Two year follow-up results for Spiral Flow Grafts in AV Access

Presented at the 37th Charing Cross International Symposium, April 2015, London, UK Prim. Univ.-Doz. Dr. Wolfgang J. Hofmann, Department of Vascular Surgery, Landeskrankenhaus, (LKH) Feldkirch, Austria

Introduction
The AV access strategy at LKH Feldkirch focusses primarily on utilising native fistula and Duplex mapping of the upper extremity is undertaken to identify the most appropriate approach.

AV grafts are only used in patients not suitable for a native fistula.

Conventional AV grafts typically require one to two revisions per year.

Methods
Since September 2010, a series of 16 grafts have been implanted in 15 patients. All patients have had previous
surgery (mean of 4.3 previous procedures (0-24).  Mostly loop grafts in the forearm are utilised.
• 11 loop forearm
• 2 loop upper arm
• 2 straight upper arm
• 1 loop thigh
• 4 graft occlusions / two successful thrombectomies
• 4 graft explants (2 due to steal, 2 due to infection)

Results
The results from 16 Spiral FlowTM AV Grafts, implanted between September 2010 and August 2013 were reviewed. Median follow up was 22 months and all grafts were Duplex scanned every three months to confirm the presence of Spiral Flow. Additional scans were performed if there was any suspicion of graft failure.

At 22 months, the primary rate was 72%; secondary patency was 85.5%

The results were compared to a series of 79 conventional PTFE grafts implanted by Dr Hofmann between January 2005 and December 2009. A Kaplan-Meier analysis highlighted primary patency rates at 18 months of 72% for Spiral FlowTM and 36.7% for conventional PTFE grafts. (P=0.01)

Conclusion
Changing the flow pattern at the venous anastomosis of AV grafts using the Spiral Flow Technology seems to be a simple but valuable tool in order to improve patency rates of PTFE AV grafts

Intermediate results of using spiral flow av graft: is it a breakthrough solution to a difficult problem?

In Abstracts from VAS 9th International Congress, April 15-18, 2015 Barcelona, Spain. J Vasc Access 2015; 16(2): 31 Hosam F. El Sayed, Houston Methodist Hospital, Houston, United States

Introduction
AV access grafts are used in those patients where there are no available superficial veins for native AV fistula creation.  Their usable life and patency rates are far from being ideal requiring frequent interventions to maintain their use for dialysis. Their failure is usually related to neointimal hyperplasia leading to stenosis of the venous outflow near the venous anastomosis. Studies have shown that, Spiral laminar flow is the normal pattern of flow in most of the large and medium sized vessels in vivo as well as many functioning native AV fistulas. The Spiral flow graft has a design that creates a spiral laminar flow at the venous end that is a hypothetically reduces intimal hyperplasia and graft failure. We here report the midterm results of the largest reported series of using the graft in AV access.

Material & Methods
After IRB approval, a prospective study of using Spiral Flow graft for AV access in our institution between Jan 2012 to Dec 2014 was performed. Enrolled patients had no suitable superficial veins for native AV fistula creation. Patient demographics and comorbidities were recorded.

Kaplan Meier curve analysis was used to calculate patency rates compared to historic controls of straight ePTFE and heparin bonded grafts in our institution.

Complications were also recorded.

Results
48 cases were included. The access site was the upper arm (32), the forearm (13), and chest wall (3). Mean age of 61 and mean follow up of 14 months. At 12 month, the assisted primary and secondary patency rates were 70% and 82%, respectively that was significantly better than historic controls using straight ePTFE and heparin bonded grafts in our own institution.

Complications included 4 graft infections; 3 severe steal syndrome, 4 seromas and 3 arm swelling. There were only 2 early graft failures.

Conclusions
Spiral flow grafts are a valid successful option for AV access.  One year results are superior to using straight ePTFE and heparin bonded grafts. This may be explained on the basis of the hemodynamic environment created by the spiral laminar flow and may be a significant contribution to preventing neointimal hyperplasia and hence AV access graft failure.

Spiral Flow Technology a year on: Results of the North American experience

Presented at the 36th Charing Cross International Symposium April 2014, London, UK Hosam El Sayed, MD, Assistant Professor of Cardiovascular Surgery, Methodist DeBakey Heart and Vascular Center, Houston, Texas, USA.

Introduction

Prosthetic graft failure is a normal tissue response to an abnormal flow environment. Endothelial cells at the anastomosis are sensitive to non-laminar flow environment (turbulence, stagnation, low shear stress, increased oscillatory index). These cells respond by signalling neo-intimal hyperplasia thus promoting failure. Results with prosthetic AV access grafts are far from ideal. We decided to use the Spiral flow graft for AV access based on early encouraging reports.

Patients and methods

This is a retrospective review of all cases that had Spiral Flow graft placement for AV access in the upper extremities.

From January, 2012 – January, 2014, 38 Spiral Flow™ AV Access Grafts (Vascular Flow Technologies Ltd) were placed in 37 patients.

The mean age was 61 years (range 42-88 years); 47% (18) were male. Patients presented with the following comorbidities: Diabetes: 25 (66%); Hypertension: 33 (87%); CAD: 8 (21%); CHF: 7 (18%); CVA: 7 (18%); PVD: 8 (21%).

Grafts were implanted as: Upper arm: 24; Forearm: 11; Chest wall: 3

Results

The mean follow-up was nine months. 15 patients completed 12 months follow up. There are 20 grafts (53%) currently in use. Three grafts were removed for infection, 3 grafts were ligated for severe steal and 1 graft was ligated for severe arm swelling. Seven patients are deceased, all with their grafts patent.

Complications were as follows: Graft infection: 3 (8%); Significant Steal: 3 (8%); Thrombosis: 7 (18%); Venous stenosis: 3 (8%); Seroma: 4 (10%); Wound complications: 3 (7%); Venous hypertension: 7(18) and Pseudo-aneurysm: 0

Overall patency (%) results at 12 months are as follows:

Primary AssistedSecondary
81% ± 983% ± 9

Conclusions

Spiral Flow Grafts are a valid and successful option for AV access. Early results are encouraging and tend to be better compared to standard straight ePTFE and heparin bonded grafts.

This may be explained on the basis of improved hemodynamics created by the spiral laminar flow.

Early results of using Spiral Flow AV Graft: Is it a breakthrough solution to a difficult problem?

Poster at Society for Clinical Vascular Surgery (SCVS) symposium March 2014, Carlsbad, California, USA. Hosam F. El Sayed, MD, Javier E. Anaya-Ayala, MD, Mark Davies, MD. Houston Methodist DeBakey Heart & Vascular Center, Houston, Texas, USA

Objective

Although, the preferred method to create an access is native AV fistula, there is still a significant number of patients where this is not feasible. AV access grafts are used in those patients and their patency rates are far from being ideal requiring frequent interventions to maintain their use. Their failure is usually related to stenosis of the venous outflow due to intimal hyperplasia, near the venous anastomosis of the graft. Neo-intimal hyperplasia may, in part, be a normal cellular response to an abnormal (turbulent) flow environment created by the AV access. Studies have shown that, Spiral laminar flow is the normal pattern of flow in most of the large and medium sized vessels in vivo. The Spiral flow graft has a design that creates a more natural spiral laminar flow at the venous end that is a hypothetically a more friendly hemodynamic environment thus reducing intimal hyperplasia and graft failure. We here report the early results of the largest available series of using the graft in AV access.

Method

Retrospective review of all cases using the Spiral Flow graft for AV access in our institution, Jan 2012 to Jan 2014. Patients selected had no suitable superficial veins for native AV fistula. Patient demographics and comorbidities were recorded. Kaplan Meier curve analysis was used to calculate primary, assisted primary and secondary patency rates in comparison to historic controls of straight ePTFE and heparin bonded grafts for the same indication in our institution. Complications were also recorded.

Results

A total of 38 cases were included. The access site was the arm (24), the forearm (11), and chest wall (3). Two thirds were females, mean age of 60 years and mean follow up of 8 months. At 12 month, the primary, assisted primary and secondary patency rates were 73%, 73% and 79%, respectively. Complications included 4 graft infections; 3 severe steal syndrome, 4 seromas and 2 arm swelling. There was only 1 early graft failure. There was only one early graft failure in less than 30 days in a patient with known hypercoagulable state who was not therapeutic on anticoagulation.

 PrimaryPrimary assistedSecondary
Spiral AVG78 ± 873 ± 879 ± 8
Heparin banded56 ± 860 ± 859 ± 8
Standard ePTFE38 ± 1047 ± 1066 ± 11
P-Value0.0550.160.042

12 month patency rates

Conclusion

Spiral flow grafts are a valid and successful option for AV access. One year results tend to be significantly superior to using straight ePTFE and heparin bonded grafts. This may be explained on the basis of the hemodynamic environment created by the spiral laminar flow and may be a significant contribution to preventing neointimal hyperplasia and hence AV access graft failure.

Early experience with the SLF (Spiral Laminar Flow) AV Access Graft

Inston N1 , Hofmann WJ2 .
1 Department of Renal Surgery, Queen Elizabeth Hospital, University Hospitals Birmingham, Birmingham, UK
2 Department for Vascular Surgery, Feldkirch General Hospital, Feldkirch, Austria
In Abstracts from VAS 8th International Congress, April 25-27, 2013 Prague, Czech Republic. J Vasc Access 2013; 14(1): 43

Background

Arteriovenous grafts for dialysis are associated with a high incidence of outflow stenosis requiring re-intervention and increased risk of failure. (more…)

A new choice for vascular access: Spiral Flow AV Graft

Cetingok U
Department of Cardiovascular Surgery, Kavaklidere Umut Hospital, Ankara, Turkey
In Abstracts from VAS 8th International Congress, April 25-27, 2013 Prague, Czech Republic. J Vasc Access 2013; 14(1): 36-37

Background

The most commonly used grafts for vascular access are the polytetraflouroethylene (PTFE) grafts. Different types of PTFE grafts are used in the vascular access applications for a long time. (more…)

Vascular Flow Technology: Another run of the mill graft or a breakthrough technology? Experience and perspective from a European centre.

Prim. Univ.-Doz. Dr. Wolfgang J. Hofmann
Department of Vascular Surgery, Landeskrankenhaus (LKH) Feldkirch, Austria
Presented at the 35th Charing Cross International Symposium, 7th April, 2013, London, UK

Background

The AV access strategy at LKH Feldkirch focusses primarily on utilising native fistula and Duplex mapping of the upper extremity is undertaken to identify the most appropriate of the following approaches: (more…)

Vascular Flow Technology: Another run-of-the-mill graft or a breakthrough technology? Experience and perspective from a US centre

Presented at the 35th Charing Cross International Symposium, London, UK 7 April 2013. Hosam El Sayed, MD, Assistant Professor of Cardiovascular Surgery. Methodist DeBakey Heart and Vascular Center, Houston, Texas, USA.

Patients and methods

From January, 2012 – February, 2013, 19 Spiral Flow™ AV Access Grafts (Vascular Flow Technologies Ltd) were placed in 18 patients. The mean age was 60 years (range 42-84 years); 37% (7) were male. Patients presented with the following comorbidities: six diabetes (32%); 17 hypertension (90%); five CAD (26%); four CHF (21%); five CVA (26%); six PVD (32%). Grafts were implanted as: 11 upper arm; two forearm; five femoral; and one chest wall.

Results

The mean follow-up was six months. There are 11 grafts (58%) still in use. Three grafts (15%) were removed for infection; two grafts thrombosed (10%); two grafts were ligated for severe steal (10%). There were two grafts with seroma (10%), but they remained functional. There were three wound complications (15%) and three arm swelling (15%). One graft was ligated (5%). There were no pseudoaneurysms. Two patients died with functioning grafts.

Overall patency results are as follows:

PrimaryPrimary assistedSecondary
90% ± 9%90% ± 9%100% ± 0%

Conclusion

The early results are encouraging and tend to be better compared to standard straight ePTFE and heparin bonded grafts. This might be explained on the basis of improved haemodynamics created by the spiral laminar flow.