Arteriovenous Fistula Creation and Estimated Glomerular Filtration Rate Decline in Advanced CKD: A Matched Cohort Study

Impact of arteriovenous fistula formation on trajectory of kidney function decline: a target trial emulation

Background

Prior nonrandomized studies have suggested nephroprotective effects of arteriovenous fistula (AVF) formation, but these are plausibly susceptible to immortal time and selection biases.

Methods

We studied patients attending nephrology clinics in the West of Scotland during 2010-22 with an estimated glomerular filtration rate (eGFR) ≤15 mL/min/1.73 m2 and no prior AVF. Using target trial emulation and a sequential trial design, we simulated a hypothetical trial that would randomize patients to either undergo AVF formation immediately or not to undergo AVF formation. The primary outcome was the difference in eGFR slope for the first 6 months of follow-up, estimated using a mixed-effects model. The secondary outcomes were 5-year absolute risks of dialysis and death, estimated using the Aalen-Johansen and Kaplan-Meier estimators respectively.

Results

A total of 1364 unique patients (mean age 51.1 years, 55.7% male) contributed 3125 person-trials, with 561 in the AVF and 2564 in the no AVF group. Mean eGFR was 12.6 mL/min/1.73 m2 and the median number of eGFR measurements per person-trial was 7 (interquartile range 4-12). Slope of eGFR decline did not differ significantly between the AVF and no AVF groups (between-group difference -0.67 mL/min/1.73 m2/year, 95% CI -1.43, 0.10). The 5-year absolute risk of dialysis was 87% (95% CI 84, 91) in the AVF group and 75% (95% CI 73, 77) in the no AVF group, and the 5-year survival probability was 77% (95% CI 70, 83) in the AVF group and 67% (95% CI 64, 69) in the no AVF group.

Conclusions

In this study of patients with advanced chronic kidney disease, there was no evidence of a nephroprotective effect of AVF formation.

Late creation of vascular access increased post-hemodialysis mortality, hospitalization, and health-care expenditure: A population-based cohort study in Taiwan

BACKGROUND/PURPOSE

The optimal timing of vascular access (VA) creation for hemodialysis (HD) and whether this timing affects mortality and health-care utilization after HD initiation remain unclear. Thus, we conducted a population-based study to explore their association.

METHODS

We used Taiwan's National Health Insurance Research Database to analyze health-care outcomes and utilization in a cohort initiating HD during 2003-2013. We stratified patients by the following VA creation time points: >180, 91-180, 31-90, and ≤30 days before and ≤30 days after HD initiation and examined all-cause mortality, ambulatory care utilization/costs, hospital admission/costs, and total expenditure within 2 years after HD. Cox regression, Poisson regression, and general linear regression were used to analyze mortality, health-care utilization, and costs respectively.

RESULTS

We identified 77,205 patients who started HD during 2003-2013. Compared with the patients undergoing VA surgery >180 days before HD initiation, those undergoing VA surgery ≤30 days before HD initiation had the highest mortality-15.92 deaths per 100-person-years, crude hazard ratio (HR) 1.56, and adjusted HR 1.28, the highest hospital admissions rates- 2.72 admission per person-year, crude rate ratio (RR) 1.48 and adjusted RR 1.32, and thus the highest health-care costs- US$31,390 per person-year, 7% increase of costs and 6% increase with adjustment within the 2-year follow-up after HD initiation.

CONCLUSION

Late VA creation for HD can increase all-cause mortality, hospitalization, and health-care costs within 2 years after HD initiation. Early preparation of VA has the potential to reduce post-HD mortality and healthcare expenses for the ESKD patients.

Arteriovenous fistula in predialysis chronic kidney disease patients and rate of decline of glomerular filtration rate

PURPOSE

To quantify the evidence for the role of arteriovenous fistula (AVF) in predialysis CKD patients for the rate of decline of glomerular filtration rate (GFR).

BACKGROUND

Pre-emptive placement of arteriovenous fistula (AVF) in late-stage chronic kidney disease (CKD) patients is being advocated by all the major guidelines. Recent studies have suggested that pre-emptive AVF has a beneficial effect on glomerular filtration rate (GFR) also.

METHODS

We conducted a literature search to retrieve all published studies related to the effect of AVF on the rate of decline of GFR using the electronic databases Google Scholar, PubMed, Central, Cochrane Library, clinialtrial.gov. Screening of studies and data extraction were done according to the PRISMA guidelines. We used the NIH assessment tool for the methodological quality assessment of the included studies. Extracted data from the six studies were pooled and analyzed.

RESULTS

Six studies involving 3871 patients reported the effect of AVF creation on the rate of decline of GFR in late CKD patients. Evidence for statistically significant decline of eGFR after AVF creation compared to prior status (SMD -1.57, 95% CI -3.08 to -0.07, p < 0.001) was observed.

CONCLUSION

Our meta-analysis observed preliminary evidence that the creation of AVF might have a potential added benefit in terms of estimated GFR improvement, though to a very small extent with a low level of certainty. More scientific data with high-quality studies are needed to substantiate this finding.

Cardiac implications of upper-arm arteriovenous fistulas: A case series

BACKGROUND

Cardiovascular disease is a major cause of morbidity and mortality in patients with end-stage kidney disease. Arterio-venous fistulas (AVF), the gold standard for hemodialysis vascular access, are known to alter cardiac morphology and circulatory hemodynamics. We present a prospective case series of patients after creation of an AVF, explore the timeline for changes in their cardiac morphology, and detail considerations for clinicians.

METHODS

Patients were recruited in 2010 at multiple centers immediately prior to the creation of an upper-arm AVF and the initiation of hemodialysis. Cardiovascular magnetic resonance images were taken at intake before the creation of the AVF, 6-month follow-up, and 12-month follow-up. Image segmentation was used to measure left ventricular volume and mass, left atrial volume, and ejection fraction.

RESULTS

Eight patients met eligibility criteria. All eight patients had a net increase in left ventricular mass over enrollment, with a mean increase of 9.16 g (+2.96 to +42.66 g). Five participants had a net decrease in ejection fraction, with a mean change in ejection fraction of -5.4% (-21% to +5%). Upon visual inspection the patients with the largest ejection fraction decrease had noticeably hypertrophic and dilated ventricles. Left atrial volume change was varied, decreasing in five participants, while increasing in three participants. Changes in morphology were present at 6-month follow-up, even in patients who did not maintain AVF patency for the entirety of the 6-month period.

CONCLUSION

All patients included in this prospective case series had increases in left ventricular mass, with variability in the effects on the ejection fraction and left atrial volume. As left ventricular mass is an independent predictor of morbidity and mortality, further research to determine appropriate vascular access management in both end-stage kidney disease and kidney transplant populations is warranted.

Increased Excess Pressure After Creation of an Arteriovenous Fistula in End-Stage Renal Disease

BACKGROUND

Reservoir-wave analysis (RWA) separates the arterial waveform into reservoir and excess pressure (XSP) components, where XSP is analogous to flow and related to left ventricular workload. RWA provides more detailed information about the arterial tree than traditional blood pressure (BP) parameters. In end-stage renal disease (ESRD), we have previously shown that XSP is associated with increased mortality and is higher in patients with arteriovenous fistula (AVF). In this study, we examined whether XSP increases after creation of an AVF in ESRD.

METHODS

Before and after a mean of 3.9 ± 1.2 months following creation of AVF, carotid pressure waves were recorded using arterial tonometry. XSP and its integral (XSPI) were derived using RWA through pressure wave analysis alone. Aortic stiffness was assessed by carotid-femoral pulse wave velocity (CF-PWV).

RESURLTS

In 38 patients (63% male, age 59 ± 15 years), after AVF creation, brachial diastolic BP decreased (79 ± 10 vs. 72 ± 12 mm Hg, P = 0.002), but the reduction in systolic BP, was not statistically significant (133 ± 20 vs. 127 ± 26 mm Hg, P = 0.137). However, carotid XSP (14 [12-19] to 17 [12-22] mm Hg, P = 0.031) and XSPI increased significantly (275 [212-335] to 334 [241-439] kPa∙s, P = 0.015), despite a reduction in CF-PWV (13 ± 3.6 vs. 12 ± 3.5 m/s, P = 0.025).

CONCLUSIONS

Creation of an AVF resulted in increased XSP in this population, despite improvement in diastolic BP and aortic stiffness. These findings underline the complex hemodynamic impact of AVF on the cardiovascular system.

Flow reduction of a high-flow arteriovenous fistula in a hemodialysis patient reveals changes in natriuretic and renin-angiotensin system hormones of relevance for kidney function

Arteriovenous fistulas (AVFs) are iatrogenic vascular connections established to allow high-flow intravascular access for patients with chronic kidney disease requiring hemodialysis. The left-right flow shunt results in changes in extracellular fluid volume and blood pressure-controlling hormones that could affect the residual kidney function. We present a case where a female patient with a brachiocephalic AVF had a fistula flow of >4 L/min. To reduce the flow, a banding procedure was performed. The patient was examined prior to banding and 1 and 2 weeks thereafter. Banding resulted in a marked decrease in AVF flow from >4 to 1 L/min and was associated with reductions in N-terminal pro-brain natriuretic peptide of 51% and 67% at 1- and 2-weeks post-banding, respectively. Mid-regional pro-atrial natriuretic peptide concentrations were reduced post-banding by 17% after 1 week and 25% after 2 weeks. After 1 week, renin, angiotensin II, and aldosterone levels in plasma decreased transiently by 44%, 47%, and >86%, respectively, and returned to pre-banding levels after 2 weeks. Creatinine clearance tended to decrease while blood pressure and total body water increased 2 weeks after banding. This indicates that high-flow AVF is associated with increased natriuretic peptides and hormones of the renin-angiotensin-aldosterone system, that may balance each other regarding fluid retention and hypertension and support remaining kidney function.