A P ilotS tudyinEvaluationof DysfunctionalHemodialysisVascular … · 2018-04-01 · 2 Background • Dysfunctional hemodialysis vascular access remains a major contributor of morbidity

A P ilotS tudy inEvaluationofDysfunctionalHem odialysisVascular

A ccessU singS yngoiFlowR u Yu T AN ,Fu ChiehT S AI,T zeT ecCHO N G,ApporvaGO GN A,KianGuanL EE,S uh

ChienP AN G,AliciaHuiyingO ng,ChiehS uaiT AN

2

Background

• Dysfunctional hemodialysis vascular access remains amajor contributor of morbidity and mortality in patientswith end stage renal disease.

• Percutaneous methods of intervention is now standard ofcare

• Two-dimensional (2D) digital subtraction angiography(DSA) is the current gold standard imaging duringpercutaneous transluminal angioplasty (PTA) of vascularaccess.

1. Doelman C, Duijm LEM, Liem YS, et al. Stenosis detection in failing hemodialysis access fistulas and grafts:Comparison of color Doppler ultrasonography, contrast-enhanced magnetic resonance angiography, and digitalsubtraction angiography. Journal of Vascular Surgery. 2005;42(4)

3

Background

• Traditionally, diagnosis and the severity of stenosis isdetermined by anatomic measure of the lesion.

• Angiographic diameter measurement in percentreduction in vessel diameter however may not behemodynamically or clinically significant

• Anatomic with hemodynamic examination is thereforerecommended for measurement of disease severity

2. Gray RJ, Sacks D, Martin LG, Trerotola SO. Reporting standards for percutaneous interventions in dialysis access.Journal of vascular and interventional radiology : JVIR. 2003;14(9 Pt 2):S433-42

4

Background

• Currently available methods for hemodynamicassessment:

5

Background

• Syngo iFlow was developed with the intention to providean automatic tool for quantitative blood flow analysis.

• The temporal evolution of the contrast agent at a fixedposition can be recorded in a pixel-specific time-intensitycurve, computed mathematically and visualized as aparametric image.

• As such, the flow of contrast captured by DSA in manysequences can be combined into one single color-codedimage which can be used to assess quantitative bloodflow.

6

Hypothesis and Aim

• We hypothesize that– Parametric color coded DSA provided by syngo iFlow enables

hemodynamic quantification during percutaneous intervention ofhemodialysis vascular access

• Aim– To determine quantitative utility of syngo iFlow in assessment of

vascular access intervention outcome.

7

Methods

• Single center, retrospective study of patients whounderwent percutaneous intervention for dysfunctionaldialysis access

• DSA acquisitions (pre- and post-intervention) of 20patients (10 AVFs, 5 AVG, 5 central veins) were obtainedand converted to color image and anaysed using thesyngo iflow software

• Complex cases with multiple lesions were excluded

8

Methods

• Evaluation of conventional DSA– Diameter of stenotic and normal segment for each access was

measured pre- and post-intervention

– Percent stenosis = [1 − (Dstenosis/Dnormal)] × 100

– Improvement in percent stenosis =

(%pre-angioplasty - %post-angioplasty)/ %pre-angioplasty x 100

9

Methods

Pre-PTA % stenosis = 76%

Post-PTA% stenosis = 30%

Improvement in % = 60%

Dstenosis= 4.91 m mDstenosis= 1.69 m mDnorm al= 7.02 m m

10

Methods

• Evaluation of color coded DSA– ROIs were chosen before and after stenosis

– Time to peak (TTP) or time to maximum contrast opacificationwas obtained for each ROI

– The difference between the TTP of these 2 ROIs (dTTP)wereobtained, it represent the flow across the stenosis.

11

Methods

• Differences between pre- and post-PTA dTTP

P re-P T A P ost-P T A

dT T P =1s dT T P =0s

12

Time Attenuation Curve

• Quantification of contrast wash-out before and afterintervention was also obtained using the time attenuationcurve (TAC).

13


50%

50 %ContrastW ash-outtim e=0.75s

ContrastW ash-in

ContrastW ash-out

14


50 % ContrastW ash-outtim e= 0.5s

ContrastW ash-in

ContrastW ash-out

50%

15

Statistical Analysis

• Data analyses were performed using SPSS version 21.Differences between percent of stenosis, dTTP and 50%contrast washout time pre and post angioplasty werecompared using paired sample t-test

• Pearson correlation was used to analyse the relationshipbetween dTTP and change in percentage of stenosis

16

Baseline Demographics

Characteristics N = 20

Age, years 67.5 (IQR 61.5, 70.75)

Female, n (%) 12 (60)

Ethnicity, n (%)

ChineseMalayIndian

14 (70)5 (25)1 (5)

Type of Access, n (%)

Arteriovenous fistulaArteriovenous graft

15 (75)5 (25)

Etiology of ESRD, n (%)

Diabetes MellitusHypertensionGlomerulonephritisOthers

8 (40)3 (15)8 (40)1 (5)

17

Characteristics Vascular AccessesPatient No. Type of Access Site of Anastomosis Lesion

12345678910

AVFAVFAVFAVFAVFAVFAVFAVFAVFAVF

BrachiocephalicBrachiocephalicRadiocephalicRadiocephalic

BrachiocephalicRadiocephalic

BrachiocephalicBrachiocephalicBrachiobasilicRadiocephalic

Peripheral veinJuxta-anastomosisJuxta-anastomosisJuxta-anastomosisJuxta-anastomosisJuxta-anastomosisJuxta-anastomosisJuxta-anastomosis

Peripheral veinJuxta-anastomosis

1112131415

AVFAVFAVFAVFAVF

BrachiobasilicBrachiocephalicBrachiocephalicBrachiobasilicBrachiobasilic

Central veinCentral veinCentral veinCentral veinCentral vein

1617181920

AVGAVGAVGAVGAVG

BrachiobasilicBrachiobasilic

Femoral-femoralFemoral-femoralFemoral-femoral

Venous anastomosisVenous anastomosisVenous anastomosisVenous anastomosisVenous anastomosis

18

Anatomic and Hemodynamic Changes

Variable P -value

Percent of stenosis, %

Pre-angioplasty

Post-angioplasty

70.55 ±19.36

29.75 ±19.81

<0.0001

dTTP, s

Pre-angioplasty

Post-angioplasty

0.41 ± 0.77

0.18 ± 0.13

0.011

50% Contrast Washout time, s

Pre-angioplasty

Post-angioplasty

0.80 ± 0.43

0.49 ± 0.31

0.024

All results were reported as mean ± SD unless otherwise specified

19

All Access

P earsonCorrelation0.40,p=0.072

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

0 20 40 60 80 100 120

dT

TP,s

P ercentChange inS tenosis,%

20

AVF


-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

0 10 20 30 40 50 60 70 80 90 100

dT

TP,

s


21

AVG

P earsonCorrelation-0.568,p=0.299

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 10 20 30 40 50 60 70 80 90

dT

TP,

s


22

Central


0

0.1

0.2

0.3

0.4

0.5

0.6

0 20 40 60 80 100 120

dT

TP,

s


23

Discussions

• The ability to assess TTP at various ROIs before andafter PTA is useful in assessing blood flow rate whichwas previously impossible with standard DSA

• There was significant improvement in dTTP and 50%contrast wash-out time post-angioplasty – indicateimprovement in blood flow rate across stenosis

• dTTP correlates with percent change in stenosis on AVFlesions

• However, the same correlation was not seen in AVG andcentral veins – small numbers?

24

Limitations

• Single centre, retrospective study

• Small number – insufficient statistical power forcorrelation analysis

• Hand injection of contrast – risk of deviation of flow rate

• Quality of color image may be affected by movementartefacts

25

Conclusions

• Nevertheless, this is the first study on adjunctive use ofparametric color coding as a postprocessing algorithm inhemodialysis access and we found that it provides usefulhemodynamic information in evaluation of adequacy oftreatment of vascular access.

• A larger scale prospective study with correlation withhemodynamic parameters such as pressure andtransonic flow rate, using injector should be performed

T HA N K YO U

27

Prospective Study – Preliminary Results

28


Mean TTPs (s) Pre Angioplasty Post Angioplasty P-value

ROIRef 1.87 ± 0.55 1.50 ± 0.33 <0.01

ROI0 1.99 ± 0.71 1.43 ± 0.36 <0.01

ROI1 2.15 ± 0.67 1.56 ± 0.35 <0.01

ROI2 2.27 ± 0.70 1.72 ± 0.29 <0.01

29


Mean Transonic Flow

(mL/min)

syngo iFlow Pearson’s

Correlation

P-

value

Calculated Flow

(mL/min)

970.6 ± 440.4 968.6 ±

633.9

0.359 0.19

Post-Angioplasty

TTP (s)

RRef 970.6 ± 440.4 1.50 ± 0.33 -0.428

R0 970.6 ± 440.4 1.43 ± 0.36 -0.019 0.94

R1 970.6 ± 440.4 1.56 ± 0.35 -0.171 0.50

R2 970.6 ± 440.4 1.72 ± 0.29 -0.307 0.22

Documents

A P ilotS tudyinEvaluationof DysfunctionalHemodialysisVascular … · 2018-04-01 · 2 Background • Dysfunctional hemodialysis vascular access remains a major contributor of morbidity