assessing radiocephalic wrist avf of obtuse anastomosis ......various size and width of anastomosis...
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Assessing radiocephalic wrist AVFof obtuse anastomosis
using CFDs and clinical application
Sun Cheol Park, MD, PhD, RVT, RPVI
Jinkee Lee*, PhD
Division of Vascular Surgery, Department of Surgery,
College of Medicine, The Catholic University of Korea
*Sungkyunkwan University, School of Mechanical Engineering
LINC 2017 January 26
AV Access for HD
AVF
- artery - vein anastomosis
radio cephalic AVF brachio antecubital (cephalic) AVF
AVG
- artery – graft anastomosis
- graft – vein anastomosis
Brachio antecubital loop AVG
Radio-cephalic arterio-venous fistula (AVF)
- best and first choice for achieving vascular access (VA)
for haemodialysis (HD)
- but relatively high rates of early failure
Failure of radio-cephalic AVF
- impossible use of the vascular access (VA) for dialysis
- usually due to a juxta-anastomotic stenosis
- important predictors for AVF maturation
- anatomic factors - diameter or intimal thickness of feeding a.
- intact draining upper vein
3
Radial-cephalic AVF
Clinical practice guidelines for vascular access2006The CARI guidelines. Vascular access surveillance.Nephrology (Carlton). 13(Suppl 2):S1–S11, 2008
Nephrol Dial Transplant (2012) 27: 358–368
hemodynamic wall shear stress (WSS)
- physiological WSS ranges - 10 to 70 dyne/cm2 in normal arteries
- Lower values of WSS - induce atherosclerotic plaques formation
- ‘atherosclerosis prone’ and intimal hyperplasia (IH)
- higher than normal range - provoke endothelial cells cleavage
- consequently ‘high-shear’ induced thrombosis
- contributes to pathophysiology of AVF failure
- thrombosis secondary to stenosis formation as well as
- re-occlusion after percutaneous interventions (PTA)
JAMA 1999; 282: 2035–2042
AV Access
Disturbed flow (at anastomosis site of AVF)
- condition of endothelium exposed to low average shear stress
- constantly changing gradients of shear stress
- oscillatory shear stress according heart beat
- multidirectional secondary flows
main cause of VA failure
- thrombosis secondary to development of stenosis
- stenosis caused by intimal hyperplasia (IH)
fibro-muscular thickening of vessel wall
Anastomosis site of AV Access
effect of anastomosis angle on disturbed flow patterns in AVF
- not yet be investigated
Computational fluid dynamics (CFD)
- numerical techniques
- proper calculation of spatial distribution of WSS
among other haemodynamic variables of interest
- velocity field and pressure
Effect of AVF anastomosis pattern
3D meshes design of arterio-venous end to side anastomosis
- according various angles (45°, 90°)
- including 135’ of “reverse anastomosis”
- using CAD SolidWorks 2013
(Solid Works Corporation)
COMSOL Multiphysics (COMSOL corporation)
- 3D multiphysics simulation software
- various hemodynamic factors influencing
on WSS of anastomosis site
including parabolic velocities and viscosity of blood
complete cardiac pulse cycles and maximal shear stress
Methods
Geometry Mesh designs
2
3
Vein : 2.5 – 3.5 mm
Artery : 2mm diameter
Area : 4.7 to 6.3 mm square
Same area of 45, 90, 135JVA 2010
NDT 2012
90’
135’
45’
width
diameter
3D meshes design of arterio-venous end to side anastomosis
- according various angles (45°, 90°)
- including 135’ of “reverse anastomosis”
- using CAD SolidWorks 2013
(Solid Works Corporation)
COMSOL Multiphysics (COMSOL corporation)
- 3D multiphysics simulation software
- various hemodynamic factors influencing
on WSS of anastomosis site
including parabolic velocities and viscosity of blood
complete cardiac pulse cycles and maximal shear stress
Methods
Blood condition
Cardiac contraction - 1/sec
P.A. – proximal artery (black),
D.A. – distal artery (red),
V. – volume
P.A.
D.A.
V.
Anti viscosity fluid
Blood - Shear stress increase,
viscosity decrease- modified Carreau-Yasuda model- non-Newtonian fluid flow’s
continuity
Vessel simulation conditions
density, Young’s modulous and Possion ratio of blood vessel
- set as 1120kg/m^2, 3.26e6 Pa and 0.45, respectively
- radial thickness of artery and vein - 0.2875mm and 0.1mm
contraction and expansion of vessel wall
- solved by elastic equation
viscosity values
WSS defined 𝝉 = 𝝁 ቚ𝒅𝒗
𝒅𝒓 𝒓=𝑹
v is velocity, t is WSS, m is blood viscosity,
R is the inner surface of blood vessel
Shear Stress (45’)
0.2초
shear stress of central line
Maximal shear stress
0.2 sec
Shear Stress (90’)
shear stress of central line
Maximal shear stress
0.2 sec
Shear Stress (135’)
shear stress of central line
Maximal shear stress
0.2 sec
Maximal WSS (0.2 sec)
554Pa
557Pa
457Pa
WSS
(Pa)
(a) A = 45° (d)
(b) A = 90° (e)
(c) A = 135° (f)
- Wall shear stress
of 45, 90, 135
- Maximal flow volume (Lt)
Minimal flow volume (Rt)
- More larger angle
- decreased the high
WSS area (rea)
Angles
Part Proximal Artery Distal Artery Vein
Property PSV Volume Velocity PSV Volume Velocity PSV Volume Velocity
Unit cm/s ml/m m/s cm/s ml/m m/s cm/s ml/m m/s
A 271 951 2.71 52 48 0.52 265 1626 2.65
B 138 1009 1.38 34 137 0.34 240 1743 2.4
C 318 1358 3.18 46 57 0.46 209 1606 2.09
D 249 861 2.49 67 202 0.67 220 1125 2.2
E 198 653 1.98 149 277 1.49 124 852 1.24
F 235 793 2.35 95 150 0.95 161 806 1.61
G 161 715 1.61 40 46 0.4 250 1079 2.5
H 189 1072 1.89 63 129 0.63 360 1435 3.6
I 368 1213 3.68 55 61 0.55 144 1134 1.44
J 253 1517 2.53 76 38 0.76 245 2042 2.45
K 248 683 2.48 78 18 0.78 280 633 2.8
L 281 1213 2.81 47 142 0.47 169 1451 1.69
M 171 1664 1.71 74 38 0.74 190 1680 1.9
Average 236 1054 2.37 67 103 0.67 219 1324 2.20
Distal artery blood flow direction
Direction of flow (F/U Duplex)
Direction of flow (F/U Duplex)
Distal artery blood flow direction
during heart beat
0.0 0.2 0.4 0.6 0.8 1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
Proximal Artery
Distal Artery
Vein
Ve
locity [m
/s]
Time [s]
Displacement of vessels
45° 90 ° 135 °
Displacement of vessels (45°, 90°, 135°)
A(mm)
V(mm)
Width(mm)
Diameter(mm)
angle
Case1 2 3 7.068582 3 2 4.712388 45
Angle2 3 7.068582 3 2 4.712388 90
2 3 7.068582 3 2 4.712388 135 standard
Case2 2 2.5 4.9087375 3 2 4.712388 135
Vein diameter
2 3 7.068582 3 2 4.712388 135
2 3.5 9.6211255 3 2 4.712388 135
Case3 2 3 7.068582 3 2 4.712388 135
Anastomosis area
2 3 7.068582 3.5 2 5.497786 135
2 3 7.068582 4 2 6.283184 135
Various size and width of anastomosis
More larger vein size
- Decreased lateral
Maximal shear
stress area
WSS
(Pa)
(a) V = 2.5mm (d)
(b) V = 3.0mm (e)
(c) V = 3.5mm (f)
Sizes of vein
More larger
anastomosis area
- decreased lateral
maximal shear
stress
Changes of anastomosis area
WSS
(Pa)
(a) L = 3.0mm (d)
(b) L = 3.5mm (e)
(c) L = 4.0mm (f)
Clinical application for RC AVF wrist Lt.
Clinical application for RC reverse AVF wrist Lt.
Clinical study
2009. Jan – 2014. Feb
Single institute - random
Single surgeon
RC AVF Reverse AVF
N 72 129
Follow up (mon) 17.9 ± 3.8 11.4 ± 2.0
Sex M 50 (69.4%) 86 (66.7%)
F 22 (30.6%) 43 (33.3%)
Age 54.8 ± 5.6 59.7 ± 3.7
Co-mobidity DM 52 (72.2%) 90 (69.8%)
HTN 51 (70.8%) 87 (67.4%)
Before HD (preemtive) 58 (80.6%) 76 (58.9%)
Previous PD 5 7
Patency 3mon
(%)
N 6 mon
(%)
N 12 mon
(%)
N 24 mon
(%)
N
Classical AVF
(N=72)
Primary 82.8 50 67.7 37 54.6 22 45.7 12
Assistant primary 90.7 55 82.4 46 76.1 34 76.1 17
Secondary 98.6 60 91.8 51 89.9 40 89.9 19
Patency 3mon
(%)
N 6 mon
(%)
N 12 mon
(%)
N 24 mon
(%)
N
Reverse AVF
(N=129)
Primary 82.9 86 70.5 56 59.8 34 53.2 9
Assistant primary 92.1 94 84.5 65 80.1 43 80.1 11
Secondary 93.1 96 88.8 69 84.1 46 84.1 14
CM curve (primary, assisted primary, secondary patency)
primary, assisted primary, secondary patency ratesat 3, 6, 12 and 24 months with number of AVF at the end of the interval
Obtuse anastomosis angle (135°)
- smaller shear stress than the other angles
- advantage for reducing AVF failures
Among differ anastomosis angle, we considered in this study
- 135° angle - (“obtuse anastomosis”) preferred choice
- minimizes development of anastomotic stenosis
Although need more dissection of cephalic vein for more steady
curve
consider this “obtuse AVF”
Conclusions and Suggestions
Thanks for Your Attention!!
Assessing radiocephalic wrist AVFof obtuse anastomosis
using CFDs and clinical application
Sun Cheol Park, MD, PhD, RVT, RPVI
Jinkee Lee*, PhD
Division of Vascular Surgery, Department of Surgery,
College of Medicine, The Catholic University of Korea
*Sungkyunkwan University, School of Mechanical Engineering
LINC 2017 January 26