Inferiority of arteriovenous grafts, in comparison to autogenous fistulas, is underestimated by standard survival measures alone

Comparing post-maturation outcomes of arteriovenous grafts and fistulae

BACKGROUND

Though arteriovenous grafts (AVG) mature more reliably than arteriovenous fistulae (AVF) and require fewer maturation procedures (MP) to obtain functional patency, AVG are thought to have worse function after maturation. We explored differences in post-maturation outcomes between the following groups: AVF patients who did (AS-AVF) and did not (unAS-AVF) require assisted maturation and AVG patients who did (AS-AVG) and did not (unAS-AVG) require assisted maturation.

METHODS

Using the US Renal Data System (2012-2017), we retrospectively identified patients who initiated dialysis with a central venous catheter, underwent AVF or AVG placement and achieved successful two-needle cannulation. Primary patency and access abandonment after maturation were compared across groups using competing risks regression methods, generating sub-hazards ratios (sHR).

RESULTS

We identified 42,664 AVF and 12,335 AVG that met inclusion criteria. A larger proportion of AVFs required interventions: 18,408 AVF (43.2%) versus 2594 AVG (21.0%; p < 0.01). Both AS-AVG and AS-AVF patients experienced patency loss at 1 year more frequently compared with unAS-AVG (67.5% & 57.5% vs 55.2% respectively). Patency loss was lowest in unAS-AVF (38.9%). These trends were robust on adjusted analysis (unAS-AVG reference, AS-AVG sHR = 1.44, p < 0.01; AS-AVF sHR = 1.08, p < 0.01, unAS-AVF sHR = 0.67, p < 0.01). AS-AVGs were more likely to be abandoned than unAS-AVGs (11.7% unAS-AVG vs 17.2% AS-AVG). Fistulae, assisted or not, had lower unadjusted rates of 1-year abandonment than grafts (8.9% AS-AVF vs 7.3% unAS-AVF). On adjusted analysis, AVF usage was protective against abandonment (unAS-AVG, reference; AS-AVF sHR = 0.67, p < 0.01; unAS-AVF sHR = 0.59, p < 0.01) while AS-AVG was not (AS-AVG sHR = 1.32, p < 0.01).

CONCLUSIONS

unAS-AVF have the best long-term outcomes. AS-AVF lose primary patency at a higher rate than unAS-AVG. AVGs may be a better choice than AVFs if veins are marginal and likely to require assisted maturation. Further research is needed to identify anatomic and physiologic factors that affect long-term performance and influence conduit choice.

Forearm Basilic Vein Transposition: A Single-Centre Experience

INTRODUCTION

Forearm basilic vein transposition (FBVT) is a viable alternative for arteriovenous grafts (AVGs) and can be used as secondary vascular access as well, as it allows for the use of veins that are remote from the arterial source of inflow. FBVT involves two main steps: first, the basilic vein is dissected from its original location; and second, the basilic vein is transposed to a subcutaneous tunnel on the volar aspect of the forearm and anastomosed to a suitable artery, usually the radial or ulnar artery.

OBJECTIVE

This paper aims to present a series of FBVT cases performed at our hospital and present it as a viable option for secondary vascular access. We also aim to review the available literature relating to FBVT fistula in terms of surgical technique, patency rates, maturation time, and one-year outcome, and to establish a comparison with our clinical experience.

MATERIALS AND METHODS

This is a retrospective descriptive case series. The data were collected from online medical records, and patients were contacted by telephone to make a follow-up visit. For a review of the literature, a search was done on PubMed for articles containing the following keywords in either the title or the abstract: basilic, transposition, fistula, and forearm. Similarly, a search was done on Google Scholar for articles with the following words in the title: basilic, transposition, and forearm. The data are expressed as mean and standard deviation. Statistical analysis was done using SPSS 26.0 software (IBM Corp., Armonk, NY).

CONCLUSION

The primary patency rate of FBVT in our study makes it a suitable solution to opt for before moving to AVGs. FBVT should be considered before moving more proximally in patients with inadequate forearm cephalic veins.

Optimal flow volume measurements in forearm versus arm arteriovenous fistulas

OBJECTIVES

Successful haemodialysis is dependent on optimal arteriovenous (AV) access flow. Although 600 ml/min is frequently quoted as the critical level for functional flow volume (Qa) according to the National Kidney Foundation guideline, this may not be applicable for the different configurations of AV fistulas (AVF) or AV grafts (AVG). This study evaluates ultrasound derived Qa measurement in the inflow brachial artery to autologous AVF in the forearm radiocephalic and arm brachiocephalic/basilic configurations in relation to significant flow related AV dysfunction.

METHODS

Five hundred and eleven duplex ultrasound (DUS) scans were analysed in 193 patients. The end points were therapeutic intervention and/or thrombosis of AVF versus no complication within 3 months of the scan. Receiver operating characteristic (ROC) curves were used to determine the optimal threshold Qa of the brachial artery supplying the AVF.

RESULTS

Of the 511 scans, 155 scans were assigned to the intervention group, that is, AVF requiring intervention or thrombosing within 3 months of the DUS. Using ROC curve analysis, the area under the curve (AUC) for all AVF is 0.90 (CI: 0.88-0.93) with an optimal threshold Qa of 686 ml/min. In forearm AVF, the threshold Qa is 589 ml/min while in arm AVF the threshold Qa is 877 ml/min. Forearm Qa is statistically different from arm Qa.

CONCLUSION

Forearm AVF Qa threshold at 589 ml/min is distinct from arm AVF Qa at 877 ml/min and these are predictive of the need for impending intervention or thrombosis due to flow-limiting stenosis.

Receiver operating characteristic curve analysis of arteriovenous dialysis access flow using ultrasound

BACKGROUNDS

Despite numerous studies investigating the use of ultrasound (US) in assessing arteriovenous fistulas (AVF), there are no universally agreed threshold flow velocities in diagnosing significantly abnormal flow that are useful in predicting thrombotic flow-related dysfunction. This study evaluates a predictive model using receiver operating characteristic curve (ROC) analyses to establish threshold velocities.

METHODS

Five hundred and eleven US scans were analysed. ROC curves were used to determine the optimal threshold time average mean velocity (TAMV), peak systolic velocity (PSV) and end diastolic velocity (EDV) of the brachial artery supplying the AVF in determining the need for intervention or thrombosis within 3 months of the scans. Estimated flow volume (FV) ROC was used as an evaluative comparison.

RESULTS

There were 356 negative and 155 positive scan results in relation to the need for intervention or thrombosis. Empirical flow velocity parameters of TAMV, EDV and PSV were analysed using ROC curves, yielding an area under the curve (AUC) of 0.95, 0.92 and 0.86, respectively. FV ROC analysis yields a comparative AUC of 0.90. A TAMV cut-off at 48.6 cm/s yielded the highest AUC. Subgroup analysis yielded an optimal TAMV cut-off of 45 cm/s for forearm and 49 cm/s for arm AVF. The EDV was also highly predictive of outcomes. PSV has the lowest accuracy.

CONCLUSION

The TAMV of inflow brachial artery to AVF is highly predictive of outcomes of thrombotic flow-related dysfunction. Our study confirms TAMV cut-offs of 45 cm/s for forearm and 49 cm/s for arm AVF. These results require prospective validation.

Single-Institution Learning Curve for Management of Mega-Fistulae Revision

Mega-fistulae are generalized aneurysmal dilations of a high flow (1500-4000 mL/min) autogenous arteriovenous (AV) access which may result in hemorrhage and/or high-output cardiac failure. Current treatment options for mega-fistula include ligation with and without prosthetic jump graft, aneurysmorrhaphy, aneurysmectomy with vein transposition, and imbrication. These options may not be suitable for advanced disease; may leave the patient without working AV access, poor cosmetic results, and possible recurrence. We describe our early experience with a technique of complete mega-fistula resection and replacement with an early use prosthetic graft that both maintains existing AV access and eliminates the need for long-term catheter placement; including lessons learned.