The Hybrid Vascular ePTFE Graft as an Alternative for Hemodialysis

AccessJoseph J. Naoum, MD, FACS

Assistant Professor of Surgery

Lebanese American University

Vascular & Endovascular Surgery

University Medical Center Rizk Hospital

Beirut, Lebanon

Joseph.naoum@umcrh.com

+96176933937

BACKGROUND

• Native arteriovenous fistulas (AVF) are the firstoption for dialysis access creation.– However, not all patients have adequate veins for the

creation of autologous access.

• With the recent trend of an increasing hemodialysis population with diabetes and longer survival, the exhaustion of autologous sites is becoming more prevalent . – End-stage Renal Disease (ESRD) patients requiring

chronic hemodialysis are increasingly requiring alternatives for the challenging creation of long-term arteriovenous (AV) access sites.

Akoh JA. J Vasc Access. 2009 Jul-Sep;10(3):137-47.Vascular Access 2006 Work Gruup. Am J kideney Dis 2006; 48 (Supp 1);S176-247.Anaya-Ayala JE, et al. Ann Vasc Surg. 2011 Jan;25(1):108-19.

THE PROBLEM• The poor long-term prognosis of prosthetic grafts

generally results from development of intimal hyperplasia and consequently stenosis at the graft-vein or graft-artery anastomosis.

• For instance, a few in vitro studies utilizing computational fluid dynamics (CFD) have described the complex hemodynamics of the AVG anastomosis (in dialysis access).– This complexity is the result of the connection of the

high pressure, high velocity arterial flow to a low pressure low velocity venous system. The effect of the shear forces are primarily a problem of the standard graft configuration.

Hakim R,et al. Kidney Intl 1998;54:1029-40.Heise M, et al.J Vasc Surg. 2011 Jun;53(6):1661-7. Epub 2011 Apr 2.Dixon BS, et al. N Engl J Med. 2009 May 21;360(21):2191-201.Heise M, et al. Eur J. Vasc Endovasc Surg 2003;26:367-73.Krueger U, et al. Artif Organs. 2004;28:623-8.

Structural graft modifications

• The development of intimal hyperplasia is one of the culprits for bypass or graft failure.

• Structural modifications of the conduit that alter the flow hemodynamics at the distal anastomosis have been introduced.

– The concept hinges on creating laminar flow at the distal anastomosis, which in turn can influence and decrease the occurrence of intimal hyperplasia.

Naoum JJ, et al. MDHVJ 2012, 8(4): 43-6

Flow and Shear Stress

Littele S, et al. http://www.goremedical.com/resources/dam/assets/AQ0560EN1.HVG.STUDY.FLYER.FNL.MR.pdfJackson ZS, et al. J Vasc Surg 2001;34(2):300-307.

• In the conventional end-to-side anastomosis, intimal hyperplasia occurs in part due to alterations in shear stress at the toe and heel of the AVG anastomosis.

Flow and Shear Stress• The GORE® Hybrid

Vascular Graft altered the wall shear stress region at the toe and the heel of the graft anastomosis site, which corresponds to the development of intimal hyperplasia in the conventional end-to-side anastomosis.

Littele S, et al. http://www.goremedical.com/resources/dam/assets/AQ0560EN1.HVG.STUDY.FLYER.FNL.MR.pdfJackson ZS, et al. J Vasc Surg 2001;34(2):300-307.

• Due to the GORE® Hybrid Vascular Grafts occlusion of the venous inflow, flow remained laminar, where the conventional construct exhibited irregular flow patterns downstream from the entry site.– Irregular, oscillating flow patterns have also been identified as a precursor

to the development of intimal hyperplasia and graft occlusion.

• These observations suggest that the GORE® Hybrid Vascular Graft provides optimized flow characteristics as compared to a conventional end-to-side anastomosis thus potentially reducing the incidence of arteriovenous access graft stenosis due to intimal hyperplasia.

Littele S, et al. http://www.goremedical.com/resources/dam/assets/AQ0560EN1.HVG.STUDY.FLYER.FNL.MR.pdfJackson ZS, et al. J Vasc Surg 2001;34(2):300-307.Ojha M. Circulation Res 1994;74(6):1227-1231

The use of covered nitinol stents to salvage dialysis grafts after multiple failures.

Naoum JJ, et al. Vasc Endovasc Surg 2006;40:275-79

Begovac PC, et al. Eur J of Vasc Endovasc Surg

2003;25(5):432-437.

Heparin Bonded Vascular Graft

Control

At 2 hrs

THE IDEA

HYBRID ePTFE HEPARIN BONDED GRAFT

THE SOLUTION?• The stent graft component of the hybrid graft has

been proposed to overcome some of the hemodynamic features that may contribute to the development of intimal hyperplasia at the venous anastomosis.

• This is because the laminar flow through the graft is in line with the host vessel.– Unlike the conventional end-to-side anastomosis, this

device deploys as a sutureless outflow anastomosis with a nitinol reinforced stent section which presumably shields the vessel lumen area most susceptible to injury and failure.

PREVIOUS EXPERIENCES

• Experimental devices capable to create a suturelessarterial anastomosis have demonstrated safety and efficacy in porcine models.

• Some have described the use of modified devices utilizing a standard Viabahn stent graft (WL Gore, Flagstaff, AZ) and an ePTFE graft for bypass in peripheral arterial disease with encouraging initial technical and clinical outcomes.

• The initial experience with “non-hybrid” heparin bonded PTFE grafts for dialysis access patients has resulted in 15 to 20% benefit improved graft patency at 12 months.

Taam SA, et al. J Vasc Surg. 2011 Dec 1. [Epub ahead of print]Ferretto L, et al Ann Vasc Surg.2011 Oct 21. [Epub ahead of print]Bonvini S, et al. J Vasc Surg. 2011 Sep;54(3):889-92.

Patient selection

• Previous AV Access involving the axilla

– Previous graft anastomosis or a stent in the venous target at the axilla

– Failed brachial-basilic or brachial-brachial upper arm transposition arteriovenous fistula

• A target vein < 0.3 cm within the axilla.

• NO option for AVF creation by vein mapping and exam.

PATIENT CHARACTERISTICS

Demographics

No (%) or

Mean ± SD (range)

Patient Total 25 (100)

Age, years 62 ± 14 (29-88)

Men 13 (52)

Women 12(48)

Medical Comorbidities

Diabetes Mellitus 18 (72)

Hypertension 25 (100)

Coronary Artery Disease 10 (40)

Congestive Heart Failure 10 (40)

Myocardial Infarction 2 (8)

COPD 2 (8)

CVA 7 (28)

Hyperlipidemia 12 (48)

PAD 4 (16)

OPEN TECHNIQUE

Venous access with Stiff Glide wire in the IVC for support

Wire goes into the IVC for support

14 Fr. Split Sheath access into the vein

Introduction of the Hybrid Graft over the wire and through the sheath

Keep forward pressure as the split sheath is removed. Advance the stent graft > 2.5 cm into the vessel.

Tunneled Hybrid graft

Balloon Angioplasty of the stent graft segment and venous entry site

Venotomy site

Balloon Angioplasty of Viabahn stent graft segment and venous entrance site

(Usually with a 7 mm Balloon)

Low Volume Venogram

Completion

Arterial sutured anastomosis

Venous stent-grafted outflow segment

Completion Fistulogram

Two Incisions

PERCUTANEOUS TECHNIQUEYES:

US GUIDED VENOUS PUNCTURE

NO:“BLIND” VENOUS

PUNCTURE

A WORD OF CAUTION: WATCH THE NERVE

R. Brachial artery

R. Brachial/Axillaryvein

R. Nerve Bundle

Nerve Bundle

Wire is in the IVC for support

COMPLETION FISTULOGRAM AND PTA

Crossed long segment axillary vein severe stenosis and PTA with extravasation

Covered Axillary/subclavian vein with an 8 mmx10 cm stent graft

Hybrid graft utflowstent-graft segment

• 7 patients required a stent-graft extension.

• 2 patients required PTA to improve venous outflow at the axillary and/or subclavian vein.

“Percutaneous Venous Access”

12 MONTH Patency rate

Primary Secondary

70 % 92

Predicted

Primary Patency

J Vasc Surg, Volume 38(6) December 2003, 1206–1212

CONCLUSION

• New graft technologies can be successfully used to handle clinical and anatomic challenges with complex dialysis patients.

• The Hybrid graft is a safe and efficacious alternative for access creation.

– However, further studies will determine whether this graft provides long term results equivalent or superior to those achieved with other prostheses.

THANK YOU

Steps• Venous access:

– US guided: Micro-puncture kit with etched needle and a stiff wire.• Make a 1 cm incision and use a hemostat to dissect free the

tissues and create a small pocket. Blunt dissection.

– Open exposure: Micro-puncture kit with etched needle and a stiff wire

Steps

– Venogram

• Hybrid graft venous insertion and deployment:

– Place 14 Fr. Sheath over a wire

– Introduce/deploy Hybrid graft (over the wire)

Steps

– Low volume venogram and PTA stent graft segment, especially at venotomy site.

• Arterial segment:

– Tunnel the graft.

– Perform the arterial anastomosis.

Steps

• Check function and patency:

– If a thrill is not evident, consider fistulogramand PTA graft/stent confluence to expand the graft (that is a transition site with ↓ radial support).