1
Can a policy of careful clinical examination and preference towards upper arm fistulae in high risk
2
patients improve maturation rates of native arteriovenous fistulae?
3
S. Verest, P. Logghe, K. Claes*, D. Kuypers*, I. Fourneau
4
Department of Vascular Surgery, University Hospitals Leuven, Belgium.
5
* Department of Nephrology, University Hospitals Leuven, Belgium.
6
Introduction: Maximal use of native arteriovenous fistulas (AVFs) for patients on hemodialysis therapy
7
remains a clinical challenge. Primary failure rates remain high with risk factors such as female gender,
8
diabetes mellitus, lower arm AVF and higher age. We wondered if a strategy of careful clinical examination
9
prior to AVF creation and a preference towards an upper arm AVF in case of doubt about the quality of the
10
vein in patients with any of the above mentioned risk factors, would lead to better maturation rates.
11
Methods: The records of all patients who received an AVF between January 2005 and December 2009 at
12
our University Hospitals Leuven were studied retrospectively. Demographic data, comorbidity, fistula
13
characteristics, fistula maturation and fistula complications were recorded and analyzed.
14
Results: Of 344 patients enrolled, 156 (45.3%) received a lower arm AVF and 188 (54.7%) an upper arm
15
AVF. Two hundred and seventy-six (80.2%) fistulas had a normal maturation. Lower arm AVF was a
16
significant risk factor for non-maturation in this series (73.1% versus 86.2%; p= 0,0024). Female gender,
17
diabetes and high age were not, but female gender showed a significant difference in distribution in upper
18
arm versus lower arm fistulas (62.40% versus 37.6%; p=0,0218).
19
Conclusion: Careful clinical examination prior to upper or lower arm AVF creation together with the
20
integration of risk assessment in the planning of AVF is worthwhile. A preference towards upper arm
21
fistulas if major risk factors are present can improve overall maturation rates and lead to the same
22
maturation rates as in the overall dialysis population. Therefore, the presence of risk factors for non-
23
maturation should not lead to the underuse of native AVFs.
24
25
26
27
28
Introduction
29
30
The article by Brescia and Cimino in 1966 constituted a revolution in the creation of dialysis vascular
31
access(1). Studies over several decades have demonstrated that native arteriovenous fistulas (AVF) have
32
better patency rates and require fewer interventions compared to arteriovenous grafts (AVG)(2-6).
33
Construction of an AVF in end stage renal disease (ESRD) patients is therefore recommended by the Fistula
34
First and Kidney Dialysis Outcome Quality Initiative. Unfortunately, despite exhaustive experience and
35
much research, AVF primary failure rates of 30 to 50% have been reported in the past
36
factors have been isolated (8; 10; 13-15). Lower arm fistula, female gender and high age have been found to be
37
dominant predictors of primary failure. For a high-risk patient, it is still unclear what the best vascular
38
access is.
39
In this article, we describe the experience with AVFs in our tertiary center. The specific aim of this study
40
was to document if our strategy of careful clinical examination, prior to AVF creation and a preference
41
towards upper arm AVFs in case of doubt about the quality of the vein in patients with risk factors, led to
42
better maturation rates in these high-risk patients compared to findings found in the literature.
(7-12).
Multiple risk
43
44
45
Methods
46
47
Patient data
48
All AVFs constructed between January 2005 and December 2009 were retrospectively reviewed by
49
consulting a prospectively maintained database at the University HospitalsLeuven (Belgium). All patients
50
were either treated in our hospital for ESRD or referred to our center for the creation of a fistula only. Fistula
51
placement was decided based on patient’s medical history and clinical examination of the upper limbs.
52
Phlebography was performed only in cases where the clinical examination was inconclusive.
53
To make sure that patients at high risk for failure were not primarily refused for AVF creation, we also
54
studied the patient characteristics of our overall hemodialysis population anno 2009. Over this period of
55
time, 167 patients were dialyzed at our center.
56
57
Data extraction
58
We recorded demographic data (gender, age at fistula creation, need for dialysis at assessment of
59
maturation), comorbidities (smoking, alcohol use, previous heart surgery, pacemaker, diabetes mellitus,
60
obesity, peripheral vascular disease, hypertension), fistula characteristics (anatomical position,
61
maturation) and fistula complications (infection, thrombosis, stenosis and ligation).
62
Comorbidities were defined as follows: smoking as current smoking or a history of smoking, alcohol as
63
current abuse or treated alcoholism, cardiac surgery as patients who underwent a coronary artery bypass
64
graft or percutaneous transluminal coronary angioplasty, pacemaker, diabetes with both insulin and non-
65
insulin dependent patients, peripheral vascular disease as an investigation for claudication intermittens or
66
a history of vascular surgery and hypertension or medically controlled hypertension.
67
68
Primary failure, primary patency and secondary patency were defined as follows:
69
*Primary failure was defined as abandonment of an AVF that never came to maturation or a thrombotic
70
event without successful salvage attempt, in an interval from AVF creation up to 12 weeks thereafter.
71
Normal maturation was considered to have occurred if the fistula was able to support dialysis 12 weeks
72
after construction or if a hemodialysis access nurse considered the AV-fistula as feasible for use in patients
73
that were still not hemodialysis dependent.
74
*Primary patency was defined as the length of time between access placement and either permanent failure
75
or a first intervention to restore or maintain patency. An intervention was defined as either a
76
thrombectomy, angioplasty, thrombolysis or placement of an interposition graft.
77
*Secondary patency was defined as the length of time between access placement and failure after a previous
78
successful intervention. Access failure was considered to have occurred when a new vascular access was
79
created or if an AVF thrill had disappeared in patients not yet in need of dialysis. The 1-year primary and
80
secondary patency rate was defined as the number of functioning AVFs at 1 year, following the definition
81
above, divided by the total number of AVFs created.
82
Accesses were censored if the patient had a transplant, died or reached the end of the study with a patent
83
access (September 30, 2010).
84
85
Statistical analysis
86
Statistical analysis was performed using Statistica, version 8.0.
87
Comparisons between patients with and without primary fistula failure were made. Primary fistula failure
88
was considered as the dependent variable. Also a comparison of the fistula site was conducted. Continuous
89
data were compared using the unpaired student’s t- test. The chi-square test was used to compare the
90
categorical data. A p-value of < 0.05 was considered statistically significant. Kaplan-Meier survival curves
91
were used to determine overall patency rates. Patency rates for gender, age, fistula site and the presence of
92
diabetes were calculated independently. Means are expressed ± their Standard Deviation (SD).
93
94
Results
95
96
Retrospective review of our database revealed a total of 425 native AVFs created for ESRD at the institution
97
between January 2005 and December 2009. For 17 patients no records were available and they were
98
excluded from this series. Sixty-four patients received a second fistula during this period of time. For
99
statistical reasons, only first fistulas were analyzed in this series. We were left with 344 native AVFs created
100
in 344 different patients (figure 1). The mean follow-up time was 1055 days ranging from 64 to 2046 days
101
after assessment of maturation. Relevant demographic data and comorbidities were registered and
102
summarized as shown in table I. Odds ratios, p-values, relative risks and confidence intervals were analyzed
103
accordingly (table II). Ninety-two patients (26,7%) died during follow-up (average time = 783 days) and 55
104
(16%) patients received a kidney transplant (average time = 780 days). Two-hundred sixty-six (77,3%)
105
were in need of dialysis 3 months after creation of their native arteriovenous fistula.
106
Of the 344 fistulas included, 68 (19,8%) suffered from primary failure and 276 (80,2%) met the definition
107
of maturation. The overall 1-year primary and secondary patency was 64% and 77% respectively and
108
showed large differences between upper and lower arm fistula as shown in figure 2. Analysis of
109
demographic data and comorbidities showed that patients younger than 65 years of age (p=0,0035) and
110
lower arm fistula (p=0,0024) were significant predictors of fistula failure (Table II). Female gender (p=
111
0,3024), need for dialysis at assessment of maturation (p= 0,1531), peripheral vascular disease (p= 0,3023)
112
and hypertension (p= 0,0795) showed a tendency towards failure, but no levels of significance were met.
113
Difference in primary patency rate for risk factors like gender, age and diabetes were calculated as shown
114
in figure 3-5. The same demographics data and comorbidities were documented according to the anatomical
115
position of the fistula to see whether differences in distribution could be found between upper and lower
116
arm fistulas (see table III). One hundred fifty-six (45,3%) of the fistulas were lower arm fistulas compared
117
to 188 (54,7%) upper arm fistulas. Differences in distribution could be found in every documented risk
118
factor, but significant more upper arm fistulas were found in females (p= ,0218).
119
120
As it was impossible to retrieve the risk profile of the overall hemodialysis patient population in the same
121
period retrospectively and as we wanted to check if patients with a risk profile were refused for the creation
122
of a fistula, we analyzed the risk profile of the overall patient population on hemodialysis at our unit anno
123
2009 as a control group. Of these 167 patients, 111 patients (66,5%) were dialyzed through an AVF, while
124
56 (33,5%) were dialyzed through a catheter. The distribution of women, diabetics and mean age over both
125
groups is shown in table IV. In the catheter group, 20 patients had received a fistula that suffered failure, 19
126
were dialyzed because of acute kidney failure and received a fistula later or died before one could be
127
constructed. Only 17 patients were refused for the creation of a native fistula. Eight were refused for a
128
cardiac reason, 2 refused creation of a fistula themselves and 4 were technically unable after a
129
phlebography. In 3 patients we were unable to state the reason. The distribution of females, diabetics and
130
mean age differed only slightly in the catheter group compared to the fistula group suggesting that patients
131
with a high risk profile were not excluded for the creation of a native AVF.
132
133
Discussion
134
For a vascular access, one can choose for an AVF, an AVG or a central vein catheter (CVC). Catheters have
135
excellent patency rates, but are associated with higher rates of infection which could compromise the
136
adequacy of hemodialysis patients.
137
Although reporting methods concerning patency rates and failure differ dramatically in the literature, most
138
studies confirm that AVFs have longer patency rates, a smaller risk of infection and thrombosis, better blood
139
flow and a lower risk of morbidity and mortality compared to AVGs and CVCs (2-6; 16; 17).
140
Because of the reasons mentioned above and the fact that AVG and catheter complications cause a huge
141
economic cost and morbidity, a native AVF is considered the first choice for a vascular access in
142
hemodialysis patients with AVF use in up to 66% of the cases for 2009 (2; 18-20). The current hemodialysis
143
population however is older, more frequently diabetic, has a higher percentage of females and more
144
comorbidities. Whereas studies from 20 to 25 years ago observed a primary fistula failure rate of about
145
10%, more recent investigations report a 20 to 50% primary failure rate (11; 14; 21; 22). Some authors state that
146
these high failure rates are caused by the creation of AVFs in patients that have a high risk profile and
147
therefore miss the desired results.
148
149
Today, many reviews are written about the creation of a vascular access, techniques, native fistula options
150
and their possible complications (21; 23-26). Biological and physical explanations of why fistulas could fail to
151
mature are offered and guidelines on how to intervene if fistulas fail are summarized in these papers
152
28).
153
hemodialysis dependence, stroke or transient ischemic attack, quality/diameter of the vessels, access type,
154
experience of the surgeon, presence of cardiovascular diseases (peripheral vascular disease, coronary
155
artery diseases and heart failure), older age, gender, diabetes and race have all been described as possible
156
risk factors to predict fistula failure (8; 10; 13-15). Of these factors female gender, older age and site of fistula
157
creation are considered dominant risk factors
158
showed a lower incidence of AVF use if patients had any of these characteristics (12; 29; 30). A valid and reliable
159
diagnostic test for predicting fistula failure has not been developed yet, although a recent study of 2006
160
performed by Lok et al. created a clinical prediction algorithm for fistula failure based on age, coronary
161
artery disease, peripheral vascular disease and race (14).
162
At our institution, we believe that the construction of a native fistula has to be considered even in patients
163
prone to failure. We performed this study to see if our strategy of careful clinical examination prior to AVF
164
creation and a preference towards upper arm AVFs in patients with any of these risk factors led to better
165
maturation rates.
(23; 27;
Nevertheless, studies have tried to isolate risk factors responsible for AVF failure. Risk factors like
(10; 15).
Large studies in 28,712 adult hemodialysis patients
166
167
In our study population, we found that only the site of fistula placement (p = 0,0024) and younger age (p=
168
,0035) were prone to primary failure. Surprisingly, older age turned out to be a protective factor in our
169
series, whereas it is found to be a risk factor in the literature (10). This can be explained by our preference to
170
construct upper arm fistula in high age groups. These upper arm AVFs have a higher success rate, mostly
171
due to a bigger vein diameter, but have more complications like steal and hypertrophy (26).
172
Female gender and diabetes have also been described as major risk factors, but were not significant in our
173
series. A possible explanation for the higher failure rate in women could lie in the smaller size of their
174
vessels and in postmenopausal states, conditions that may produce a form of accelerated atherosclerosis (9).
175
An explanation for the higher failure rate in diabetics could possibly be found in the existence of the vascular
176
disease, media calcinosis and therefore the lack of substantial arterial dilatation after fistula creation (15).
177
As we prefer to construct upper arm fistulas in patients at risk, we compared the distribution of risk factors
178
in upper and lower arm fistulas. The distribution of risk factors in upper and lower arm fistulas was
179
different for every factor. Although only gender distribution had a p-value <0.05 these findings confirm the
180
assumption that upper arm fistula were preferred in presence of risk factors for primary failure. Only
181
current or past nicotine abuse did not follow this pattern. As we compared patency rates between females
182
and males, diabetics and non-diabetics and elderly and young patients, similar patency rates were found as
183
shown in the figures 3-5. These results suggest that good maturation rates can be achieved even in patients
184
at risk for failure with a good choice of the anatomical position of the AVF.
185
186
As we believe that the construction of a native fistula has to be considered even in patients prone to failure,
187
we wanted to know how many ESRD patients were refused for the construction of an AVF. Our current
188
dialysis population anno 2009 was therefore analyzed and showed that only a minority was denied a native
189
fistula and no significant differences in distribution of risk factors were found between the catheter group
190
and the overall AVF group. These results suggest that no negative selection has occurred prior to the
191
creation of AVFs in patients at risk.
192
With a primary failure rate of 19,8% and comparable patency rates to those found in the literature, we
193
believe that risk assessment through careful review of a patient’s medical background and clinical
194
examination prior to fistula creation leads to better maturation rates. We therefore suggest that patients
195
with major and minor risk factors cannot be excluded from an AV fistula, but a preference towards upper
196
arm fistulas has to exist in patients with risk factors present or in case of doubt about the quality of the vein.
197
If major risk factors (female gender, high age, diabetes) or multiple minor risk factors are present, we
198
recommend the construction of an upper arm fistula. If only minor factors are present, one could still choose
199
for a lower arm fistula. These suggestions have also been proposed by others in the past (31; 32).
200
Further research is needed by means of prospective randomized controlled trails to verify these new
201
findings. Consistent definitions for primary failure, primary and secondary patency are necessary to
202
uniformily study these important questions and to draw the right conclusions. The literature states that
203
after creation, the fistula ideally should be left to mature for at least 14 days before the first cannulation (33).
204
We used a 12 week period as endpoint for our definition of maturation because blood flow reaches a
205
maximum in the fistula within 4–12 weeks after creation (23).
206
207
Generally, preoperative vascular mapping is being advised before the construction of AVFs to decrease the
208
surgeon’s likelihood to utilize marginal forearm veins in preference of an upper arm AVF (2; 16). Diameter of
209
the vessels is in some studies the major predictor for fistula failure
210
this preoperative mapping show conflicting results, with some studies finding clear advantages
211
others could not find increasing maturation results
212
plethysmography has also been suggested (36). Because of these conflicting results, our center decides the
213
site of fistula creation solely based on thorough clinical examination. As maturation rates up to 80% were
214
found in this study, we do not feel that pre-operative mapping has to occur vigorously before fistula
215
creation.
(7; 35).
(8).
However, studies on the impact of
(34),
while
Venous distensibility measured by
216
217
Conclusion
218
219
Native AVFs are considered the vascular access of choice. We believe that the construction of a native
220
fistula has to be considered even in patients prone to failure, and conducted this study to see whether
221
carefulclinical examination in combination with a preference towards upper arm fistulae in case of major
222
risk factors for non-maturation could help to improve maturation rates. Our results identify location of an
223
AV fistula and age as the major predictors of primary failure, but analysis showed that the distribution of
224
risk factors was different in upper and lower arm fistulas with a preference towards proximal fistulas if
225
risk factors were present. With a maturation rate of 80,2%, similar patency rates for females, diabetics
226
and elderly and a comparable distribution of risk factors in our fistula group and catheter group anno
227
2009, our results suggest that creation of a functional native AVF is possible even with major risk factors
228
present. We suggest that a preference towards upper arm fistulas in women, high age groups and patients
229
with a combination of other risk factors may lead to better maturation rates in these patients prone to
230
failure. A distal site should not be excluded if minor risk factors are present.
231
232
Acknowledgements
233
Special thanks to Mr. Op De Beeck for providing the data out of the database concerning the patients
234
included in this series.
235
236
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237
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List of figures
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Figure 1: Selection flowchart.
315
Figure 2: Overall primary and secondary patency rates for the AVFs constructed at our center according to the anatomical
316
location.
317
Figure 3: Difference in primary patency rate for males and females.
318
Figure 4: Difference in primary patency rate for diabetics and non diabetics.
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Figure 5: Difference in primary patency rate for years of age.
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Table I: General distribution of demographic and clinical characteristics.
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Table II: Analysis of demographic and clinical characteristics in relation to occurrence of primary failure.
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357
358
359
360
361
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Comorbidities are defined as described in the section Methods. OR: Odds Ratio, RR: Relative Risk, CI: Confidence Interval
363
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Table III: Analysis of risk factors in relation to the fistula site.
365
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368
369
370
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372
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374
375
376
377
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OR: Odds Ratio, RR: Relative Risk, CI: Confidence Interval
379
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384
385
386
387
388
389
390
391
392
393
394
395
396
Table IV: Distribution of female gender, diabetes and age in our current dialysis group anno 2009 in relation to the access type.