Role of platelet factor 4 in arteriovenous fistula maturation failure: What do we know so far?

The rate of arteriovenous fistula (AVF) maturation failure remains unacceptably high despite continuous efforts on technique improvement and careful pre-surgery planning. In fact, half of all newly created AVFs are unable to be used for hemodialysis (HD) without a salvage procedure. While vascular stenosis in the venous limb of the access is the culprit, the underlying factors leading to vascular narrowing and AVF maturation failure are yet to be determined. We have recently demonstrated that AVF non-maturation is associated with post-operative medial fibrosis and fibrotic stenosis, and post-operative intimal hyperplasia (IH) exacerbates the situation. Multiple pathological processes and signaling pathways are underlying the stenotic remodeling of the AVF. Our group has recently indicated that a pro-inflammatory cytokine platelet factor 4 (PF4/CXCL4) is upregulated in veins that fail to mature after AVF creation. Platelet factor 4 is a fibrosis marker and can be detected in vascular stenosis tissue, suggesting that it may contribute to AVF maturation failure through stimulation of fibrosis and development of fibrotic stenosis. Here, we present an overview of the how PF4-mediated fibrosis determines AVF maturation failure.

Photochemically Aided Arteriovenous Fistula Creation to Accelerate Fistula Maturation

Rates of arteriovenous fistula maturation failure are still high, especially when suboptimal size veins are used. During successful maturation, the vein undergoes lumen dilatation and medial thickening, adapting to the increased hemodynamic forces. The vascular extracellular matrix plays an important role in regulating these adaptive changes and may be a target for promoting fistula maturation. In this study, we tested whether a device-enabled photochemical treatment of the vein prior to fistula creation facilitates maturation. Sheep cephalic veins were treated using a balloon catheter coated by a photoactivatable molecule (10-8-10 Dimer) and carrying an internal light fiber. As a result of the photochemical reaction, new covalent bonds were created during light activation among oxidizable amino acids of the vein wall matrix proteins. The treated vein lumen diameter and media area became significantly larger than the contralateral control fistula vein at 1 week (p = 0.035 and p = 0.034, respectively). There was also a higher percentage of proliferating smooth muscle cells in the treated veins than in the control veins (p = 0.029), without noticeable intimal hyperplasia. To prepare for the clinical testing of this treatment, we performed balloon over-dilatation of isolated human veins and found that veins can tolerate up to 66% overstretch without notable histological damage.

Association between anaesthesia type and arteriovenous fistula maturation

BACKGROUND

Whereas general anaesthesia is commonly used for haemodialysis fistula creation, regional or local anaesthesia has been posited to lead to better fistula maturation outcomes. We sought to measure the association between anaesthesia type and arteriovenous fistula maturation.

METHODS

We performed a secondary analysis of data from the Hemodialysis Fistula Maturation study, a multicentre prospective cohort study of advanced chronic kidney disease patients who underwent single-stage upper extremity fistula creation between 2010 and 2013. We evaluated the relationship between anaesthesia type and unassisted (without maturation-facilitating interventions) or overall (unassisted or assisted) fistula maturation using multivariable logistic regression.

RESULTS

Among 602 participants, 336 (55.8%) received regional/local anaesthesia and 266 (44.2%) received general anaesthesia. Unassisted maturation occurred in 164/309 patients (53.1%) after regional/local vs 91/226 patients (40.3%) after general anaesthesia (P=0.003). After adjustment for patient factors and fistula type, regional/local anaesthesia was associated with greater odds of unassisted maturation than general anaesthesia (odds ratio 1.72, 95% confidence interval 1.24-2.39; P=0.001). However, after further adjustment for clinical centre fixed effects, odds of unassisted maturation did not differ by anaesthesia type (odds ratio 1.03, 95% confidence interval 0.78-1.36; P=0.830). Similar findings were observed for overall maturation and composite endpoints accounting for potential survivorship bias.

CONCLUSIONS

Regional/local anaesthesia was associated with increased odds of fistula maturation when adjusting for patient factors and fistula type. However, this association did not persist after adjusting for centre fixed effects. Future research is needed to better understand the relationship between anaesthesia type and centre factors to optimise outcomes after fistula surgery.

Monitoring the Patient Following Radio-Cephalic Arteriovenous Fistula Creation: Current Perspectives

Autogenous radial–cephalic direct wrist arteriovenous fistula (RC-AVF) in the non-dominant arm is the gold standard for dialysis vascular access. However, the RC-AVF non-maturation rate is significant (≃ 40%) due to an increasingly elderly and comorbid population incidence. A detailed identification of the biological cascade underlying arteriovenous fistula (AVF) maturation could be the key to clinical research aimed at identify the group of patients at risk of primary AVF failure. Currently, careful post-operative monitoring remains the most crucial aspect to overcome the problem of impaired maturation. Up to 80% of patients with immature RC-AVF have problems potentially solvable with early endovascular or surgical correction. Physical examination by experienced practitioners in conjunction with duplex ultrasound examination (DUS) can identify physical signs of non-maturation, understand the underlying cause, and drive for a tailored early planning to treat the complication. New approaches for the early assessment of AVF maturation are under study. Techniques to promote RC-AVF maturation performed through the administration of pre-or peri-operative drugs have missed up to now to prove an efficacy in improving fistula success. The new techniques tested after surgery appear to hold future promise for improving fistula maturation.

Agreement between physical and ultrasound examination for arteriovenous fistula maturation diagnostics in Thai hemodialysis patients

INTRODUCTION

Physical examination (PE) is used to determine if arteriovenous fistula (AVF) meets criteria for first hemodialysis (HD) cannulation in chronic kidney disease (CKD) with HD patients. Three ultrasound (US) based criteria are adopted to investigate maturation: (i) Rule of Six: blood flow ⩾600 milliliters per minute (mL/min), vein diameter ⩾6 millimeters (mm), vein depth ⩽6 mm); (ii) Rule of Five: blood flow ⩾500 mL/min, vein diameter ⩾5 mm, vein depth ⩽6 mm; and (iii) Rule of Four: blood flow ⩾500 mL/min, vein diameter ⩾4 mm, vein depth ⩽6 mm. In Thai, no study determined optimal US criteria for predicting AVF maturation measured by PE before first cannulation. This study examined the significance of these US criteria on the physical AVF maturation in Thai.

METHODS

Fifty CKD patients, operated brachiocephalic AVF, were enrolled and examined on the operative day and 6 weeks afterwards. PE was evaluated by an experienced vascular surgeon, and US measurements were obtained by an experienced US technologist. Matching mature number between US criteria and PE was computed using McNemar test. Agreement between US criteria and PE was measured using Kappa. Mature and immature discrimination were evaluated by the Receiver Operator Characteristics (ROC) curve and Youden index.

RESULTS

Rule of Six and Rule of Five had higher non-mature matching number than Rule of Four (p < 0.001 both). Regarding Kappa statistics, Rule of Six and Rule of Five agreed with the PE (p < 0.01 both). The ROC curve of Rule of Six and Rule of Five were 0.75 and 0.74, respectively (p <0.01 both). Youden index (maturity and immaturity discriminating performance) of both rules was 0.5 and 0.47, respectively.

CONCLUSION

Rule of Six and Rule of Five agreed with the PE, with the highest performance of the Rule of Six to predict first successful cannulation in Thai.

Implanted blood vessel external support device (VasQ™) for creation of hemodialysis arteriovenous fistula: A single-center experience

INTRODUCTION

the external support device VasQ is intended to promote arteriovenous fistula (AVF) maturation by maintaining the optimal anastomotic angle in order to minimize blood flow disturbances around the anastomotic area. The aim of the study is to assess efficacy and safety of the VasQ device both in brachiocephalic and radiocephalic fistulae.

METHODS

a single institution prospective study was conducted with implantation of the VasQ device during AVF creation. Clinical and Doppler ultrasounds evaluations were performed at day-1, 1, 6, and 12 months for assessment of device-related adverse events, AVF maturation and patency. Moreover, volume flow rate and diameter of outflow vein were measured. A total of 16 patients were enrolled. Ten brachiocephalic and 6 radiocephalic AVFs were created with VasQ. Preoperatively cephalic vein diameter was 3.6 ± 0.9 mm.

RESULTS

our population included 13 male and 3 females patients, 9 end stage kidney disease in conservative therapy, 4 dialysis treated patients, and 3 transplanted patients; mean age was 74.0 ± 8.1 years; no severe device-related adverse events were observed. Primary patency at 1, 6, and 12 months was 100%, 87.5%, and 67.7%, respectively, while secondary patency was 100%, 100%, and 78.3%, respectively. Comparing brachiocephalic to radiocephalic AVFs no significant differences in patency rates were seen. Overall maturation rate was 94% (15/16). Mean vein diameter measured with Doppler ultrasound at postoperative day-1 and at 1, 6, and 12 months was 5.0 ± 1.0, 5.9 ± 0.9, 7.2 ± 1.6, and 7.9 ± 1.4 mm, respectively, with a mean flow rate at the brachial artery of 841 ± 176, 1052 ± 224, 1261 ± 490, and 1348 ± 477 ml/min, respectively.

CONCLUSIONS

in our limited experience VasQ was safe, with high maturation and patency rates. Positive results suggest a potential benefit for VasQ in AVF.

A prospective cohort study of predictors of upper extremity arteriovenous fistula maturation

BACKGROUND

A substantial proportion of arteriovenous fistulas fail to function adequately for hemodialysis. Existing studies on arteriovenous fistula failure prediction assess patency rather than the more clinically relevant outcome of arteriovenous fistula function. We hypothesized that preoperative demographic and ultrasound characteristics, and postoperative assessment by an experienced vascular access nurse would predict which arteriovenous fistulas will not function adequately for hemodialysis.

METHODS

Prospective cohort study of chronic kidney disease patients at a tertiary care center in Vancouver, Canada, with arteriovenous fistula creation between 2009 and 2013. Pre and postoperative clinical assessment and ultrasound blood vessel mapping were performed by an experienced vascular access nurse. The primary outcome was failure to achieve a fistula used successfully for hemodialysis (FUSH).

RESULTS

Outcomes were assessed in 200 patients; 123 (61.5%) arteriovenous fistulas were radiocephalic. Overall, 26.5% of arteriovenous fistulas had FUSH failure (34.1% of lower arm vs 14.3% of upper arm, p = 0.002). Univariate predictors of FUSH failure included older age (p = 0.03), female sex (p = 0.05), smaller arterial diameter (p ⩽ 0.001), lower artery volume flow (p = 0.04), and smaller vein diameter (p = 0.01). In multivariable analysis, artery diameter (odds ratio: 0.44, 95% confidence interval: 0.28-0.68) most significantly predicted FUSH failure. Vascular access nurse assessment 6 weeks postoperatively correctly predicted outcome in 83.8% of FUSH and 65.0% of FUSH failure.

CONCLUSION

Smaller artery diameter most strongly predicted FUSH failure. Early postoperative nursing assessment was more useful to predict FUSH than FUSH failure, and as such was insufficient in determining which arteriovenous fistulas should be abandoned as many predicted to fail could be salvaged with further intervention.

Oral prostacycline analog and clopidogrel combination provides early maturation and long-term survival after arteriovenous fistula creation: A randomized controlled study

Vascular access is used as a lifeline for hemodialysis in patients with end stage renal disease failure (ESRD). Failure of arteriovenous fistula (AVF) maturation is still high. The purpose of this study was to research the effects of clopidogrel in combination with oral iloprost, a synthetic analog of prostacyclin PGI2. Ninety-six diabetic ESRD patients were divided into two groups. In the first group (Group 1, N = 50), clopidogrel (75 mg daily dose) and an oral prostacycline analog (200 mg daily dose) were administered. In the second group (Group 2, N = 46), placebo was given. All patients took study medication 7-10 days prior to surgery. A Doppler ultrasound (USG) was performed for measurement of arterial and venous diameters, and peak systolic velocity of arterial flow based on subsequent fistula adequacy. Autogenous AVFs were constructed in forearm as distally as possible in all patients. Both groups were followed-up for a year. In the placebo group, early AVF thrombosis was detected in two patients (4.3%). AVF maturation failure was noted in 14 patients (30.4%) in placebo group and in four patients (8%) in clopidogrel plus oral prostacycline analog group in the early postoperative period (P = 0.001). The mean maturation time was 38 ± 6.5 and 53 ± 12.8 days in study and placebo groups, respectively (P = 0.023). The mean blood flow was 352 ± 94 mL/min in placebo group and 604 ± 125 mL/min in study group (P = 0.001). The arterial end diastolic velocity was 116 ± 14 cm/s in study group and 72 ± 21 cm/s in placebo group (P = 0.036) 1 year after the surgery. Our data indicated that clopidogrel and oral prostacycline analog combination is effective and safe for the prevention of primary AVF failure in hemodialysis patients and decreased acute and chronic thrombotic events.