Association of Preexisting Arterial Intimal Hyperplasia with Arteriovenous Fistula Outcomes

Management of Immature Arteriovenous Fistulas

In patients requiring long-term hemodialysis for chronic kidney disease, an arteriovenous fistula is the preferred mode of hemodialysis access over synthetic arteriovenous graft or hemodialysis catheters. The National Kidney Foundation recommended in their Kidney Dialysis Outcomes Quality Initiative (KDOQI) Clinical Practice Guidelines that the creation of an autogenous arteriovenous fistula should initially be sought whenever possible. In 2003, a program named the Fistula First Breakthrough Initiative was initiated in the U.S. to increase the use of arteriovenous fistula for hemodialysis and to ultimately surpass the goal of 50% fistula use in incident and 40% fistula use in prevalent hemodialysis patients per recommendation by KDOQI Guidelines. While this goal was achieved, the encouraged creation of arteriovenous fistulas saw a rise in fistulas that failed to mature. Researchers have focused on developing strategies to optimize fistula maturation. Studies have revealed that the presence of stenoses and accessory draining veins may contribute to unsuccessful fistula maturation. Endovascular treatment, including balloon angioplasty and accessory vein embolization, aim to correct anatomical factors that negatively affect the maturation process. This article reviews the techniques and outcomes of endovascular treatment in the management of immature fistulas.

Association of Shear Stress with Subsequent Lumen Remodeling in Hemodialysis Arteriovenous Fistulas

BACKGROUND

Blood flow-induced wall shear stress is a strong local regulator of vascular remodeling, but its effects on arteriovenous fistula (AVF) remodeling are unclear.

METHODS

In this prospective cohort study, we used computational fluid dynamics simulations and statistical mixed-effects modeling to investigate the associations between wall shear stress and AVF remodeling in 120 participants undergoing AVF creation surgery. Postoperative magnetic resonance imaging data at 1 day, 6 weeks, and 6 months were used to derive current wall shear stress by computational fluid dynamic simulations and to quantify subsequent changes in AVF lumen cross-sectional area at 1-mm intervals along the proximal artery and AVF vein.

RESULTS

Combining artery and vein data, prior mean wall shear stress was significantly associated with lumen area expansion. Mean wall shear stress at day 1 was significantly associated with change in lumen area from day 1 to week 6 (11% larger area per interquartile range [IQR] higher mean wall shear stress, 95% confidence interval [95% CI], 5% to 18%; n =101), and mean wall shear stress at 6 weeks was significantly associated with change in lumen area from 6 weeks to month 6 (14% larger area per IQR higher, 95% CI, 3% to 28%; n =52). The association of mean wall shear stress at day 1 with lumen area expansion from day 1 to week 6 differed significantly by diabetes ( P =0.009): 27% (95% CI, 17% to 37%) larger area per IQR higher mean wall shear stress without diabetes and 9% (95% CI, -1% to 19%) with diabetes. Oscillatory shear index at day 1 was significantly associated with change in lumen area from day 1 to week 6 (5% smaller area per IQR higher oscillatory shear index, 95% CI, 3% to 7%), and oscillatory shear index at 6 weeks was significantly associated with change in lumen from 6 weeks to month 6 (7% smaller area per IQR higher oscillatory shear index, 95% CI, 2% to 11%). Wall shear stress spatial gradient was not significantly associated with subsequent remodeling. In a joint model, wall shear stress and oscillatory shear index statistically significantly interacted in their associations with lumen area expansion in a complex nonlinear fashion.

CONCLUSIONS

Higher wall shear stress and lower oscillatory shear index were associated with greater lumen expansion after AVF creation surgery.

Snuff-Box Versus Wrist Radiocephalic Arteriovenous Fistulas for Hemodialysis: Maturation Tend and its Affecting Factors

BACKGROUND

Thanks to its well proved long-term patency rates, native radiocephalic arteriovenous fistula remains the most commonly used vascular access type. Many articles had approached the criteria leading to a mature fistula. The aims of this work are to evaluate variables that may affect the maturation of distal fistulas and to determine if wrist fistulas have less risk of maturation failure than the snuff-box fistulas.

METHODS

We recorded all distal radiocephalic fistulas that had been created from January 2018 to February 2021. Epidemiological and clinical profile of patients, characteristics of performed fistulas and per and post-operative data were recorded and analyzed.

RESULTS

From January 2018 to February 2021, 165 upper limb vascular accesses for hemodialysis had been created including 47 (28.5%) distal radiocephalic fistulas. Among the latter, 39 (83%) fistulas were performed at the wrist and 8 (17%) at snuff-box area. There were 34 men (72.3%). Mean age was 67 years (37-87). Both types of fistulas had approximately an identic frequency of primary maturation failure (50% for radiocephalic versus 47.2% for snuff-box fistulas). Secondary maturation had been achieved in 9 fistulas. Patients with medical history of dyslipidemia, peripheral arterial disease (PAD), central catheter placement, and bad quality of vessels tend to develop an immature fistula.

CONCLUSIONS

No significant differences in maturation tend between snuff-box and wrist fistulas had been demonstrated. Thus, it seems reasonable to privilege the creation of the most distal fistulas allowing preservation of wrist fistulas as a second option in case of snuff-box fistulas maturation failure. However, selection of the most suitable cases for snuff-box fistulas creation, based on clinical and duplex ultrasound data, remains primordial.

Heme Oxygenase 1/Peroxisome Proliferator-Activated Receptor Gamma Pathway Protects Intimal Hyperplasia and Mitigates Arteriovenous Fistula Dysfunction by Regulating Oxidative Stress and Inflammatory Response

Purpose

An arteriovenous fistula (AVF) is the preferred vascular access mode for maintenance hemodialysis, and access stenosis and thrombosis are the primary causes of AVF dysfunction. This study is aimed at exploring the molecular mechanisms underlying AVF development and the roles of the heme oxygenase 1/peroxisome proliferator-activated receptor gamma (HO-1/PPAR-γ) pathway in AVF.

Method

AVF model mice were established, and the vascular tissues from the arteriovenous anastomosis site were sent for mRNA sequencing. Differentially expressed mRNAs (DEmRNAs) were screened and subjected to functional analysis. Thereafter, the mice with HO-1 knockdown and coprotoporphyrin IX chloride (COPP) pretreatment were used to investigate the roles of the HO-1/PPAR-γ pathway in AVF.

Results

By sequencing, 2514 DEmRNAs, including 1323 upregulated and 1191 downregulated genes, were identified. These DEmRNAs were significantly enriched in the PPAR signaling pathway, AMPK signaling pathway, glucagon signaling pathway, IL-17 signaling pathway, and Toll-like receptor signaling pathway. High expression of HO-1 and PPAR-γ reduced endothelial damage and intimal hyperplasia during AVF maturation. After AVF was established, the levels of transforming growth factor-β (TGF-β), interleukin-1β (IL-1β), interleukin-18 (IL-18), and reactive oxygen species (ROS) were significantly increased (P < 0.05), and HO-1 normal expression and COPP pretreatment evidently decreased their levels in AVF (P < 0.05). Additionally, AVF significantly upregulated HO-1 and PPAR-γ and downregulated MMP9, and COPP pretreatment and HO-1 normal expression further upregulated and downregulated their expression.

Conclusion

The HO-1/PPAR-γ pathway may suppress intimal hyperplasia induced by AVF and protect the intima of blood vessels by regulating MMP9 and ROS, thus mitigating AVF dysfunction.

Morphological Lesion Types Are Associated with Primary and Secondary Patency Rates after High-Pressure Balloon Angioplasty for Dysfunctional Arteriovenous Fistulas

BACKGROUND

Neointimal hyperplasia (NIH) is believed to be the main reason for arteriovenous fistula (AVF) dysfunction, but other mechanisms are also recognized to be involved in the pathophysiological process. This study investigated whether different morphological types of AVF lesions are associated with the patency rate after percutaneous transluminal angioplasty (PTA).

METHODS

This retrospective study included 120 patients who underwent PTA for autogenous AVF dysfunction. All the cases were evaluated under Doppler ultrasound (DU) before intervention and divided into 3 types: Type I (NIH type), Type II (non-NIH type), and Type III (mixed type). Prognostic and clinical data were analyzed by Kaplan-Meier analysis and the Cox proportional hazards model.

RESULTS

There was no statistical difference in baseline variables among groups, except for lumen diameter. The primary patency rates in Type I, Type II, and Type III groups were 78.4, 93.2, and 83.2% at 6 months and 59.5, 84.7, and 75.5% at 1 year, respectively. The secondary patency rates in Type I, Type II, and Type III groups were 94.4, 97.1, and 100% at 6 months and 90.5, 97.1, and 94.7% at 1 year, respectively. The Kaplan-Meier curve showed that the primary and secondary patency rates of Type I group were lower than those of Type II group. Multivariable Cox regression analysis demonstrated that postoperative primary patency was correlated with end-to-end anastomosis (hazard ratio [HR] = 2.997, p = 0.008, 95% confidence interval [CI]: 1.328-6.764) and Type I lesion (HR = 5.395, p = 0.004, 95% CI: 1.730-16.824).

CONCLUSIONS

NIH-dominant lesions of AVF evaluated by DU preoperatively were a risk factor for poor primary and secondary patency rate after PTA in hemodialysis patients.