency and limb salvage. Materials and methodsRetrospective cohort study of patients with critical limb ischemia undergoing a prosthetic infrainguinal bypass graft between 1997 and 2013 in a single centre. The pre- and post-operative data were collected, and the cohort was divided into 3 groups according to the location of the distal anastomosis: Above-knee popliteal artery (POP1), below-knee popliteal artery (POP3), or femorodistal. An assessment was made of the primary patency, assisted primary patency, secondary patency, limb salvage, and survival. Stratified statistical analysis using the Kaplan-Meier for patency, limb salvage and survival. Univariate and multivariate analysis of risk factors associated with the results using Cox regression. ResultsA total of 154 prosthetic graft bypass, divided into POP1 36.4% (n=56), POP3 50% (n=77), and femorodistal 13.6% (n=21). Differences were found in mean age (POP1 68.9 years, POP3 77.2 years, femorodistal 76.8 years; P<.001). Median follow-up was 11 months. The best outcomes were found in POP1, and the worse in femorodistal in terms of patency and limb salvage (Log Rank P1 0.004, P1A 0.001, P2 0.001 and SE 0.025), with no differences in survival time (Log Rank 0.068). Coronary artery disease and femorodistal bypass were independent risk factors in patency and limb salvage. Older patients and those with chronic renal failure had higher mortality rates. ConclusionsProsthetic infrainguinal bypass graft has fairly good outcomes in critical limb ischemia. The worst outcomes may be expected in patients with coronary artery disease and femorodistal bypass.

Collagen implant with gentamicin sulphate reduces surgical site infection in vascular surgery: A prospective cohort study

Introduction: Surgical site infection (SSI) is a common complication after vascular surgery. It may cause exposure of the underlying prosthesis causing graft infection, which may require the removal of the vascular graft, increasing amputation and mortality risks. Graft contamination usually occurs during operative procedure or by direct spread from an infected wound. It is therefore advisable to a strong effort in reducing SSI. Topic antibiotics have not been fully studied in vascular surgery, but collagen implant with gentamicin sulphate has shown to reduce SSI in cardiac surgery, orthopaedics, and general surgery procedures. Methods: Sixty (60) non-diabetic and non-obese patients with lower limb ischaemia with indication for femoropopliteal PTFE prosthetic bypass were allocated into 2 groups of 30 patients. A collagen implant impregnated with gentamicin sulphate (Collatamp®) was applied in the groin incision adjacent to the prosthesis in one group, and the other was a control group. The same surgical team operated all patients. Szilagyi classification was used. Results: There was no SSI (0% – 0/30) in the collagen implant with gentamicin sulphate group, contrasting with 6 cases (20% – 6/30) of SSI (grade I and II) in the control group (p = 0.024). In-hospital day's data shows a significant difference between the two groups (p = 0.004) with a mean of 5.66 days for implant group and 8.10 days for control group. There was no SSI grade III. Conclusion: Collagen implant with gentamicin sulphate (Collatamp®) reduces SSI in the groin incision in ischaemic patients submitted to femoropopliteal PTFE prosthetic bypass. Days of hospitalization are also reduced. Decreasing SSI rate and in-hospital days, this implant may also reduce health care costs. Because this is a small pilot study, a multicentre RCT is necessary for validation.

Role of the latest endovascular technology in the treatment of intermittent claudication.

Intermittent claudication is a serious symptom in patients with peripheral arterial disease, and severely limits activities of daily living. Conservative treatment (optimal medical therapy and exercise rehabilitation programs) and revascularization procedures (endovascular treatment [EVT] or open bypass surgery) can relieve intermittent claudication. Among these treatment options, EVT has developed dramatically during the past decade, and has enabled physicians to offer less invasive treatment options with increasing durability. EVT for aortoiliac lesions has matured, and its long-term patency now approaches that of open bypass surgery. The latest EVT technologies include drug-eluting stents, stent grafts, drug-coated balloons, and bioresorbable stents. The recently reported patency of stent grafts in the femoropopliteal lesions was comparable with that of the prosthetic bypass graft. In the course of the paradigm shift from bypass surgery to EVT, evidence of any long-term benefit of EVT compared with supervised exercise is still inconclusive. EVT could improve walking performance in the short-term, while supervised exercise could improve walking performance more efficiently in the long-term. Combined treatment with EVT and exercise may offer the most sustainable and effective symptom relief. This paper reviews the relevant literature on the treatment of intermittent claudication, focusing on the latest EVT technologies, and outlines a strategy for achieving long-term benefits.

Attachment of Human Endothelial Cells to Polyester Vascular Grafts: Pre-Coating With Adhesive Protein Assemblies and Resistance to Short-Term Shear Stress

Cardiovascular prosthetic bypass grafts do not endothelialize spontaneously in humans, and so they pose a thrombotic risk. Seeding with cells improves their performance, particularly in small-caliber applications. Knitted tubular polyethylene-terephthalate (PET) vascular prostheses (6 mm) with commercial type I collagen (PET/Co) were modified in the lumen by the adsorption of laminin (LM), by coating with a fibrin network (Fb) or a combination of Fb and fibronectin (Fb/FN). Primary human saphenous vein endothelial cells were seeded (1.50 × 10(5)/cm2), cultured for 72 h and exposed to laminar shear stress 15 dyn/cm(2) for 40 and 120 min. The control static grafts were excluded from shearing. The cell adherence after 4 h on PET/Co, PET/Co +LM, PET/Co +Fb and PET/Co +Fb/FN was 22%, 30%, 19% and 27% of seeding, respectively. Compared to the static grafts, the cell density on PET/Co and PET/Co +LM dropped to 61% and 50%, respectively, after 120 min of flow. The cells on PET/Co +Fb and PET/Co +Fb/FN did not show any detachment during 2 h of shear stress. Pre-coating the clinically-used PET/Co vascular prosthesis with LM or Fb/FN adhesive protein assemblies promotes the adherence of endothelium. Cell retention under flow is improved particularly on fibrin-containing (Fb and Fb/FN) surfaces.