Preoperative radial artery volume flow is predictive of arteriovenous fistula outcomes

Doppler ultrasound assessment of calcified radial arteries prior to radio-cephalic arterio-venous fistula placement: an observational study

BACKGROUND

In elderly and diabetic patients, arterial calcifications are prevalent and result in worse outcomes of arterio-venous fistulas (AVFs). Optimal ultrasound criteria for assessment of calcified arteries are unknown. We report our experience with ultrasound assessment of calcified arteries prior to placement of radio-cephalic (RC) AVFs.

MATERIAL AND METHODS

We included 85 patients in whom a RC-AVF placement was planned. Patients were divided according to the presence of radial artery calcifications into a calcified group (moderate/severe calcifications, N = 18) and control group (no changes/mild atherosclerosis, N = 67). Doppler ultrasound parameters were analyzed in the calcified group with focus on assessment of the artery, including grading of calcifications and Doppler measurements at rest and during reactive hyperemia (RH).

RESULTS

In the calcified group mean patients' age was 72 ± 11 years, 72% were diabetics, mean resistance index (RI) during RH was 0.78 ± 0.09 (range 0.63-0.90). In 14 (78%) patients an AVF was successfully placed and in 12 it matured (67% maturation rate). A lower RI at rest was observed in the primary failure sub-group with high area under the ROC curve (0.89) and a cut-off value of 0.90 for RI. There was no difference in RI at RH between failed and matured AVFs. 1-year secondary patency was 66% and in eight patients with follow-up ultrasound available, blood flow was 350-1300 ml/min. For comparison, in the control group a radio-cephalic AVF was placed in all patients, primary failure rate was 6%, maturation rate 85% and 1-year secondary patency was 77%.

CONCLUSIONS

Our very limited experience suggests that successful RC-AVF placement and maturation with good 1-year patency rates is possible in patients with moderately/severely calcified arteries and RI during RH of up to 0.90.

In Vivo Labeling and Detection of Circulating Tumor Cells in Mice Using OTL38

PURPOSE

We recently developed an optical instrument to non-invasively detect fluorescently labeled circulating tumor cells (CTCs) in mice called 'Diffuse in vivo Flow Cytometry' (DiFC). OTL38 is a folate receptor (FR) targeted near-infrared (NIR) contrast agent that is FDA approved for use in fluorescence guided surgery of ovarian and lung cancer. In this work, we investigated the use OTL38 for in vivo labeling and detection of FR + CTCs with DiFC.

PROCEDURES

We tested OTL38 labeling of FR + cancer cell lines (IGROV-1 and L1210A) as well as FR- MM.1S cells in suspensions of Human Peripheral Blood Mononuclear cells (PBMCs) in vitro. We also tested OTL38 labeling and NIR-DIFC detection of FR + L1210A cells in blood circulation in nude mice in vivo.

RESULTS

62% of IGROV-1 and 83% of L1210A were labeled above non-specific background levels in suspensions of PBMCs in vitro compared to only 2% of FR- MM.1S cells. L1210A cells could be labeled with OTL38 directly in circulation in vivo and externally detected using NIR-DiFC in mice with low false positive detection rates.

CONCLUSIONS

This work shows the feasibility of labeling CTCs in vivo with OTL38 and detection with DiFC. Although further refinement of the DiFC instrument and signal processing algorithms and testing with other animal models is needed, this work may eventually pave the way for human use of DiFC.

Randomized comparison of Glidesheath Slender with conventional 5Fr arterial sheaths for coronary angiography through the distal radial artery

BACKGROUND

The potential benefits of the thin-walled 5F Glidesheath Slender sheath in the distal transradial access (dTRA) have not been investigated. This study aimed to compare the Glidesheath Slender versus conventional 5Fr arterial sheaths in patients undergoing diagnostic coronary angiography (CAG) through the dTRA.

METHODS

A total of 352 consecutive patients with an indication for CAG were randomized (1:1) to Glidesheath Slender 5Fr versus a conventional 5Fr arterial sheath for dTRA. The primary endpoint was the rate of successful hemostasis at 30 minutes after sheath removal. Follow-up ultrasound of the right radial and distal radial artery was performed 7-10 days after the procedure.

RESULTS

After exclusion of patients where a 6Fr sheath or crossover of access site was required, 108 patients in the Glidesheath Slender and 105 patients in the conventional 5Fr arterial sheath group were included in the analysis. The crossover rate to conventional radial access and the rate of successful hemostasis at 30 minutes after sheath removal were similar between the two groups (18.9% in the Glidesheath slender vs. 22% in the control group; P=0.460, and 62% vs. 51.4%; P=0.118, respectively). The level of pain associated with the procedure was significantly lower in the Glidesheath Slender group (2.69 vs. 3.29 in the control group; P=0.02). No significant difference was recorded between the two groups in the rate of access-related complications.

CONCLUSIONS

Use of Glidesheath Slender for dTRA did not increase the rate of early hemostasis compared with conventional arterial sheath.

Ratiometric fluorescence sensing and quantification of circulating blood sodium sensors in mice in vivo

In this work, we introduce ratiometric diffuse in vivo flow cytometry (R-DiFC) for quantitative measurement of circulating fluorescent red blood cell (fRBC) sensors for systemic blood sodium levels. Unlike in our previous work in measuring circulating fRBC sensors, R-DiFC allows simultaneous measurement of two fluorophores encapsulated in the sensor, the ratio of which enables self-calibration of the fluorescence signal with different fRBC depths in biological tissue. We show that the R-DiFC signal varies significantly less than either fluorescence signal alone. This work holds promise for personalized monitoring of systemic sodium for bipolar patients in the future.

Model and online calculator for prediction of fistula maturation based on vein dilation and age: A retrospective cohort study in a single-center

OBJECTIVE

A model that considers the characteristics of dialysis patients may help predict successful fistula maturation. We evaluated factors associated with radiocephalic arteriovenous fistula (RCAVF) maturation at 3 months in dialysis patients with end-stage renal disease (ESRD).

METHODS

A total of 184 patients who received an initial RCAVF at Beijing Haidian Hospital (Haidian Section of Peking University Third Hospital) were recruited. Fistula maturation was assessed within 3 months. Patient characteristics and preoperative vascular assessment indices were examined. Factors associated with fistula maturation were analyzed using logistic regression and least absolute shrinkage and selection operator (LASSO) binary logistic regression. Boostrapping was used for internal validation.

RESULTS

The development data consisted of 184 ESRD patients receiving an initial RCAVF, 140 (76%) of whom achieved fistula maturation. The main predictors of RCAVF maturation in the final model were sex, age-adjusted vein dilation (eVD), radial artery volume (Vartery), and diastolic blood pressure. The difference of vein diameter with and without a tourniquet was significantly larger in the mature RCAVF group (3.0 ± 0.5 vs. 2.2 ± 0.5 mm). The area under receiver operating characteristic (AUROC) curve for prediction of fistula maturation was 0.77, and the Hosmer-Lemeshow statistic indicated agreement between observed and predicted values (P = 0.792). Analysis of internal validation using bootstrapping indicated the C-index was 0.75.

CONCLUSION

The ratio of vein dilation and age were the major predictors of fistula maturation at 3 months in our patients. The resulting online prediction model may help in clinical decision-making for patients receiving a RCAVF.

The Role of Ultrasound Examination in the Assessment of Suitability of Calcified Arteries for Vascular Access Creation-Mini Review

Arterial calcifications are present in 20-40% of patients with end-stage kidney disease and are more frequent among the elderly and diabetics. They reduce the possibility of arterio-venous fistula (AVF) formation and maturation and increase the likelihood of complications, especially distal ischemia. This review focuses on methods for detecting arterial calcifications and assessing the suitability of calcified arteries for providing inflow before the construction of an AVF. The importance of a clinical examination is stressed. A grading system is proposed for quantifying the severity of calcifications in the arteries of the arm with B-mode and Doppler ultrasound exams. Functional tests to assess the suitability of the artery to provide adequate inflow to the AVF are discussed, including Doppler indices (peak systolic velocity and resistive index during reactive hyperemia). Possible predictors of the development of distal ischemia are discussed (finger pressure, digital brachial index, acceleration and acceleration time), as well as the outcomes of AVFs placed on calcified arteries. It is concluded that a noninvasive ultrasound examination is probably the best tool for a morphologic and functional assessment of the arteries. An arterial assessment is of utmost importance if we are to create distal radiocephalic AVFs in our elderly patients whenever possible without burdening them with futile surgical attempts.

Tensor decomposition and machine learning for the detection of arteriovenous fistula stenosis: An initial evaluation

Duplex ultrasound (DUS) is the most widely used method for surveillance of arteriovenous fistulae (AVF) created for dialysis. However, DUS is poor at predicting AVF outcomes and there is a need for novel methods that can more accurately evaluate multidirectional AVF flow. In this study we aimed to evaluate the feasibility of detecting AVF stenosis using a novel method combining tensor-decomposition of B-mode ultrasound cine loops (videos) of blood flow and machine learning classification. Classification of stenosis was based on the DUS assessment of blood flow volume, vessel diameter size, flow velocity, and spectral waveform features. Real-time B-mode cine loops of the arterial inflow, anastomosis, and venous outflow of the AVFs were analysed. Tensor decompositions were computed from both the 'full-frame' (whole-image) videos and 'cropped' videos (to include areas of blood flow only). The resulting output were labelled for the presence of stenosis, as per the DUS findings, and used as a set of features for classification using a Long Short-Term Memory (LSTM) neural network. A total of 61 out of 66 available videos were used for analysis. The whole-image classifier failed to beat random guessing, achieving a mean area under the receiver operating characteristics (AUROC) value of 0.49 (CI 0.48 to 0.50). In contrast, the 'cropped' video classifier performed better with a mean AUROC of 0.82 (CI 0.66 to 0.96), showing promising predictive power despite the small size of the dataset. The combined application of tensor decomposition and machine learning are promising for the detection of AVF stenosis and warrant further investigation.

Vein and artery diameter influence on arteriovenous fistula maturation and patency in a Mexican population

BACKGROUND

There is no consensus of the optimal arterial and venous sizes on arteriovenous fistula (AVF) function and patency. The purpose of our study was to determine the influence of vein and artery sizes on maturation and patency in autologous first time AVF in a vascular access clinic of Mexican Social Security.

METHODS

Approved IRB single-center retrospective study in patients referred for their first AVF from 01/2018/ to 04/2020. Perianastomotic inner vein diameter and single inner artery diameter was recorded by duplex ultrasound. Outcomes were: failure to mature (FTM) and cumulative primary patency survival.

RESULTS

Eighty-six AVF's were created (mean age 45.5 ± 15.1 years; 62.8% male; mean BMI 25.9 ± 4.3 kg/m2). About 86% were brachiocephalic AVF. Eight (8.1%) AVF had FTM. Mean follow-up was 19.7 ± 8.5 months. Two-year patency survival was 81.4%. FTM vein and artery diameters (2.1 ± 0.3 and 2.8 ± 0.7 mm respectively) were smaller than successful AVF's (3.1 ± 0.9 and 3.5 ± 0.6 mm) (p < 0.05). ROC curve calculated a 2.15 mm vein diameter cutoff (AUC: 0.86) and a 2.95 mm artery diameter cutoff (AUC: 079) for FTM AVF's (83% sensitivity, 72% specificity both) (p < 0.05). AVF's created with a vein diameter <2.15 mm and <2.95 mm artery diameter had statistically significant lower patency survival than AVF's with larger vein and artery diameters (p < 0.05).

CONCLUSION

Vein diameter <2.15 mm and artery diameter <2.95 mm influences AVF maturation and patency in a Mexican population.

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.

Effect of primary balloon angioplasty on draining vein diameter and volume flow in patients with arteriovenous fistula: A cohort study

Background

Chronic kidney disease (CKD) and end-stage kidney disease (ESKD) cause major morbidity and mortality in 10% of the global population with CKD. The most common renal replacement therapy is hemodialysis with arteriovenous fistula (AVF) access. AVF often undergoes maturation failure due to feeding artery and draining vein inadequacy. Mechanical dilatation, such as primary balloon angioplasty (PBA), can overcome AVF maturation failure. The volume flow (VF) and diameter of the draining veins in AVF patients must be known to evaluate the effect of PBA on AVF maturation. This study aims to analyze the impact of PBA on VF and draining vein diameter in ESKD patients undergoing AVF surgery.

Methods

A retrospective cohort clinical trial was conducted at our institution. A total of 75 participants had AVF with an arterial diameter >1.5 mm or vein diameter at the AVF creation site of 2–4 mm. The subjects were divided into 2 groups: the intervention group undergoing PBA (n = 36) and the control group, without PBA (n = 39). PBA was performed using a Mustang ballon (3–6 mm, Medtronic). Follow-ups were conducted at 1 week, 2 weeks, and 6 weeks after AVF creation.

Results

Based on the data, the diameter and VF of the draining veins were significantly larger in the intervention group than in the control group (p < 0.001). Furthermore, we found significant differences in the mean diameter and VF of the draining veins between the control and intervention groups at all stages of examination, from preoperatively to 6 weeks postoperatively (p < 0.001). The strength of the analysis was more than 80%.

Conclusion

PBA can increase the diameter and VF of the draining veins in patients with AVF.

•

Mechanical dilatation (i.e., primary balloon angioplasty [PBA]) can prevent arteriovenous fistula (AVF) maturation failure.

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Volume flow and diameter of draining veins in AVF patients must be known to evaluate the effect of PBA on AVF maturation.

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PBA 1.5 × larger than nominal vein size can increase the diameter and volume flow of draining veins in the AVF procedure.

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AVF with PBA 1.5 × larger than nominal vein size had a higher probability of AVF maturation than control.

Signal and measurement considerations for human translation of diffuse in vivo flow cytometry

SIGNIFICANCE

"Diffuse in vivo flow cytometry" (DiFC) is an emerging technology for fluorescence detection of rare circulating cells directly in large deep-seated blood vessels in mice. Because DiFC uses highly scattered light, in principle, it could be translated to human use. However, an open question is whether fluorescent signals from single cells would be detectable in human-scale anatomies.

AIM

Suitable blood vessels in a human wrist or forearm are at a depth of ∼2 to 4 mm. The aim of this work was to study the impact of DiFC instrument geometry and wavelength on the detected DiFC signal and on the maximum depth of detection of a moving cell.

APPROACH

We used Monte Carlo simulations to compute fluorescence Jacobian (sensitivity) matrices for a range of source and detector separations (SDS) and tissue optical properties over the visible and near infrared spectrum. We performed experimental measurements with three available versions of DiFC (488, 640, and 780 nm), fluorescent microspheres, and tissue mimicking optical flow phantoms. We used both computational and experimental data to estimate the maximum depth of detection at each combination of settings.

RESULTS

For the DiFC detection problem, our analysis showed that for deep-seated blood vessels, the maximum sensitivity was obtained with NIR light (780 nm) and 3-mm SDS.

CONCLUSIONS

These results suggest that-in combination with a suitable molecularly targeted fluorescent probes-circulating cells and nanosensors could, in principle, be detectable in circulation in humans.

Bridge of Tunneled Cuffed Catheter as a Risk for Future Arteriovenous Fistulae Failure

Background: A clinically tunneled cuffed catheter (TCC) for hemodialysis (HD) is often inserted into end-stage renal disease patients, who have an immature or no arteriovenous fistula (AVF), for the performance of HD to relieve uremic syndrome or to solve uncontrolled fluid overload, hyperkalemia, or metabolic acidosis. The catheter is primarily regarded as a bridge until the AVF matures and can be cannulated for HD. However, the effect of the bridge of the TCC on the future patency of AVFs remains elusive. Methods: This nationwide population-based observational study compared the hazards of AVF failure and the time to AVF failure. We enrolled 24,142 adult incident patients on HD, who received HD via AVFs for at least 90 days between 1 January 2010 and 31 December 2015. The subjects were divided into two groups, according to the history of TCC, and were followed-up until the failure of the AVF, mortality, or the end of the study. A propensity score-matched analysis based on 1:1 matching of age, sex, and baseline comorbidities was utilized to reduce bias and confounding variables. Results: A Kaplan−Meier survival curve revealed that patients with and without a history of TCC had significantly better AVF survival rates (log-rank test; p < 0.001). A history of TCC was independently associated with a higher risk of new AVF or AVG creation due to AVF failure, after the adjustment of the Charlson comorbidity index score (corresponding adjusted hazard ratios of 2.17 and 1.52; 95% confidence intervals of 1.77−2.67 and 1.15−1.99). For the impact of time on AVF failure, patients with a TCC bridge had a significantly higher incidence of new AVF creation during the first year after the AVF cannulation. Conclusion: A history of a TCC bridge was an independent risk factor for AVF failure and the time of AVF failure was significantly higher during the first year after the fistula cannulation in the TCC bridge group.

Clinical and ultrasound evaluation for hemodialysis access creation

Chronic kidney disease (CKD) is an emerging global burden with an increasing number of patient's requiring renal replacement therapy (RRT), with hemodialysis being the most prevalent dialysis modality. A functioning vascular access remains the main constrain for an adequate treatment. Clinical and, in some patients, ultrasound evaluation are fundamental for better access planning. Access planning is dependent not only on patient clinical characteristics and preference but also in vascular patrimony. As such, ultrasound evaluation aids in characterizing patient arterial and venous upper arm anatomy and provides information for which access would better suit each patient. Doctors dealing with CKD patients should be familiar with the role of ultrasound and Doppler use in access planning.

Distal or Traditional Transradial Access Site for Coronary Procedures: A Single-Center, Randomized Study

OBJECTIVES

This study aimed to compare the efficacy and safety of the distal transradial approach (dTRA) versus the conventional transradial approach (TRA) for coronary angiography and percutaneous coronary interventions.

BACKGROUND

The recommended approach for coronary procedures is TRA. However, it is associated with radial artery occlusion (RAO). The dTRA could potentially decrease the incidence of RAO.

METHODS

One thousand forty-two consecutive patients were randomized (1:1) to right dTRA or TRA. The primary endpoint was the rate of RAO, which was evaluated by Doppler ultrasound at 60 days after randomization.

RESULTS

Five hundred eighteen and 524 patients were randomized to dTRA and TRA, respectively. Follow-up Doppler evaluation of the radial artery was accomplished in 404 (78.0%) patients in the dTRA group and 392 (74.8%) in the TRA group. The rate of RAO was significantly reduced in the dTRA group compared with TRA group (3.7% vs 7.9%, respectively; P = 0.014). The rate of successful sheath insertion was lower in the dTRA group compared with the TRA group (78.7% vs 94.8%, respectively; P < 0.001). More punctures (median = 2 [IQR: 1-3] vs median = 1 [IQR: 1-2]; P < 0.001) and a longer time (120 vs 75 seconds; P < 0.001) were required for sheath insertion in the dTRA group compared with the TRA group. The hemostasis time was shorter in the dTRA group compared with the TRA group (60 vs 120 minutes; P < 0.001). The dose area product was higher in the dTRA group (median = 32,729 in the dTRA vs 28,909 cGy/cm² in the TRA group; P = 0.02). No significant differences were observed in the secondary safety endpoints (bleeding [Bleeding Academic Research Consortium ≥ 2] and severe radial artery spasm).

CONCLUSIONS

According to our study, dTRA was associated with a lower rate of forearm RAO, a shorter time of hemostasis, a higher crossover rate and dose area product, and a longer procedural time compared with TRA.

Maturation and survival of arteriovenous fistula: The challenge starts from the preoperative assessment stage

BACKGROUND

It is necessary to assess the association between the preoperative indicators and the maturation and survival of arteriovenous fistula (AVF).

METHODS

We retrospectively identified 236 patients with a new AVF created between 2016 and 2018 in our Dialysis Center.

RESULTS

Multivariate Logistic regression showed that preoperative arterial diameter (odds ratio [OR] = 1.452, 95% confidence interval [CI] [1.233, 1.710], p < 0.001), preoperative venous diameter (OR = 1.296, 95% CI [1.166, 1.477], p < 0.001), left ventricular ejection fraction (LVEF) (OR = 1.187, 95% CI [1.103, 1.277], p < 0.001), and diabetes mellitus (OR = 0.245, 95% CI [0.107, 0.560], p = 0.01) were independent influential factors for AVF maturation. Two years after the AVF surgery follow-up, multivariate Cox proportional-hazards model showed that the preoperative arterial diameter (OR = 0.510, 95% CI [0.320, 0.813], p = 0.005), preoperative venous diameter (OR = 0.940, 95% CI [0.897, 0.985], p = 0.010) and diabetes mellitus (OR = 1.785, 95% CI [1.117, 2.855], p = 0.016) was prognostic factors of AVF survival. The Kaplan-Meier method showed that the primary survival of AVF in patients with different preoperative arterial diameter was statistically significant (log-rank χ²  = 15.415, p < 0.001), while the secondary survival was not statistically significant (log-rank χ²  = 0.131, p = 0.717).

CONCLUSION

In our cohort, the preoperative arterial and venous diameter and diabetes mellitus were independent influential factors for AVF maturation and prognostic factors of AVF survival. However, the preoperative LVEF only associated with the maturation of AVF. Meanwhile, smaller arterial diameter (≤2.15 mm) was associated with AVF maturation failure, but did not impact secondary survival of AVF.

Fatal suicidal injury of a radiocephalic arteriovenous fistula

A 59-year-old man was found dead in his living room. His body was covered with blood, but the only injury found was a 31-mm-long, transverse incision on the radial surface of the left forearm. Autopsy revealed that the injured vessel was an enlarged cephalic vein from a radiocephalic arteriovenous fistula (RC-AVF) that had been created 23 years before for hemodialysis. Cephalic vein injury is usually not fatal, but circumstantial evidence, autopsy, and histological findings suggested that hemorrhagic shock and death occurred within a short time after the self-inflicted incised wound. This may be explained by the blood flow rate in the RC-AVF, which can reach 12 ml/s; this is 25 times higher than the normal cephalic vein blood flow.

Simulating Radial Pressure Waveforms with a Mock Circulatory Flow Loop to Characterize Hemodynamic Monitoring Systems

PURPOSE

Mock circulatory loops (MCLs) can reproducibly generate physiologically relevant pressures and flows for cardiovascular device testing. These systems have been extensively used to characterize the performance of therapeutic cardiac devices, but historically MCLs have had limited use for assessing patient monitoring systems. Here, we adapted an MCL to include peripheral components and evaluated its utility for qualitative and quantitative benchtop testing of hemodynamic monitoring devices.

METHODS

An MCL was designed to simulate three physiological hemodynamic states: normovolemia, cardiogenic shock, and hyperdynamic circulation. The system was assessed for stability in pressure and flow values over time, repeatability, waveform morphology, and systemic-peripheral pressure relationships.

RESULTS

For each condition, cardiac output was controlled to the nearest 0.2 L/min, and flow rate and mean arterial pressure remained stable and repeatable over a 60-s period (n = 5, standard deviation of ± 0.1 L/min and ± 0.84 mmHg, respectively). Transfer function analyses showed that the systemic-peripheral relationships could be adequately manipulated. The results from this MCL were comparable to those from other published MCLs and computational simulations. However, resolving current limitations of the system would further improve its utility. Three pulse contour analysis algorithms were applied to the pressure and flow data from the MCL to demonstrate the potential role of MCLs in characterizing hemodynamic monitoring systems.

CONCLUSION

Overall, the development of robust analysis methods in conjunction with modified MCLs can expand device testing applications to hemodynamic monitoring systems. Properly validated MCLs can create a stable and reproducible environment for testing patient monitoring systems over their entire operating ranges prior to clinical use.

A Comparison of Outcomes Between Open and Endovascular Arteriovenous Access Creation for Hemodialysis

OBJECTIVE

Preliminary outcomes for percutaneous endovascular autogenous access (endoAVF) have shown promising results; however, comparisons with surgical cohorts in dialysis populations are lacking. This study compares autogenous arteriovenous access created with the EverlinQ endoAVF system with accesses created by conventional surgical technique with respect to functional and patency related outcomes.

METHODS

This is a multicenter, retrospective review of autogenous arteriovenous accesses entered into a prospective database. Patients receiving radiocephalic, brachiocephalic, or endoAVF arteriovenous accesses between 2014 -2019 were included. Autogenous access maturation, primary patency, secondary patency, steal syndrome, and re-interventions were collected and analyzed using standard statistical and survival analyses.

RESULTS

A total of 369 accesses were created during the study period, including 61 endovascular accesses, 171 radiocephalic accesses, and 137 brachiocephalic accesses (median follow-up 17 months; range 1 - 71 months). Maturation failure at the end of follow-up was 27±6%, 27±5%, and 18±4% for endovascular, radiocephalic, and brachiocephalic accesses, respectively (p =.049 for brachiocephalic vs. endovascular accesses). Primary patencies at 12 and 24 months were 42±5% and 32±7% for endovascular accesses, 43±4% and 24±4% for radiocephalic accesses, and 42±4% and 29±4% for brachiocephalic accesses (p=.906). Secondary patencies at 12 and 24 months were 68±6% and 60±7% for endovascular accesses, 75±3% and 67±4% for radiocephalic accesses, and 91±3% and 81±4% for brachiocephalic accesses (p=.006 for brachiocephalic vs. endovascular accesses). There were no statistically significant differences in ischemic steal syndrome (3.3%, 4.1% and 8.0%; p=.229) or total reinterventions/year (1.0±3.1, 0.9±1.8, and 1.2±1.8; p=.289) for endovascular, radiocephalic, or brachiocephalic arteriovenous accesses, respectively.

CONCLUSIONS

EndoAVF compare favorably with respect to maturation and patency compared with surgically created accesses in a real-world cohort. Outcomes and reintervention rates are similar to conventional radiocephalic arteriovenous accesses, but are inferior with respect to patency and maturation to brachiocephalic accesses.

Clinical and ultrasound evaluation for hemodialysis access creation

Chronic kidney disease (CKD) is an emerging global burden with an increasing number of patient's requiring renal replacement therapy (RRT), with hemodialysis being the most prevalent dialysis modality. A functioning vascular access remains the main constrain for an adequate treatment. Clinical and, in some patients, ultrasound evaluation are fundamental for better access planning. Access planning is dependent not only on patient clinical characteristics and preference but also in vascular patrimony. As such, ultrasound evaluation aids in characterizing patient arterial and venous upper arm anatomy and provides information for which access would better suit each patient. Doctors dealing with CKD patients should be familiar with the role of ultrasound and Doppler use in access planning.

Remodeling of ipsilateral ulnar artery after radial artery harvesting for coronary artery bypass graft

There are controversies in the literature on the blood supply to the forearm after surgical removal of the radial artery in coronary artery bypass grafting (CABG). The objective was to investigate the arterial remodeling of the ulnar artery after the removal of the radial artery in myocardial revascularization by means of ultrasound examination with color Doppler in the pre- and post-operative periods. This paper describes an observational prospective study of the remodeling of the left brachial and ulnar arteries (donor arm) in 103 right-handed non-consecutive adult patients undergoing CABG with removal of the ipsilateral radial artery using the color Doppler ultrasound examination. In the ulnar artery, a significant increase (P < 0.05) was seen in the following measurements: lumen diameter by 13%, lumen area by 26%, peak systolic flow by 40%, and average flow by 46%. Intima-media thickness measured in the ulnar artery did not show a statistically significant difference (P = 0.22), except in diabetic patients (P = 0.007). We conclude that the ulnar artery undergoes positive physiological remodeling, adapting to the new requirements of chronic increase in flow after the ipsilateral removal of the radial artery to serve as a graft in CABG. There was no evidence of increased intima-media thickness, except in diabetic patients.

KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has provided evidence-based guidelines for hemodialysis vascular access since 1996. Since the last update in 2006, there has been a great accumulation of new evidence and sophistication in the guidelines process. The 2019 update to the KDOQI Clinical Practice Guideline for Vascular Access is a comprehensive document intended to assist multidisciplinary practitioners care for chronic kidney disease patients and their vascular access. New topics include the end-stage kidney disease "Life-Plan" and related concepts, guidance on vascular access choice, new targets for arteriovenous access (fistulas and grafts) and central venous catheters, management of specific complications, and renewed approaches to some older topics. Appraisal of the quality of the evidence was independently conducted by using a Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach, and interpretation and application followed the GRADE Evidence to Decision frameworks. As applicable, each guideline statement is accompanied by rationale/background information, a detailed justification, monitoring and evaluation guidance, implementation considerations, special discussions, and recommendations for future research.

Preoperative noninvasive artery flow volume and maturation of arteriovenous fistulae: A single surgeon's experience from 403 cases

BACKGROUND

Preoperative Doppler ultrasound evaluation of arteriovenous fistula inflow artery includes measurements of arterial diameter and flow volume. The purpose of this study was to evaluate the significance of flow volume to arteriovenous fistula maturation rate.

STUDY DESIGN

Review of consecutive patients who underwent arteriovenous fistula creation by a single surgeon. Cases with available preoperative arterial diameter and flow volume were analyzed. Primary end point was arteriovenous fistula failure to mature. Information collected included demographics, Doppler ultrasound reports, level of inflow artery, operative reports, and outcomes to the time of arteriovenous fistula maturation or failure. Risk factors were identified by logistic regression analysis. Outcomes were compared by odds ratio.

RESULTS

Four hundred and three cases were identified. Arterial diameter and flow volume were both independent significant risk factors affecting arteriovenous fistula maturation rate (p = 0.001). Arterial diameter of <2.5 mm and flow volume of <20 mL/min predicted failure to mature with 95% specificity. Further comparison of cases with optimal arterial diameter but flow volume of <20 mL/min showed increased failure to mature rate compared to the combination of optimal arterial diameter with optimal flow volume (p = 0.01).

CONCLUSION

Preoperative arterial diameter and flow volume values were both significant independent variables affecting arteriovenous fistula maturation rate. However, flow volume of <20 mL/min remained a significant risk factor to failure-to-mature rate, despite optimal arterial diameter.

Patients referred for arteriovenous fistula construction: a retrospective outcome analysis

OBJECTIVES

With lower rates of sepsis and re-interventions, arteriovenous fistula (AVF) is the preferred vascular access modality. The aim of this study is to evaluate the outcomes of patients referred for AVF construction at a single center in Cork, Ireland.

METHODS

The current study is a single-center retrospective review of all patients who underwent AVF creation between 2015 and 2017. Additionally, the kidney disease clinical patient management system was used to provide statistics on AVF use in Ireland.

RESULTS

39.3% of hemodialysis patients in Ireland use an AVF for vascular access. Regional use ranged from 50 to 20% across Irish hemodialysis centers. At Cork University Hospital, 192 AVFs were created. The population was 69.3% male (n = 133), 30.7% female (n = 59) with a mean (±SEM) age of 58.8 ± 1.03 years. 69.5% of females received a brachiocephalic AVF (BCAVF) while 13.6% had a radiocephalic AVF (RCAVF) constructed. Significance was seen when comparing gender and AVF type (p < 0.001). Fifty-four percent of the fistulae were brachiocephalic (n = 103), 33% were radiocephalic (n = 63), and 4% were brachiobasilic (n = 8). BCAVF patients (62.7 ± 1.2 years) were significantly older than patients receiving a RCAVF (54.5 ± 1.9 years, p < 0.001). A post-operative thrill or continuous flow on Doppler was present in 99% of patients (n = 190) with maturation and complication rates of 82.7% (n = 153) and 5.7% (n = 11) respectively. 69.9% of AVFs were needled for hemodialysis (n = 114).

CONCLUSIONS

AVF outcomes at this center are consistent with reported statistics in the literature. Patient age, sex, and diabetic status may influence the use of proximal AVF. AVF creation rates in Ireland are below international reported recommendations.

Arteriovenous conduits for hemodialysis: how to better modulate the pathophysiological vascular response to optimize vascular access durability

Vascular access is the lifeline for patients on hemodialysis. Arteriovenous fistulas (AVFs) are the preferred vascular access, but AVF maturation failure remains a significant clinical problem. Currently, there are no effective therapies available to prevent or treat AVF maturation failure. AVF maturation failure frequently results from venous stenosis at the AVF anastomosis, which is secondary to poor outward vascular remodeling and excessive venous intimal hyperplasia that narrows the AVF lumen. Arteriovenous grafts (AVGs) are the next preferred vascular access when an AVF creation is not possible. AVG failure is primarily the result of venous stenosis at the vein-graft anastomosis, which originates from intimal hyperplasia development. Although there has been advancement in our knowledge of the pathophysiology of AVF maturation and AVG failure, this has not translated into effective therapies for these two important clinical problems. Further work will be required to dissect out the mechanisms of AVF maturation failure and AVG failure to develop more specific therapies. This review highlights the major recent advancements in AVF and AVG biology, reviews major clinical trials, and discusses new areas for future research.

Baseline characteristics of arm vessels by preoperative duplex ultrasonography in Korean patients for hemodialysis vascular access

BACKGROUND

Preoperative mapping with duplex ultrasonography is crucial for successful vascular access creation for hemodialysis. The aims of this study are to assess the baseline characteristics of arm vessels by preoperative duplex ultrasonography in Korean patients, to find out a preoperative duplex ultrasonography parameter precluding distal arteriovenous fistula creation, to assess the maturation failure rate of arteriovenous fistulas, and to identify associated risk factors.

METHODS

Preoperative duplex ultrasonography mapping for vascular access creation was done in all patients with end-stage renal diseases during the year 2015. The baseline data of duplex ultrasonography were retrospectively analyzed with follow-up clinical data.

RESULTS

A total of 299 end-stage renal disease patients (mean age = 62 years, 62% male) were included. On preoperative duplex ultrasonography, mean diameters of radial artery and cephalic vein at wrist were 2.03 and 2.40 mm in the non-dominant arm and 2.10 and 2.26 mm in the dominant arm, respectively. The most common reason for precluding radial-cephalic arteriovenous fistula at wrist was small-sized cephalic vein. Multivariate logistic regression analysis revealed that the risk factors for inadequate vessels were warfarin treatment, old age (⩾75 years), and peripheral arterial occlusive disease. The rate of arteriovenous fistula maturation failure was 21% and vein diameter <2.5 mm was the only risk factor for arteriovenous fistula maturation failure by multivariate logistic regression analysis.

CONCLUSION

Preoperative duplex ultrasonography evaluation is important to find out inadequate vessels for native arteriovenous fistula and to determine the location of vascular access.

The effect of endothelial nitric oxide synthase on the hemodynamics and wall mechanics in murine arteriovenous fistulas

Creation of a hemodialysis arteriovenous fistula (AVF) causes aberrant vascular mechanics at and near the AVF anastomosis. When inadequately regulated, these aberrant mechanical factors may impede AVF lumen expansion to cause AVF maturation failure, a significant clinical problem with no effective treatments. The endothelial nitric oxide synthase (NOS3) system is crucial for vascular health and function, but its effect on AVF maturation has not been fully characterized. We hypothesize that NOS3 promotes AVF maturation by regulating local vascular mechanics following AVF creation. Here we report the first MRI-based fluid-structure interaction (FSI) study in a murine AVF model using three mouse strains: NOS3 overexpression (NOS3 OE) and knockout (NOS3−/−) on C57BL/6 background, with C57BL/6 as the wild-type control (NOS3+/+). When compared to NOS3+/+ and NOS3−/−, AVFs in the OE mice had larger lumen area. AVFs in the OE mice also had smoother blood flow streamlines, as well as lower blood shear stress at the wall, blood vorticity, inner wall circumferential stretch, and radial wall thinning at the anastomosis. Our results demonstrate that overexpression of NOS3 resulted in distinct hemodynamic and wall mechanical profiles associated with favorable AVF remodeling. Enhancing NOS3 expression may be a potential therapeutic approach for promoting AVF maturation.

Careful Patient Selection Achieves High Radiocephalic Arteriovenous Fistula Patency in Diabetic and Female Patients

BACKGROUND

The radiocephalic arteriovenous fistula (rcAVF) is considered the first-choice site for hemodialysis access; however, it has been associated with decreased rates of patency and maturation in women and diabetic patients in some studies. We hypothesized that careful preoperative selection of patients for an rcAVF fistula would result in a high 1-year patency rate and that external factors, such as female gender and diabetes mellitus (DM), would not adversely affect fistula patency.

METHODS

This is a retrospective study of all patients who underwent rcAVF creation at a single institution from January 2011 to June 2016. Patients were carefully selected based on clinical examination and preoperative, B-mode, ultrasound findings. Primary patency and primary assisted patency at 1 year were calculated. Survival analysis was also conducted to evaluate for factors associated with rcAVF patency.

RESULTS

There were 158 patients identified who underwent rcAVF fistula creation and were seen in follow-up. The 1-year primary and primary assisted patency rates were 62% and 81%, respectively. On Kaplan-Meier survival analysis, there was no difference in rcAVF patency with respect to gender, Hispanic race, anesthesia type, DM, and smoking status. Patients with a prior AVF, most often received in the nondominant arm and now receiving an rcAVF in the dominant arm, had a significantly higher risk of fistula failure, in both primary and primary assisted patency survival (hazard ratio 5.1, 95% confidence interval 1.6-16.2, P = 0.06). Patients without a history of hypertension (HTN), as noted in the electronic medical records, trended toward a higher risk of primary assisted patency rcAVF failure, compared to those who had a history of HTN (hazard ratio 3.0, 95% confidence interval 1.1-7.9, P = 0.03).

CONCLUSIONS

With careful patient selection, the rcAVF can achieve a high 1-year primary assisted patency rate. Female gender and DM were not significantly associated with an increase in rcAVF failure and should not be heavily relied on in-patient selection. First-time AVF patients and patients with a history of HTN may be associated with increased rcAVF patency.

Patient factors and haemodialysis arteriovenous fistula outcomes

Arteriovenous fistulas (AVF) improve survival and morbidity for most haemodialysis (HD) patients. Are they better for all patients? In the enthusiastic pursuit of AVFs for all, concerns have been raised regarding high primary AVF failure rates, continued high incident central venous catheter (CVC) use in some countries, and the limited life expectancy of some HD patients. “Fistula first” is changing to “catheter last”. The focus must be on decreasing AVF failure to mature and decreasing incident CVC use. An optimal outcome should be sought for each individual patient, and multiple failed attempts at AVF creation avoided.