Genetic causation of neointimal hyperplasia in hemodialysis vascular access dysfunction

Quantitative hemodynamics of draining veins in brain arteriovenous malformation: a preliminary study based on computational fluid dynamics

Objective

This study initiated a preliminary computational fluid dynamics (CFD)-based study to investigate the relationship between quantitative hemodynamics of arteriovenous malformation (AVM) draining veins and rupture.

Methods

The quantitative hemodynamics of AVM draining veins were generated from computed tomography angiography (CTA)-based steady-state CFD models. Morphological and hemodynamic parameters were compared between the ruptured and unruptured groups. The boundary conditions of the drainage vein were obtained from quantitative digital subtraction angiography (QDSA). The draining veins were divided into 15 consecutive segments to analyze the spatial distribution of the hemodynamic parameters by linear regression analysis.

Results

From 11 AVMs, it was revealed that morphological parameters of drainage veins in ruptured and unruptured AVMs were similar. The intravascular pressure of the draining vein in the ruptured AVMs was significantly higher than those of the unruptured AVMs (pressure average: p = 0.006; pressure maximum: p = 0.045), and the WSS of the posterior segment was higher in ruptured AVMs (p = 0.045). WSS of draining veins in ruptured AVMs showed a linear increase trend with segmenting (R = 0.731, p < 0.001), and ruptured AVMs were more likely to be accompanied by high-velocity segments in the draining vein (40.0% vs. 14.7%, p = 0.037), especially in the posterior segment (p = 0.011).

Conclusion

The draining veins of ruptured AVMs had significantly higher intravascular pressure and posterior segment WSS. WSS showed a linear increase with segmentation in ruptured AVMs, and they often had more high-velocity segments in the draining vein, especially in the posterior segment.

Patients, healthcare providers, and general population preferences for hemodialysis vascular access: a discrete choice experiment

Background

A patient-centered dialysis treatment option requires an understanding of patient preferences for alternative vascular accesses and nephrologists often face difficulties when recommending vascular access to end-stage kidney disease (ESKD) patients. We aimed to quantify the relative importance of various vascular access characteristics to patients, healthcare providers and general population, and how they affect acceptability for patients and healthcare providers.

Methods

In a discrete choice experiment, patients with maintenance hemodialysis (MHD), healthcare providers, and individuals from the general population were invited to respond to a series of hypothetical vascular access scenarios that differed in five attributes: cumulative patency, infection rate, thrombosis rate, cost, and time to maturation. We estimated the respondents' preference heterogeneity and relative importance of the attributes with a mixed logit model (MXL) and predicted the willingness to pay (WTP) of respondents via a multinomial logit model (MNL).

Results

Healthcare providers (n = 316) and the general population (n = 268) exhibited a favorable inclination toward longer cumulative patency, lower access infection rate and lower access thrombosis rate. In contrast, the patients (n = 253) showed a preference for a 3-year cumulative patency, 8% access infection rate, 35% access thrombosis rate and 1.5 access maturity time, with only the 3-year cumulative patency reaching statistical significance. Among the three respondent groups, the general population found cumulative patency less important than healthcare providers and patients did. Patients demonstrated the highest WTP for cumulative patency, indicating a willingness to pay an extra RMB$24,720(US$3,708) for each additional year of patency time.

Conclusion

Patients and healthcare providers had a strong preference for vascular access with superior patency. While the general population preferred vascular access with lower thrombosis rates. These results indicate that most patients prefer autogenous arteriovenous fistula (AVF) as an appropriate choice for vascular access due to its superior patency and lower complications than other vascular access types.

MSCTA imaging analysis of autologous arteriovenous fistula dysfunction in maintenance hemodialysis patients

OBJECTIVE

To observe the multi-slice spiral CT angiography (MSCTA) imaging features of arteriovenous fistula dysfunction in patients undergoing maintenance hemodialysis and analyze the significance of the imaging examination.

METHODS

Altogether 90 patients with end-stage renal disease treated by maintenance hemodialysis in General Hospital of China Resources & Wisco from June 2020 to February 2023 were divided into a normal function group (n=68) and a dysfunction group (n=22) according to the function of autogenous arteriovenous fistula. The clinical data of the two groups were recorded. The MSCTA was performed in each patient, and the manifestations of arteriovenous fistula dysfunction were analyzed. Additionally, the vascular access stenosis, vascular access lumen stenosis, arteriovenous diameter, blood flow, and hemodynamic indices were tested, and the value of MSCTA in predicting arteriovenous fistula function was analyzed by Logistic regression.

RESULTS

The degree of vascular access stenosis and vascular access lumen stenosis in the normal group were less than those in the dysfunctional group (P<0.05). The arteriovenous diameter, blood flow, blood flow velocity at anastomotic vein end, dialysis adequacy (spKt/V), and von Willebrand factor (vWF) function in the normal group were larger than those in the dysfunction group, and the radial artery shear force was lower than in the dysfunction group, with statistical significance (P<0.05). Among the arteriovenous fistula dysfunction, there were 3 patients with anastomotic + outflow vein stenosis, 4 patients with outflow vein stenosis, 9 patients with inflow artery + anastomosis + outflow vein stenosis, and 6 patients with superior vena cava stenosis. Logistic regression analysis showed that slow blood flow velocity at the venous end of anastomosis and high shear force of radial artery were influencing factors of arteriovenous fistula dysfunction, and the area under ROC curve of blood flow velocity at the venous end of anastomosis plus shear force of radial artery was 0.93, with a sensitivity of 0.87 and a specificity of 0.85.

CONCLUSION

MSCTA can be used to evaluate the dysfunction of autologous arteriovenous fistula in patients undergoing maintenance hemodialysis, and provide important reference information for the formulation of the next best clinical treatment plan.

Association of Retinol-Binding Protein 4 with Arteriovenous Fistula Dysfunction in Hemodialysis Patients

BACKGROUND

Arteriovenous fistula (AVF) is the most common vascular access for patients undergoing hemodialysis (HD). Neointimal hyperplasia (NIH) might be a potential mechanism of AVF dysfunction. Retinol-binding protein 4 (RBP4) may play an important role in the pathogenesis of NIH. The aim of this study was to investigate whether AVF dysfunction is associated with serum concentrations of RBP4 in HD subjects.

METHODS

A cohort of 65 Chinese patients undergoing maintenance HD was recruited between November 2017 and June 2019. The serum concentrations of RBP4 of each patient were measured with the ELISA method. Multivariate logistic regression was used to analyze data on demographics, biochemical parameters, and serum RBP4 level to predict AVF dysfunction events. The cutoff for serum RBP4 level was derived from the highest score obtained on the Youden index. Survival data were analyzed with the Cox proportional hazards regression analysis and Kaplan-Meier method.

RESULTS

Higher serum RBP4 level was observed in patients with AVF dysfunction compared to those without AVF dysfunction events (174.3 vs. 168.4 mg/L, p = 0.001). The prevalence of AVF dysfunction events was greatly higher among the high RBP4 group (37.5 vs. 4.88%, p = 0.001). In univariate analysis, serum RBP4 level was statistically significantly associated with the risk of AVF dysfunction (OR = 1.015, 95% CI 1.002-1.030, p = 0.030). In multivariate analysis, each 1.0 mg/L increase in RBP4 level was associated with a 1.023-fold-increased risk of AVF dysfunction (95% CI for OR: 1.002-1.045; p = 0.032). The Kaplan-Meier survival analysis indicated that the incidence of AVF dysfunction events in the high RBP4 group was significantly higher than that in the low-RBP4 group (p = 0.0007). Multivariate Cox regressions demonstrated that RBP4 was an independent risk factor for AVF dysfunction events in HD patients (HR = 1.015, 95% CI 1.001-1.028, p = 0.033).

CONCLUSIONS

HD patients with higher serum RBP4 concentrations had a relevant higher incidence of arteriovenous dysfunction events. Serum RBP4 level was an independent risk factor for AVF dysfunction events in HD patients.

Risk factors for hemorrhage of brain arteriovenous malformation

Patients with brain arteriovenous malformation (bAVM) are at risk of intracranial hemorrhage (ICH). Overall, bAVM accounts for 25% of hemorrhagic strokes in adults <50 years of age. The treatment of unruptured bAVMs has become controversial, because the natural history of these patients may be less morbid than invasive therapies. Available treatments include observation, surgical resection, endovascular embolization, stereotactic radiosurgery, or combination thereof. Knowing the risk factors for bAVM hemorrhage is crucial for selecting appropriate therapeutic strategies. In this review, we discussed several biological risk factors, which may contribute to bAVM hemorrhage.

[Effect of genetic polymorphisms on functioning of a permanent vascular access in patients on dialysis]

Thromboses and stenoses of permanent vascular access appear to be a serious hazard for patients with end-stage kidney disease on programmed haemodialysis. Relapses of these pathological conditions are the cause of repeated hospitalization, secondary surgical interventions and may eventually lead to impossibility of carrying out procedures of haemodialysis. Often, vascular access dysfunction occurs for no apparent reason, thus underlying the importance of studies aimed at revealing additional factors of intravascular thrombogenesis and neointimal formation in a vascular access, including the works dedicated to studying genetic predictors of the development of the above-mentioned complications. The authors examined herein the role of polymorphisms of the genes of endothelin-1 (END-1), nitric oxide synthase-3 (NOS-3), angiotensinogen-2 (AGT-2), angiotensinogen-1 (AGT-1), angiotensinogen 2 receptor type 1 (AGTR1), mitochondrial superoxide dismutase-2 (SOD-2), catalase (CAT) superoxide dismutase-1 (SOD-1) and angiotensin converting enzyme (ACE) in the functional state of permanent vascular access in patients on dialysis. The obtained results demonstrated direct cause-and-effect relationships between polymorphisms lys-198 asn in the END-1 gene, C60T, T58C in the SOD-2 gene and the function of vascular access. The presence of END-1 gene lys-198 asn polymorphism in a homozygous state (allele 1) was associated with a high risk of an unsatisfactory condition of permanent vascular access (p=0.019).

Randomized pilot study to compare metal needles versus plastic cannulae in the development of complications in hemodialysis access

BACKGROUND

Hemodialysis requires needle insertions every treatment. Needle injury (mechanical or hemodynamic) may cause complications (aneurysms/stenosis) that compromise dialysis delivery requiring interventions. Metal needles have a sharp slanted "V"-shaped cutting tip; plastic cannulae have a dull round tip and four side holes. Preliminary observations demonstrated a difference in intradialytic blood flow images and mean Doppler velocities at cannulation sites between the two devices. Complications from mechanical and hemodynamic trauma requiring interventions were compared in each group.

MATERIALS AND METHODS

In all, 33 patients (13 females and 17 new accesses) were randomized to metal group (n = 17) and plastic group (n = 16). Mechanical trauma was minimized by having five nurses performing ultrasound-guided cannulations. Complications were identified by the clinician and addressed by the interventionalists, both blinded to study participation. Patients were followed for up to 12 months.

RESULTS

Baseline characteristics were not significant. Procedures to treat complications along cannulation segments increased from 0.41 to 1.29 per patient (metal group) and decreased from 1.25 to 0.69 per patient (plastic group; p = 0.004). The relative risks of having an intervention (relative risk = 1.5, 95% confidence interval = 0.88-2.67) and having an infiltration during hemodialysis (relative risk = 2.26, 95% confidence interval = 1.03-4.97) were higher for metal needles. Time to first intervention trended in favor of plastic cannula (p = 0.069). Cost of supplies for these interventions was approximately CAD$20,000 lower for the plastic group.

CONCLUSION

Decreased burden of illness related to cannulation (less infiltrations during hemodialysis) and Qb were associated with plastic cannulae. Decreased procedure costs were suggested during the study period in the plastic group.

Is there an association between central vein stenosis and line infection in patients with tunnelled central venous catheters (TCVCs)?

PURPOSE

Central vein stenosis (CVS) and line infection are well-recognized complications of tunnelled central venous catheters (TCVCs) in patients on haemodialysis. The aim of this study was to evaluate any relationship between CVS and line infection.

METHODS

Analysis of 500 consecutive patients undergoing TCVC insertion was undertaken. Data were collected on patient demographics, details of line insertion and duration, culture-proven bacteraemia and presence of symptomatic CVS. Logistic regression analysis was used to determine risk factors for CVS and bacteraemia.

RESULTS

Mean patient age was 59.0 years (range: 17-93). Mean number of catheter days was 961.1 ± 57.6 per TCVC; 39.4% of TCVCs were associated with culture-proven bacteraemia and 23.6% developed symptomatic CVS. Bacteraemia and CVS were inevitable complications of all TCVCs. The time to symptomatic CVS was longer in patients with bacteraemia than without (1230.91 ± 101.29 vs. 677.49 ± 61.59 days, p<0.001). Patients who had early infection within 90 days of TCVC insertion were less likely to develop CVS (5.9% vs. 22.8%, p<0.001). There was no difference in the bacteraemia rate per 1,000 catheter days between patients with and without CVS (2.62 ± 1.41 vs. 2.35 ± 0.51; p = 0.98). Number of line days (odds ratio (OR) 1.02, p = 0.003), age (OR 1.04, p = 0.04) and culture-proven line infection (OR 0.59, p = 0.014) were all independently associated with CVS.

CONCLUSIONS

Our results suggest that early line infection may be protective against CVS. Alternatively, there may be two distinct predisposition states for CVS and line infection. Further studies are needed to confirm our association and investigate causation.

Paclitaxel Drug-eluting Balloons to Recurrent In-stent Stenoses in Autogenous Dialysis Fistulas: A Retrospective Study

Purpose

To assess the effect of the Medtronic paclitaxel drug-eluting balloon (DEB) on re-intervention to in-stent stenoses in autogenous dialysis arteriovenous fistulas (AVFs).

Background

AVF is the optimum haemodialysis access. The commonest problem is stenosis, preventing maturation, causing inadequate dialysis or precipitating occlusion. Conventional angioplasty has a high recurrence rate. Successful drug elution in the coronary circulation led us to use DEBs in recurrent AVF stenoses since 2010.

Methods

This is a retrospective study, based on prospective audit data, using DEBs on recurrent in-stent stenotic lesions in the AVF circuit of our haemodialysis population. To analyse the effect of DEBs on re-intervention, we created two Kaplan–Meier curves. The first curve compares the last “disease-free-interval” pre-DEB intervention to the first “disease-free interval” post-DEB, giving us “re-intervention-free percentage at 12 months” pre- and post-DEB. The second curve takes into account the multiple pre- and post-DEB interventions to the index lesion, and uses a marginal proportional hazards model to estimate the hazard ratio for “DEBpresent vs. DEBabsent”.

Results

From 1 September 2010 to 1 December 2013, we treated 625 AVF stenoses with endovascular techniques. In 86 of these stenoses, DEBs were used. Of the 86 DEB interventions, 37 were included for this study, 49 were excluded. In the study group, there was a significant difference in “re-intervention-free percentage at 12 months” before and after DEB: 19% vs. 69%. The hazard ratio for “DEBpresent” vs. “DEBabsent” was 0.23 (95% CI 0.14 to 0.36, p<0.001).

Conclusions

This retrospective study suggests that DEBs significantly reduce re-intervention on recurrent in-stent AVF stenoses.

Functioning of an arteriovenous fistula requires heme oxygenase-2

Heme oxygenase-2 (HO-2), the constitutive isoform of the heme-degrading enzyme heme oxygenase, may serve as an anti-inflammatory vasorelaxant, in part, by generating carbon monoxide. Arteriovenous fistulas (AVFs) are employed as hemodialysis vascular accesses because they provide an accessible, high-blood-flow vascular segment. We examined the role of vascular expression of HO-2 in AVF function. An AVF was created in mice by anastomosing the carotid artery to the jugular vein. HO-2 expression was detected by immunohistochemistry in the intact carotid artery, mainly in endothelial cells and smooth muscle cells; expression of HO-2 protein and mRNA was modestly increased in the artery of the AVF. Creating an AVF in HO-2(-/-) mice compared with an AVF in HO-2(+/+) mice led to markedly reduced AVF blood flow and increased numbers of nonfunctioning AVFs. The impairment of AVF function in the setting of HO-2 deficiency could not be ascribed to either preexisting intrinsic abnormalities in endothelium-dependent and endothelium-independent relaxation of the carotid artery in HO-2-deficient mice or to impaired vasorelaxant responses in the intact carotid artery in vivo. HO-1 mRNA was comparably induced in the AVF in HO-2(+/+) and HO-2(-/-) mice, whereas the AVF in HO-2(-/-) mice compared with that in HO-2(+/+) mice exhibited exaggerated induction of matrix metalloproteinase (MMP)-9 but similar induction of MMP-2. HO-2 deficiency also led to lower AVF blood flow when AVFs were created in uremia, the latter induced by subtotal nephrectomy. We conclude that HO-2 critically contributes to the adequacy of AVF blood flow and function.

Early outcomes of the intraluminal flow guard device for secondary renal access

PURPOSE

The Flixene Intraluminal Flow Guard (IFG) is a novel arteriovenous graft for use in complex renal access patients. The IFG is a PTFE graft with a covered nitinol stent at the venous end implanted into the axillary vein rather than anastomosed. The purported benefits are improved hemodynamic flow in the vein with reduced neointimal hyperplasia. Our primary aim was to assess its early patency and complications. Our center is the first to publish early outcomes.

METHODS

All patients on whom we would have otherwise performed a standard brachial-axillary graft from April to November 2011 were instead given an IFG graft if they were suitable and consented. The only exclusion criteria was an axillary vein size under 5.5 mm as this would not accommodate the intraluminal stent graft. Data were collected prospectively and follow-up was identical to our usual graft surveillance.

RESULTS

A total of 12 patients (mean age 64, mean follow-up 393 days) had IFG grafts implanted during the study period. There were no exclusions and all patients consented. All patients were having secondary access following previous failed fistulae or grafts and no patient had an autogenous hemodialysis option. On average each patient had already had 1.1 previous ipsilateral access procedures. Mean operating time was 109 minutes. Functional patency at one year was 65.6%, with a mean functional patency of 162 days. There was only one early complication (wound hematoma) and one graft infection requiring explantation.

CONCLUSIONS

The IFG device provides an alternative to standard brachial-axillary grafts and brings similar early patency and complication profile. Continued monitoring of outcomes, however, is required to determine long-term results.