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Interventional
Management of Hemodialytic Arteriovenous Fistula
Jarturon
Tantivatana, M.D.
Akkawat Janchai, M.D.
Permyot Kosolbhand, M.D.
Unit of Interventional Radiology
Department of Radiology
Faculty of Medicine
Chulalongkorn University
Objectives
At the completion of this topic, the audience should be able to
:
1. Define common types of hemodialytic
AVF
2. Systematically approach problems
of HDAVF
3. Describe common site of stenosis
in HDAVF
4. Describe indication and technique
of interventional treatment
5. Address complication, difficulty
and limitation of interventional procedure
Background
Patients with end stage renal disease
need long term hemodialysis, either as live time palliation or awaiting
for renal transplantation. Installation of double lumen central
venous catheter provides only short term maintenance of hemodialytic
accessible route, usually lasts for 1 to 2 months. Although cuffed
or semi-permanent double lumen catheter has been developed for mid-term
maintenance, this device posses problems of infection and induction
of central venous stenosis.
Since the introduction of standard
surgically created arteriovenous fistula in 1978, this option provides
promising long term vascular access for hemodialysis and was practiced
world wide. However, many of these shunts compromise after decent
period of time as a result of stenosis or thrombosis. Surgical correction
is invasive and sometime ends up in second creation of arteriovenous
shunt. Recent development in technique and equipment enable interventional
radiologist to manage this problem quite successfully with endovascular
procedure.
Surgical creation of arteriovenous fistula
Basically, there are two types of
artificially created arteriovenous fistula. These two types differ
surgically, having their own advantages and disadvantages as follow.
1. Native arteriovenous fistula (NAVF):
This popular option is created by side to end anastomosis of the
radial artery with the cephalic vein. In general, it takes 1 to
2 months for the fistula to become matured with sufficient size
and flow. Blood is withdrawn for dialysis from proximal venous limb
close to the fistula and return to the patient at distal limb of
the same vein. Please note that the arterial limb is never used
as an access.
2. Arteriovenous bridging graft (AVBG):
This option is need if the artery or vein is not in optimal anatomical
position for conventional shunt creation. The shunt is created with
intervening synthetic graft between the artery and vein. Since direct
connection is achieved via graft of decent size, time of maturation
is minimized and the shunt can be used earlier. Hemodialytic access
is obtained at the graft.
The optimal location of either NAVF
or AVBG is forearm, involving radial artery and cephalic vein. This
site provides convenient access and is easy for maintenance. Other
possible locations are brachial and femoral region, both sites are
inconvenient, while the latter have higher rate of infection.
Natural history of HDAVF
Many reports showed various primary
patency rates. NAVF and AVBG behave differently. At 2 and 4 years,
patency rates were 60 and 45% for NAVF, respectively. AVBG had poorer
patency rate than NAVF with 43 and 10% patency at 2 and 4 years,
respectively.
In cases of NAVF, stenosis usually
occurred at proximal venous limb just distal the fistula site. The
native vein was not developmentally designed for rapid flow rate
and high pressure. Intimal hyperplasia gradually developed at vulnerable
site, obviously, at venous end of the fistula and proximal venous
limb. Repetitive injury with fibrosis acted in conjunction with
intimal hyperplasia, further aggravating stenosis. This outflow
stenosis results in diversion of venous drainage from compromised
main venous limb into multiple small tortuous collaterals which
are not optimal for hemodialysis.
AVBGs have their own specific
problems. Myointimal hyperplasia developed at artery - graft anastomosis
as well as vein - graft anastomosis. Intimal hyperplasia also tends
to occur at venous limb just distal to vein - graft anastomosis,
where flow stress is maximized. Slow flow rate in compromised graft
induces thrombosis and rapidly progress to complete occlusion.
How to approach problems of HDAVF
Systematic assessment should be exercised
before deciding of further investigation and treatment. The following
pattern of approach is suggested.
1. The exact location of the shunt.
2. Time of creation and history of
prior double lumen catheterization.
3. Arterial pulse and venous thrill.
4. Maximal flow rate achieved during
hemodialysis before it collapsed.
5. Presence or absence of brachial
or antebrachial edema.
6. Evidence of skin change, ulceration,
discoloration.
These gathered data from history and
physical examination provide valuable information for planning of
management and even suggest diagnosis. Weakened arterial pulse indicates
stenosis of the artery and diminished thrill indicates compromised
venous outflow. Brachial edema usually reflects stenosis of central
venous drainage such as occlusion of axillary or subclavian veins.
Investigation and evaluation of malfunctioned HDAVF
Color doppler with duplex sonography
is a good screening for site and severity of stenotic malfunctioning
HDAVF, although not mandatory. Flow rate can be calculated from
measurement of flow velocity and luminal diameter. Angiography and
fistulography provides excellent anatomical was well as functional
information prior to treatment. Interventional treatment is usually
performed in the same setting for convenient and cost-saving. Urgent
treatment is needed if flow rate falls below 200-300 ml/min, otherwise
the fistula system will eventually thrombosed. Prophylactic angioplasty
is recommended if flow rate is less than 400-600 ml/min.
Preparation and counseling
The patient must be well-informed
about risk and benefit of the interventional procedure. Informed
consent should always be obtained. One should explain possible complication
and treatment options if the procedure fails. Blood tests for CBC,
PT, PTT, BUN and Creatinine are also obtained as routine premedication.
The procedure should be schedule as elective on the day followed
by hemodialysis for removal of contrast material. Most of interventional
procedures can be performed on out patient basis.
Interventional procedure
We recommend transarterial approach,
preferably distal brachial or proximal radial route. The arterial
supply, fistula and venous outflow can be evaluated completely in
one injection. Venous approach is easier but evaluation of the fistula
and arterial limb is suboptimal. Large amount of contrast material
must be injected with high pressure in order to retrogradely opacified
the arterial side. A 20G needle is used for puncture in conjunction
with a 0.025" guidewire. Small access system makes puncture
of small, mobile brachial or radial artery possible. An 18G needle
can be used with a 0.035" guidewire in case of matured fistula
with large artery. Either 5F or 6F introducer sheath is suitable
but the latter allows more flexible choice of angioplasty balloon
catheter. We usually use continuous heparinized saline flushing
system for maintenance of introducer sheath and balloon catheter.
If the system is not available, systemic intravenous heparinization
of 3000-5000 units is given.
The venous limb is sometime difficult
to cannulated via arterial approach due to acute angle of the arteriovenous
anastomosis. A 4 or 5F Cobra catheter may be needed to access venous
limb for placement of exchange guidewire, followed by introduction
of the balloon catheter. Optimal length of the balloon catheter
is 65-80 cm. for brachial approach. High pressure, low profile balloon
catheter with hydrophilic coating is preferred for successful angioplasty.
The stenotic site is gradually dilated with angioplasty balloon
catheter. High inflation pressure of 10-15 ATM should be maintained
for 45 to 90 seconds. In general, 3-4 mm. of arterial and 5-6 mm.
of venous luminal diameter are adequate for flow rate of 600-800
ml/min.
In cases of thrombosed AVBG, local
intravascular thrombolysis is the treatment of choice. Up to 1,000,000
units of Urokinase or equivalent thrombolytic agent may be needed
to open up the occluded graft loop. Recent development of thrombectomy
catheter using Venturi effect allows direct suction of fresh thrombus
and markedly reduces amount of thrombolytic agent needed. After
removal of the thrombus, the underlying stenosis is treated as that
in case of simple AVF stenosis.
After the procedure, the punctured site
is compressed firmly with optimal pressure for hemostasis. Excessive
compressing force may ruin all work by causing thrombosis of the
fistula system.
Figure 1.
Radial angiography was performed via brachial sheath. Tip of the
sheath was in proximal radial artery. Severe segmental stenosis
is noted at cephalic vein distal to the fistula. A = distal radial
artery, F = fistula, S = stenotic site, V = cephalic vein.
Figure 2.
A 5x40 mm. balloon catheter
was introduced via brachial sheath across the stenotic site for
angioplasty with inflation pressure of 10-15 ATM for 60 seconds.
Figure 3.
Reopening of cephalic vein was achieved up to 6 mm. after angioplasty.
Increase flow is observed through the fistula system.
Result of Treatment in :
Complication
The most common procedure-related
complication is limited intimal dissection from high pressure angioplasty.
Minimal dissection requires no treatment but large flap may need
short term heparinization or stenting. Rupture of the venous limb
is treated by band compression of the affected site or stent graft,
depends on severity and site of leakage. Symptomatic pulmonary emboli
are rare but possible in treatment of extensive AVBG thrombosis.
Limitation of interventional
procedure
Complete fibrotic occlusion of either
arterial or venous limb is relatively contraindicated for endovascular
treatment. Vigorous attempts of cannulation and dilatation usually
lead to vascular rupture. Poorly developed NAVF with diffusely small
arterial and venous component is also not eligible for intervention.
Conclusion
Interventional management of malfunctioned
hemodialytic AVF has been widely accepted and proven cost-effective.
However, experience in clinical evaluation and specific procedural
skills are needed for good outcome.
References :
1. Bell D, Rosenthal J. Arteriovenous
graft life in chronic hemodialysis. Arch Surg 1988;123:1169-1172
2. Glanz S, Gordon D, Butt K, et al. The role of percutaneous angioplasty
in the management of chronic hemodialysis fistulas. Ann Surg 1987;206:777-781
3. Beathard G. Percutaneous transvenous angioplasty in the treatment
of vascular access stenosis. Kidney Intern 1992;42:1390-1397
4. Zijlstra J. Percutaneous transluminal angioplasty in vascular
access for hemodialysis. Proefschrift ter verkrijging van de graad
van doctor aan de Rijksuniversiteit te Utrecht. Utrecht, 1989
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