Arteriovenous Fistula Blood Flow Research Articles

Artificial neural networks analysis predicts long-term fistula function in hemodialysis patients following percutaneous transluminal angioplasty

Kidney failure is particularly common in the United States, where it affects over 700,000 individuals. It is typically treated through repeated sessions of hemodialysis to filter and clean the blood. Hemodialysis requires vascular access, in about 70% of cases through an arteriovenous fistula (AVF) surgically created by connecting an artery and vein. AVF take 6 weeks or more to mature. Mature fistulae often require intervention, most often percutaneous transluminal angioplasty (PTA), also known as fistulaplasty, to maintain the patency of the fistula. PTA is also the first-line intervention to restore blood flow and prolong the use of an AVF, and many patients undergo the procedure multiple times. Although PTA is important for AVF maturation and maintenance, research into predictive models of AVF function following PTA has been limited. Therefore, in this paper we hypothesize that based on patient-specific information collected during PTA, a predictive model can be created to help improve treatment planning. We test a set of rich, multimodal data from 28 patients that includes medical history, AVF blood flow, and interventional angiographic imaging (specifically excluding any post-PTA measurements) and build deep hybrid neural networks. A hybrid model combining a 3D convolutional neural network with a multi-layer perceptron to classify AVF was established. We found using this model that we were able to identify the association between different factors and evaluate whether the PTA procedure can maintain primary patency for more than 3 months. The testing accuracy achieved was 0.75 with a weighted F1-score of 0.75, and AUROC of 0.75. These results indicate that evaluating multimodal clinical data using artificial neural networks can predict the outcome of PTA. These initial findings suggest that the hybrid model combining clinical data, imaging and hemodynamic analysis can be useful to treatment planning for hemodialysis. Further study based on a large cohort is needed to refine the accuracy and model efficiency.

Deep learning analysis of blood flow sounds to detect arteriovenous fistula stenosis

For hemodialysis patients, arteriovenous fistula (AVF) patency determines whether adequate hemofiltration can be achieved, and directly influences clinical outcomes. Here, we report the development and performance of a deep learning model for automated AVF stenosis screening based on the sound of AVF blood flow using supervised learning with data validated by ultrasound. We demonstrate the importance of contextualizing the sound with location metadata as the characteristics of the blood flow sound varies significantly along the AVF. We found the best model to be a vision transformer trained on spectrogram images. Our model can screen for stenosis at a performance level comparable to that of a nephrologist performing a physical exam, but with the advantage of being automated and scalable. In a high-volume, resource-limited clinical setting, automated AVF stenosis screening can help ensure patient safety via early detection of at-risk vascular access, streamline the dialysis workflow, and serve as a patient-facing tool to allow for at-home, self-screening.

Comparing the hemodynamic effect of a large arteriovenous fistula during high and low cardiac output states.

Background: A large arteriovenous fistula (AVF) is a low-resistant circuit that affects organ perfusion and systemic hemodynamics even in standard conditions. The extent of its' effect in critical states has not been elucidated yet. We used norepinephrine to create systemic vasoconstriction, dobutamine to create high cardiac output, and rapid right ventricle pacing as a model of acute heart failure in a porcine model of high-flow AVF circulation. Methods: The protocol was performed on nine domestic female pigs under general anesthesia. AVF was created by connecting two high-diameter ECMO cannulas inserted in the femoral artery and vein. Continuous hemodynamic monitoring was performed throughout the protocol. Three interventions were performed-moderate dose of norepinephrine (0.25ug/kg/min), moderate dose of dobutamine (10ug/kg/min) and rapid right ventricle pacing to simulate low cardiac output state with mean arterial pressure under 60mmHg. Measurements were taken with opened and closed arteriovenous fistula. Results: Continuous infusion of norepinephrine with opened AVF significantly increased mean arterial pressure (+20%) and total cardiac output (CO) (+36%), but vascular resistance remained virtually unchanged. AVF flow (Qa) rise correlated with mean arterial pressure increase (+20%; R = 0.97, p = 0.0001). Effective cardiac output increased, leading to insignificant improvement in organ perfusion. Dobutamine substantially increased cardiac output with insignificant effect on AVF flow and mean arterial pressure. Carotid artery blood flow increased significantly after dobutamine infusion by approximately 30%, coronary flow velocity increased significantly only in closed AVF state. The effective cardiac output using the heart failure model leading to decrease of carotid artery flow and worsening of brain and peripheral tissue oximetry. AVF blood flow also dropped significantly and proportionally to pressure, but Qa/CO ratio did not change. Therefore, the effective cardiac output decreased. Conclusion: In abovementioned extreme hemodynamic conditions the AVF flow was always directly proportional to systemic perfusion pressure. The ratio of shunt flow to cardiac output depended on systemic vascular resistance. These experiments highlight the detrimental role of a large AVF in these critical conditions' models.

#5803 ARTERIOVENOUS FISTULA BLOOD FLOW ESTIMATION THROUGH AI MODEL EXPLOITING THE PATIENT'S ROUTINELY COLLECTED DATA

Abstract Background and Aims Clinical monitoring and surveillance are key pillars of Arteriovenous Fistula (AVF) management in hemodialysis patients. They are aimed at limiting the risk of suboptimal dialysis dose and Vascular Access (VA) failure. AVF blood flow (Qa) is commonly used to assess VA function. Several methods have been proposed for the measurement of Qa including doppler ultrasound, and Body Thermal Monitor, among others. All these diagnostic tests are, in general, time-consuming for clinical staff, operator dependent, and costly for healthcare providers. To overcome limitations in the uptake of current Qa measurement techniques, we used data automatically recorded by dialysis machine sensors and medical information captured in electronic charts records to estimate Qa using a machine learning technique. Method For this historical cohort study, we analyzed electronic health records (EHR) of adult patients from four different European countries (Czech Republic, Portugal, Slovakia, and Spain), receiving in-center hemodialysis therapy in Fresenius Medical Care dialysis clinics between January 1st, 2015 and June 30th, 2022 registered in the European Clinical Database (EuCliD®). All patients consented their pseudo-anonymized data be used for secondary data analysis. The input dataset included 49 variables representing the health status of the patients, functional parameters of AVF function and the HD treatment parameters. The input variables were collected in the 90 days before the Qa measure. We constructed metrics representing the 90-day average and trend of each functional and medical parameter. Qa was classified in three levels: < 525 ml/h (very low), 525 ml/h - 925 ml/h (low), > 925 ml/h (normal). We estimated Qa as ordinal classification problem. Therefore, we used 2 binary classifiers based on the XGBoost algorithm. The estimation of the first-class, P(Qa<525), is given by the first classifier and the estimation of the third class, P(Qa≥925), is given by the second classifier. The probability of the middle class is computed as P(Qa≥525)⋅(1-P(Qa≥925)). The Qa estimation accuracy was assessed computing mean absolute error (MAE), precision and recall, F1-score and confusion matrix. Results Our dataset included 46,292 Qa measurements referred to 5,940 different hemodialysis patients. We obtained an overall precision of 0.77, a recall of 0.76, a F1-score of 0.76, a MAE of 0.27. The same metrics for each class are shown in Table 1. The model was able to detect fistula with “very low flow” with a precision of 0.9 and 16% of the missed “very low flow” AVFs are predicted as “low flow” and 4.7% are predicted as normal flow. The Confusion Matrix for each class is shown in Figure 1. Conclusion In this study we showed that clinically relevant Qa classes can be accurately predicted by resorting to routinely collected clinical data extracted from a electronic health record without any additional effort from healthcare professionals, training or instrumentation. Qa assessment is an important parameter in the evaluation of AVF function. Our algorithm accurately discriminated patients with “very low flow” that may be referred to vascular surgeon evaluation. It might help the AVF surveillance process, without adding time-consuming procedures for clinical staff or costs for healthcare provider.

#4520 THE USE OF FAR INFRARED LIGHT DURING HEMODIALYSIS SEEMS TO MAINTAIN ARTERIOVENOUS FISTULA BLOOD FLOW BETTER THAN USING A HEAT PAD - A PILOT STUDY

Abstract Background and Aims The use of the native arteriovenous fistula (AVF) in chronic hemodialysis (HD) patients yields great challenges to keep a patent AVF, especially among those with diabetes mellitus and cardiovascular disease. Often repeated radiological interventions or surgery of the AVF is necessary. Accumulation of advanced glycation end products (AGE) in tissue is shown to contribute to the complications of diabetes mellitus and uremia [1]. Far infrared light (FIR) irradiation of the AVF have shown protective effects in maintaining AVF blood flow [2,3]. Using a heat pad (HP) to stimulate vascular flow is another alternative. Primary aim of the study was to compare if the use of a HP is as good as FIR to maintain AVF blood flow. Secondary aim: Evaluate change in AGE accumulation in tissue after FIR and HP treatment. Method This pilot study included HD patients with a native lower arm AVF. Eighteen patients were randomly assigned to treatment during HD; Ten patients to FIR and another group of eight patients to use HP (Two of the HP-patients refused to fulfill the study). Before and after a period of 15 HD treatments each, blood tests, AVF blood-flow measured with a Transsonic® and skin autofluorescence (SAF, measuring AGE) were analyzed. The distance of the FIR emitter to the AVF puncture area was 25 cm. The HP-group was exposed to a waterfilled rubber HP that kept a temperature of 40-41°C and was positioned to the backside of the AVF arm to avoid dislodgement of or compressing needles. The patient was her/his own control and non-parametric Mann-Whitney U- and Wilcoxon sign ranked tests were used. Results The blood flow of the AVF was similar at start in the FIR group versus the HP-group median 921 ml/min IQR (714-1210) vs. 610 ml/min, IQR (538-861), p = 0.118, while after 15 treatments the blood flow was maintained in the FIR group but was lower in the HP-group; median 902 ml/min IQR (718-1241) vs. 635 ml/min IQR (531-772), p = 0.022. The FIR exposure did not alter the SAF content (in arbitrary units -AU) after treatment and was similar in the FIR group (median 3.2 AU, IQR 2.2-3.6) and in the HP group (median 3.2, IQR 2.4-3.3), p-value = 0.864.During the follow-up period after 3 and 6 months, PTA was performed due stenosis with decreased blood flow of the AVF in 3/10 patients in the FIR group and 1/6 patients in the HP group. Data are given as median and interquartile range (IQR). A two-sided p-value of <0.05 was defined as significant. Conclusion This pilot study showed that the access flow after FIR versus HP exposure during 15 HD treatments was better maintained among patients treated with FIR than with HP. SAF as a predictor for atherosclerosis was not changed. Long-term exposure to FIR may be necessary.

#5411 CARDIO-FISTULA RECIRCULATION REDUCTION IN OLDER ADULTS: IT'S NOT THAT EASY

Abstract Background and Aims Older adults are approximately 40% of all prevalent HD patients [ERA Annual report]. Cardiovascular disease is the leading cause of death in this cohort. It is well-known that the cardiotoxic effect of arterio-venous fistula (AVF) is fully realized when cardio-fistula recirculation (CFR) is above 20-30%. We believe that the reduction of AVF blood flow (Qa) in the elderly is often less effective than in the younger patients. Aim: to evaluate the outcomes of Qa reduction in the elder and the younger HD patients. Method The prospective cohort study included 21 patients over 60 years old and 36 patients under 60 years old: the median age was 74 years [IQR 69; 78, min-max 64-81] and 41 years [IQR 35; 45, min-max 31; 55], respectively. In all patients, GFR before reduction was more than 25%: 32.8% [IQR 29.2; 35.1, min-max 27.3; 38.9] and 33% [IQR 31; 35.125, min-max 27.1; 39.3], respectively. Qa reduction was performed by banding of the paraanastomotic AVF segment with intraoperative control (Doppler ultrasonography) until reaching Qa of 1.5 l / min or less. Results In all patients, we noted a significant (p<0.0001 in all cases) decrease in Qa as a result of the banding: in older adults from 2.1 l / min [IQR 1.9; 2.4, min-max 1.8; 2.8] to 1.2 l / min [IQR 1; 1.4, min-max 0.8; 1.5], delta Qa was -1 l / min [IQR -1.2; -0.9, min-max -1.5; -0.7], in younger patients from 2.8 l / min [IQR 2.5; 3.1, min-max 1.9; 3.5] to 1.3 l / min [IQR 1.1; 1.4, min-max 0.9; 1.5], -1.5 l / min [IQR -1.7; -1.3, min-max -2.3; -0.9], respectively. In both elder and younger patients, we noted a significant decrease in CFR - Fig. 1. However, after Qa reduction, only 5 of 21 elderly patients had CFR value less than 20%. Thus, 17 of 21 patients had CFR in the «gray zone» - 20-30%: 22.8% [IQR 21.85; 27.3, min-max 21; 29.2]. In younger patients, 25 of 36 had CFR less than 20% after Qa reduction, while 11 stayed in the «gray zone»: 21.15% [IQR 20.575; 22.3, min-max 20.3; 23.4]. The probability of reducing CFR to a safe level (less than 20%) after surgery was significantly less in the elder patients: RR = 0.3429 [95% CI 0.1495; 0.6852], p = 0.0011. We consider the lower baseline cardiac output in the elderly to be the main reason of the lower efficacy of Qa reduction: the difference between medians (older adults-younger patients before Qa reduction, Hodges-Lehmann method) was 1.9 l / min [95% CI 1.5; 2.4], p <0.0001. At the same time, Qa before reduction did not differ much between the older and the younger: 0.6 l / min [95% CI 0.4; 0.8], p <0.0001. Moreover, the reduction of Qa in elderly patients led to a decrease in the ejection fraction (EF), which was not noticed in young patients - Fig. 2. Notably, in all patients of both groups the initial value of the EF was more than 55%. We believe that this can be explained by an abrupt increase in afterload against the background of a decreased compensatory heart capability in the elderly. At the same time, decrease in the EF after Qa reduction in the elderly may indirectly indicate that conventional EF in the elderly is maintained by a presence of a high-flow AVF. Evaluation of EF against this background creates a putative picture of well-being and can mask the development of heart failure with reduced EF for a long time. Conclusion We noted a lower efficacy of Qa reduction as a method of reducing both cardio-fistula recirculation and cardiovascular risk in the elder patients compared to the younger patients on maintenance HD. Elder patients seem to require a different approach to reduce cardiovascular risk than younger patients.

Effect of proximal artery restriction on flow reduction and cardiac function in hemodialysis patients with high-flow arteriovenous fistulas

ObjectiveArteriovenous fistula is the preferred vascular access for hemodialysis patients. High-flow arteriovenous fistula may cause high-output heart failure. Various procedures are used to reduce high-flow arteriovenous fistula. This study aimed to assess the efficacy of proximal artery restriction combined with distal artery ligation on flow reduction for high-flow arteriovenous fistula and on cardiac function and echocardiographic changes in patients undergoing hemodialysis. MethodsA retrospective analysis was performed on data collected from the medical records of patients undergoing hemodialysis with heart failure and high-flow arteriovenous fistula between May 2018 and May 2021. Thirty-one patients were treated with proximal artery restriction (banding juxta-anastomosis of the proximal artery) combined with distal artery ligation (anastomosis distal artery ligation). Changes in the Acute Dialysis Quality Initiative Workgroup cardiac function class, blood pressure, and echocardiography before and 6 months after flow restriction were compared, and post-intervention primary patency was followed-up. ResultsThe technical success rate of the surgery was 100%, and no surgery-related adverse events occurred. Blood flow and blood flow/cardiac output decreased significantly after flow restriction. Blood flow decreased from 2047.21 ± 398.08 mL/min to 1001.36 ± 240.42 mL/min, and blood flow/cardiac output decreased from 40.18% ± 6.76% to 22.34% ± 7.21% (P < .001). Post-intervention primary patency of arteriovenous fistula at 6, 12, and 24 months was 96.8%, 93.5%, and 75.2%, respectively. The Acute Dialysis Quality Initiative Workgroup cardiac function class improved significantly after 6 months of flow restriction (P < .001). The systolic and diastolic left heart function improved, as evidenced by a significant decrease in left atrial volume index, left ventricular end-diastolic/end-systolic diameters, left ventricular end-diastolic volume, left ventricular mass index, cardiac output, and cardiac index and an increase in lateral peak velocity of longitudinal contraction, average septal-lateral s', and lateral early diastolic peak velocity after flow restriction (P < .05). Systolic pulmonary artery pressure decreased from 32.36 ± 8.56 mmHg to 27.57 ± 8.98 mmHg (P < .05), indicating an improvement in right heart function. ConclusionsProximal artery restriction combined with distal artery ligation effectively reduced the blood flow of high-flow arteriovenous fistula and improved cardiac function.

The impact of vascular access location on pulmonary arterial pressure in chronic kidney disease patients undergoing hemodialysis.

It is feared that among chronic kidney disease patients undergoing hemodialysis, arteriovenous fistula (AVF) itself could contribute to pulmonary hypertension (PH). The impact of AVF location on PH is yet to be assessed. We hypothesize that patients with proximal AVF have higher access blood flow and hence higher pulmonary arterial systolic pressure (PASP) than those with distal AVF. We aimed to compare the PASP between patients with proximal and distal AVF. In this cross-sectional study, PASP was estimated using Doppler echocardiography and blood flow in the AVF was assessed by Doppler ultrasound. PASP was modeled by multivariate linear regression. AVF location was the primary exposure of interest. Out of 89 patients undergoing hemodialysis, 72 (81%) had PH defined as PASP >35 mmHg. The mean blood flow in proximal and distal AVF was, respectively, 1240 and 783 mL/min (mean difference 457 mL/min, p < 0.001). Mean PASP in patients with proximal AVF was 16.6mmHg higher than those with distal AVF (p < 0.001, 95% CI 8.3-24.9). There was a positive correlation between access blood flow and PASP (r = 0.28, p = 0.007). If access blood flow was included as a covariate in the multivariate model, the association between AVF location and PASP ceased to exist. Patients with proximal AVF have a significantly higher PASP than those with distal AVF, and this could be attributed to the higher blood flow in proximal AVF compared to distal AVF.

Far-Infrared Therapy Improves Arteriovenous Fistula Patency and Decreases Plasma Asymmetric Dimethylarginine in Patients with Advanced Diabetic Kidney Disease: A Prospective Randomized Controlled Trial.

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase and plays a significant role in the pathogenesis of arteriovenous fistula (AVF) dysfunction. The aim of this study is to evaluate the effect of far-infrared (FIR) therapy on the maturation and patency of newly-created AVFs in patients with advanced diabetic kidney disease (DKD) as well as the concurrent change in plasma ADMA. The study enrolled 144 participants with advanced DKD where 101 patients were randomly allocated to the FIR therapy group (N = 50) and control group (N = 51). Patients receiving FIR therapy had a decreased AVF failure rate within 12 months (16% versus 35.3%; p = 0.027); decreased incremental change of ADMA concentration at the 3rd and 12th month; increased AVF blood flow at the 1st, 3rd, and 12th month; increased 3-month physiologic maturation rate (88% versus 68.6%; p = 0.034); increased 1-year unassisted AVF patency rate (84% versus 64.7%; p = 0.017); and increased clinical AVF maturation rate within 12 months (84% versus 62.7%; p = 0.029) compared to the control group. The study demonstrates that FIR therapy can reduce the incremental changes in plasma ADMA concentration, which may be associated with the improvement of AVF prognosis in patients with advanced DKD.

Reduction of arteriovenous access blood flow in kidney transplant patients.

Cardiovascular disease is the most frequent cause of death in kidney transplant patients. High-flow arteriovenous fistula (AVF) increases cardiac output and may contribute to hyperkinetic heart failure. AVF follow-up is not implemented in kidney transplant patients. The aim of this study was to reduce AVF blood flow in a group of patients with a high-flow AVF following kidney transplantation to reduce cardiac strain. This prospective study was performed in kidney transplant patients who had a vascular access created before transplantation. The AVF of these patients was examined by ultrasound with a focus on AVF flow and brachial artery size. If high-flow AVF was detected, flow reduction was performed in the indicated group of patients. The study examined 164 patients, of whom 24 had a hyperfunctional AVF (14.8%). A total of 16 AVF flow reductions were performed, which led to an average decrease in cardiac index by 0.77 L/min/m2. Primary patency of the reconstructions was 93.33% after 12 months. All patients experienced a subjective improvement in dyspnea. Reduction in AVF flow leads to an improvement in the quality of life of kidney transplant patients. Maintaining a functional AVF is beneficial, especially for patients after repeated surgeries, where the option of creating an autologous AVF is limited.

Recanalization of thrombosed aneurysmal hemodialysis arterovenous fistulas using a hybrid technique based on data from a single center

ObjectiveTo explore the technical specifications and clinical outcomes of thrombosed aneurysmal haemodialysis arteriovenous fistula (AVF) treated with ultrasound-guided percutaneous transluminal angioplasty combined with minimal aneurysmotomy.MethodsThis case series study included 11 patients who had thrombosed aneurysmal AVF and underwent salvage procedures over a 13-month period. All procedures were performed under duplex guidance. Minimal aneurysmotomy was performed, along with manual thrombectomy and thrombolytic agent infusion, followed by angioplasty to macerate the thrombus and sufficiently dilate potential stenoses. A successful procedure was defined as immediate restoration of flow through the AVF.ResultsThe 11 patients (four males and seven females) had a mean age of 49.6 years ± 11.9 years. Six patients (54.5%) had two or more aneurysms. The mean aneurysm maximal diameter was 21.5 mm (standard deviation: ± 5.0 mm), and the mean thrombus length was 12.9 cm (8–22 cm). Ten (83.3%) of the 12 procedures were technically successful. The mean duration of operation was 150.9 minutes (standard deviation: ± 34.2 minutes), and mean postoperative AVF blood flow was 728.6 ml/min (standard deviation: ± 53.7 mi/min). The resumption of hemodialysis was successful in all 11 cases, with a clinical success rate of 100%. The primary patency rates were 90.0% and 75.0% at three and four months over a mean follow-up time of 6.3 months (3–12 months). The secondary patency rates were 90.4% at three and four months.ConclusionA hybrid approach combining ultrasound-guided percutaneous transluminal angioplasty and minimal aneurysmotomy might be a safe and effective method for thrombosed aneurysmal AVF salvage.

MO793: AVF Blood Flow Reduction in the Older Adults

Abstract BACKGROUND AND AIMS Older adults are approximately 40% of all prevalent HD patients (ERA-EDTA Annual report, 2019). Cardiovascular disease is the leading cause of death in this cohort. It is well-known that the cardiotoxic effect of arterio-venous fistula (AVF) is fully realized when cardio-fistula recirculation (CFR) is above 20–30%. We believe that the reduction of AVF blood flow (Qa) in the elderly is often less effective than in younger patients. To evaluate the outcomes of Qa reduction in the elder and the younger HD patients. METHOD The prospective cohort study included 21 patients ˃ 60 years and 36 patients ˂60 years: the median age was 74 years [interquartile range (IQR) 69; 78, min-max 64–81] and 41 years (IQR 35; 45, min-max 31; 55), respectively. In all patients, glomerular filtration rate (GFR) before reduction was more than 25%: 32.8% (IQR 29.2; 35.1, min-max 27.3; 38.9) and 33% (IQR 31; 35.125, min-max 27.1; 39.3), respectively. Qa reduction was performed by banding of the para-anastomotic AVF segment with intraoperative control (Doppler ultrasonography) until reaching Qa of 1.5 L/min or less. RESULTS In all patients, we noted a significant (P &amp;lt; 0.0001 in all cases) decrease in Qa as a result of the banding: in older adults from 2.1 L/min (IQR 1.9; 2.4, min-max 1.8; 2.8) to 1.2 L/min (IQR 1; 1.4, min-max 0.8; 1.5), delta Qa was −1 L/min (IQR −1.2; −0.9, min-max −1.5; −0.7), in younger patients from 2.8 L/min (IQR 2.5; 3.1, min-max 1.9; 3.5) to 1.3 L/min (IQR 1.1; 1.4, min-max 0.9; 1.5), −1.5 L/min (IQR −1.7; −1.3, min-max −2.3; −0.9], respectively. In both elder and younger patients, we noted a significant decrease in CFR—Figure 1. However, after Qa reduction, only 5/21 elderly patients had CFR value less than 20%. Thus, 17/21 patients had CFR in the ‘gray zone’ —20–30%: 22.8% (IQR 21.85; 27.3, min-max 21; 29.2). In younger patients, 25/36 had CFR ˂ 20% after Qa reduction, while 11 stayed in the ‘gray zone’: 21.15% (IQR 20.575; 22.3, min-max 20.3; 23.4). The probability of reducing CFR to a safe level (˂ 20%) after surgery was significantly less in the elder patients: RR = 0.3429 [95% confidence interval (95%CI) 0.1495; 0.6852], P = 0.0011. We consider the lower baseline cardiac output in the elderly to be the main reason for the lower efficacy of Qa reduction: the difference between medians (older adults-younger patients before Qa reduction, Hodges–Lehmann method) was 1.9 L/min (95% CI 1.5; 2.4), P &amp;lt; 0.0001. At the same time, Qa before reduction did not differ much between the older and the younger: 0.6 L/min (95% CI 0.4; 0.8), P &amp;lt; 0.0001. Moreover, the reduction of Qa in elderly patients led to a decrease in the ejection fraction (EF), which was not noticed in young patients—Figure 2. Notably, in all patients of both groups, the initial value of the EF was more than 55%. We believe that this can be explained by an abrupt increase in afterload against the background of a decreased compensatory heart capability in the elderly. At the same time, a decrease in the EF after Qa reduction in the elderly may indirectly indicate that conventional EF in the elderly is maintained by a presence of a high-flow AVF. Evaluation of EF against this background creates a putative picture of well-being and can mask the development of heart failure with reduced EF for a long time. CONCLUSION We noted a lower efficacy of Qa reduction as a method of reducing both cardio-fistula recirculation and cardiovascular risk in the elder patients compared to the younger patients on maintenance HD. Elder patients seem to require a different approach to reduce cardiovascular risk than younger patients.

Abstract 473: Cilostazol Decreases Venous Outflow Inflammation And Improves Avf Patency Inmurine Arteriovenous Fistula

Background: Arteriovenous fistula (AVF) have high failure rates, and no pharmacotherapeutics can improve AVF patency. The most common cause of AVF failure is inflammation-driven neointimal hyperplasia and thrombosis. Limited observational data suggests that cilostazol (CIL), an FDA-approved phosphodiesterase-3 inhibitor that inhibits platelet activation and smooth muscle cell proliferation, could help improve AVF maturation. Here, we investigated the effects of cilostazol on murine AVF patency, and further assessed the fibrinogenesis and anti-inflammatory effects using intravital fluorescence molecular imaging. Methods: One week prior to fistula creation, mice were randomized to CIL (40mg/kg/day) or PBS group (n=20 each). AVF was created using an end-to-side external jugular vein and carotid artery anastomosis. AVF blood flow was measured post-operatively (Transonic) and then every 7 days until AVF was occluded (&lt;0.1 ml/min). Macrophages and fibrin were imaged after 10mg/kg FMX-AF555 and/or 4.5nmol FTP11CyAm7 i.v. injection prior to imaging on day 7 or day 14, respectively. The target-to-background ratio (TBR) was calculated as mean signal intensity (MSI) of the fistula divided by the MSI of the contralateral vein. Results: Post-operative AVF blood flow was similar between CIL and PBS treated groups (p=0.3). Average AVF patency was significantly longer in CIL group compared to PBS group (42 vs 21 days, p&lt;0.01, figure 1A). Both day 7 and day 14 venous outflow fibrinogenesis signal assessed by IVM was significantly lower in CIL group compared to PBS group (ps&lt;0.05, Figure 1B). On day 14, CIL significantly lower venous outflow FMX signals compared to PBS group (p&lt;0.05). Conclusion: Oral cilostazol therapy prolongs AVF patency, and decreases venous outflow inflammation and fibrinogenesis in experimental AVF in vivo. The current data supports investigating cilostazol as a clinical pro-AVF patency pharmacotherapeutic strategy in dialysis patients.

New Porcine Model of Arteriovenous Fistula Documents Increased Coronary Blood Flow at the Cost of Brain Perfusion.

Background: Arteriovenous fistulas (AVF) represent a low resistant circuit. It is known that their opening leads to decreased systemic vascular resistance, increased cardiac output and other hemodynamic changes. Possible competition of AVF and perfusion of other organs has been observed before, however the specific impact of AVF has not been elucidated yet. Previous animal models studied long-term changes associated with a surgically created high flow AVF. The aim of this study was to create a simple AVF model for the analysis of acute hemodynamic changes. Methods: Domestic female pigs weighing 62.6 ± 5.2 kg were used. All the experiments were held under general anesthesia. The AVF was created using high-diameter ECMO cannulas inserted into femoral artery and vein. Continuous hemodynamic monitoring was performed throughout the protocol. Near-infrared spectroscopy sensors, flow probes and flow wires were inserted to study brain and heart perfusion. Results: AVF blood flow was 2.1 ± 0.5 L/min, which represented around 23% of cardiac output. We observed increase in cardiac output (from 7.02 ± 2.35 L/min to 9.19 ± 2.99 L/min, p = 0.0001) driven dominantly by increased heart rate, increased pulmonary artery pressure, and associated right ventricular work. Coronary artery flow velocity rose. On the contrary, carotid artery flow and brain and muscle tissue oxygenation measured by NIRS decreased significantly. Conclusions: Our new non-surgical AVF model is reproducible and demonstrated an acute decrease of brain and muscle perfusion.

Quantification and Visualization of Reliable Hemodynamics Evaluation Based on Non-Contact Arteriovenous Fistula Measurement.

The condition of arteriovenous fistula (AVF) blood flow is typically checked by using auscultation; however, auscultation should require a qualitative judgment dependent on the skills of doctors, and further attention to contact infection is required. For these reasons, this study developed a non-contact and non-invasive medical device to measure the pulse wave of AVFs by applying optical imaging technology. As a first step toward realization of the quantification judgment based on non-contact AVF measurement, we experimentally validated the developed system, whereby the hemodynamics of 168 subjects were visually and quantitatively evaluated based on clinical tests. Based on the evaluation results, the fundamental statistical characteristics of the non-contact measurement, including the average and median values, and distribution of measured signal-to-noise power ratio, were demonstrated. The clinical test results contributed to the future construction of quantified criteria for the AVF condition with the non-contact measurement.

Risk Factors and Utility of Intraoperative Arteriovenous Fistula Blood Flow Level as a Surrogate Marker of Arteriovenous Fistula Failure in Patients with End-stage Renal Disease.

An arteriovenous fistula (AVF) can fail for different reasons at each stage after its creation. The study aimed to analyze the associations of the clinical and laboratory parameters, including the intraoperative AVF blood flow, with AVF failure at different periods (3 weeks and 3, 6, 9, 12, 24, and 36 months) after the AVF's creation and to evaluate the usefulness of the intraoperative AVF blood flow as a surrogate marker of AVF failure in patients with end-stage renal disease (ESRD). This was a single-center, retrospective cohort study that included 130 patients with ESRD who underwent the creation of new radiocephalic AVFs. The associations of the preoperative clinical and laboratory parameters and intraoperative flow with AVF failure in the different observation periods were investigated. Intraoperative AVF blood flow was significantly associated with AVF failure from 3 weeks to 24 months (P <0.05). Hemoglobin level and the size of the anastomosis were significantly associated with AVF failure at 6 months (P <0.05). In the analysis of the receiver operating characteristic curve, intraoperative AVF blood flow was significant from 3 weeks to 24 months (P <0.05). The intraoperative blood flow with the greatest sensitivity and specificity was 205-225 mL/min. Intraoperative blood flow was independently associated with AVF failure from 3 weeks to 24 months after the AVF's creation. An intraoperative AVF blood flow of >225 mL/min is crucial for long-term AVF patency. The intraoperative AVF blood flow level could be a surrogate marker of AVF failure in ESRD patients.

Analysis of Geometric and Hemodynamic Profiles in Rat Arteriovenous Fistula Following PDE5A Inhibition.

Arteriovenous fistula (AVF) is essential for chronic kidney disease (CKD) patients on hemodialysis, but treatment for AVF maturation failure remains an unmet clinical need. Successful AVF remodeling occurs through sufficient lumen expansion to increase AVF blood flow and lumen area. Aberrant blood flow is thought to impair AVF remodeling, but previous literature has largely focused on hemodynamics averaged over the entire AVF or at a single location. We hypothesized that hemodynamics is heterogeneous, and thus any treatment’s effect size is heterogeneous in the AVF. To test our hypothesis, we used the PDE5A inhibitor sildenafil to treat AVFs in a rat model and performed magnetic resonance imaging (MRI) based computational fluid dynamics (CFD) to generate a detailed spatial profile of hemodynamics in AVFs. 90 mg/kg of sildenafil was administered to rats in their drinking water for 14 days. On day 14 femoral AVFs were created in rats and sildenafil treatment continued for another 21 days. 21 days post-AVF creation, rats underwent non-contrast MRI for CFD and geometrical analysis. Lumen cross-sectional area (CSA) and flow rate were used to quantify AVF remodeling. Parameters used to describe aberrant blood flow include velocity magnitude, wall shear stress (WSS), oscillatory shear index (OSI), and vorticity. Geometrical parameters include arterial-venous (A-V) distance, anastomosis angle, tortuosity, and nonplanarity angle magnitude. When averaged across the entire AVF, sildenafil treated rats had significantly higher CSA, flow rate, velocity, WSS, OSI, and vorticity than control rats. To analyze heterogeneity, the vein was separated into zones: 0–5, 5–10, 10–15, and 15–20 mm from the anastomosis. In both groups: 1) CSA increased from the 0–5 to 15–20 zone; 2) velocity, WSS, and vorticity were highest in the 0–5 zone and dropped significantly thereafter; and 3) OSI increased at the 5–10 zone and then decreased gradually. Thus, the effect size of sildenafil on AVF remodeling and the relationship between hemodynamics and AVF remodeling depend on location. There was no significant difference between control and sildenafil groups for the other geometric parameters. Rats tolerated sildenafil treatment well, and our results suggest that sildenafil may be a safe and effective therapy for AVF maturation.

Plan, Do, Check, Act (PDCA) Cycle Nursing Model Reduces the Risk of Hemangioma in Hemodialysis Patients.

Background:We aimed to explore the effect of Plan, Do, Check, Act (PDCA) circulation nursing on the prevention of aneurysm after hemodialysis.Methods:A total of 139 hemodialysis patients from Oct 2018 to Jan 2020 in Nephrology Department of the First People’s Hospital of Lianyungang, China were enrolled. They were randomly divided into control group and PCDA group, including 58 patients in control group and 81 patients in PCDA group. Patients’ satisfaction, blood flow in arteriovenous internal fistula and the incidence of post-dialysis vascular-related complications were statistically investigated in the two groups.Results:The satisfaction of patients in PDCA group was significantly higher than that in control group (P<0.001). In addition, when there was no statistical difference in blood flow between the two groups, the probability of complications such as internal fistula obstruction, thrombosis, infection, secondary puncture and aneurysm was lower in patients in the PDCA group, none of which occurred aneurysm.Conclusion:PDCA circulation nursing can effectively improve the quality of care and medical effect of hemodialysis patients with internal arteriovenous fistula, improve patient satisfaction and reduce the incidence of complications.

Computational modeling of the cephalic arch predicts hemodynamic profiles in patients with brachiocephalic fistula access receiving hemodialysis

The most common configuration for arteriovenous fistula is brachiocephalic which often develop cephalic arch stenosis leading to the need for numerous procedures to maintain access patency. The hemodynamics that contributes to the development of cephalic arch stenosis is incompletely understood given the inability to accurately determine shear stress in the cephalic arch. In the current investigation our aim was to determine pressure, velocity and wall shear stress profiles in the cephalic arch in 3D using computational modeling as tools to understand stenosis. Five subjects with brachiocephalic fistula access had protocol labs, Doppler, venogram and intravascular ultrasound imaging performed at 3 and 12 months. 3D reconstructions of the cephalic arch were generated by combining intravascular ultrasounds and venograms. Standard finite element analysis software was used to simulate time dependent blood flow in the cephalic arch with velocity, pressure and wall shear stress profiles generated. Our models generated from imaging and flow measurements at 3 and 12 months offer snapshots of the patient's cephalic arch at a precise time point, although the remodeling of the vessel downstream of an arteriovenous fistula in patients undergoing regular dialysis is a dynamic process that persists over long periods of time (~ 5 years). The velocity and pressure increase at the cephalic bend cause abnormal hemodynamics most prominent along the inner wall of the terminal cephalic arch. The topology of the cephalic arch is highly variable between subjects and predictive of pathologic stenosis at later time points. Low flow velocity and wall pressure along the inner wall of the bend may provide possible nidus of endothelial activation that leads to stenosis and thrombosis. In addition, 3D modelling of the arch can indicate areas of stenosis that may be missed by venograms alone. Computational modeling reconstructed from 3D radiologic imaging and Doppler flow provides important insights into the hemodynamics of blood flow in arteriovenous fistula. This technique could be used in future studies to determine optimal flow to prevent endothelial damage for patients with arteriovenous fistula access.

MO746CARDIAC REMODELING AND PULMONARY HYPERTENSION IN HEMODIALYSIS PATIENTS

Abstract Background and Aims An important predictor of cardiovascular mortality and morbidity in hemodialysis patients is left ventricular hypertrophy. Also, pulmonary hypertension is a risk factor for mortality and cardiovascular events in hemodialysis patients. The aim of this study was to investigate cardiac remodeling and the dynamics of pulmonary arterial pressure during a year-long hemodialysis treatment and to evaluate relationship between pulmonary arterial pressure and blood flow in arteriovenous fistula. Method Hemodialysis patients (n=88; 42 males, 46 females, mean age was 51.7±13.0 years) were studied. Echocardiography and Doppler echocardiography were performed in the beginning of hemodialysis treatment and after a year. Echocardiographic evaluation was carried out on the day after dialysis. Left ventricular mass index (LVMI) was calculated. Left ventricular ejection fraction (LVEF) was measured by the echocardiographic Simpson method. Arteriovenous fistula flow was determined by Doppler echocardiography. Pulmonary hypertension was diagnosed according to criteria of Guidelines for the diagnosis and treatment of pulmonary hypertension of the European Society of Cardiology. Results Pulmonary hypertension was diagnosed in 47 (53.4%) patients. Left ventricular hypertrophy was revealed in 71 (80.7%) patients. Only 2 (2.3%) patients had LVEF&amp;lt;50%. At the beginning of hemodialysis correlation was detected between systolic pulmonary arterial pressure and LVMI (r=0.52; P&amp;lt;0.001). Systolic pulmonary arterial pressure negatively correlated with left ventricular ejection fraction (r=-0.20; P=0.04). After a year of hemodialysis treatment LVMI decreased from 140.49±42.95 to 123.25±39.27 g/m2 (р=0.006) mainly due to a decrease in left ventricular end-diastolic dimension (from 50.23±6.48 to 45.13±5.24 mm, p=0.04) and systolic pulmonary arterial pressure decreased from 44.83±14.53 to 39.14±10.29 mmHg (р=0.002). Correlation wasn’t found between systolic pulmonary arterial pressure and arteriovenous fistula flow (r=0.17; p=0.4). Conclusion Pulmonary hypertension was diagnosed in half of patients at the beginning of hemodialysis treatment. Pulmonary hypertension in hemodialysis patients was associated with left ventricular hypertrophy, systolic left ventricular dysfunction. After a year-long hemodialysis treatment, a regress in left ventricular hypertrophy and a partial decrease in pulmonary arterial pressure were observed. There wasn’t correlation between arteriovenous fistula flow and systolic pulmonary arterial pressure.