Impact of stage-specific limb function exercises guided by a selfmanagement education model on arteriovenous fistula maturation status

BACKGROUND The exercise of limb function is the most economical and safe method to promote the maturation of arteriovenous fistula(AVF).However,due to the lack of a uni-fied exercise standard in China,many patients have insufficient awareness of the importance of AVF,leading to poor effectiveness of limb function exercise.The self-management education model can effectively promote patients to take pro-active health-related actions.This study focuses on the characteristics of patients during the peri-AVF period and conducts a phased limb function exercise under the guidance of the self-management education model to observe changes in fac-tors such as the maturity of AVF.AIM To assess the impact of stage-specific limb function exercises,directed by a self-management education model,on the maturation status of AVFs.METHODS This study is a randomized controlled trial involving 74 patients with forearm AVFs from the Nephrology Department of a tertiary hospital in Sichuan Province,China.Patients were randomly divided into an observation group and a control group using a random number table method.The observation group underwent tailored stage-specific limb func-tion exercises,informed by a self-management education model which took into account the unique features of AVF at various stages,in conjunction with routine care.Conversely,the control group was given standard limb function exercises along with routine care.The assessment involves the maturity of AVFs post-intervention,post-operative complications,and the self-management level of the fistula in both groups patients.Analyses were conducted using SPSS version 23.0.Count data were represented by frequency and percentage and subjected to chi-square test comparisons.Measurement data adhering to a normal distribution were presented as mean±SD.The independent samples t-test was utilized for inter-group comparisons,while the paired t-test was used for intra-group comparisons.For measurement data not fitting a normal distribution,the median and interquartile range were presented and analyzed using the Wilcoxon rank sum test.RESULTS At the 8-wk postoperative mark,the observation group demonstrated significantly higher scores in AVF symptom recognition,symptom prevention,and self-management compared to the control group(P<0.05).However,the variance in symptom management scores between the observation and control groups lacked statistical signi-ficance(P>0.05).At 4 wk after the operation,the observation group displayed a superior vessel diameter and depth from the skin of the drainage vessels in comparison to the control group(P<0.05).While the observation group did manifest elevated blood flow rates in the drainage vessels relative to the control group,this distinction was not statistically significant(P>0.05).By the 8-wk postoperative interval,the observation group outperformed the control group with notable enhancements in blood flow rates,vessel diameter,and depth from the skin of drainage vessels(P<0.01).Seven days following the procedure,the observation group manifested significantly diminished limb swelling and an overall reduced complication rate in contrast to the control group(P<0.05).The evaluation of infection,thrombosis,embolism,arterial aneurysm stenosis,and incision bleeding showed no notable differences between the two groups(P>0.05).By the 4-wk postoperative juncture,complications between the observation and control groups were statistically indistinguishable(P>0.05).CONCLUSION Stage-specific limb function exercises,under the guidance of a self-management education model,amplify the capacity of AVF patients to discern and prevent symptoms.Additionally,they expedite AVF maturation and miti-gate postoperative limb edema,underscoring their efficacy as a valuable method for the care and upkeep of AVF in hemodialysis patients.

Ruptured venous aneurysm associated with a dural arteriovenous fistula:Two case reports

BACKGROUND In general,venous aneurysm associated with dural arteriovenous fistula(dAVF)is considered to be developed under long standing venous hypertension and manifested as venous ectasia of draining vein itself.However,discrete saccular shaped venous aneurysm without angiographic evidence of venous hypertension arising from the draining vein,like cerebral arterial aneurysm,is quite rare and its pathomechanism remains unclear in patients with dAVF.CASE SUMMARY In this report,we present two cases of ruptured saccular venous aneurysms associated with dAVF without venous hypertension or venous ectasia.In both cases,significant curve or stenosis is observed in draining vein,which is located in just distal portion of the venous aneurysms.These aneurysms were successfully treated with a transarterial embolization.Underlying mechanism of venous aneurysms in these cases is discussed.CONCLUSION Although there is little doubt that hemodynamic stress has a critical role in the development of venous aneurysms in patients with dAVF,preceding venous hypertension or venous ectasia is not necessary for development and enlargement of venous aneurysms.Considering the significant risk of rupture,a careful review of draining vein features including tortuosity or stenosis is needed,especially in venous aneurysms without evidence of venous hypertension.

Surgical treatment of a rare brachial artery aneurysm postarteriovenous fistula closure after kidney transplant:A case report

BACKGROUND Brachial artery aneurysms are defined as dilations greater than 50%of the normal diameter,which are rare among all peripheral arterial aneurysms.While they are often present as pseudoaneurysms,true brachial artery aneurysms are also detected rarely.In this case report,the surgical repair method of true brachial artery aneurysms,which is a rare condition,is explained.CASE SUMMARY Herein,we present a 61-year-old male patient with complaints of swelling and pain in the right arm antecubital region that had been progressing over 6 mo.Upon the diagnosis of a true brachial artery aneurysm associated with arteriovenous fistula,the aneurysm was surgically repaired with an autologous saphenous vein graft.The patient was discharged without any neurovascular complications postoperatively.CONCLUSION True brachial artery aneurysms are rare and there are not any recommendations for their management in the current literature.Even though the treatment of true aneurysms in this artery is primarily based on a surgical treatment,endovascular repair also might be an option.

The Preventive Effect of Comprehensive Nursing Intervention on Arteriovenous Fistula Failure in Patients in the Hemodialysis Room

Objective:To explore the preventive effect of comprehensive nursing intervention on arteriovenous fistula failure in patients in the hemodialysis room.Methods:82 patients with arteriovenous fistula in the hemodialysis chamber treated in our hospital from July 2022 to October 2023 were selected as the research subjects.The random number table method divided them into a control group and an experimental group of 41 cases each.The control group received general nursing intervention measures,while the experimental group underwent comprehensive nursing intervention.The incidence of complications(internal fistula failure,bleeding,thrombosis,infection),psychological emotions(SAS scale,SDS scale),quality of life(physical pain,physiological function,emotional function,social function),and nursing satisfaction(very satisfied,basically satisfied,satisfied,dissatisfied)were compared between the two groups of patients.Results:The incidence of complications in the experimental group(4,9.76%)was significantly lower than that in the control group(29,70.73%);the SAS scores and SDS scores of the patients in the experimental group after intervention were both lower than those in the control group;the quality of life score(physical pain,physiological function,emotional function,and social function)was all higher than those of the control group;the post-intervention nursing satisfaction of the experimental group(40,97.57%)was also significantly higher than that of the control group(29,73.17%);and the listed differences were statistically significant(P<0.01).Conclusion:For patients with hemodialysis ventricular arteriovenous fistula failure,comprehensive nursing intervention can reduce the incidence of complications,relieve anxiety and stress,improve quality of life and nursing satisfaction,and achieve better preventive effects.

Application of Clinical Care Pathway in Perioperative Patients with Autologous Arteriovenous Fistula Balloon Expansion

[Objective] To explore the effect of clinical care pathways in perioperative patients with autologous arteriovenous fistula balloon expansion. [Method] 202 patients undergoing autologous arteriovenous fistula from July 2021 to June 2022 were randomly divided into a control group (101 cases) and an observation group (101 cases) to compare the incidence rates of postoperative complications, hospitalization days, hospitalization expenses, knowledge of self-management of arteriovenous fistula and nursing satisfaction. [Results] In the observation group, the incidence of arteriovenous fistula was higher than that of the control group, and the hospitalization days and hospitalization costs were lower than that of the control group. The difference between the two groups was statistically significant (P < 0.05). [Conclusion] The application of the clinical nursing path to intervene in patients with autologous arteriovenous fistula balloon dilation can reduce the incidence of postoperative complications, shorten the hospital length of time, reduce hospitalization costs and improve patient satisfaction, which is clinical promotion significance.

Transient ischemic attack induced by pulmonary arteriovenous fistula in a child:A case report

BACKGROUND Cerebral ischemic stroke is attributed to paradoxical cerebral embolism.Pulmonary arteriovenous fistula(PAVF)is a rare potential cause of cerebral ischemic stroke,and cerebral ischemic stroke induced by PAVF in children is rare.CASE SUMMARY We report a case of right PAVF that presented as a transient ischemic attack(TIA)in a 13-year-old boy.The patient underwent embolization therapy and remained clinically stable for 2 years after treatment.CONCLUSION TIA induced by PAVF in children is rare,lacks typical clinical manifestations,and should not be ignored.

Multimodal MRI diagnosis and transvenous embolization of a basicranial emissary vein dural arteriovenous fistula:A case report

A dural arteriovenous fistula(DAVF) is an abnormal linkage connecting the arterial and venous systems within the intracranial dura mater. A basicranial emissary vein DAVF drains into the cavernous sinus and the ophthalmic vein, similar to a cavernous sinus DAVF. Precise preoperative identification of the DAVF location is a prerequisite for appropriate treatment. Treatment options include microsurgical disconnection, endovascular transarterial embolization(TAE), transvenous embolization(TVE), or a combination thereof. TVE is an increasingly popular approach for the treatment of DAVFs and the preferred approach for skull base locations, due to the risk of cranial neuropathy caused by dangerous anastomosis from arterial approaches. Multimodal magnetic resonance imaging(MRI) can provide anatomical and hemodynamic information for TVE. The therapeutic target must be precisely embolized in the emissary vein, which requires guidance via multimodal MRI. Here, we report a rare case of successful TVE for a basicranial emissary vein DAVF, utilizing multimodal MRI assistance. The fistula had vanished, pterygoid plexus drainage had improved, and the inferior petrosal sinus had recanalized, as observed on 8-month follow-up angiography. Symptoms and signs of double vision, caused by abduction deficiency, disappeared. Detailed anatomic and hemodynamic assessment by multimodal MRI is the key to guiding successful diagnosis and treatment.

A Computational Analysis of the Influence of Anastomosis Angle on Stenosis-Prone Locations during Radio-Cephalic Arteriovenous Fistula Maturation

In dialysis treatment, the radio-cephalic arteriovenous fistula (RCAVF) is a commonly used fistula, yet its low maturation rate remains a challenge. To enhance surgical outcomes, the relationship between stenosis-prone locations and RCAVF anastomosis angle is studied during maturation by developing two sets of RCAVF models for early (non-mature) and mature RCAVFs at five anastomosis angles. The impact of hemodynamics and wall shear stress (WSS) is examined to determine optimal anastomotic angles. Results indicate that acute angles produce more physiological WSS distributions and fewer disturbed regions, with early stenosis-prone regions located near the anastomosis that shift to the bending venous segment during remodeling. A pilot study comparing clinical and numerical results is conducted for validation.

Impact and Management under Extracorporeal Circulation of a Patient with Renal Insufficiency on Dialysis with a High-Flow Arteriovenous Fistula in the Cardiac Surgery Department of the Angers Teaching Hospital about a Case and Review of the Literature

Arteriovenous fistulas have a substantial impact on systemic hemodynamics, however their effect on extracorporeal circulation is not well understood. We report our clinical observation on the management under extracorporeal circulation of a patient with renal insufficiency with a high-flow arteriovenous fistula. This is a 59-year-old man who was referred to us for surgical treatment of ischemic coronary artery disease in a context of anuric chronic renal failure. Hypothermia at 32°C is started from the start in CEC due to hyperflow at the level of the arteriovenous fistula. We performed two coronary artery bypasses of the marginal and IVA via the two internal thoracic arteries. The patient is hemofiltered in order to avoid hyperkalaemia and possibly avoid fluid overload related to filling per CEC. The clamping time was 71 minutes and the SCC lasted 141 minutes. There was no homologous transfusion in the operating room. It turns out that the input/output balance is zero at the end of the CEC. The postoperative course was simple.

Pitfalls in internal jugular vein cannulation

Central venous catheter insertion in the internal jugular vein(IJV)is frequently performed in acute care settings,facilitated by its easy availability and increased use of ultrasound in healthcare settings.Despite the increased safety profile and insertion convenience,it has complications.Herein,we aim to inform readers about the existing literature on the plethora of complications with potentially disastrous consequences for patients undergoing IJV cannulation.

Splenic arteriovenous fistula and sudden onset of portal hypertension as complications of a ruptured splenic artery aneurysm: Successful treatment with transcatheter arterial embolization. A case study and review of the literature

Splenic arteriovenous fistula （SAVF） accounts for an unusual but well-documented treatable cause of portal hypertension. A case of a 50-year-old multiparous female who developed suddenly portal hypertension due to SAVF formation is presented. The patient suffered from repeated episodes of haematemesis and melaena during the past twelve days and thus was emergently admitted to hospital for management. Clinical and laboratory investigations established the diagnosis of portal hypertension in the absence of liver parenchymal disease. Endoscopy revealed multiple esophageal bleeding varices. Abdominal computed tomography （CT） and transfemoral celiac arteriography documented the presence of a tortuous and aneurysmatic splenic artery and premature filling of an enlarged splenic vein, findings highly suggestive of an SAVF. The aforementioned vascular abnormality was successfully treated with percutaneous transcatheter embolization. Neither recurrence nor other complications were observed.

Inferior mesenteric arteriovenous fistula: Case report and world-literature review

Arteriovenous fistulas between the inferior mesenteric artery and vein are rare, with only 26 primary and secondary cases described in the literature. Secondary fistulas occur following operations of the left hemicolon and manifest as abdominal pain, abdominal mass, gastrointestinal bleeding, colonic ischemia and portal hypertension. Symptom intensities are flow-dependent, and can range from minimal symptoms to severe heart failure due to left to right shunt. Diagnosis is usually established by radiological or intraoperative examination. Treatment options include embolization and/or surgical resection. Therapeutic decisions should be adapted to the unique characteristics of the fistula on an individual basis. A new case of a primary arteriovenous fistula is described and discussed along with a complete review of the literature. The patient in this report presented with signs and symptoms of colonic ischemia without portal hypertension. The optimal treatment for this pa-tient required a combination of embolization and surgical operation. The characteristics of these rare inferior mesenteric arteriovenous fistulas are examined and some considerations concerning diagnostic and therapeutic strategies that should be followed are presented.

Self-care actions for the maintenance of the arteriovenous fistula:An integrative review

Objective:To identify self-care actions for the maintenance of arteriovenous fistula of renal patients.Method:An integrative review study was conducted and literature were searched in Medline/PubMed,Scopus,CINAHL LILACS,BDENF and SciELO Library databases using the descriptors chronic renal insufficiency,arteriovenous fistula,self-care,and knowledge.The inclusion criteria were that the documents be written in Portuguese,English,and Spanish,full text available,published in the last five years,and that they address the research question.Reflection articles,theses,dissertations,editorials of nonscientific journals,and research studies that did not follow the necessary methodological rigor were excluded.Data were analyzed with the IRAMUJTEQ software.Results:Fifteen articles were selected and comprised the final sample.Seven classes of self-care actions emerged from the text segments analysis and grouped into three categories:(1)Self-care actions that maintain the arteriovenous fistula;(2)Self-care actions for the prevention and the monitoring of complications with arteriovenous fistula;(3)Self-care actions directed at the perioperative period of arteriovenous fistula preparation.Conclusion:The results allowed us to identify important care for the maintenance of arteriovenous fistula functionality.The self-care actions identified in this study can guide a nursing care policy for implementation with protocols that help identify problems related to self-care actions and,thus,subsidize the development of actions aimed at the renal patient.However,more studies with high levels of evidence that identify self-care actions with arteriovenous fistula and the factors involved in its implementation are needed.

Melena-associated regional portal hypertension caused by splenic arteriovenous fistula

Regional portal hypertension is a rare cause of upper gastrointestinal bleeding.We reported an extremely rare case in which regional portal hypertension was associated with both the splenic arteriovenous fistula and chronic pancreatitis.In June 2010,our patient,a 41-year-old man,was admitted to a local hospital due to a sudden melena and dizziness without haematemesis and jaundice.The splenic arteriovenous fistula in this patient was successfully occluded through transcatheter arterial embolization.At the 12-mo follow-up,our patient was in good condition.

Effect of cryotherapy on pain management at the puncture site of arteriovenous fistula among children undergoing hemodialysis

Objective: To evaluate the effectiveness of cryotherapy in managing the pain at the puncture site of Arterio-Venous Fistula (AVF) among children undergoing maintenance hemodialysis (HD).Methods: A one-group pre-post quasi-experiment was performed in two HD centers affiliated with Cairo University.The experiment involved 40 children with AVF undergoing HD.Before puncturing,cryotherapy was applied using 2 cm-3 cm pieces of frozen distilled water in a plastic bag.Pain was assessed subjectively and objectively in two dialysis sessions before and after cryotherapy.A part from a physiological assessment of vital signs,pain was assessed using the Wong-Baker Faces Pain and the Observed Pain Behavior rating scales.All research ethics were applied.Results: HD had a median duration of four years,while cryotherapy had a median application time of 8.8 min.The Wong-Baker Faces Pain score and almost all observed pain behaviors significantly decreased after cryotherapy.Significant improvements were observed in respiratory rate before and after needle puncture and in oxygen saturation after needle puncture.A lower skin dryness was observed after cryotherapy (12.5%) than before cryotherapy (52.5%;p < 0.001).Conclusions: Cryotherapy can effectively reduce the venipuncture pain among children with AVF undergoing maintenance HD.However,the confounding effects of distraction and the non-randomized design used must be both considered when interpreting the findings.This study recommends the use of cryotherapy in managing needle puncture pain.Further research must adopt a randomized trial design with a placebo to support further the benefits of this procedure.

Combined functional and anatomical diagnostic endpoints for assessing arteriovenous fistula dysfunction

Failure of arteriovenous fistulas(AVF) to mature and thrombosis in matured fistulas have been the major causes of morbidity and mortality in hemodialysis patients. Stenosis, which occurs due to adverse remodeling in AVFs, is one of the major underlying factors under both scenarios. Early diagnosis of a stenosis in an AVF can provide an opportunity to intervene in a timelymanner for either assisting the maturation process or avoiding the thrombosis. The goal of surveillance strategies was to supplement the clinical evaluation(i.e., physical examination) of the AVF for better and earlier diagnosis of a developing stenosis. Surveillance strategies were mainly based on measurement of functional hemodynamic endpoints, including blood flow(Q a) to the vascular access and venous access pressure(VAP). As the changes in arterial pressure(MAP) affects the level of VAP, the ratio of VAP to MAP(VAPR = VAP/MAP) was used for diagnosis. A Q a < 400-500 m L/min or a VAPR > 0.55 is considered sign of significant stenosis, which requires immediate intervention. However, due to the complex nature of AVFs, the surveillance strategies have failed to consistently detect stenosis under different scenarios. VAPR has been primarily developed to detect outflow stenosis in arteriovenous grafts, and it hasn't been successful in accurate diagnosis of outflow lesions in AVFs. Similarly, AVFs can maintain relatively high blood flow despite the presence of a significant outflow stenosis and thus, Q a has been found to be a better predictor of only inflow lesions. Similar shortcomings have been reported in the detection of functional severity of coronary stenosis using diagnostic endpoints that were based on either flow or pressure. This limitation has been associated with the fact that both pressure and flow change in the presence of a stenosis and thus, hemodynamic diagnostic endpoints that employ only one of these parameters are inherently prone to inaccuracies. Recent attempts have resulted in development of new diagnostic endpoints that can combine the effects of pressure and flow. These new hemodynamic diagnostic endpoints have shown to be better predictors of functional severity of lesions as compared to either flow or pressure based counterparts. In this review article, we discussed the advantages and limitations of current functional and anatomical diagnostic endpoints in AVFs.

Arteriovenous fistulas and digital hypoperfusion ischemic syndrome in patients on hemodialysis

AIM： To determine survival parameters as well as char-acteristics of patients with this syndrome. METHODS： The investigation was conducted over a period of eight years, as a prospective, non-random-ized, clinical study which included 204 patients, treated by chronic hemodialysis. Most patients received hemo-dialysis 12 h per week. As vascular access for hemodi-alysis all subjects had an arteriovenous fstulae. Based on surveys the respondents were divided into groups of patients with and without digital hypoperfusion isch-emic syndrome. Gender, demographic and anthropo-metric characteristics, together with comorbidity and certain habits, were recorded. During this period 34.8% patients died.RESULTS： Patients with digital hypoperfusion ischemic syndrome were older than those without ischemia （P = 0.01）. Hemodialysis treatment lasted signifcantly lon-ger in the patients with digital hypoperfusion ischemic syndrome （P = 0.02）. The incidence of cardiovascular disease （P 〈 0.001） and diabetes mellitus （P = 0.01）, as well as blood fow through the arteriovenous fstula （ P = 0.036）, were higher in patients with digital hypoper-fusion ischemic syndrome. Statistically significant dif-ferences also existed in relation to oxygen saturation （P = 0.04）. Predictive parameters of survival for patients with digital hypoperfusion ischemic syndrome were： adequacy of hemodialysis （B = -3.604, P 〈 0.001）, hypertension （B = -0.920, P = 0.018）, smoking （B = -0.901, P = 0.049）, diabetes mellitus （B = 1.227, P = 0.005）, erythropoietin therapy （B = 1.274, P = 0.002） and hemodiafltration （B = -1.242, P = 0.033）. Kaplan-Meier survival analysis indicated that subjects with and without digital hypoperfusion ischemic syndrome dif-fered regarding the length of survival （P 〈 0.001）, i.e. , patients with confrmed digital hypoperfusion ischemic syndrome died earlier.CONCLUSION： Survival was signifcantly longer in the patients without digital hypoperfusion ischemic syn-drome.

Ischemic colitis secondary to inferior mesenteric arteriovenous fistula and portal vein stenosis in a liver transplant recipient

Arteriovenous fistula （AVF） involving the inferior mesenteric vessels is rare, and the affected patients usually present with abdominal pain, mass, or features of established portal hypertension. Colonic ischemia is a less common and more serious manifestation of AVE We report a case of ischemic colitis secondary to inferior mesentedc AVF in a patient who underwent a previous liver transplantation, subsequently developed portal vein stenosis, and then presented with acute lower gastrointestinal bleeding. He underwent percutaneous transhepatic placement of a portal vein stent and left colectomy.

Overview of multimodal MRI of intracranial Dural arteriovenous fistulas

Dural arteriovenous fistulas(DAVFs)include a wide range of pathological conditions that are associated with intracranial vessel abnormalities.While some types of DAVFs present with typical neuroimaging characteristics,others share overlapping pathological and neuroimaging features that can hinder accurate differentiation.Hence,misclassification of the various types of DAVFs is common.Thorough knowledge of DAVF imaging findings is essential to avoid such misinterpretations.Traditional digital subtraction angiography(DSA)is considered the gold standard for diagnosing and evaluating DAVFs.However,angiography cannot detect changes in a patient’s brain structure.Conventional magnetic resonance imaging(MRI)sequences,including MR angiography(MRA),allow the evaluation of DAVFs without ionizing radiation or invasiveness.Advanced MRI techniques,such as susceptibility-weighted imaging(SWI)and dynamic contrast-enhanced MRA,provide added value to real-time physio-pathological data regarding the hemodynamics of DAVFs.Beyond these techniques,new insights using high-resolution vascular wall MRI are incorporated for the noninvasive evaluation of DAVFs.This article reviews the pathophysiology of DAVFs,focusing on the specifics of MRI findings that facilitate their classification.The role of conventional and advanced MRI sequences for DAVFs was assessed using insights derived from the data provided by structured reports of multimodal MRIs to evaluate DAVFs.

Optimization of Maturation of Radio-Cephalic Arteriovenous Fistula Using a Model Relating Energy Loss Rate and Vascular Geometric Parameters

The main reason for the early failure of radio-cephalic arteriovenous fistula (RCAVF) is non-maturity, which means that the blood flow rate in the fistula cannot increase to the expected value for dialysis. From a mechanical perspective, the vascular resistance at the artificially designed anastomosis causes an energy loss that affects blood flow rate growth and leads to early failure. This research studied how to maximize the RCAVF maturity and primary patency by controlling the energy loss rate. We theoretically analyzed and derived a model that evaluates the energy loss rate Eavf in RCAVF as a function of its blood vessel geometric parameters (GPs) for given flow rates. There was an aggregate of five controllable GPs in RCAVF: radial artery diameter (Dra), cephalic vein diameter (Dcv), blood vessel distance between artery and vein (h), anastomotic diameter (Da), and anastomotic angle (θ). Through this analysis, it was found that Eavf was inversely proportional to Dra, Dcv, Da, and θ, whereas proportional to h. Therefore, we recommended surgeons choose the vessels with large diameters, close distance, and increase the diameter and angle of the anastomosis to decrease the early failure of RCAVF. Simultaneously, we could explain the results of many clinical empiricisms with our formula. We found that increasing Dcv and θ was more significant in reducing Eavf than increasing Dra and Da. Based on our model, we could define two critical energy loss rates (CELa, CELb) to help surgeons evaluate the blood vessels and choose the ideal range of θ, and help them design the preoperative RCAVF plan for each patient to increase the maturity and the primary patency of RCAVF.