Frequency of critical stenosis in primary arteriovenous fistulae before hemodialysis access: Should duplex ultrasound surveillance be the standard of care?

From the Society for Vascular Surgery

Frequency of critical stenosis in primaryarteriovenous fistulae before hemodialysis access:Should duplex ultrasound surveillance be thestandard of care?Jennifer Grogan, MD, Maria Castilla, BS, RVT, Laurie Lozanski, BS, RVT, Andrea Griffin, RDMS,Frank Loth, PhD, and Hisham Bassiouny, MD, Chicago, Ill

Objective: Increasing use of primary arteriovenous fistulae (pAVFs) is a desired goal in hemodialysis patients (NationalKidney Foundation /Dialysis Outcome Quality Initiative guidelines). However, in many instances, pAVFs fail toadequately mature due to ill-defined mechanisms. We therefore investigated pAVFs with color duplex ultrasound (CDU)surveillance 4 to 12 weeks postoperatively to identify hemodynamically significant abnormalities that may contribute topAVF failure.Methods: From March 2001 to October 2003, 54 upper extremity pAVFs were subjected to CDU assessment before access.A peak systolic velocity ratio (SVR) of >2:1 was used to detect >50% stenosis involving arterial inflow and venousoutflow, whereas an SVR of >3:1 was used to detect >50% anastomotic stenosis. CDU findings were compared withpreoperative vein mapping and postoperative fistulography when available.Results: Of 54 pAVFs, there were 23 brachiocephalic, 14 radiocephalic, and 17 basilic vein transpositions. By CDUsurveillance, 11 (20%) were occluded and 14 (26%) were negative. Twenty-nine (54%) pAVFs had 38 hemodynamicallysignificant CDU abnormalities. These included 16 (42%) venous outflow, 13 (34%) anastomotic, and 2 (5%) inflowstenoses. In seven (18%), branch steal with reduced flow was found. In 35 of 54 (65%) pAVFs, preoperative vein mappingwas available and demonstrated adequate vein size (>3 mm) and outflow in 86% of cases. Twenty-one fistulograms (38%)were available for verifying the CDU abnormalities. In each fistulogram, the arterial inflow, anastomosis, and venousoutflow were compared with the CDU findings (63 segments). The sensitivity, specificity, and accuracy of CDU indetecting pAVF stenoses >50% were 93%, 94%, was 97%, respectively.Conclusions: Before initiation of hemodialysis, an unexpectedly high prevalence of critical stenoses was found in patentpAVFs using CDU surveillance. These de novo stenoses appear to develop rapidly after arterialization of the upperextremity superficial veins and can be reliably detected by CDU surveillance. Turbulent flow conditions in pAVFs mayplay a role in inducing progressive vein wall and valve leaflet intimal thickening, although stenoses may be due to venousabnormalities that predate AVF placement. Routine CDU surveillance of pAVFs should be considered to identify and
correct flow-limiting stenoses that may compromise pAVF long-term patency and use. (J Vasc Surg 2005;41:1000-6.)
More than 290,000 individuals are hemodialysis de-pendent in the United States, and it is estimated that thispopulation will double by 2010.1 Hemodialysis access fail-ure is a major cause of morbidity and multiple hospitaladmissions. Furthermore, the estimated cost for vascularaccess morbidity exceeds 2 billion dollars annually.1,2 Arte-riovenous fistulae (pAVFs) are recognized as the gold stan-dard of hemodialysis access because of superior long-termpatency and lower infection and intervention rates whencompared with prosthetic conduits.3-5

The Vascular Access Work Group, of the NationalKidney Foundation (NKF), identified two primary goals toimprove quality of life and overall outcomes for patients on

From the Department of Surgery, Vascular Section, University of Chicago.Competition of interest: none.Presented at the Fifty-eighth Annual Meeting of the Society for Vascular

Surgery, Anaheim, Calif, June 5, 2004.Reprint requests: Hisham S. Bassiouny, MD, Department of Surgery, Vas-

cular Section, University of Chicago, 5841 South Maryland Avenue, MC5028, Chicago, IL 60637 (e-mail: [email protected]).

0741-5214/$30.00Copyright © 2005 by The Society for Vascular Surgery.
doi:10.1016/j.jvs.2005.02.019
1000

hemodialysis. The first is to increase the prevalence and useof native AVFs. The second is to detect access dysfunctionbefore occlusion. These goals are addressed in the DialysisOutcome Quality Initiative (DOQI) guidelines.3 The ulti-mate goal is that pAVFs be constructed in at least 50% of allnew patients with end-stage renal disease and that 40% ofpatients undergo hemodialysis via a pAVF. Currently in theUnited States, only 31% of patients on hemodialysis dialyzethrough an AVF, and the incidence of AVF creation is adisappointing 28%. This failure is particularly concerningwhen one considers that 80% of prevalent patients onhemodialysis in Europe dialyze through pAVFs.6 Ascher etal4 have reported an increase in pAVF placement to at least80% in their study cohort when DOQI guidelines arestrictly followed, with a 1-year primary patency rate of 85%.The etiology of such poor pAVF prevalence rates in theUnited States is multifactorial and includes inadequatepatient selection, surgical preference, and suboptimal tech-nique during traumatic cannulation.

In April 2004, the need to improve AVF use wasfurther emphasized when the Centers for Medicare and
Medicaid announced a national initiative (National Vascu-

JOURNAL OF VASCULAR SURGERYVolume 41, Number 6 Grogan et al 1001

lar Access Improvement Initiative [NVAII]) to foster prac-tice patterns that would increase pAVF use in patients onMedicare. The NVAII statement recommends a multidis-ciplinary implementation of protocol-driven surveillanceprograms for early detection and treatment of failing vas-cular access conduits.7 The value of a multidisciplinaryapproach to hemodialysis access was emphasized in a pro-spective study by Allon et al,8 which demonstrated a de-crease in access failure and an increase in AVF creation innew patients on dialysis from 33% to 69%.

To date, the results of color duplex ultrasound (CDU)pAVF surveillance in the first 2 to 3 months postoperativelyare not known. The purpose of this retrospective study wasto determine the prevalence of hemodynamically significantabnormalities in pAVFs before access cannulation using astandard protocol of CDU surveillance. We further vali-dated the CDU surveillance results with correspondingfistulograms.

METHODS

Patient population

In this retrospective study (March 2001 to October2003), we reviewed the CDU surveillance findings of pa-tients referred for evaluation of upper extremity pAVFs in54 patients within 3 months of fistula creation and beforeinitiation of hemodialysis. During this study period, a totalof 263 patients underwent AVF placement and 186 pa-tients underwent nonautologous arteriovenous graft place-ment. CDU evaluation of the pAVFs was conducted toassess several aspects of fistula maturation including diam-eter, depth from the skin surface, side branch steal, and the

Table I. Patient demographics

GenderMale (%) 39Female (%) 61

Age (y) 55 � 15 (24-80)Type of fistula

Radiocephalic 14Brachiocephalic 23Basilic transposition 17

Table II. Results of color duplex ultrasound examinations

Radiocephal(n � 14)

No abnormality 5 (36%)Hemodynamically significant abnormalities 6 (43%)Arterial inflow 0Anastomosis 3Venous outflow 4Branch 3

Occlusion 3 (21%)

Chi-square analysis showed no statistical difference between groups, P � .24
abnormalities were found in 29 abnormal examinations.
presence of �50% stenosis in the arterial inflow, anastomo-sis, or venous outflow of the arterialized vein. The CDUsurveillance results were compared with preoperative veinmapping and fistulography when available.

CDU evaluation

CDU examinations were performed by an experiencedsonographer using an ATL HDI 5000/3000 series (Ad-vanced Technology Laboratories, Bothell, Wash) or Acu-son Sequoia 512 (Acuson Corporation, Mountain View,Calif) ultrasound machine with a 4- to 7- or a 5- to10-MHz linear array transducer. A standard protocol forpAVF CDU evaluation was followed that included interro-gation of the arterial inflow, anastomosis, and venous out-flow tract. pAVF examination included Doppler spectralanalysis and B-mode imaging complemented with colorflow mapping.

Pulsed Doppler spectral analysis. Doppler spectralanalysis was used to measure peak systolic velocity (PSV) ata 60-degree angle of insonation. An initial sweep of thearterial inflow, anastomosis, and fistula body with pulsed-wave Doppler was performed to identify areas of increasedvelocity. Representative measurements were taken at thearterial inflow, anastomosis, and proximal, mid, and distalvenous outflow. The venous outflow was examined to thelevel of the axilla, including the central venous system whenpossible. Criteria for a hemodynamically significant stenosis(�50%) were based on previously published reports.9,10

Two parameters were used, the PSV and the systolic veloc-ity ratio (SVR). The SVR was determined by calculating theratio of the highest PSV at the suspect stenosis normalizedto the prestenosis PSV. Hemodynamically significant ste-nosis of the arterial inflow or venous outflow was indicatedwhen the SVR was �2. Anastomotic stenoses were deter-mined by an SVR of 3 and a minimum PSV of 400 cm/s.Stricter criteria were used at the anastomoses because ofinherently turbulent flow conditions and elevated velocitiescaused by the steep pressure gradient.

Side branch steal was defined as high-velocity flowthrough a side branch with a significant reduction in veloc-ity through the main venous outflow. Gray scale mediananalysis was first used to identify the branch. PSV was then

ifferent primary arteriovenous fistula types

Brachiocephalic(n � 23)

Brachiobasilictransposition

(n � 17)Total

(n � 54)

8 (35%) 1 (6%) 14 (26%)11 (48%) 12 (71%) 29 (54%)

0 2 25 4 126 6 163 1 7

374 (17%) 4 (23%) 11 (20%)

pes of abnormalities that were found are listed for each group. A total of 37

in d

ic

9. Ty

JOURNAL OF VASCULAR SURGERYJune 20051002 Grogan et al

measured before the branch, in the branch, and after thebranch. A PSV in the branch that was twofold higher thanin the main venous outflow, with a significant velocitydecrease in the main outflow after the branch, was used toidentify side branch steal.

B-mode and color ultrasound examination. B-mode ultrasound scanning was used to evaluate vein diam-eter and depth (2 to 5 mm), to help determine presence ofa vein wall thickening and luminal stenosis, and to discrim-inate between arterial inflow and anastomotic suture linestenosis. Color flow imaging was used to identify sidebranch steal at regions of elevated SVR.

Preoperative vein mapping

The superficial venous system was evaluated for com-pressibility and diameter using a 4- to 7- or 5- to 10-MHzlinear array probe. The cephalic vein was evaluated from thelevel of the wrist to the subclavian vein and the basilic veinfrom the forearm to the subclavian vein. Upper extremityveins �3 mm with tourniquet application and withoutevidence of phlebitic mural thickening or intraluminal webswere considered suitable for pAVF creation. These resultswere compared with the results of the postoperative CDUpAVF surveillance.

Fistulography

Before fistulography, physical examination was used toselect location of the cannulation site and direction of theintroduced sheath in the pAVF venous outflow. Initially,antegrade fistulography was performed to visualize thefistula and the draining veins, including the central veins.Retrograde fistulography with manual downstream occlu-sion was performed to examine the arterial inflow, distalvein, and the anastomosis. A hemodynamically significantstenosis on fistulography was identified as a 50% luminaldiameter reduction on uni- or biplanar views. Other abnor-malities, including kinking, side branches, and central ste-nosis, were also identified. The CDU scan and fistulogramswere compared to determine the sensitivity, specificity,negative predictive value, positive predictive value, andaccuracy of CDU surveillance in detecting hemodynami-cally significant abnormalities in pAVFs.

Statistical methods

Chi-square analysis was used to compare the differencein the prevalence of hemodynamically significant abnormal-ities between fistula types. Difference were considered sta-tistically significant at P � .05

RESULTS

This retrospective analysis had 14 patients with radio-cephalic (RC), 23 with brachiocephalic (BC), and 17 withbasilic transposition (BT) pAVFs. Patient demographics areshown in Table I.

CDU evaluation

Of these 54 patients, 14 (26%) had no abnormality on
their CDU examination; 29 (54%) had a hemodynamically
significant abnormality, and 11 (20%) had complete AVFocclusion. In Table II, patients with abnormal CDU exam-inations are separated according to pAVF type. The differ-ence between groups was not significant (P � .25). In the29 abnormal CDU examinations of patent pAVFs, 37hemodynamically significant abnormalities were found(Table II). These included 16 (43%) venous outflow, 12(33%) anastomotic, and 2 (5%) inflow stenoses. In seven(19%), branch steal with reduced flow was found. Of the 16with venous out flow stenosis, two of these patients hadstenosis in their subclavian vein, most likely from previous

Fig 1. Color duplex ultrasound (CDU) and B-mode findings ofvenous stenosis in the mid-segment of the venous outflow of abrachiobasilic transposition primary arteriovenous fistula. A, CDUvelocity profiles: peak systolic velocity (PSV) at stenosis � 227cm/s and PSV prestenosis � 85 cm/s. Systolic velocity ratio � 2.7,indicating a luminal stenosis �50%. B, B-mode ultrasound assess-ment of venous stenosis demonstrating focal valve leaflet
thickening.

steno


catheterization. Figure 1A shows CDU evaluation of abrachiobasilic vein transposition with a hemodynamicallysignificant abnormality in the mid-segment of the venousoutflow and the corresponding B-mode evaluation. Figure1B is representative of the culprit stenosis as visualized byB-mode imaging.

Preoperative vein mapping

Thirty-five of 54 patients (65%) had preoperative veinmapping. The frequency of preoperative vein mappingvaried among the different surgeons involved in this study.Although some surgeons obtained preoperative vein map-ping for 100% of their patients, others only obtained itwhen physical examination did not reveal prominent veins.Thirty (86%) of these studies showed adequate outflow veinas described in the Methods section. Of five patients withinadequate veins, two pAVFs were occluded by CDU ex-amination, two developed hemodynamically significant ab-normalities, and one pAVF remained patent. Only 2 of the5 achieved functional patency and both required revision.Seven of the 11 pAVFs that occluded had preoperative veinmapping, 5 demonstrated adequate veins, and 2 demon-

Fig 2. Radiocephalic fistulogram demonstrates a �50%tion demonstrates a hemodynamically significant abnormvelocity (PSV) at anastomosis � 438 cm/s and PSV pre

strated inadequate veins.

Fistulography

Fistulography was performed in 21 (39%) patentpAVFs. In each fistulogram, three areas, the arterial inflow(n � 21), anastomosis (n � 21), and venous outflow (n �21), were identified and compared with the CDU findings(63 segments). Figure 2 demonstrates a fistulogram of aRC pAVF with an arterial inflow stenosis. The CDU exam-ination had identified the lesion as an anastomotic stenosis.Figure 3 demonstrates a fistulogram of a BC pAVF with ananastomotic stenosis that had been previously identified byCDU examination. A color flow map is shown in the inset.

In our study, there were 29 patients who had patentabnormalities found on ultrasound scanning; 18 of thesepatients went on to have fistulography. Ten of these fistulaewere revised and remained patent, three were revised andfailed, three remained patent without revision, and in two,the defect was considered unsalvageable and new access wascreated. Three patients with normal ultrasound examina-tions had normal fistulograms.

CDU validation by fistulography is shown in Table III.The sensitivity and specificity of CDU examination were

rial stenosis. Color duplex ultrasound (CDU) examina-at the anastomosis. CDU velocity profiles: peak systolicsis � 130 cm/s. Systolic velocity ratio � 3.4.

arteality

93% and 94%, respectively, and accuracy was 97%. The


positive predictive value was 82%, and the negative predic-tive value was 98%.

DISCUSSION

The high early attrition rate in pAVFs is a well-recog-nized problem that deserves further investigation. We hy-pothesized that CDU surveillance may also play an impor-tant role in defining the etiology of early pAVF failure. Toour knowledge, this is the first report that addresses theresults of CDU surveillance in pAVFs in the intermediatepostoperative period before pAVF cannulation.

In this study, CDU surveillance was employed to assess54 pAVF within 3 months of creation. The majority of thepatients were referred for postoperative duplex scanningprimarily as a screening evaluation for vein size, depth, andflow assessment. Patients who were identified as having anabnormal physical examination (absent thrill, failure tomature) were excluded. It is our impression, however, thatthe physical examination, even when normal, may fail todetect hemodynamic abnormalities in many instances. We

Fig 3. Brachiobasilic transposition fistulogram demonssound (CDU) velocity profiles: peak systolic velocity (PS711 cm/s, and systolic velocity ratio � 3.8, indicating anthe anastomotic region.

Table III. Probability values of CDU examinationresults compared with fistulography to detecthemodynamically significant abnormalities

Probability value (%) CDU vs fistulography

Sensitivity 93Specificity 94Positive predictive value 82Negative predictive value 98Accuracy 97

CDU, Color duplex ultrasound.

chose the time interval of 1 to 3 months to ensure healing

of the surgical incisions, to give the fistulae adequate timeto mature and adapt to the altered hemodynamic environ-ment, and to address the role of CDU examination indetecting abnormalities that may lead to early AVF failure.Our goal was to identify hemodynamically significant ste-noses that may contribute to early pAVF failure. To oursurprise, only 26% of the patent pAVFs were devoid of anysignificant abnormalities. An alarming 54% had hemody-namically significant stenoses, and the remaining 20% hadalready occluded at the time of examination. In patientswith patent abnormalities, often there was no abnormalitydetected on physical examination. There was not a statisti-cally significant difference between RC, BC, or basilictransposition pAVFs, although the sample size may havebeen too small. Abnormalities were found in patients withadequate preoperative vein mapping. This suggests that denovo hemodynamic abnormalities develop after arterializa-tion of the target vein. This may be attributed to venousvalve malposition and venous intimal hyperplasia due toinherent turbulent flow conditions or to preexisting veinwall abnormalities, such as vein wall thickening or occultcentral venous stenosis not detected by vein mapping.Lesions were also identified in fistulae that were created inthe presence of abnormalities identified on preoperativevein mapping, suggesting that preoperative vein mappingcould be useful in predicting longevity of fistulae. The major-ity of abnormalities were found in the venous outflow tract,either stenosis (43%) or side branch steal (19%), suggestingthat they were not caused by poor surgical technique.

Eleven patients were occluded at the time of ultrasoundexamination. Two of these patients had inadequate veinmapping. Four did not have vein mapping, and five patientswith occlusion at the time of ultrasound examination had

a �50% anastomotic stenosis (C). Color duplex ultra-arterial inflow � 185 cm/s (A), PSV at anastomosis �omotic stenosis (B). Inset shows color flow mapping for

tratesV) atanast

adequate preoperative vein mapping. The reason for these


occlusions may be similar to those listed previously or maybe due to surgical technique. Of the 11 occlusions, twooccurred within the first 2 weeks. It is unlikely that earlierexamination/intervention would have improved the out-come in these cases. Of the remaining nine, three wereexamined at 6 weeks and six were examined at 2 to 3months. It is possible that these occlusions, particularly thesix that were examined at 2 to 3 months, could have beenprevented by earlier intervention. We would recommend adelay of 4 to 6 weeks to allow for wound healing and initialfistula maturation, but it is likely that waiting longer than 8weeks to perform ultrasound surveillance may lead to oc-clusion secondary to undetected hemodynamic abnormal-ities.

Preoperative CDU upper extremity vein mapping hasbeen shown to increase the incidence of pAVF creation andimprove early patency rates by helping to identify suitablevein conduits for the optimal pAVF creation. Silva et al11

compared a group of patients who received routine preop-erative vein mapping with historical controls and showedthat pAVF creation improved 14% to 63% of all vascularaccess placements. Additionally, improved primary cumu-lative patency was found in both the pAVF and arterio-venous graft placed. Other groups have reported increasedrates of pAVF creation using vein mapping but with persis-tently high or increased rates of primary failure, defined asearly thrombosis or failure to mature.12,13 A report byAllon et al12 showed that although fistula placement in-creased from 34% to 64%, initial adequacy rates for dialysisshowed only a slight improvement, from 46% to 54% (P �.34).

In our study, only 65% of patients had preoperative veinmapping due to variability in the different surgeons’ prac-tices. The impact of preoperative vein mapping on type ofaccess (ie, AVF vs AVG) was not the focus of this study.Because of the small sample size, it is difficult to assess theimpact of vein mapping on AVF patency. However, func-tional patency was approximately 60% in patients withadequate vein mapping and those without vein mapping.Functional patency is defined as patients who went on todialyze through the pAVF. Five patients had AVF placedafter vein mapping showed inadequate (�3 mm) vein. Inthis group, functional patency was only 40%, with threeoccluding and the other two requiring revision. Theseresults suggest that preoperative vein mapping is helpfulwhen an adequate outflow is defined. Additionally, thefinding of inadequate outflow may lead to the creation ofaccess at an alternate site. However, in some instances, theuse of a marginal venous outflow is the only remainingoption for the surgeon to create an autogenous access.

Several studies have compared CDU examination ofarteriovenous fistula and grafts to fistulography (digitalsubtraction angiography). Wong et al14demonstrated thatCDU examination was more reliable than clinical assess-ment in predicting RC fistula failure. Tordoir et al10 com-pared CDU examination with fistulography in a large seriesof 58 diverse patients. The patients varied significantly in
access type (graft vs fistula), age of the access (1 to 160
months), and clinical presentation (eg, asymptomatic, lowflow, distal ischemia, aneurysm). Using diagnostic criteriaof PSV alone, they achieved accuracy of 81% to 96% andsensitivity of 79% to 96%. Chao et al9 compared CDUexamination with digital subtraction angiography in a seriesof 38 failing RC fistulae and found a specificity of 96% andoverall accuracy of 97% using combination criteria of PSVand SVR. These and other studies were invaluable in iden-tifying CDU surveillance as a valid tool for noninvasiveinterrogation of arteriovenous fistulae and grafts. In thisstudy, we were able to confirm the validity of our findingswith fistulography in 21 patients, with a sensitivity of 93%and a specificity of 94%. Limitations of CDU examinationin this and other studies include difficulty in interrogatingthe anastomotic region. Because of transition of laminarpulsatile flow to turbulence in the anastomotic region, it isdifficult to distinguish between anastomotic and inflowarterial stenosis in proximity to the anastomosis.15 B-modeimaging is helpful in this regard.

Although 29 patients had patent abnormalities onCDU examination, 11 of these patients did not undergofistulography. Four of these patients were lost to follow-up.Of the other seven, four remained patent, two occluded,and one was revised at a later date and remained patent afterrevision. Fistulography was not performed on these pa-tients with abnormal CDU evaluation because of surgeonpreference. We would nonetheless recommend fistulogra-phy after abnormal CDU examination.

Previous studies have shown that aggressive treatmentof nonmaturing and nonfunctioning fistulae is often suc-cessful.16-18 Such treatments include open revision, percu-taneous angioplasty or venoplasty, and side branch ligation.Many lesions can be readily corrected using percutaneousendoluminal techniques. The findings of this study stronglysuggest that hemodynamically significant abnormalities arerelatively frequent and can be reliably detected using CDUexamination in pAVFs before hemodialysis. In our study, ofthe 29 patients who had patent abnormalities, 14 patientshad percutaneous or open intervention and 11 of the 14(78%) achieved functional patency. It is our contention thatroutine CDU surveillance of pAVFs 4 to 6 weeks postop-eratively will lead to increased early intervention and anincreased functional utilization rate of pAVFs. This topicdeserves further investigation, with a prospective study tocompare patency and utilization rates among patients whoundergo CDU surveillance and those who do not. In sucha study, it would be important that all patients undergopreoperative vein mapping and that the results of CDUsurveillance be verified with digital subtraction contrastfistulography.

REFERENCES

1. US Renal Data System. USRDS 2003 Annual Report: Atlas of End-Stage Renal Disease in the United States. Bethesda, Md: The NationalInstitutes of Health, National Institute of Diabetes and Digestive andKidney Disease, 2003.

2. Hakin R, Himmelfarb J. Hemodialysis access failure: a call to action.
Kidney Int 1998;54:1029-40.


3. National Kidney Foundation. K/DOQI Clinical Practice Guidelines forHemodialysis Adequacy, 2000. Am J Kidney Dis 2001;37(Suppl 1):S7-S64, 2001.

4. Ascher E, Gade P, Hingorani A, Mazzariol F, Gunduz Y, Fodera M,Yorkovich W. Changes in the practice of angioaccess surgery: Impact ofdialysis outcome and quality initiative recommendations. J Vasc Surg2000;31:84-92.

5. Gibson KD, Gillen DL, Kohler TR, Sherrard DJ, Stehman-Breen CO.Vascular access survival and incidence of revisions: a comparison ofprosthetic grafts, simple autogenous fistulas, and venous transpositionfistulas from the United States Renal Data System Dialysis Morbidityand Mortality Study. J Vasc Surg 2001;34:694-700.

6. Pisoni RL, Young EW, Dykstra DM, Greenwood RN, Hecking E,Gillespie B, et al. Vascular access use in Europe and the United States:results from the DOPPS. Kidney Int 2002;61:305-16.

7. Beasley C, Nolan K, Steinfield R, and the Vascular Access WorkingGroup. National Vascular Access Improvement Initiative (NVAII).Boston, Mass: Institute for Healthcare Improvement, 2003 (www.qualityhealthcare.org).

8. Allon M, Bailey R, Ballard R, Deierhoi MH, Hamrick K, Oser R, et al.A multidisciplinary approach to hemodialysis access: prospective evalu-ation. Kidney Int 1998;53:473-9.

9. Chao A, Daley T, Gruenewald S, Larcos G, Harris DC, Yuill E, et al.Duplex ultrasound criteria for assessment of stenoses in radiocephalichemodialysis fistulas. J Vasc Technol 2001;25:203-8.

10. Tordoir JH, de Bruin HG, Hoeneveld H, Eikelboom BC, Kitslaar PJ.Duplex ultrasound scanning in the assessment of arteriovenous fistulascreated for hemodialysis access: comparison with digital subtraction
angiography. J Vasc Surg 1989;10:122-8.
optimizing selection of location for AV fistula placement.

11. Silva MB, Hobson RW, Pappas PJ, Jamil Z, Araki CT, Goldberg MC, etal. A strategy for increasing use of hemodialysis access procedures:impact of preoperative noninvasive evaluation. J Vasc Surg 1998;27:302-8.

12. Allon M, Lockhart ME, Lilly RZ, Gallichio MH, Young CJ, Barker J, etal. Effect of preoperative sonographic mapping on vascular accessoutcomes in hemodialysis patients. Kidney Int 2001;60:2013-20.

13. Patel ST, Hughes J, Mills JL. Failure of arteriovenous fistula matura-tion: an unintended consequence of exceeding Dialysis Outcome Qual-ity Initiative guidelines for hemodialysis access. J Vasc Surg 2003;38:439-45.

14. Wong V, Ward R, Bakran A. Factors associated with early failure ofarteriovenous fistulae for haemodialysis access. European Journal ofVascular and Endovascular Surgery 1996;12:207-213.

15. Loth F, Fischer PF, Arslan N, Bertram CD, Lee SE, Royston TJ, et al.Transitional flow at the venous anastomosis of an arteriovenous graft:potential activation of the ERK1/2 mechanotransduction pathway.J Biomech Eng 2003;125:49-61.

16. Berman SS, Gentile AT. The impact of secondary procedures in autog-enous arteriovenous fistula maturation and maintenance. J Vasc Surg2001;34:866-71.

17. Higorani A, Ascher E, Kallakuri S, Greenberg S, Khanimov Y. Impact ofreintervention for failing upper-extremity arteriovenous autogenousaccess for hemodialysis. J Vasc Surg 2001;34:1004-9.

18. Beathard GA, Arnold P, Jackson J, Litchfield T. Aggressive treatment ofearly fistula failure. Kidney Int 2003;64:1487-94.

Submitted Jun 10, 2004; accepted Feb 7, 2005.

DISCUSSION

Dr Enrico Ascher (Brooklyn, NY). The authors of this paperrecommend duplex scan evaluation of autologous AV access beperformed prior to cannulation or for hemodialysis. Yet, only 65%of their patients had preoperative duplex studies. Were the patencyand maturation results between the patients who had preoperativescanning different from the ones who had physical examinationalone?

I’m surprised that 20% of your primary AV fistulas and trans-positions thrombosed within 3 months. Even more interesting,was the observation that only 1 out of 17 brachiobasilic transposi-tions was found not to have a hemodynamically significant stenoticlesion or occlusion. These findings are divergent from the onesreported in the literature. It is possible that your criteria to indicatea hemodynamically significant lesion are too stringent. I believethat calculation of peak systolic velocity ratios may be misleading,particularly at or near the anastomosis where size mismatch can besignificant. Additionally, I believe that measurements of the resid-ual lumen diameter may better reflect the significance of theflow-limiting lesion than peak systolic velocities and ratios. Forexample, a 5-mm residual lumen in a 10-mm vein, which is a 50%diameter reduction, may be less flow restrictive than a 3-mmresidual lumen in a 5-mm vein, which is 40% diameter reduction.Dr. Grogan, do you agree with this concept?

It makes intuitive sense that a noninvasive exam such as duplexscanning of a primary arteriovenous reconstruction be performedprior to cannulation for hemodialysis. Unfortunately, the datapresented today still need to be corroborated by a larger prospec-tive study where volume flows rather than peak systolic velocitiesalone are measured, since these appear to be better indicators offistula maturation. Did you measure volume flows? And if yes, didthey correlate with the findings found in the fistulograms?

Dr Grogan. Unfortunately, because of the retrospective na-ture of this study, we do not have preoperative vein mapping on allof our patients. It has been shown by groups such as your own thatpreoperative vein mapping can significantly improve not only therate of AV fistula creation, but also AV fistula patency rates, by

We do not think that physical exam is adequate for selectingthe location or the type of vascular access. However, it wouldrequire a randomized prospective trial in which all patients hadundergone preoperative vein mapping to really differentiate theeffect of preoperative versus postoperative ultrasound evaluation.

In regards to your second question, it is true that we foundnumerous abnormalities in our brachiobasilic transpositions,which, in the published literature, have the highest primary pa-tency rates. This may be due to increased turbulent flow in thesefistulas as they generally have the biggest vein diameter. Thenatural history of these lesions that we identified is not known. Andit’s possible that, although we didn’t use different criteria whenlooking at arm or forearm fistulas, different criteria may be re-quired. We did look at patients using gray-scale criteria and an SVRof 3:1 and found that the sensitivity of our exam decreased fromthe 90% to the 70%. So because we were trying to screen patientsand find as many abnormalities as possible, we chose the criteriathat I mentioned in my presentation.

Finally, flow rates were performed in many of our patients,however, not all of them. Generally, we found flow rates between300 and 700 even when hemodynamic abnormalities were found.

Dr F. LoGerfo (Boston, Mass). I was interested in yourconcept of vein valve malposition due to the high flow rate, whichcould occur, because the valve itself, even though it’s in essentiallyin a reversed position, as the vein is completely distended, canbecome a partial obstruction, and that these very high flow ratesthen create a very significant flow disturbance. How many of yourlesions would you ascribe to this category? Does it occur inspecifically one type of fistula or another? And do you think thatincising those valves beforehand might reduce this phenomenon?

Dr Grogan. I can’t speak to the different causes for thehemodynamic abnormalities we found. It’s our feeling that prob-ably this finding would be more common in brachiobasilic trans-positions because of the higher flow rates that we found there. But
it’s a topic that would require further investigation.

Documents

Frequency of critical stenosis in primary arteriovenous fistulae before hemodialysis access: Should duplex ultrasound surveillance be the standard of care?