Background Arteriovenous fistulas (AVFs) for hemodialysis frequently fail to mature because of inadequate dilation or early stenosis. The pathogenesis of AVF nonmaturation may be related to ...pre-existing vascular pathologic states: medial fibrosis or microcalcification may limit arterial dilation, and intimal hyperplasia may cause stenosis. Study Design Observational study. Setting & Participants Patients with chronic kidney disease (N = 50) undergoing AVF placement. Predictors Medial fibrosis, microcalcification, and intimal hyperplasia in arteries and veins obtained during AVF creation. Outcome & Measurements AVF nonmaturation. Results AVF nonmaturation occurred in 38% of patients despite attempted salvage procedures. Preoperative arterial diameter was associated with upper-arm AVF maturation ( P = 0.007). Medial fibrosis was similar in patients with nonmaturing and mature AVFs (60% ± 14% vs 66% ± 13%; P = 0.2). AVF nonmaturation was not associated with patient age or diabetes, although both variables were associated significantly with severe medial fibrosis. Conversely, AVF nonmaturation was higher in women than men despite similar medial fibrosis in both sexes. Arterial microcalcification (assessed semiquantitatively) tended to be associated with AVF nonmaturation (1.3 ± 0.8 vs 0.9 ± 0.8; P = 0.08). None of the arteries or veins obtained at AVF creation had intimal hyperplasia. However, repeated venous samples obtained in 6 patients during surgical revision of an immature AVF showed venous neointimal hyperplasia. Limitations Single-center study. Conclusion Medial fibrosis and microcalcification are frequent in arteries used to create AVFs, but do not explain AVF nonmaturation. Unlike previous studies, intimal hyperplasia was not present at baseline, but developed de novo in nonmaturing AVFs.
Background Arteriovenous fistulas (AVFs) often fail to mature, but the mechanism of AVF nonmaturation is poorly understood. Arterial microcalcification is common in patients with chronic kidney ...disease (CKD) and may limit vascular dilatation, thereby contributing to early postoperative juxta-anastomotic AVF stenosis and impaired AVF maturation. This study evaluated whether preexisting arterial microcalcification adversely affects AVF outcomes. Study Design Prospective study. Setting & Participants 127 patients with CKD undergoing AVF surgery at a large academic medical center. Predictors Preexisting arterial microcalcification (≥1% of media area) assessed independently by von Kossa stains of arterial specimens obtained during AVF surgery and by preoperative ultrasound. Outcomes Juxta-anastomotic AVF stenosis (ascertained by ultrasound obtained 4-6 weeks postoperatively), AVF nonmaturation (inability to cannulate with 2 needles with dialysis blood flow ≥ 300 mL/min for ≥6 sessions in 1 month within 6 months of AVF creation), and duration of primary unassisted AVF survival after successful use (time to first intervention). Results Arterial microcalcification was present by histologic evaluation in 40% of patients undergoing AVF surgery. The frequency of a postoperative juxta-anastomotic AVF stenosis was similar in patients with or without preexisting arterial microcalcification (32% vs 42%; OR, 0.65; 95% CI, 0.28-1.52; P = 0.3). AVF nonmaturation was observed in 29%, 33%, 33%, and 33% of patients with <1%, 1% to 4.9%, 5% to 9.9%, and ≥10% arterial microcalcification, respectively ( P = 0.9). Sonographic arterial microcalcification was found in 39% of patients and was associated with histologic calcification ( P = 0.001), but did not predict AVF nonmaturation. Finally, among AVFs that matured, unassisted AVF maturation (time to first intervention) was similar for patients with and without preexisting arterial microcalcification (HR, 0.64; 95% CI, 0.35-1.21; P = 0.2). Limitations Single-center study. Conclusions Arterial microcalcification is common in patients with advanced CKD, but does not explain postoperative AVF stenosis, AVF nonmaturation, or AVF failure after successful cannulation.
Background Arteriovenous grafts (AVGs) are prone to neointimal hyperplasia leading to AVG failure. We hypothesized that pre-existing pathologic abnormalities of the vessels used to create AVGs ...(including venous intimal hyperplasia, arterial intimal hyperplasia, arterial medial fibrosis, and arterial calcification) are associated with inferior AVG survival. Study Design Prospective observational study. Setting & Participants Patients with chronic kidney disease undergoing placement of a new AVG at a large medical center who had vascular specimens obtained at the time of surgery (n = 76). Predictor Maximal intimal thickness of the arterial and venous intima, arterial medial fibrosis, and arterial medial calcification. Outcome & Measurements Unassisted primary AVG survival (time to first intervention) and frequency of AVG interventions. Results 55 patients (72%) underwent interventions and 148 graft interventions occurred during 89.9 years of follow-up (1.65 interventions per graft-year). Unassisted primary AVG survival was not associated significantly with arterial intimal thickness (HR, 0.72; 95% CI, 0.40-1.27; P = 0.3), venous intimal thickness (HR, 0.64; 95% CI, 0.37-1.10; P = 0.1), severe arterial medial fibrosis (HR, 0.58; 95% CI, 0.32-1.06; P = 0.6), or severe arterial calcification (HR, 0.68; 95% CI, 0.37-1.31; P = 0.3). The frequency of AVG interventions per year was associated inversely with arterial intimal thickness (relative risk RR, 1.99; 95% CI, 1.16-3.42; P < 0.001 for thickness <10 vs >25 μm), venous intimal thickness (RR, 2.11; 95% CI, 1.39-3.20; P < 0.001 for thickness <5 vs >10 μm), arterial medial fibrosis (RR, 3.17; 95% CI, 1.96-5.13; P < 0.001 for fibrosis <70% vs ≥70%), and arterial calcification (RR, 2.12; 95% CI, 1.31-3.43; P = 0.001 for <10% vs ≥10% calcification). Limitations Single-center study. Study may be underpowered to demonstrate differences in unassisted primary AVG survival. Conclusions Pre-existing vascular pathologic abnormalities in patients with chronic kidney disease may not be associated significantly with unassisted primary AVG survival. However, vascular intimal hyperplasia, arterial medial fibrosis, and arterial calcification may be associated with a decreased frequency of AVG interventions.
Recognizing the impact of the decision making by the dialysis access surgeon on the successful placement of autogenous arteriovenous hemodialysis access, the Society for Vascular Surgery assembled a ...multispecialty panel to develop practice guidelines in arteriovenous access placement and maintenance with the aim of maximizing the percentage and functionality of autogenous arteriovenous accesses that are placed. The Society commissioned the Knowledge and Encounter Research Unit of the Mayo Clinic College of Medicine, Rochester, Minnesota, to systematically review the available evidence in three main areas provided by the panel: timing of referral to access surgeons, type of access placed, and effectiveness of surveillance. The panel then formulated practice guidelines in seven areas: timing of referral to the access surgeon, operative strategies to maximize the placement of autogenous arteriovenous accesses, first choice for the autogenous access, choice of arteriovenous access when a patient is not a suitable candidate for a forearm autogenous access, the role of monitoring and surveillance in arteriovenous access management, conversion of a prosthetic arteriovenous access to a secondary autogenous arteriovenous access, and management of the nonfunctional or failed arteriovenous access. For each of the guidelines, the panel stated the recommendation or suggestion, discussed the evidence or opinion upon which the recommendation or suggestion was made, detailed the values and preferences that influenced the group's decision in formulating the relevant guideline, and discussed technical remarks related to the particular guideline. In addition, detailed information is provided on various configurations of autogenous and prosthetic accesses and technical tips related to their placement.
Abstract Objective The Kidney Disease Outcome Quality Initiative and Fistula First Breakthrough Initiative call for the indiscriminate creation of arteriovenous fistulas (AVFs) over arteriovenous ...grafts (AVGs) without providing patient-specific criteria for vascular access selection. Although the U.S. AVF rate has increased dramatically, several reports have found that this singular focus on increasing AVFs has resulted in increased AVF nonmaturation/early failure and a high prevalence of catheter dependence. The objective of this study was to determine the appropriateness of vascular access procedures in clinical scenarios constructed with combinations of relevant factors potentially influencing outcomes. Methods The RAND/UCLA Appropriateness Method was used. Accordingly, a comprehensive literature search was performed and a synthesis of results compiled. The RAND/UCLA Appropriateness Method was applied to 2088 AVF and 1728 AVG clinical scenarios with varying patient characteristics. Eleven international vascular access experts rated the appropriateness of each scenario in two rounds. On the basis of the distribution of the panelists' scores, each scenario was determined to be appropriate, inappropriate, or indeterminate. Results Panelists achieved agreement in 2964 (77.7%) scenarios; 860 (41%) AVF and 588 (34%) AVG scenarios were scored appropriate, 686 (33%) AVF and 480 (28%) AVG scenarios were scored inappropriate, and 542 (26%) AVF and 660 (38%) AVG scenarios were indeterminate. Younger age, larger outflow vein diameter, normal or obese body mass index (vs morbidly obese), larger inflow artery diameter, and higher patient functional status were associated with appropriateness of AVF creation. Older age, dialysis dependence, and smaller vein size were associated with appropriateness of AVG creation. Gender, diabetes, and coronary artery disease were not associated with AVF or AVG appropriateness. Dialysis status was not associated with AVF appropriateness. Body mass index and functional status were not associated with AVG appropriateness. To simulate the surgeon's decision-making, scenarios were combined to create situations with the same patient characteristics and both AVF and AVG options for access. Of these 864 clinical situations, 311 (36%) were rated appropriate for AVG but inappropriate or indeterminate for AVF. Conclusions The results of this study indicate that patient-specific situations exist wherein AVG is as appropriate as or more appropriate than AVF. These results provide patient-specific recommendations for clinicians to optimize vascular access selection criteria, to standardize care, and to inform payers and policy. Indeterminate scenarios will guide future research.
Central venous stenosis (CVS) is encountered frequently among hemodialysis patients. Prior ipsilateral central venous catheterization and cardiac rhythm device insertions are common risk factors, but ...CVS can also occur in the absence of this history. Chronic CVS can cause thrombosis with partial or complete occlusion of the central vein at the site of stenosis. CVS is frequently asymptomatic and identified as an incidental finding during imaging studies. Symptomatic CVS presents most commonly as an upper- or lower-extremity edema ipsilateral to the CVS. Previously unsuspected CVS may become symptomatic after placement of an ipsilateral vascular access. The likelihood of symptomatic CVS may be affected by the central venous catheter (CVC) location; CVC side; duration of CVC dependence; type, location, and blood flow of the ipsilateral access; and extent of collateral veins. Venous angiography is the gold standard for diagnosis. Percutaneous transluminal angioplasty and stent placement can improve the stenosis and alleviate symptoms, but CVS typically recurs frequently, requiring repeated interventions. Refractory symptomatic CVS may require ligation of the ipsilateral vascular access. Because no available treatment option is curative, the goal should be to prevent CVS by minimizing catheters and central vein instrumentation in patients with chronic kidney disease and dialysis patients.
Objective Arteriovenous fistulas (AVFs) are considered superior to arteriovenous grafts (AVGs) because of longer secondary patency after successful cannulation for dialysis. We evaluated whether ...access interventions before successful cannulation affect the relative longevity of AVFs and AVGs after successful use. Methods This retrospective study of a prospective database identified patients who initiated dialysis with a catheter and subsequently had a permanent access (289 AVFs and 310 AVGs) placed between January 1, 2006, and December 31, 2011, and were successfully cannulated for dialysis at a large medical center. Patients were monitored until June 30, 2014, and we evaluated the clinical outcomes (secondary patency and frequency of interventions) of the vascular accesses. Results An intervention before successful cannulation was required more frequently with AVFs than with AVGs (50.5% vs 17.7%; odds ratio, 4.74; 95% confidence interval CI, 3.26-6.86; P < .0001). Compared with AVFs that matured without interventions, those that required intervention had shorter secondary patency after successful cannulation (hazard ratio, 1.84; 95% CI, 1.30-2.60; P < .0001) and required more interventions per year after successful use (rate ratio RR, 1.81; 95% CI, 1.49-2.20; P < .0001). Similarly, AVGs that required intervention before successful cannulation had shorter secondary patency than those without prior intervention (odds ratio, 1.98; 95% CI, 1.52-4.02; P < .0001) and required more interventions per year after successful use (RR, 1.49; 95% CI, 1.27-1.74; P < .0001). AVFs requiring intervention before maturation had inferior secondary patency compared with AVGs that were cannulated without prior intervention (hazard ratio, 1.45; 95% CI, 1.08-2.01; P = .01), but required fewer annual interventions after successful use (RR, 0.57; 95% CI, 0.49-0.66; P < .0001). Conclusions The patency advantage of AVFs over AVGs is no longer evident in patients requiring an AVF intervention before successful cannulation, but the AVFs require fewer interventions after successful use.
Background Anticoagulation management is difficult in chronic kidney disease, with frequent supratherapeutic international normalized ratios (INRs ≥ 4) increasing hemorrhagic risk. We evaluated ...whether the interaction of INR and lower estimated glomerular filtration rate (eGFR) increases hemorrhage risk and whether patients with lower eGFRs experience slower anticoagulation reversal. Study Design Prospective cohort study. Setting & Participants Warfarin pharmacogenetics cohort (1,273 long-term warfarin users); warfarin reversal cohort (74 warfarin users admitted with INRs ≥ 4). Predictor eGFR, INR as time-dependent covariate, and their interaction in the pharmacogenetics cohort; eGFR in the reversal cohort. Outcomes & Measurements In the pharmacogenetics cohort, hemorrhagic (serious, life-threatening, and fatal bleeding) risk was assessed using proportional hazards regression. In the reversal cohort, anticoagulation reversal was assessed from changes in INR, warfarin and metabolite concentrations, clotting factors (II, VII, IX, and X), and PIVKA-II (protein induced by vitamin K absence or antagonist II) levels at presentation and after reversal, using linear regression and path analysis. Results In the pharmacogenetics cohort, 454 (35.7%) had eGFRs < 60 mL/min/1.73 m2 . There were 137 hemorrhages in 119 patients over 1,802 person-years of follow-up (incidence rate, 7.6 95% CI, 6.4-8.9/100 person-years). Patients with lower eGFRs had a higher frequency of INR ≥ 4 ( P < 0.001). Risk of hemorrhage was affected significantly by eGFR-INR interaction. At INR < 4, there was no difference in hemorrhage risk by eGFR (all P ≥ 0.4). At INR ≥ 4, patients with eGFRs of 30 to 44 and <30 mL/min/1.73 m2 had 2.2-fold (95% CI, 0.8-6.1; P = 0.1) and 5.8-fold (95% CI, 2.9-11.4; P < 0.001) higher hemorrhage risks, respectively, versus those with eGFRs ≥ 60 mL/min/1.73 m2 . In the reversal cohort, 35 (47%) had eGFRs < 45 mL/min/1.73 m2 . Patients with eGFRs < 45 mL/min/1.73 m2 experienced slower anticoagulation reversal as assessed by INR ( P = 0.04) and PIVKA-II level ( P = 0.008) than those with eGFRs ≥ 45 mL/min/1.73 m2. Limitations Limited sample size in the reversal cohort, unavailability of antibiotic use and urine albumin data. Conclusions Patients with lower eGFRs have differentially higher hemorrhage risk at INR ≥ 4. Moreover, because the INR reversal rate is slower, hemorrhage risk is prolonged.
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