Correlates of vascular access occlusion in hemodialysis

The association of long-term blood pressure variability with hemodialysis access thrombosis

Background

Blood pressure variability (BPV) is an important risk factor for cardiovascular events in hemodialysis patients. We sought to determine the impact of BPV on hemodialysis access thrombosis.

Methods

We enrolled 1,011 prevalent hemodialysis patients from 12 hemodialysis centers since January 2018 and followed them until December 2020. Predialysis blood pressure (BP) was assessed at 12-week intervals. The coefficient of variation derived from 36 consecutive BP measurements was used as the metric for variability. The primary outcome was incident hemodialysis access thrombosis. Linear regression models were used to assess factors associated with BPV at baseline. Kaplan-Meier curves of the time until vascular access events were drawn and log-rank tests were calculated. Cox proportional hazards models were performed to assess the association of BPV with incident vascular access events.

Results

The average coefficient of variance for systolic BPV was 10.9%. BPV was associated with age, body mass index, mean BP, diabetes, coronary and peripheral artery disease, history of access dysfunction, graft access, intradialytic hypotension, and use of antihypertensive medications. There were 194 access thrombosis events and 451 access stenosis events during a median follow-up period of 30 months. After adjustment of potential confounding factors, BPV was associated with increased risk of access thrombosis [hazard ratio = 1.27, 95% confidence interval (CI), 1.18–1.44, per 1 standard deviation increase in BPV]. The patients in the highest BPV quartile had 2.45 times the risk of thrombosis (CI, 1.62–3.70). The association was independent of average BP, intradialytic hypotension, and comorbidities. Similar trends of association were found in the subgroups analyzed. Comparative analysis using a time-varying variable model and different metrics of BPV showed consistent results.

Conclusion

Our findings underscored the impact of BP fluctuation on vascular access thrombosis.

Influence of intradialytic systolic blood pressure changes on arteriovenous access thrombosis in maintenance hemodialysis patients

BACKGROUND

Arteriovenous access (AV) thrombosis is an important and preventable problem amongst chronic hemodialysis (HD) patients. Systolic blood pressure (SBP) fluctuation relates to higher cardiovascular mortality amongst these patients. We proposed there is a close relation between SBP changes and arteriovenous (AV) access thrombosis. We also determined other risk factors and biochemical parameters related to AV access failure.

METHODS

50 HD patients with thrombosis and 50 HD patients without thrombosis were included in the study. Odds ratios and 95% confidence intervals were estimated with multivariate-adjusted logistic regression models to determine the association between potential thrombosis-related risk factors and thrombosis risk.

RESULTS

Elder adults, women, and patients with AV grafts, lower intradialytic SBP and higher SBP variations during HD sessions had higher incidence of AV access thrombosis. AV access infection and decreased blood flow (BF) velocity were associated with an increased incidence of thrombotic events, whereas the use of anti-thrombotic agents was associated with a decreased incidence of thrombotic events. Further, anaemia, hypoalbuminemia, hyperlipidemia, and impaired mineral metabolism parameters were also found to be associated with AV access thrombosis.

CONCLUSIONS

Close monitoring and management of intradialytic hypotension and SBP fluctuation in every HD session are important. Some important and novel modifiable risk factors related to AV access thrombosis were identified in this study (eg, AV access infection, decreased BF and abnormal biochemical parameters, etc). Earlier surveillance and modification of these risk factors is crucial to prevent AV access failure in HD patients.

The effects of preoperative blood pressure on early failure rate of distal arteriovenous fistulas for hemodialysis access

INTRODUCTION

The first choice of vascular access for hemodialysis in patients with end-stage renal disease is a distal radiocephalic arteriovenous fistula (AVF). Early failure rates for these AVFs vary from 10% to 53%. The effects of predialysis hypotension on failure of AVFs have been described in the literature. Weather lower blood pressures affect early AVF failure has not been extensively studied. We conducted this study to evaluate the effects of preoperative blood pressures on early AVF failure.

METHODS

Ours was a prospective observational study over a period of 2 years that included 224 patients who underwent distal radiocephalic AVF creation. Only those patients were included whose fistulas were made by surgeons with an experience of greater than five cases. The systolic, diastolic, and mean arterial pressures (MAPs) were recorded preoperatively. Early failure was defined as failure to achieve vascular access from the fistula within first 4 months of its creation.

FINDINGS

The overall early failure rate was 27.7%. Early failure was more common in females and diabetic patients. The systolic, diastolic, and MAPs were significantly lower in patients with early failure (P < 0.05). In a multivariable adjusted analysis, lower preoperative diastolic and MAPs were predictors for early failure of distal radiocephalic AVF.

DISCUSSION

Our study shows that patients with early failure of AVFs have lower preoperative blood pressure. A larger study is required to substantiate our findings and define target preoperative blood pressure for AVF creation.

Significant association of anti-platelet factor 4/heparin antibody with cardiovascular disease in hemodialysis patients: a longitudinal 7-year study

BACKGROUND

Hemodialysis patients have a high incidence of anti-platelet factor 4/heparin antibody (PF4-H Ab) and are at a high risk of cardiovascular disease. This study determines the association between PF4-H Ab and cardiovascular events including coronary artery disease (CAD), ischemic stroke (IS), and native arteriovenous fistula thrombosis (AVFT), in a longitudinal 7-year follow-up.

PATIENTS AND METHODS

84 hemodialysis patients were enrolled. Data collection included chart reviews and assessments of laboratory records. PF4-H Ab was evaluated by ELISA and a titer ≥ 0.4 was defined to have PF4-H Ab.

RESULTS

30 patients were PF4-H Ab positive, 30 patients had CAD, 29 patients had IS, and 43 patients had AVFT. In Cox proportional hazard regression analysis, PF4-H Ab (HR 2.72, p = 0.01) was a significant risk factor for CAD. Age (HR 1.06, p = 0.003), PF4-H Ab (HR 4.53, p < 0.001), 7-year averaged serum phosphate levels (HR 0.53, p = 0.012), and 7-year averaged blood platelet count (HR 1.01, p = 0.029) were risk factors for IS. Age (HR 1.03, p = 0.047), PF4-H Ab (HR 3.57, p < 0.001), and 7-year averaged serum triglyceride levels (HR 1.01, p = 0.005) were risk factors for AVFT. In PF4-H Ab-positive groups, thrombocytopenia was not associated with CAD, IS, and AVFT by Fisher's test analysis.

CONCLUSION

This study reveals that PF4-H Ab is a risk factor for developing CAD, IS, and AVFT among hemodialysis patients.

Factors Influencing Arteriovenous Fistula Dysfunction in Japanese Patients on Chronic Hemodialysis

Arteriovenous fistula dysfunction is a constant problem in chronic hemodialysis patients. We investigated the factors influencing fistula dysfunction in 184 patients on chronic hemodialysis. Stepwise regression analysis and Cox proportional hazards model were used to assess the relationship between fistula dysfunction and age, sex, duration of hemodialysis, diabetes mellitus, hematocrit, serum creatinine, blood urea nitrogen, KW, prothrombin time, blood pressure, anticoagulant therapy, dose of erythropoietin, calcium channel blocker therapy, and angiotensin-converting enzyme inhibitor therapy. Fistula dysfunction showed a significant relationship with a low systolic blood pressure, a low hematocrit, the presence of diabetes mellitus, and angiotensin-converting enzyme inhibitor therapy. These results suggested that treatment with angiotensin-converting enzyme inhibitors may help to prevent fistula dysfunction.

Survival of Arteriovenous Fistula for Dialysis at Different Centers in the North of England

Background

Renal failure patients rely on their vascular access for hemodialysis. Surgery for construction of arteriovenous fistulae is provided by a range of specialists. The aim of this review was to assess the survival of arteriovenous fistulae for hemodialysis patients in different centers of Northern England.

Methods

Data was collected on 473 hemodialysis patients in the North of England. Risk factors for failure were determined for each patient (age, sex, diabetes), together with their current mode of dialysis and history of surgical access procedures. This was expressed against their duration of dialysis. The dialysis units were then compared for fistula survival using the Kaplan Meier method.

Results

68.3% (323) patients were dialysed through via arteriovenous fistulae and 31.7% (150) via neck line. Overall fistula survival rates were 85.1% at 1 year, 82.5% at 2 years and 72.7% at 3 years. The best 1 year survival was 91.6% and worst 76.1%. These were 74.4% and 53.1% at 5 years and 74.4% and 29.5% at 10 years; these differences were highly statistically significant (p=0.0033).

Conclusion

Though graft survival is affected by many things, surgical training in access surgery is not mandatory and a review of surgical practice is urgently needed.

Efficacy of statin on vascular access patency in diabetic hemodialysis patients

INTRODUCTION

An effective approach to prevent hemodialysis vascular access dysfunction is still unclear despite previous studies, which have shown conflicting results of several drugs on vascular access outcomes. In this study, we focused on diabetic hemodialysis patients with native arteriovenous fistula and evaluated the impact of statin treatment on vascular access patency.

METHODS

A retrospective cohort study of 268 consecutive patients who newly started hemodialysis due to diabetic nephropathy between January 2011 and December 2013 at Japan Community Health Care Organization Sendai Hospital was performed and the patients were followed for two years. The primary outcome was vascular access dysfunction. Effect of statin treatment was examined using Kaplan Meier analysis and Cox proportional hazard, after adjusting for covariates.

RESULTS

The mean follow-up period was 426.7 days, and 117 (52.2%) patients developed vascular access dysfunction. The two-year patency rate was 55.0% among statin users and 36.1% in non-users. Vascular access survival period was significantly longer among statin users (log-rank test, p = 0.004). In multivariable analysis, statin treatment is significantly associated with better vascular access outcomes, in which the hazard ratio was 0.71 (95% CI, 0.52 to 0.97; p = 0.028) in the unadjusted model and 0.63 (95% CI, 0.45 to 0.88; p = 0.007) after adjustment for covariates.

CONCLUSIONS

Statin treatment could be associated with improved vascular access dysfunction among diabetic hemodialysis patients.

A novel factor for primary arteriovenous fistula failure: hyperinsulinism

INTRODUCTION

Dysfunction of vascular access is an important reason of morbidity for dialysis patients and it is a major factor affecting the economical burden of hemodialysis. The preferred type of vascular access is creation of an arteriovenous fistula (AVF). However, the problem of fistula maturation rate is still a challenge. Herein, we tried to search the role of hyperinsulinism and insulin resistance as a new predictor of primary AVF failure (pAVFF) that may be a cause of intimal damage.

METHODS

We included 119 patients (73 male and 46 female) with a diagnosis of end-stage renal disease (ESRD) who had undergone an AVF operation by a vascular surgeon. The AVF was examined for presence of thrill on the first postoperative day. A successful cannulation with two fistula needles with a blood flow of 250 mL/min for at least one complete dialysis session, after 4 weeks of AVF surgery was defined as functioning access. Insulin resistance in our patients was determined by the standard homeostasis model assessment (homa-IR). A logistic-regression analysis was performed to investigate the independent factors related with pAVFF.

FINDINGS

Detection of pAVFF occurred in 27 (22.7%) patients. The presence of thrill, amount of daily proteinuria, insulin levels, homa-IR, and serum albumin levels were found to be significantly different between patients with fistula failure and those without pAVFF. The logistic-regression analysis of preoperative factors revealed the following OR (odds ratio) and 95% CI values: homa-IR 1.205 (1.063-1.366) (p = 0.004), serum albumin 0.398 (0.178-0.892) (p = 0.025), and the amount of daily proteinuria 1.307 (1.012-1.688) (p = 0.041). Even after addition of the presence of postoperative thrill on AVF, which was a postoperative strong clinical factor to the analysis, mean homa-IR and mean serum albumin continued to be independent predictors of pAVFF.

DISCUSSION

Insulin resistance or hyperinsulinism may be a significant cause of pAVFF, which emphasizes the role of endothelium in fistula dysfunction.

The relationship between Lp(a) and CVD outcomes: a systematic review

Robust associations between lipoprotein(a) [Lp(a)] and CVD outcomes among general populations have been published in previous studies. However, associations in high risk primary prevention and secondary prevention populations are less well defined. In order to investigate this further, a systematic review was performed including prospective studies, which assessed the relationship between Lp(a) and CVD outcomes using multivariable analyses. Additional information was gathered on Lp(a) assays, multivariable modelling and population characteristics. Literature searches from inception up to December 2015 retrieved 2850 records. From these 60 studies were included. Across 39 primary prevention studies in the general population (hazard ratios ranged from 1.16 to 2.97) and seven high risk primary prevention studies (hazard ratios ranged from 1.01 to 3.7), there was evidence of a statistically significant relationship between increased Lp(a) and an increased risk of future CVD. Results in 14 studies of secondary prevention populations were also suggestive of a modest statistically significant relationship (hazard ratios ranged from 0.75 to 3.7).Therefore current evidence would suggest that increased Lp(a) levels are associated with modest increases in the risk of future CVD events in both general and higher risk populations. However, further studies are required to confirm these findings.

ADAMTS13 and Von Willebrand factor in patients undergoing hemodialysis

Hemodialysis (HD) is associated with increasing thrombotic trend. Vascular access thrombosis (VAT) increases morbidity in HD patients. The aim of this study was to evaluate ADAMTS13 and VWF plasma levels from patients undergoing HD as putative biomarkers of the hypercoagulability state, as well the association between these markers and VAT occurrence. This study included 195 patients on HD for more than 6 months. HD patients were allocated into two groups according to the occurrence or not of previous episode of VAT; HD with VAT (N = 46) and HD without VAT (N = 149). ADAMTS13 and VWF were performed by ELISA. There was no significant difference between HD patients with and without VAT for ADAMTS13 and VWF levels. However, VWF levels were higher (P < 0.001) and ADAMTS13 were lower (P < 0.001) in HD patients, comparing to the control group composed by healthy subjects without kidney disease, age and sex-matched (N = 80). Taken together our data suggest a potential role of the kidneys function compromised on ADAMTS13 synthesis or metabolism, regardless other known sources of ADAMTS13. The imbalance between ADAMTS13 and VWF levels does not explain the development of VAT in HD patients by itself, although it should contribute for the hypercoagulability state. Therefore, additional studies to identify other risk factors are warranted and essential for better management of HD patients.

An experience of arteriovenous fistulas created for hemodialysis in the largest health center in eastern Turkey

BACKGROUND

The aim of the study was to evaluated the primary and secondary (after reoperation) patency rates and some effect factors in fistula patency for hemodialysis patients.

MATERIAL AND METHODS

Over a 10-year period, 1529 arteriovenous fistulas (AVFs) were fashioned in 1003 (611 males, 392 females; median age range 7-72) patients using the native vascular tissue and prosthetic graft material. We also evaluated the effects of various factors in fistula patency and primary and secondary patency rates in AVF patients.

RESULTS

The primary patencies of fistulas in this series were 72%, 64%, 51%, 41%, and 26%, and secondary patencies were 79%, 70%, 56%, 46%, and 33% at 6 months, 1, 2, 4, and 6 years, respectively. There was no statistically significant difference between the primary and secondary patencies (p = 0.082) in the 6-year follow-up. Factors affecting the patency of fistulas were diabetes mellitus (p < 0.005), hypertension (p < 0.005), and smoking habits (p < 0.005).

CONCLUSION

Even if shown to be not statistically significant, successful surgical revision after fistula occlusion improves secondary patency with potential benefits in terms of patient morbidity. Besides, the AVF patency was shortened in chronic renal-insufficiency patients with diabetes mellitus, hypertension, and smoking habits.

Intradialytic hypotension and vascular access thrombosis

Identifying potential modifiable risk factors to reduce the incidence of vascular access thrombosis in hemodialysis could reduce considerable morbidity and health care costs. We analyzed data from a subset of 1426 HEMO study subjects to determine whether more frequent intradialytic hypotension and/or lower predialysis systolic BP were associated with higher rates of vascular access thrombosis. Our primary outcome measure was episodes of vascular access thrombosis occurring within a given 6-month period during HEMO study follow-up. There were 2005 total episodes of vascular access thrombosis during a median 3.1 years of follow-up. The relative rate of thrombosis of native arteriovenous fistulas for the highest quartile of intradialytic hypotension was approximately twice that of the lowest quartile, independent of predialysis systolic BP and other covariates. There was no significant association of intradialytic hypotension with prosthetic arteriovenous graft thrombosis after multivariable adjustment. Higher predialysis systolic BP was associated with a lower rate of fistula and graft thrombosis, independent of intradialytic hypotension and other covariates. In conclusion, more frequent episodes of intradialytic hypotension and lower predialysis systolic BP associate with increased rates of vascular access thrombosis. These results underscore the importance of including vascular access patency in future studies of BP management in hemodialysis.

Bleeding and thrombotic complications of kidney disease

With the rising prevalence of kidney disease, clinicians are increasingly faced with concerns about potential thrombotic and bleeding complications. Thrombotic risk, both arterial and venous, predominates with all severities of kidney disease but bleeding manifestations become an additional concern particularly with uraemia. This article reviews these contrasting problems and discusses strategies for prevention and management in the context of renal impairment, renal replacement therapy and renal transplantation.

Blood Loss through AV Fistula: A Case Report and Literature Review

Little has been written about acute blood loss from hemodialysis vascular access. We describe a 57-year-old Caucasian male with an approximately 7 gm/dL drop in hemoglobin due to bleeding from a ruptured aneurysm in his right brachiocephalic arteriovenous fistula (AVF). There was no evidence of fistula infection. The patient was successfully managed by blood transfusions and insertion of a tunneled dialysis catheter for dialysis access. Later, the fistula was ligated and a new fistula was constructed in the opposite arm. Aneurysm should be considered in cases of acute vascular access bleeding in chronic dialysis patients.

Primary Arteriovenous Fistulas in the Forearm for Hemodialysis: Effect of Miscellaneous Factors in Fistula Patency

BACKGROUND

The provision and maintenance of vascular access remains a major cost to end-stage renal failure programs. In addition, vascular access occlusion, results in significant morbidity in hemodialysis patients. Age, gender, diabetes mellitus, malignancy, smoking habits, administration of heparin per hemodialysis session, previous dialysis catheter insertion, number of hemodialysis sessions and location of the fistula may be associated with survival of the primary arteriovenous fistula. We examined the effects of various factors on fistulas in 412 chronic renal insufficiency patients.

METHODS

From 1995 to 2004, 412 arteriovenous fistulas were created by the Department of Cardiovascular Surgery at the Medical Faculty of Atatürk University for hemodialysis. The mean age of the patients was 45 years (range 6 to 62 years). We evaluated the effects of various factors for patency rates in the patients who had primary arteriovenous fistulas. Primary patency was defined as the duration of fistula patency without revision. Twenty-eight patients (6.7%) with ischemic cardiac disease did not require surgical interference. Analyzed data were age, gender, smoking habits, diabetes mellitus, malignant neoplasm, previous dialysis catheter insertion, number of hemodialysis sessions, and fistula location.

RESULTS

In 298 patients, where lower-arm radiocephalic fistulas were created, the fistula patency was 74.1%, 64.2%, 49.8%, 33.7%, and 4.1% after 1, 2, 3, 4, and 5 years, respectively, in the other 114 patients, where upper-arm fistulas were created, these rates were 84.0%, 72.2%, 53.3%, 39.8%, and 12.3%, respectively. There was no significantly difference between the upper-arm fistulas and the lower-arm fistulas statistically (p = 0.069). Factors affecting the primary patency of arteriovenous fistulas were diabetes mellitus (p = 0.0001), hemodialysis counts > or =3 per week (p < 0.0005), presence of malignancy (p < 0.0005), previous catheter insertion (p < 0.0007), and administration of heparin per hemodialysis session (p = 0.0008).

CONCLUSION

While primary arteriovenous fistula patency was shortened in chronic renal insufficiency patients with diabetes mellitus, presence of malignancy, and previous catheter insertion, patency was longer in patients with heparin used for hemodialysis and hemodialysis count per week (> or =3).

Comparison of classical and non-classical cardiovascular risk factors influencing the patency of native arteriovenous fistulas after percutaneous transluminal angioplasty therapy among haemodialysis patients

OBJECTIVE

To evaluate the classical and non-classical cardiovascular risk factors that effect patency of native arteriovenous fistulas (AVF) in end stage renal disease (ESRD) patients who are undergoing regular haemodialysis treatment and have a percutaneous transluminal angioplasty (PTA) procedure.

METHODS

All PTAs performed between 1 October 2002 and 30 September 2004 were identified from case notes and the computerised database and follow up to 31 March 2005. The definition of patency of AVF after PTA was including primary or secondary patencies. Risks were analysed to assess the influence on survival following PTAs of age, sex, serum cholesterol, serum triglyceride, diabetes, use of aspirin, current smoking and hypertension, serum albumin, serum calcium-phosphate product, intact parathyroid hormone (I-PTH), and urea reduction ratio (URR).

RESULTS

The patency rate of AVFs of all interventions was 65% at 6 months. Factors with poor patencies of AVFs after PTA procedures were higher serum calcium-phosphate product (p = 0.033), higher URR (p<0.001), lower serum albumin (p<0.001), non-hypertension (p = 0.010) and "non-smoker + ex-smoker group" (p = 0.033). The hypertensive patients and current smokers had lower patency failure after PTAs (p<0.01 and p<0.05, respectively).

CONCLUSIONS

Unfavourable cumulative patency rates are observed in haemodialysis patients with higher URR, higher serum calcium-phosphate product and hypoalbuminaemia (lower serum albumin before the PTA procedure). Hypertension and current smoking were associated with better patency rates of AVF after PTA.

Medical factors affecting patency of arteriovenous access

Arteriovenous access failure is multifactorial in nature with contributions from both medical and surgical etiologies. Medical causes of arteriovenous access failure are rare, and therefore infrequently identified as a major contributing source of malfunction. Although they account for only 10-15% of all cases of access failure, their importance should not be underestimated, especially in cases where a surgical source cannot be identified. Most medical causes are derived from Virchow's triad of endothelial cell injury, stasis, and hypercoaguability. Endothelial cell injury occurs through oxidative stress, activated platelets, increased levels of circulating tumor necrosis factor-alpha, and preexisting intimal hyperplasia. Stasis can occur through prolonged access compression, hypotension, or hypoalbuminemia. Finally, patients with renal failure requiring hemodialysis are frequently at increased risk for hypercoaguable states, except for situations of platelet dysfunction, and therefore access failure. Potential treatments include identifying and removing the offending source, as well as innovative, new medications to prevent their reoccurrence. Treatment is aimed at improving quality of life, as well as decreasing morbidity and hospital admissions in this difficult patient population.

The association of initial hemodialysis access type with mortality outcomes in elderly Medicare ESRD patients

BACKGROUND

Dialysis access is critical for therapy delivery. Few studies have linked type of dialysis access to patient survival in the elderly population.

METHODS

We included 1995 to 1997 incidence Medicare hemodialysis patients (N = 66,595) who were 67 years and older at dialysis therapy initiation. Medicare Physician/Supplier claims were used to determine initial access type: simple fistula, autologous vein graft, synthetic graft, and hemodialysis catheter. We used International Classification of Diseases, Ninth Revision, Clinical Modification, codes to determine vascular access placement for renal failure. A Cox regression analysis assessed risk for death within 1 year, with explanatory variables of incidence year, age, sex, race, diabetes, initial access type, body mass index, days from first access placement date to initial dialysis date, and serum albumin, creatinine, and blood urea nitrogen levels.

RESULTS

One-year crude death rates were 24.9%, 27.2%, 28.1%, and 41.5% for patients with simple fistulae, autologous vein grafts, synthetic grafts, and hemodialysis catheters, respectively. Patients with simple fistulae (the reference) had the lowest (P < 0.0001) likelihood of death compared with those with synthetic grafts (hazard ratio [HR], 1.160; 95% confidence interval [CI], 1.084 to 1.241) or catheters (HR, 1.696; 95% CI, 1.593 to 1.806). No difference (P > 0.09) in mortality risk was detected between simple fistulae and autologous vein grafts or between autologous vein grafts and synthetic grafts.

CONCLUSION

In the US Medicare dialysis population, type of initial hemodialysis access was associated with 1-year mortality. Mortality risks were (in ascending order) fistulae, grafts, and catheters.

Re-endothelialization of punctured ePTFE graft: an in vitro study under pulsed perfusion conditions

BACKGROUND

When used as arteriovenous (AV) shunts for haemodialysis, small diameter expanded polytetrafluoroethylene (ePTFE) grafts have a high failure rate in vivo. Attempts to improve graft patency are various, and focus on either improvement of implantation techniques or graft tissue engineering. The tissue engineering approach attempts to reproduce in grafts the properties of pristine vasculature. As shown in previous experiments, it is possible to grow on ePTFE grafts under shear stress in vitro an autologous endothelial cell layer, which will withstand physiological stress under in vivo conditions of blood flow. The aim of this study was to investigate in an in vitro model the regenerative potency of a tissue-engineered prosthetic vascular graft after repeated cannulation with a haemodialysis cannula.

METHODS

Pig endothelial cells were harvested from an external jugular vein. Following processing of the endothelial cells, seven ePTFE grafts were coated with an inner cell layer and were kept under pulsed perfusion. Each graft was then cannulated three times with a standard shunt needle. The endothelium was then left to regenerate for a maximum of 48 h. The grafts were stained with haematoxylin/eosin before histological study.

RESULTS

All grafts were endothelialized over the puncture sites within 48 h. Histological analysis revealed a confluent endothelial cell lining at each puncture site. Cell morphology and cell pattern over puncture sites were not different from randomly picked locations over the graft lumen.

CONCLUSION

Our results underline the potential of endothelial tissue engineering in vascular shunt surgery. Vascular bio-hybrids that have the properties of pristine vascular endothelium may be a key step forward in maintaining angio-access in patients who require haemodialysis.

Predictors of successful arteriovenous fistula maturation

BACKGROUND

Understanding the factors associated with successful arteriovenous fistula (AVF) maturation may provide an opportunity to improve vascular access outcomes.

METHODS

This prospective cohort study enrolled 348 hemodialysis patients receiving an AVF and followed them until ascertainment of successful AVF maturation. Multivariable logistic regression was used to develop (1) explanatory models of factors associated with AVF success and (2) models for predicting success based on sociodemographic and comorbidity profiles. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the discriminative ability of our predictive model. Predictive probabilities of AVF maturation under the assumption of optimal surgical technique defined by explanatory models were calculated.

RESULTS

A total of 55.5% of AVFs successfully matured. A history of stroke or transient ischemic attack, increasing age, and dependence on dialysis at the time of access placement were associated with lower probabilities of maturation. Of potentially modifiable variables, maturation was associated with greater intraoperative doses of heparin, use of large-diameter veins, and mean arterial pressure of 85 mm Hg or greater. Using optimal surgical technique, the probability of successful AVF maturation would have been as high as 84%. A predictive logistic regression model had moderate ability to predict AVF maturation under optimal surgical therapy with an area under the ROC curve of 0.69.

CONCLUSION

Surgical technique potentially may be modified to yield a greater probability of successful AVF maturation. Predictive probabilities of successful AVF maturation under optimal surgical technique reinforce the view that functioning AVFs can be achieved in a large proportion of hemodialysis patients, consistent with experience in selected regions of the United States and abroad.

Race-specific association of lipoprotein(a) with vascular access interventions in hemodialysis patients: the CHOICE Study

BACKGROUND

Elevated serum levels of lipoprotein(a) [Lp(a)] and low molecular weight apolipoprotein(a) [apo(a)] isoforms are associated with atherothrombotic disease in the general population and in patients with kidney failure. Lp(a) may be more atherothrombotic in whites than in blacks. Data on the relation of Lp(a) and apo(a) isoform size to hemodialysis vascular access complications are limited.

METHODS

We analyzed the intervention-free survival of the first arteriovenous (AV) access among 215 white and 112 black incident hemodialysis patients participating in the CHOICE Study, a national multicenter prospective cohort study.

RESULTS

Median levels of Lp(a) protein were higher among blacks than whites (81.0 versus 37.5 nmol/L; P < 0.001) and inversely correlated with apo(a) isoform size (r = -0.57; P < 0.001). The incidence rate of access interventions was much higher in synthetic grafts (N = 193) than native fistulae (N = 134; 1.0 vs. 0.5 interventions per access-year; P < 0.001) and in patients with kidney failure primarily due to diabetes mellitus (N = 161) than others (N = 166; 0.9 vs. 0.6; P < 0.01), but did not differ by race. Blacks in the highest race-specific Lp(a) quartile (>145 nmol/L) had a significantly higher incidence rate than other blacks (1.4 vs. 0.7; P = 0.04), whereas no association was found in whites. The association in blacks remained after adjustment for access type and other characteristics (relative hazard = 1.68; 95% confidence interval: 0.98 to 2.86). No association was found with apo(a) isoform size in either race.

CONCLUSIONS

Elevated Lp(a) may be a risk factor for arteriovenous access complications among black hemodialysis patients. Future studies should explore this possibility and be adequately powered to allow race-specific analyses.

Effects of a venous cuff at the venous anastomosis of polytetrafluoroethylene grafts for hemodialysis vascular access

INTRODUCTION AND METHODS

The most frequent complication of polytetrafluoroethylene (PTFE) arteriovenous grafts for hemodialysis is thrombotic occlusion due to stenosis caused by intimal hyperplasia. This complication is also known for peripheral bypass grafts. Because the use of a venous cuff at the distal anastomosis improves the patency of peripheral bypass grafts, we considered that it might also improve the patency of PTFE arteriovenous grafts. Therefore, a randomized multicenter trial was carried out to study the effect of a venous cuff at the venous anastomosis of PTFE arteriovenous grafts on the development of stenoses and the patency rates.

RESULTS

Of the 120 included patients, 59 were randomized for a venous cuff. The incidence of thrombotic occlusion was lower in the cuff group (0.68 per patient-year) than in the no-cuff group (0. 88 per patient-year; P =.0007). However, the primary and secondary patency rates were comparable. The cuff group tended to have fewer stenoses at the venous and arterial anastomoses when examined with duplex scan. Graft failure was higher in patients with an initial anastomosing vein diameter smaller than 4 mm (7 of 18 [39%]) than in those with a vein diameter of 4 mm or larger (16 of 88 [18%]; P =. 052). Local edema, skin atrophy, and obesity yielded a higher risk on graft failure (23% vs 11%).

CONCLUSION

A venous cuff at the venous anastomosis of PTFE arteriovenous grafts for hemodialysis reduced the incidence of thrombotic occlusions; stenosis at the venous anastomosis was reduced. However, this did not result in a better patency rate. Therefore, the venous cuff should not be used routinely. Initial vein diameter and local problems (edema, obesity, or skin atrophy) appear to be the most important risk factors for graft failure.

Relation between gender and vascular access complications in hemodialysis patients

Native arteriovenous (AV) fistulae for hemodialysis vascular access are believed to be associated with fewer complications than synthetic polytetrafluoroethylene (PTFE) grafts. We conducted a study among patients in the Dialysis Morbidity and Mortality Study to compare risk factors for complications of AV fistulae and PTFE grafts in men and women and to examine the effect of age on vascular access complications. We analyzed data from 833 incident patients with end-stage renal disease who had a PTFE graft (n = 621) or AV fistula (n = 212) in use 1 month after starting hemodialysis therapy. Follow-up using inpatient and outpatient Medicare administrative data identified a 1.8-times greater risk for a subsequent vascular access procedure for PTFE grafts (0.71 procedures/access-year) than for AV fistulae (0.39 procedures/access-year). Men with grafts and women with grafts or fistulae had a greater risk for a first subsequent access procedure than did men with fistulae (0.79, 0.65, and 0.59 versus 0.33 procedures/access-year, respectively). After adjustment for age, race, presence of diabetes mellitus, and history of smoking, peripheral vascular disease, and cardiovascular disease, use of a PTFE graft compared with an AV fistula was associated with a greater risk for a first subsequent procedure in men (relative hazard, 2.2; 95% confidence interval [CI], 1.6 to 2.9), but not in women (relative hazard, 1.0; 95% CI, 0.7 to 1.4). The excess risk associated with a PTFE graft compared with an AV fistula was limited to men in the lower three quartiles of age (ie, </=72 years). These data raise concern that the potential benefits of AV fistulae over PTFE grafts are not realized in women and older men. A better understanding of the determinants of successful access maturation and maintenance in these groups is needed.

Forearm loop, upper arm straight, and brachial-internal jugular vein dialysis grafts: a comparison study of graft survival utilizing a combined percutaneous endovascular and surgical maintenance approach

PURPOSE

To determine rates and duration of patency achievable in forearm loop, upper arm straight, and brachial-internal jugular (IJ) vein hemodialysis grafts utilizing a combined percutaneous endovascular and surgical maintenance approach.

MATERIALS AND METHODS

A retrospective analysis of 74 hemodialysis grafts (forearm loop, n = 22; upper arm straight, n = 34; and brachial-IJ vein, n = 18) in 50 patients with end-stage renal disease was conducted. Operative notes, interventional procedural reports, and hospital records were used to construct a history for each of these grafts from the time of surgical placement until the time the graft was abandoned for an alternative method of dialysis. All procedures performed to maintain and/or restore patency during the usable lifetime of the grafts were documented.

RESULTS

Survival analysis using the Kaplan-Meier method demonstrated the following probabilities of primary patency at 6, 12, and 16 months, respectively: forearm loop graft = .46, .26, and .26; upper arm straight graft = .39, .22, and .16; and brachial-IJ vein graft = .19, .06, and .06 (forearm loop vs upper arm straight grafts, P > .05; forearm loop and upper arm straight vs brachial-IJ grafts, P < .001, P < .001, respectively). The probabilities of secondary patency at 12, 24, and 48 months, respectively, were: forearm loop graft = .89, .30, and NA; upper arm straight graft = .52, .35, and .17; and brachial-IJ vein graft = .54, .42, and .21 (P < .05 for all three comparisons: forearm loop > brachial-IJ > upper arm straight). Six percutaneous and two surgical procedures were compared and no significant differences in utilization were determined among the three graft types (ANOVA, P range, .38-.88).

CONCLUSION

Kaplan-Meier analysis determined the probability of primary patency for forearm loop grafts to be similar to that for upper arm straight grafts, and both were significantly greater than for brachial-IJ vein grafts. The secondary patency rates for forearm loop grafts are greater than for upper arm and brachial-IJ vein grafts, while that for the brachial-IJ vein graft is greater than the upper arm straight graft. Utilization of interventional and surgical resources required to maintain patency do not significantly differ among the three types of upper extremity hemodialysis grafts.

Factors Influencing Arteriovenous Fistula Dysfunction in Japanese Patients on Chronic Hemodialysis

Arteriovenous fistula dysfunction is a constant problem in chronic hemodialysis patients. We investigated the factors influencing fistula dysfunction in 184 patients on chronic hemodialysis. Stepwise regression analysis and Cox proportional hazards model were used to assess the relationship between fistula dysfunction and age, sex, duration of hemodialysis, diabetes mellitus, hematocrit, serum creatinine, blood urea nitrogen, Kt/V, prothrombin time, blood pressure, anticoagulant therapy, dose of erythropoietin, calcium channel blocker therapy, and angiotensin-converting enzyme inhibitor therapy. Fistula dysfunction showed a significant relationship with a low systolic blood pressure, a low hematocrit, the presence of diabetes mellitus, and angiotensin-converting enzyme inhibitor therapy. These results suggested that treatment with angiotensin-converting enzyme inhibitors may help to prevent fistula dysfunction.

Longitudinal comparison of dialysis access methods: risk factors for failure

PURPOSE

To compare dialysis access patency rates and identify risk factors for failure.

METHODS

All access procedures at our institution from 1987 to 1996 were reviewed. Primary procedures were surgically implanted dual-lumen central venous hemodialysis catheters (SIHCs), peritoneal dialysis catheters (PDCs), arteriovenous fistulas (AVFs), and prosthetic shunts (PTFEs).

RESULTS

Five hundred eighty-five primary procedures (236 PTFEs, 87 AVFs, 112 SIHCs, and 150 PDCs) and 259 secondary procedures (215 PTFEs, 14 AVFs, 0 SIHCs, and 30 PDCs) were performed on 350 patients. By life table analysis, SIHCs exhibited the lowest primary patency rate (9% at 1 year; p < 0.0001), whereas PDCs had the highest primary patency rate (57% at 1 year; p < 0.02). The primary patency rates of AVFs and PTFEs was similar, with 43% and 41% 1-year patency rates, respectively (p = 0.70). Less-stringent reporting methods would have increased apparent 1-year patency rates by 9% to 41%. With regard to secondary patency, there was no significant difference between PTFEs and PDCs, with 1-year patency rates of 59% and 70%, respectively (p = 0.62), but PTFEs were more frequently revised. In addition, there was no significant difference between AVF and PTFE secondary patency rates, with 1-year patency rates of 46% and 59%, respectively. Early differences in patency rates for AVFs, PTFEs, and PDCs diminished over time, and at 4 years AVFs had the best secondary patency rate (p = 0.6). The most common reasons for access failure were: PTFEs, thrombosis; AVFs, thrombosis and failure to mature; SIHCs, inadequate dialysis; PDCs, infection and inadequate exchange. By regression analysis, a history of a previous unsalvageable PTFE was the only significant risk factor for failure of a subsequent PTFE (p < 0.01), and the risk of graft failure increased exponentially with the number of previous PTFE shunts. Diabetes was the only significant risk factor for failure of PDCs (p < 0.02; odds ratio, 2.0).

CONCLUSIONS

The patency rate for PTFEs is similar to that for AVFs, but AVFs require fewer revisions. When replacing a failed access graft, the risk of PTFE failure increases with the number of prior unsalvageable PTFE shunts. PDCs have excellent patency rates, but failure rates are doubled in patients with diabetes. Because of poor patency rates and inadequate dialysis flow rates, SIHCs should be avoided when possible. Reporting methods dramatically affect apparent patency rates, and reporting standards are needed to allow meaningful comparisons in the dialysis access literature.

Leukocyte-polytetrafluoroethylene interaction enhances proliferation of vascular smooth muscle cells via tumor necrosis factor-alpha secretion

Intimal hyperplasia of vascular smooth muscle cells (VSMC) at the venous anastomosis of arteriovenous grafts represents the most common cause of vascular access failure in hemodialysis patients. Upstream release of growth factors from leukocytes activated by adhesion to the graft material may play a role in this lesion. We evaluated the effect of interaction of peripheral blood mononuclear cells (PBMC) with polytetrafluoroethylene (PTFE) on proliferation of VSMC. Vascular smooth muscle cell proliferation was significantly increased by conditioned media from human PBMC incubated with PTFE. Peripheral blood mononuclear cell adhesion to PTFE could not be antagonized by the beta 1 integrin ligand-containing peptide GRGDSP, but was attenuated by EDTA consistent with beta 2 integrin-mediated adhesion. Soluble scavenger receptor ligands at high concentrations had no effect on adhesion to PTFE excluding any contributory role of scavenger receptors in this interaction. Neutralizing antibodies to TNF-alpha significantly attenuated the mitogenic effect of PBMC/PTFE conditioned media and a marked increase in TNF-alpha secretion by PBMC on PTFE was detected by ELISA. These studies demonstrate that PBMC interaction with PTFE can promote proliferation of VSMC via increased production of TNF-alpha and perhaps other cytokines. Leukocyte interaction with PTFE causing enhanced secretion of TNF-alpha and consequent VSMC proliferation may account for the development of venous intimal hyperplasia in hemodialysis patients with arteriovenous grafts.