1. Balloon Angioplasty for Low Flow Access
Dheeraj K. Rajan MD, FRCPC, FSIR
Division of Vascular and Interventional Radiology
University of Toronto – University Health Network

2. Angioplasty – The Gold Standard
Goal is to relieve the stenosis
Venous stenoses associated with dialysis access is typically unyielding often requiring high pressure balloons
Following PTA, recurs in a short period of time
Complications of PTA

3. Patch Angioplasty is Surgery
Balloon versus patch angioplasty as an adjuvant Tx to surgical thrombectomy of hemodialysis grafts.
Case control study of PTA and patch angioplasty pts
RESULTS: 10 patencies of patch & PTA group: 86% vs 77% at 1 mo, 45% vs 40% at 3 mos, 17% vs 28% at 6 mos
No statistically signif diff btw the 2 groups
CONCLUSION: Balloon angioplasty offers advantages to patch angioplasty, with similar patency rates. We recommend balloon angioplasty as a comparable method to salvage dialysis access grafts
DOQI guideline  percutaneous
Bitar G et al. Am J Surg 1997;174:140-2.
Slide courtesy of Ziv Haskal

4. Angioplasty
The potential long-term patency rate following PTA is (possibly) well established.
Published series consistently report 40% to 50% 6-month unassisted patency rates from PTA. Long-term unassisted patency after surgical revision is less well established due to reporting of cumulative patency.

5. Prospective 38-63% 6 mo. (retrospective series) Probably more accurate
AVG 10 Patency after PTA
38-63% 6 mo. (retrospective series)
Probably more accurate
23-41% 6mo. (prospective series) 5 5

6. Levels of evidence: Access Interventions
Slide courtesy Ziv Haskal

7. Advances – What Advances?
K/DOQI recommends 50% 6 month primary patency following angioplasty
Technical success <30% residual stenosis
New devices – do they improve patency?
Is there any value in prophylactic intervention?
The future?

8. PTA Resistant Stenoses
Lesions resistant to PTA overall 10-15%
Clark, JVIR 2002; 51
Rajan, Radiology 2004; 508
55% of dialysis stenoses required inflation pressures > 15 atm when grafts/fistulas were combined
Trerotola, JVIR 2005; 1613.
Lesion most difficult to treat is the cephalic arch

9. Patencies Lay JP et al. Clin Radiol 1998; 53:608-611.
Clark TW et al. J Vasc Interv Radiol 2002; 13:51-59.
Manninen HI et al. Radiology 2001; 218:
Turmel-Rodrigues et al. Nephro Dial Transplant 2000; 15:

10. What else has been tried?

12. Conquest versus regular PTA
Grafts
55 PTA’s each group
No difference in patency
Only venous anastomosis grafts
10-20% stenoses require pressure >15 atm

13. Cutting Balloon Folding Design
Slow inflation & deflation
1ATM every 3-5 sec.
Atherotomes descend within the folds of balloon material
Minimizes atherotome exposure to healthy tissue
Device should not exceed 10 inflation /deflation cycles
The folding design of the balloon has been manufactured to minimize exposure of the atherotome to healthy tissue. A slow inflation technique of 1 ATM every 3-5 seconds aids in the atherotome’s descent into the folds of the balloon material. While the Peripheral Cutting Balloon can be used for multiple inflations, it is not recommended to exceed 10 cycles for each device.

14. Cutting Balloon

15. JVS -2014 623 patients – mixed grafts and fistulas
At venous anastomosis at 6 and 12 months primary assisted patency significantly better
86 vs 63; 56 vs 37%
Really treatment area primary patency
Not access circuit or secondary
Ultrasound follow-up monthly

16. Cutting Balloon - Again
Autogenous fistulas
USED if conventional PTA did not work
71/516 randomized to HPTA vs. cPTA
Six month f/u angio
66% versus 40% at 6 months
JVIR 2014; 190

17. Nitinol Stents
Since 1991, >10% of PTA procedures associated with stent placement
Chan 2008
25% versus 3% primary patency 6 mts
AVG’s
Retrospective with 64 patients
Centrally: 14.9 months
12 month: 67%
Mean primary patency peripheral: 8.9 months
12 month: 20%
Almost all were severely stenosed at 6 mts
Vogel, JVIR 2004: p

18. Kariya S, et al. Cardiovasc Intervent Radiol (2009) 32:960–966
39% 6-month 10 patency for stents
73% 6-month 10 patency for PTA p = 0.028
Kariya S, et al. Cardiovasc Intervent Radiol (2009) 32:960–966

25. Stent Usage No definite conferred long term benefit over PTA
Can convert focal lesion to lesion length of the stent
Used as bailout for:
Rupture
Reobtruction
Recoil
? rapid recurrence of stenosis (<3 mts K/DOQI)

26. Novel Technologies Cryotherapy Gene therapy Drug eluding stents
Brachytherapy
Atherectomy catheters
Dissolving stents

27. Brachytherapy cont…
Dosing scheme: Gray at 0.5mm into the vein wall Treatment times: 214 to 323 seconds

28. Brachytherapy Novoste Bravo trial Beta radiation source
Trial cancelled
Switched study population inclusion criteria part way through trial
42% target lesion primary patency end point at 6 months as compared to 0% of the control group (P = 0.015) - did not translate into an improvement in secondary patency at either 6 or 12 months.
Misra S, KI 2006 (70) p 2006

29. Cryoplasty PolarCath System
Nitrous Oxide Coolant

30. Cryoplasty Stenosis or thrombosis increased from 3 weeks to 16 weeks
Only 5 patients
Am J Kidney Dis, 2005; 45(2): e27-32.
20 patients
35% technical success
25% 6 month patency
Associated with severe pain
Gray JVIR 2008

31. Atherectomy Devices Atherectomy SilverHawk/TurboHawk/DiamondBack
T – Designed to cut through CTO’s (hard plaque)
S – Everyday plaque with no thrombus and/or calcified plaques
No iliac indication; for above/below knee
Preserves treatment options
Atherectomy
Limited studies – three
5/13 (38%) patent at 6 mts
largest study
expensive

32. Bioabsorbable Stents Constructed of polylactic acid
Two layers : anti-proliferation drug that absorbs and second is made of a harder crystalline matrix of PLA which dissolves in two years
Biodegradable magnesium alloy dissolves in months
Also a vehicle for delivery of nanoparticles

33. Drug Eluding Balloons
Targeted delivery of drugs to vascular wall or perivascular region
Antigrowth factors
Angiogenesis factors
Gene therapy
Injection of cells
Local delivery concentrations can be 500x greater than systemic therapy

34. Drug Eluding Balloons InPact Admiral Balloon (paclitaxil)
40 patients (only AVF’s) randomized 1:1
No defined prospective F/U
TLR-free survival was significantly superior in the PCB group 308 d vs 161 d.
However, device success rates were 100% in the HPB group and 35% in the PCB group
JVIR 2015 – in press

35. Drug Eluding Balloons Adventitial delivery 130 micron needle
Controlled localized delivery
Reduced toxicity

36. Drug Eluding Balloons Questions to be answered Drug dose
Pre PTA or Post PTA
Duration of dwell time

37. Question Should be PTA versus Stent Garfts
No definite evidence that proves stents are better than angioplasty for patency for peripheral and central lesions
Stents do improve technical success with some evidence of improved effect (Vogel, JVIR 2005)
Early randomized studies demonstrate clear patency advantage of stent grafts

38. Slide courtesy Bart Dolmatch
Self-expanding ePTFE Covered Stents
Viabahn
Flair
Viatorr
Fluency
Slide courtesy Bart Dolmatch

40. N Engl J Med 2010;362(6):
(Core Lab Analysis)

41. FLAIR study Survival Free from Treatment Area Primary Patency Failure
Log-Rank p= Wilcoxon p=0.008
FLAIR study 41 41

43. Of course, this is achievable with PTA, isn’t it?
2 mos 29 mos
s berman
AVG functions 5 years after placement.

44. Revise Trial Presented at SIR
Gore Viabahn device for venous anastomotic stenosis
Six month primary patency significantly different
Secondary patency the same
Renova
12-month ACPP for the stent graft group was significantly better than the PTA group, 24.1% vs. 10.3% (p=0.005), respectively.

45. Literature (Cephalic Arch)
Randomized Study
Stent versus stent graft
25 patients
Six month primary patency was 82% in the stent graft group and 39% in the bare stent group.
One-year primary patency was 32% in the stent graft group and 0% in the bare stent group
Historical PTA 42% and stent 39% (Rajan vs. Shemesh)
Shemesh, JVS (6):

46. Another Study: 14 patients mature brachiocephalic fistulas.
Five were randomized to angioplasty (PTA) and 9 to stent grafting.
Technical success 100%
Mean patency in PTA group 100 days ( days) vs 300 days ( days) for SG
Primary access circuit patency at 6 and 12 months:
PTA: 0%
Stent graft: 67 and 22% (95% CI: ; 6-75) p<0.01
Primacy target lesion patency at 3, 6 and 12 months
PTA: 60% (CI %), 0% and 0%
SG: 100%, 100% and 29% (CI: 9-93%) (p<0.01)

47. Surgical Intervention
Anatomic bypasses
Turn down cephalic vein to basilic or axillary vein
Autologous or artificial bypass
Patch
Skilled motivated surgeons needed
Literature
Not much short, medium or long term data published

48. Literature Transposition of cephalic vein to axillary or basilic vein
13 Patients
Six month primary patency rate of angioplasty before the surgical revision of 8%
Six month primary patency rate following surgical revision of 69% at 6 months.
However:
Why was PTA 8% so much lower than other studies
Surgical revision is technically creating a new access
No length of follow-up provided or standard error limiting interpretation of data
What about damage to axillary and basilic veins in the future?
Kian, Sem Dialysis 2008: 21(1): 93-6.

49. AVF Stent Grafts 17 patients Thromboses, stenoses, pseudoaneurysms
Access circuit patency: 88% at 6 and 12 months
Lesion patency: 94% at 6 and 12 months
Bent CL, JVIR April 2010

57. Why Does Most Stuff Not Work?
Intimal injury leading to intimal hyperplasia
Have to inhibit or prevent injury, exclude injured area
Most devices repeat or create injury cycle
Surgery itself associated with injury cycle
Poor reporting/study design
Mixing of grafts/fistulas/lesion types
Type of follow-up
definitions

58. Summary
No evidence to date to suggest any new devices / methods improve overall access patency compared to angioplasty for venous stenosis in hemodialysis patients
Stents should be used for salvage only, not primary intervention
Stent grafts have improved patency in graft patients – does this translate to fistulas?