Comparison of midterm results for the Talent and Endurant stent graft.

OBJECTIVE: Stent graft evolution is often addressed as a cause for improved outcomes of endovascular aneurysm repair for patients with an abdominal aortic aneurysm. In this study, we directly compared the midterm result of Endurant stent graft with its predecessor, the Talent stent graft (both Medtronic, Santa Rosa, Calif). METHODS: Patient treated from January 2005 to December 2010 in a single tertiary center in The Netherlands with a Talent or Endurant stent graft were eligible for inclusion. Ruptured abdominal aortic aneurysms or patients with previous aortic surgery were excluded. The primary end point was the Kaplan-Meier estimated freedom from secondary interventions. Secondary end points were perioperative outcomes and indications for secondary interventions. RESULTS: In total, 221 patients were included (131 Endurant and 90 Talent). At baseline, the median aortic bifurcation was narrower for the Endurant (30 mm vs 39 mm; P < .001). Median follow-up was 64.1 ± 37.9 months and 59.2 ± 25.3 months for Talent and Endurant, respectively. The estimated freedom from secondary interventions at 30 days, 1 year, 5 years, and 7 years was 94.3%, 89.4%, 72.2%, and 64.1% for Talent and 96.8%, 89.3%, 75.2%, and 69.2% for Endurant (P = .528). The indication for secondary interventions does differ; more patients required an intervention for a proximal neck-related complication (type Ia endoleak or migration) in the Talent group (18.2% vs 4.8%; P = .001), whereas more interventions for iliac limb stenosis were seen in the Endurant group (0.0% vs 4.8%; P = .044). In a binomial regression analysis, suprarenal angulation, infrarenal neck length, and type of stent graft were independent predictors of neck-related complications. CONCLUSIONS: Evolution from the Talent stent graft into the Endurant has resulted in significant reduction of infrarenal neck-related complications; on the other hand, iliac interventions increased. The overall midterm secondary intervention rate was comparable.

Determination of brachial artery stiffness prior to vascular access creation: reproducibility of pulse wave velocity assessment.

BACKGROUND: Despite routine ultrasound mapping of upper extremity arteries and veins, early thrombosis and nonmaturation remain frequent complications following vascular access (VA) surgery. Besides vascular diameters, brachial artery stiffness is assumed to play an important role; however, reproducibility of measurements has never been established. The purpose of this study was to determine within-session and between-session variabilities of pulse wave velocity (PWV) assessment by using ultrasonography and blood pressure registration. METHODS: Beat-to-beat changes in brachial artery diameter and pressure were obtained in 21 subjects in measurement sessions on Day 1 and Day 3. Each session consisted of three acquisitions. For each acquisition, systolic and diastolic diameter and pressure were determined and used for calculation of brachial artery PWV. Within-session variability of diameter and pressure, as well as the estimated PWV, was expressed using the intraclass correlation coefficient with corresponding coefficient of variation (CoV). Between-session variability was reported using Bland-Altman analysis in combination with CoV analysis. RESULTS: Significant agreement (P < 0.001) was obtained for all diameter and pressure measurements obtained on Day 1 and Day 3. Within-session CoV of pulse pressure, diastolic diameter and distension were 7.0, 1.6 and 18.3%, respectively. Subsequent estimation of local PWV resulted in a CoV of 10.6%. Between-session CoV was 15.1, 3.8 and 18.9% for pulse pressure, diastolic diameter and distension, respectively. For PWV estimation, this resulted in a CoV of 13.5%. CONCLUSIONS: Diameter and pressure can be recorded accurately over the cardiac cycle, and calculations of distensibility, pulse pressure and PWV show a slight to moderate degree of variation. Larger studies elaborating on interindividual differences need to determine the clinical efficacy of PWV measurements prior to VA creation.

Surgical or endovascular repair of thrombosed dialysis vascular access: is there any evidence?

INTRODUCTION: Endovascular and surgical strategies have been used to manage patients with thrombosed vascular access for hemodialysis. We analyzed the evidence to see whether endovascular or surgical treatment has the best outcome in terms of primary success rate and long-term patency. METHODS: We performed a systematic literature search of endovascular and surgical repair of thrombosed hemodialysis vascular access. The analysis included meta-analysis, randomized, and population-based studies of thrombosed arteriovenous fistulae and grafts. RESULTS: One meta-analysis and eight randomized studies on the treatment of arteriovenous graft thrombosis were identified. Studies conducted before 2002 demonstrated a significantly better primary success rate and primary and secondary patencies of surgical thrombectomy vs endovascular intervention. After 2002, similar results of both techniques have been reported. Only population-based studies on the treatment of thrombosed autogenous arteriovenous fistulae have been published, showing similar outcome of surgical and endovascular intervention in terms of primary success. The long-term primary and secondary patencies are slightly better for surgical treatment, but this concerns only forearm fistulae. CONCLUSIONS: The outcome of endovascular and surgical intervention for thrombosed vascular access is comparable, in particular for thrombosed prosthetic grafts. Surgical treatment of autogenous arteriovenous fistulae is likely to have benefit compared with endovascular means. Definitive randomized trials are needed to provide the level 1 evidence to resolve this latter issue.

Hemodialysis vascular access management in the Netherlands.

PURPOSE: In the Netherlands, 86% of patients start renal replacement therapy with chronic intermittent hemodialysis (HD). Guidelines do indicate predialysis care and maintenance of a well-functioning vascular access (VA) as critical issues in the management of the renal failure patient. Referral to the surgeon and time to VA creation are important determinants of the type and success of the VA and HD treatment. METHODS AND RESULTS: Data from a national questionnaire showed that time from referral to the surgeon and actual access creation is <4 weeks in 43%, 4 to 8 weeks in 30% and >8 weeks in 27% of the centers. Preoperative ultrasonography and postoperative access flowmetry are the diagnostic methods in the majority of centers (98%). Most facilities perform rope-ladder cannulation with occasionally the buttonhole technique for selected patients in 87% of the dialysis units. Endovascular intervention for thrombosis is practiced by 13%, surgical thrombectomy by 21% and either endovascular or surgery by 66% of the centers. Weekly multidisciplinary meetings are organized in 57% of the units. Central vein catheters are inserted by radiologists (36%), nephrologists and surgeons (32%). CONCLUSIONS: We conclude that guidelines implementation has been successful in particular regarding issues as preoperative patient assessment for VA creation and postoperative surveillance in combination with (preemptive) endovascular intervention, leading to very acceptable VA thrombosis rates.

The benefit of non contrast-enhanced magnetic resonance angiography for predicting vascular access surgery outcome: a computer model perspective.

INTRODUCTION: Vascular access (VA) surgery, a prerequisite for hemodialysis treatment of end-stage renal-disease (ESRD) patients, is hampered by complication rates, which are frequently related to flow enhancement. To assist in VA surgery planning, a patient-specific computer model for postoperative flow enhancement was developed. The purpose of this study is to assess the benefit of non contrast-enhanced magnetic resonance angiography (NCE-MRA) data as patient-specific geometrical input for the model-based prediction of surgery outcome. METHODS: 25 ESRD patients were included in this study. All patients received a NCE-MRA examination of the upper extremity blood vessels in addition to routine ultrasound (US). Local arterial radii were assessed from NCE-MRA and converted to model input using a linear fit per artery. Venous radii were determined with US. The effect of radius measurement uncertainty on model predictions was accounted for by performing Monte-Carlo simulations. The resulting flow prediction interval of the computer model was compared with the postoperative flow obtained from US. Patients with no overlap between model-based prediction and postoperative measurement were further analyzed to determine whether an increase in geometrical detail improved computer model prediction. RESULTS: Overlap between postoperative flows and model-based predictions was obtained for 71% of patients. Detailed inspection of non-overlapping cases revealed that the geometrical details that could be assessed from NCE-MRA explained most of the differences, and moreover, upon addition of these details in the computer model the flow predictions improved. CONCLUSIONS: The results demonstrate clearly that NCE-MRA does provide valuable geometrical information for VA surgery planning. Therefore, it is recommended to use this modality, at least for patients at risk for local or global narrowing of the blood vessels as well as for patients for whom an US-based model prediction would not overlap with surgical choice, as the geometrical details are crucial for obtaining accurate flow predictions.

Non contrast-enhanced MRA versus ultrasound blood vessel assessment to determine the choice of hemodialysis vascular access.

PURPOSE: The aim of this work was to establish the relationship between traditional blood vessel mapping for vascular access (VA) creation by B-mode ultrasound (US) and novel non contrast-enhanced magnetic resonance angiography (NCE-MRA), and to study the potential influence of the diameter assessment technique on the choice of hemodialysis vascular access. METHODS: A total of 27 end-stage renal-disease patients were included. They received routine US and a NCE-MRA examination of the upper extremity. Diameters were measured manually on US and semi-automatically on NCE-MRA. These measurements were statistically compared for the arteries and veins and for each measurement location. Furthermore, sensitivity and specificity of both modalities to predict VA location was investigated by comparison with an experienced surgeon. This analysis gave insight into the potential influence of vessel mapping modality on decision-making. RESULTS: Comparison of NCE-MRA with US for the arteries and veins, demonstrated a bias of 9% (limits -33%-78%) and 38% (limits -36%-198%), respectively. Statistically significant differences between the modalities on the individual locations were mainly found for the venous locations. The sensitivity and specificity for US to predict VA location was 1.0 and 0.74, respectively, while for NCE-MRA this was 0.88 and 0.39, respectively. CONCLUSIONS: The results obtained indicate that extreme caution should be exercised when replacing one diameter measurement modality with the other. A further need exists to improve both vessel mapping protocols to obtain a geometric description of the upper extremity vasculature regardless of acquisition modality.

Patient-specific computational modeling of upper extremity arteriovenous fistula creation: its feasibility to support clinical decision-making.

INTRODUCTION: Inadequate flow enhancement on the one hand, and excessive flow enhancement on the other hand, remain frequent complications of arteriovenous fistula (AVF) creation, and hamper hemodialysis therapy in patients with end-stage renal disease. In an effort to reduce these, a patient-specific computational model, capable of predicting postoperative flow, has been developed. The purpose of this study was to determine the accuracy of the patient-specific model and to investigate its feasibility to support decision-making in AVF surgery. METHODS: Patient-specific pulse wave propagation models were created for 25 patients awaiting AVF creation. Model input parameters were obtained from clinical measurements and literature. For every patient, a radiocephalic AVF, a brachiocephalic AVF, and a brachiobasilic AVF configuration were simulated and analyzed for their postoperative flow. The most distal configuration with a predicted flow between 400 and 1500 ml/min was considered the preferred location for AVF surgery. The suggestion of the model was compared to the choice of an experienced vascular surgeon. Furthermore, predicted flows were compared to measured postoperative flows. RESULTS: Taken into account the confidence interval (25(th) and 75(th) percentile interval), overlap between predicted and measured postoperative flows was observed in 70% of the patients. Differentiation between upper and lower arm configuration was similar in 76% of the patients, whereas discrimination between two upper arm AVF configurations was more difficult. In 3 patients the surgeon created an upper arm AVF, while model based predictions allowed for lower arm AVF creation, thereby preserving proximal vessels. In one patient early thrombosis in a radiocephalic AVF was observed which might have been indicated by the low predicted postoperative flow. CONCLUSIONS: Postoperative flow can be predicted relatively accurately for multiple AVF configurations by using computational modeling. This model may therefore be considered a valuable additional tool in the preoperative work-up of patients awaiting AVF creation.

Ultrasound-guided central venous catheter placement by surgical trainees: a safe procedure?

BACKGROUND: Central venous catheters (CVCs) are widely used to create a temporary or long-term access to the central venous system. A variety of treatments require a functional central venous access, including hemodialysis, administration of drugs, plasmapheresis and parenteral nutrition. The aim of this study was to evaluate the results of CVC placement performed by surgical trainees, according to a strict protocol of ultrasound-guided puncture and fluoroscopy-guided catheter insertion in a large teaching hospital in an outpatient setting. METHODS: Between 1 January 2006 and 31 December 2008, 539 CVCs were placed, of which 486 were primary inserted by surgical trainees. All placements were ultrasound- and fluoroscopy-guided. After every placement operators recorded type of catheter, type of anesthesia, subcutaneous tunneling, technique of insertion and complications. RESULTS: The study population consisted of 52% males. Access sites of CVCs were the internal jugular vein (91%), subclavian vein (5%) and other veins (3%). Technical success rate was 96.5%. Complication rate was 8.4%, of which 93% were arterial punctures. Pneumothorax occurred in three patients. CONCLUSIONS: CVC placement by surgical trainees is a safe procedure when using a strict protocol of ultrasound-guided vessel puncture and fluoroscopic-guided catheter placement.