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!!

sun60278@catholic.ac.kr

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