A P ilots tudy inevaluationof DysfunctionalHem odialysisvascular A ccessu sings yngoiflow

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1 A P ilots tudy inevaluationof DysfunctionalHem odialysisvascular A ccessu sings yngoiflow R 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 a major contributor of morbidity and mortality in patients with end stage renal disease. Percutaneous methods of intervention is now standard of care Two-dimensional (2D) digital subtraction angiography (DSA) is the current gold standard imaging during percutaneous transluminal angioplasty (PTA) of vascular access. 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 digital subtraction angiography. Journal of Vascular Surgery. 2005;42(4) 2

3 Background Traditionally, diagnosis and the severity of stenosis is determined by anatomic measure of the lesion. Angiographic diameter measurement in percent reduction in vessel diameter however may not be hemodynamically or clinically significant Anatomic with hemodynamic examination is therefore recommended 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):S

4 Background Currently available methods for hemodynamic assessment: 4

5 Background Syngo iflow was developed with the intention to provide an automatic tool for quantitative blood flow analysis. The temporal evolution of the contrast agent at a fixed position can be recorded in a pixel-specific time-intensity curve, computed mathematically and visualized as a parametric image. As such, the flow of contrast captured by DSA in many sequences can be combined into one single color-coded image which can be used to assess quantitative blood flow. 5

6 Hypothesis and Aim We hypothesize that Parametric color coded DSA provided by syngo iflow enables hemodynamic quantification during percutaneous intervention of hemodialysis vascular access Aim To determine quantitative utility of syngo iflow in assessment of vascular access intervention outcome. 6

7 Methods Single center, retrospective study of patients who underwent percutaneous intervention for dysfunctional dialysis access DSA acquisitions (pre- and post-intervention) of 20 patients (10 s, 5 AVG, 5 central veins) were obtained and converted to color image and anaysed using the syngo iflow software Complex cases with multiple lesions were excluded 7

8 Methods Evaluation of conventional DSA Diameter of stenotic and normal segment for each access was measured pre- and post-intervention Percent stenosis = [1 (D stenosis /D normal )] 100 Improvement in percent stenosis = (% pre-angioplasty - % post-angioplasty )/ % pre-angioplasty x 100 8

9 Methods Pre-PTA % stenosis = 76% Post-PTA% stenosis = 30% Improvement in % = 60% Dnorm al= 7.02 m m Dstenosis= 1.69 m m Dstenosis= 4.91 m m 9

10 Methods Evaluation of color coded DSA ROIs were chosen before and after stenosis Time to peak (TTP) or time to maximum contrast opacification was obtained for each ROI The difference between the TTP of these 2 ROIs (dttp)were obtained, it represent the flow across the stenosis. 10

11 Methods Differences between pre- and post-pta dttp P re-p T A dt T P =1s 11 P ost-p T A dt T P =0s

12 Time Attenuation Curve Quantification of contrast wash-out before and after intervention was also obtained using the time attenuation curve (TAC). 12

13 Time Attenuation Curve Contrast W ash-out Contrast W ash-in 50% 50 % Contrast W ash-out tim e= 0.75s 13

14 Time Attenuation Curve Contrast W ash-in Contrast W ash-out 50% 50 % Contrast W ash-out tim e= 0.5s 14

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 were compared using paired sample t-test Pearson correlation was used to analyse the relationship between dttp and change in percentage of stenosis 15

16 Baseline Demographics 16 Characteristics N = 20 Age, years 67.5 (IQR 61.5, 70.75) Female, n (%) 12 (60) Ethnicity, n (%) Chinese Malay Indian 14 (70) 5 (25) 1 (5) Type of Access, n (%) Arteriovenous fistula Arteriovenous graft 15 (75) 5 (25) Etiology of ESRD, n (%) Diabetes Mellitus Hypertension Glomerulonephritis Others 8 (40) 3 (15) 8 (40) 1 (5)

17 Characteristics Vascular Accesses 17 Patient No Type of Access Site of Anastomosis Brachiocephalic Brachiocephalic Radiocephalic Radiocephalic Brachiocephalic Radiocephalic Brachiocephalic Brachiocephalic Brachiobasilic Radiocephalic Lesion Peripheral vein Juxta-anastomosis Juxta-anastomosis Juxta-anastomosis Juxta-anastomosis Juxta-anastomosis Juxta-anastomosis Juxta-anastomosis Peripheral vein Juxta-anastomosis Brachiobasilic Brachiocephalic Brachiocephalic Brachiobasilic Brachiobasilic Central vein Central vein Central vein Central vein Central vein AVG AVG AVG AVG AVG Brachiobasilic Brachiobasilic Femoral-femoral Femoral-femoral Femoral-femoral Venous anastomosis Venous anastomosis Venous anastomosis Venous anastomosis Venous anastomosis

18 Anatomic and Hemodynamic Changes Variable P -value Percent of stenosis, % < Pre-angioplasty ±19.36 Post-angioplasty ±19.81 dttp, s Pre-angioplasty 0.41 ± 0.77 Post-angioplasty 0.18 ± % Contrast Washout time, s Pre-angioplasty 0.80 ± 0.43 Post-angioplasty 0.49 ± 0.31 All results were reported as mean ± SD unless otherwise specified 18

19 All Access dt T P, s P ercentchange ins tenosis,% P earsoncorrelation 0.40,p=

20 dt T P,s P ercentchange ins tenosis,% P earsoncorrelation 0.631,p=

21 AVG dt T P,s P ercentchange ins tenosis,% P earsoncorrelation ,p=

22 Central dt T P,s P ercentchange ins tenosis,% P earsoncorrelation 0.104,p=

23 Discussions The ability to assess TTP at various ROIs before and after PTA is useful in assessing blood flow rate which was previously impossible with standard DSA There was significant improvement in dttp and 50% contrast wash-out time post-angioplasty indicate improvement in blood flow rate across stenosis dttp correlates with percent change in stenosis on lesions However, the same correlation was not seen in AVG and central veins small numbers? 23

24 Limitations Single centre, retrospective study Small number insufficient statistical power for correlation analysis Hand injection of contrast risk of deviation of flow rate Quality of color image may be affected by movement artefacts 24

25 Conclusions Nevertheless, this is the first study on adjunctive use of parametric color coding as a postprocessing algorithm in hemodialysis access and we found that it provides useful hemodynamic information in evaluation of adequacy of treatment of vascular access. A larger scale prospective study with correlation with hemodynamic parameters such as pressure and transonic flow rate, using injector should be performed 25

26 T HA N K YO U

27 Prospective Study Preliminary Results 27

28 Prospective Study Preliminary Results Mean TTPs (s) 28 Pre Angioplasty Post Angioplasty P-value ROIRef 1.87 ± ± 0.33 <0.01 ROI ± ± 0.36 <0.01 ROI ± ± 0.35 <0.01 ROI ± ± 0.29 <0.01

29 Prospective Study Preliminary Results Mean Transonic Flow syngo iflow (ml/min) Calculated Flow ± (ml/min) ± Pearson s P- Correlation value Post-Angioplasty TTP (s) 29 RRef ± ± R ± ± R ± ± R ± ±