Early Predictors of Arteriovenous Fistula Maturation: A Novel Perspective on an Enduring Problem.

BACKGROUND: Preoperative ultrasound mapping is routinely used to select vessels meeting minimal threshold diameters for surgical arteriovenous fistula (AVF) creation but fails to improve AVF maturation rates. This suggests a need to reassess the preoperative ultrasound criteria used to optimize AVF maturation. METHODS: We retrospectively identified 300 catheter-dependent patients on hemodialysis with a new AVF created between 2010 and 2016. We then evaluated the associations of preoperative vascular measurements and hemodynamic factors with unassisted AVF maturation (successful use for dialysis without prior intervention) and overall maturation (successful use with or without prior intervention). Multivariable logistic regression was used to identify preoperative factors associated with unassisted and overall AVF maturation. RESULTS: Unassisted AVF maturation associated with preoperative arterial diameter (adjusted odds ratio [aOR], 1.50 per 1-mm increase; 95% confidence interval [95% CI], 1.23 to 1.83), preoperative systolic BP (aOR, 1.16 per 10-mm Hg increase; 95% CI, 1.05 to 1.28), and left ventricular ejection fraction (aOR, 1.07 per 5% increase; 95% CI, 1.01 to 1.13). Overall AVF maturation associated with preoperative arterial diameter (aOR, 1.36 per 1-mm increase; 95% CI, 1.10 to 1.66) and preoperative systolic BP (aOR, 1.17; 95% CI, 1.06 to 1.30). Using receiver operating curves, the combination of preoperative arterial diameter, systolic BP, and left ventricular ejection fraction was fairly predictive of unassisted maturation (area under the curve, 0.69). Patient age, sex, race, diabetes, vascular disease, obesity, and AVF location were not associated with maturation. CONCLUSIONS: Preoperative arterial diameter may be an under-recognized predictor of AVF maturation. Further study evaluating the effect of preoperative arterial diameter and other hemodynamic factors on AVF maturation is needed.

Postoperative Ultrasound, Unassisted Maturation, and Subsequent Primary Patency of Arteriovenous Fistulas.

BACKGROUND AND OBJECTIVES: Postoperative ultrasound is commonly used to assess arteriovenous fistula (AVF) maturation for hemodialysis, but its utility for predicting unassisted AVF maturation or primary AVF patency for hemodialysis has not been well defined. This study assessed the predictive value of postoperative AVF ultrasound measurements for these clinical AVF outcomes. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We queried a prospective vascular access database to identify 246 patients on catheter-dependent hemodialysis who underwent AVF creation between 2010 and 2016 and obtained a postoperative ultrasound within 90 days. Multivariable logistic regression was used to evaluate the association of clinical characteristics and postoperative ultrasound measurements with unassisted AVF maturation. A receiver operating characteristic curve estimated the predictive value of these factors for unassisted AVF maturation. Finally, multivariable survival analysis was used to identify factors associated with primary AVF patency in patients with unassisted AVF maturation. RESULTS: Unassisted AVF maturation occurred in 121 out of 246 patients (49%), assisted maturation in 55 patients (22%), and failure to mature in 70 patients (28%). Using multivariable logistic regression, unassisted AVF maturation was associated with AVF blood flow (odds ratio [OR], 1.30; 95% confidence interval [95% CI], 1.18 to 1.45 per 100 ml/min increase; P<0.001), forearm location (OR, 0.37; 95% CI, 0.08 to 1.78; P=0.21), presence of stenosis (OR, 0.45; 95% CI, 0.23 to 0.88; P=0.02); AVF depth (OR, 0.88; 95% CI, 0.77 to 1.00 per 1 mm increase; P=0.05), and AVF location interaction with depth (OR, 0.50; 95% CI, 0.28 to 0.84; P=0.02). The area under the receiver operating characteristic curve, using all these factors, was 0.84 (95% CI, 0.79 to 0.89; P<0.001). Primary AVF patency in patients with unassisted maturation was associated only with AVF diameter (hazard ratio, 0.84; 95% CI, 0.76 to 0.94 per 1 mm increase; P=0.002). CONCLUSIONS: Unassisted AVF maturation is predicted by AVF blood flow, location, depth, and stenosis. AVF patency after unassisted maturation is predicted only by the postoperative AVF diameter.

The Clinical and Economic Effect of Vascular Access Selection in Patients Initiating Hemodialysis with a Catheter.

Patients in the United States frequently initiate hemodialysis with a central venous catheter (CVC) and subsequently undergo placement of a new arteriovenous fistula (AVF) or arteriovenous graft (AVG). Little is known about the clinical and economic effects of initial vascular access choice. We identified 479 patients starting hemodialysis with a CVC at a large medical center (during 2004-2012) who subsequently had an AVF (n=295) or AVG (n=105) placed or no arteriovenous access (CVC group, n=71). Compared with patients receiving an AVG, those receiving an AVF had more frequent surgical access procedures per year (1.01 [95% confidence interval, 0.95 to 1.08] versus 0.62 [95% confidence interval, 0.55 to 0.70]; P<0.001) but a similar frequency of percutaneous access procedures per year. Patients receiving an AVF had a higher median annual cost (interquartile range) of surgical access procedures than those receiving an AVG ($4857 [$2523-$8835] versus $2819 [$1411-$4274]; P<0.001), whereas the annual cost of percutaneous access procedures was similar in both groups. The AVF group had a higher median overall annual access-related cost than the AVG group ($10,642 [$5406-$19,878] versus $6810 [$3718-$13,651]; P=0.001) after controlling for patient age, sex, race, and diabetes. The CVC group had the highest median annual overall access-related cost ($28,709 [$11,793-$66,917]; P<0.001), largely attributable to the high frequency of hospitalizations due to catheter-related bacteremia. In conclusion, among patients initiating hemodialysis with a CVC, the annual cost of access-related procedures and complications is higher in patients who initially receive an AVF versus an AVG.

Predictors of Initiation for Predialysis Arteriovenous Fistula.

BACKGROUND AND OBJECTIVES: The optimal timing of predialysis arteriovenous fistula surgery remains uncertain. We evaluated factors associated with hemodialysis initiation in patients undergoing predialysis arteriovenous fistula surgery and derived a model to predict future initiation of dialysis. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Our study retrospectively identified 308 patients undergoing predialysis arteriovenous fistula creation at a large medical center in 2006-2012 to determine whether they initiated hemodialysis. Multiple variable logistic regression analyzed which demographic and clinical factors predicted initiation of dialysis within 2 years of arteriovenous fistula surgery. A receiver operating characteristic area under the curve was used to quantify the predictive value of preoperative factors on the likelihood of initiating hemodialysis within 2 years. RESULTS: Overall, hemodialysis was initiated within 6 months, 1 year, and 2 years in 119 (39%), 175 (57%), and 211 (68%) patients, respectively. Using multiple variable logistic regression, four factors were associated with hemodialysis initiation at 2 years: eGFR at access surgery (odds ratio, 0.45; 95% confidence interval, 0.31 to 0.64 per 5 ml/min per 1.73 m2; P<0.001), diabetes (odds ratio, 2.51; 95% confidence interval, 1.22 to 5.15; P=0.003), GFR trajectory (odds ratio, 1.54; 95% confidence interval, 1.09 to 2.17 per 3 ml/min per 1.73 m2 per year; P=0.01), and spot urine protein-to-creatinine ratio (odds ratio, 1.39; 95% confidence interval, 1.14 to 1.71 per 1 U; P<0.001). eGFR alone had a moderate predictive value for dialysis initiation (area under the curve =0.69; 95% confidence interval, 0.63 to 0.76; P<0.001), whereas the full model had a higher predictive value (area under the curve =0.83; 95% confidence interval, 0.77 to 0.88; P<0.001). CONCLUSIONS: The likelihood of initiating hemodialysis within 2 years of predialysis arteriovenous fistula surgery is associated with eGFR at access surgery, diabetes, GFR trajectory, and magnitude of proteinuria. The combined use of all four variables improves the ability to predict future hemodialysis compared with the use of eGFR alone.

Outcomes of arteriovenous fistulas and grafts with or without intervention before successful use.

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.

Preoperative arterial microcalcification and clinical outcomes of arteriovenous fistulas for hemodialysis.

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 ≥ 300mL/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.

Natural history of tunneled dialysis catheters placed for hemodialysis initiation.

PURPOSE: More than 80% of hemodialysis recipients in the United States initiate hemodialysis with a tunneled dialysis catheter (TDC). Published data on TDC outcomes are based on a case mix of prevalent and incident TDCs. The present study analyzes factors affecting patency and complications of first TDCs placed in a large cohort of incident hemodialysis recipients. MATERIALS AND METHODS: A prospective, computerized vascular access database was retrospectively queried to identify 472 patients receiving a first-ever TDC. Multiple-variable survival analysis was used to identify clinical parameters affecting TDC patency (from placement to nonelective removal) and infection (from placement to first episode of catheter-related bacteremia [CRB]). RESULTS: The median patency of all TDCs was 202 days. Left-sided placement of TDCs was the only variable associated with inferior TDC patency (hazard ratio, 1.98; 95% confidence interval, 1.39-2.81; P < .0001). The 6-month TDC patency rate was 37% for left internal jugular vein (LIJV) catheters, versus 54% for right internal jugular vein (RIJV) catheters. The 1-year patency rate was 6% for LIJV catheters, versus 35% for RIJV catheters. Catheter patency was not associated with patient age, sex, race, hypertension, diabetes, coronary artery disease, peripheral vascular disease, cerebrovascular disease, or heart failure. The median time to the first episode of CRB was 163 days. None of the clinical variables was associated with TDC infection. CONCLUSIONS: TDCs are plagued by high rates of infection. RIJV TDCs should be used preferentially to maximize catheter patency.

Long-term outcomes of arteriovenous thigh grafts in hemodialysis patients: a comparison with tunneled dialysis catheters.

BACKGROUND AND OBJECTIVE: Arteriovenous thigh grafts are a potential vascular access option in hemodialysis patients who have exhausted all upper-limb sites. This study compared the outcomes of thigh grafts with outcomes obtained with dialysis catheters. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: A prospective vascular access database was queried to identify 209 thigh grafts placed from January 1, 2003, to June 30, 2011. The following were calculated: secondary graft survival (from graft creation to permanent failure), assisted primary graft survival (from graft creation to first thrombosis), and infection-free graft survival (from graft creation to first graft infection). Graft outcomes were compared with those observed with 472 tunneled internal jugular dialysis catheters. RESULTS: The median duration of patient follow-up was 340 days for grafts and 91 days for catheters. The surgical technical failure rate of thigh grafts was 8.1% and was higher in patients with vascular disease (hazard ratio [HR], 2.94; 95% confidence interval [CI], 1.07-8.04; P=0.03). Secondary and assisted primary graft survival rates at 1, 2, and 5 years were 62%, 54%, and 38% and 38%, 27%, and 17%, respectively. Infection-free graft survival rates at 1, 2, and 5 years were 79%, 73%, and 61%. Secondary survival was much worse for dialysis catheters than thigh grafts (HR, 4.44; 95% CI, 3.65-5.22; P<0.001). Likewise, infection-free survival was far worse for catheters than for thigh grafts (HR, 3.77; 95% CI, 2.80-4.82; P<0.001). CONCLUSIONS: Thigh grafts are a viable vascular option in patients who have exhausted upper-extremity options. Outcomes with thigh grafts are superior to those obtained with dialysis catheters.

Association of hemodialysis central venous catheter use with ipsilateral arteriovenous vascular access survival.

BACKGROUND: Central venous catheters frequently are used for hemodialysis vascular access while patients await placement and maturation of an arteriovenous fistula or graft. Catheters may cause central vein stenosis, which can adversely affect vascular access outcomes. We compared vascular access outcomes in patients with a history of ipsilateral and contralateral dialysis catheters. STUDY DESIGN: Retrospective analysis of a prospective computerized vascular access database. SETTING & PARTICIPANTS: Patients at a large medical center who initiated hemodialysis therapy with a catheter and subsequently received a fistula (n = 233) or graft (n = 89). PREDICTOR: History of central venous catheter placement ipsilateral versus contralateral to the arteriovenous fistula or graft. OUTCOME & MEASUREMENTS: Primary access failure (access never suitable for dialysis) and cumulative access survival (time from successful cannulation until permanent access failure). RESULTS: For patients receiving a fistula, the primary failure rate was similar for those with ipsilateral and contralateral catheters (50% vs 53%; HR, 0.94; 95% CI, 0.71-1.26; P = 0.7), and time to fistula maturation was similar (101 ± 41 vs 107 ± 39 days; P = 0.5). However, cumulative fistula survival was inferior in patients with ipsilateral catheters (HR, 2.48; 95% CI, 1.33-7.33; P = 0.009). For patients receiving a graft, the primary failure rate was similar for those with ipsilateral and contralateral catheters (35% vs 38%; HR, 0.92; 95% CI, 0.49-1.73; P = 0.8), but cumulative graft survival tended to be shorter with ipsilateral catheters (HR, 2.04; 95% CI, 0.92-5.38; P = 0.07). LIMITATIONS: Retrospective analysis, single medical center. CONCLUSIONS: The primary failure rate of fistulas and grafts is not affected by the presence of an ipsilateral catheter. However, cumulative access survival is inferior in patients with prior ipsilateral catheters. Avoidance of ipsilateral catheters may improve long-term vascular access survival.

Arteriovenous graft placement in predialysis patients: a potential catheter-sparing strategy.

BACKGROUND: When predialysis patients are deemed unsuitable candidates for an arteriovenous fistula, current guidelines recommend waiting until just before or after initiation of dialysis therapy before placing a graft. This strategy may increase catheter use when these patients start dialysis therapy. We compared the outcomes of patients whose grafts were placed before and after dialysis therapy initiation. STUDY DESIGN: Retrospective analysis of a prospective computerized vascular access database. SETTING & PARTICIPANTS: Patients with chronic kidney disease receiving their first arteriovenous graft (n = 248) at a large medical center. PREDICTOR: Timing of graft placement (before or after initiation of dialysis therapy). OUTCOME & MEASUREMENTS: Primary graft failure, cumulative graft survival, catheter dependence, and catheter-related bacteremia. RESULTS: The first graft was placed predialysis in 62 patients and postdialysis in 186 patients. Primary graft failure was similar for pre- and postdialysis grafts (20% vs 24%; P = 0.5). Median cumulative graft survival was similar for pre- and postdialysis grafts (365 vs 414 days; HR, 1.22; 95% CI, 0.81-1.98; P = 0.3). Median duration of catheter dependence after graft placement in the postdialysis group was 48 days and was associated with 0.63 (95% CI, 0.48-0.79) episodes of catheter-related bacteremia per patient. LIMITATIONS: Retrospective analysis, single medical center. CONCLUSION: Grafts placed predialysis have primary failure rates and cumulative survival similar to those placed after starting dialysis therapy. However, postdialysis graft placement is associated with prolonged catheter dependence and frequent bacteremia. Predialysis graft placement may decrease catheter dependence and bacteremia in selected patients.

Statin therapy is not associated with improved vascular access outcomes.

BACKGROUND AND OBJECTIVES: Neointimal hyperplasia is the major cause of vascular access failure in hemodialysis patients. Statins reduce neointimal hyperplasia in experimental models, which may reduce access failure. The study presented here evaluated whether vascular access outcomes are superior in patients receiving statin therapy than in those not on statins. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: A prospective computerized vascular access database was retrospectively queried to determine the access outcomes of 601 patients receiving an upper-arm fistula or graft at a single large dialysis center. RESULTS: Primary fistula failure was observed in 37% of patients on statin therapy versus 38% not on statin therapy. Primary graft failure occurred in 20% of patients on statin therapy versus 14% not on statin therapy. A multiple variable logistic regression analysis including statin use, diabetes, coronary artery disease, peripheral artery disease, sex, and age found that only sex predicted primary fistula failure and graft failure. After excluding primary failures, cumulative fistula survival was similar for patients with or without statin therapy (hazard ratio [HR] 1.26; 95% confidence interval [CI] 0.76 to 2.16). Likewise, cumulative graft survival was similar for statin therapy versus no statin therapy (HR 0.88; 95% CI 0.59 to 1.32). Using a multivariable survival analysis model to predict cumulative fistula survival, only age predicted fistula failure (HR 1.21 per decade; 95% CI 1.02 to 1.44). None of the variables in this model predicted cumulative graft survival. CONCLUSIONS: Statin therapy is not associated with improved fistula or graft outcomes in patients with chronic kidney disease.

Temporal bacterial diversity associated with metal-contaminated river sediments.

The temporal activity, abundance and diversity of microbial communities were evaluated across a metal-contamination gradient around a Superfund site in Montana. In order to analyze short-term variability, samples were collected from six sites on four occasions over 12 months. Measurements of community activity, diversity and richness, quantified by dehydrogenase activity and through denaturant gradient gel electrophoresis (DGGE), respectively, were higher at contaminated sites adjacent to the smelter, relative to reference sites. 16S rRNA gene copy numbers, measured by quantitative PCR, showed seasonal variability, yet were generally higher within polluted sediments. Jaccard similarity coefficients of DGGE profiles, found sites to cluster based primarily on geographical proximity rather than geochemical similarities. Intra-site clustering of the most polluted sites also suggests a stable metal-tolerant community. Sequences from DGGE-extracted bands were predominantly Beta and Gammaproteobacteria, although the communities at all sites generally maintained a diverse phylogeny changing in composition throughout the sampling period. Spearman's rank correlations analysis found statistically significant relationships between community composition and organic carbon (r-value = 0.786) and metals (r-values As = 0.65; Cu = 0.63; Zn = 0.62). A diverse and abundant community at the most polluted site indicates that historical contamination selects for a metal-resistant microbial community, a finding that must be accounted for when using the microbial community within ecosystem monitoring studies. This study highlights the importance of using multiple time-points to draw conclusions on the affect of metal contamination.

Outcomes of brachiocephalic fistulas, transposed brachiobasilic fistulas, and upper arm grafts.

BACKGROUND AND OBJECTIVES: An upper arm vascular access is often placed in patients with a failed forearm fistula or with vessels unsuitable for a forearm fistula. The aim of this study was to compare the outcomes of three upper arm access types: brachiocephalic fistulas, transposed brachiobasilic fistulas, and grafts. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: A prospective, computerized access database was queried retrospectively to identify the clinical outcomes of upper arm accesses placed in 678 patients at a large dialysis center, including 322 brachiocephalic fistulas, 67 brachiobasilic fistulas, and 289 grafts. RESULTS: Primary access failures were less common for brachiobasilic fistulas and grafts compared with brachiocephalic fistulas (18%, 15%, and 38%; hazard ratio of brachiocephalic fistulas versus brachiobasilic fistulas 2.76; 95% confidence interval 1.41 to 5.38; P < 0.003). For the subset of patients receiving a brachiocephalic fistula, a multiple variable logistic regression analysis including age, sex, race, diabetes, coronary artery disease, peripheral vascular disease, cerebrovascular disease, prior access, surgeon, arterial diameter, and venous diameter found that only vascular diameters predicted primary failure (P < 0.001). When primary failures were excluded, cumulative access survival was similar for brachiobasilic and brachiocephalic fistulas, but superior to that of grafts. Total access interventions per year were lower for brachiobasilic and brachiocephalic fistulas than for grafts (0.84, 0.82, and 1.87, respectively, P < 0.001). CONCLUSIONS: Transposed brachiobasilic fistulas may be preferred, due to (1) a lower primary failure rate (similar to grafts), and (2) a lower intervention rate (similar to brachiocephalic fistulas). However, this advantage must be balanced against the more complex surgery.