New Graft for Low Friction Tunneling in Vascular Access Surgery

Structural design and mechanical performance of composite vascular grafts

This study reviews the state of the art in structural design and the corresponding mechanical behaviours of composite vascular grafts. We critically analyse surface and matrix designs composed of layered, embedded, and hybrid structures along the radial and longitudinal directions; materials and manufacturing techniques, such as tissue engineering and the use of textiles or their combinations; and the corresponding mechanical behaviours of composite vascular grafts in terms of their physical–mechanical properties, especially their stress–strain relationships and elastic recovery. The role of computational studies is discussed with respect to optimizing the geometrics designs and the corresponding mechanical behaviours to satisfy specialized applications, such as those for the aorta and its subparts. Natural and synthetic endothelial materials yield improvements in the mechanical and biological compliance of composite graft surfaces with host arteries. Moreover, the diameter, wall thickness, stiffness, compliance, tensile strength, elasticity, and burst strength of the graft matrix are determined depending on the application and the patient. For composite vascular grafts, hybrid architectures are recommended featuring multiple layers, dimensions, and materials to achieve the desired optimal flexibility and function for complying with user-specific requirements. Rapidly emerging artificial intelligence and big data techniques for diagnostics and the three-dimensional (3D) manufacturing of vascular grafts will likely yield highly compliant, subject-specific, long-lasting, and economical vascular grafts in the near-future.

Graphic abstract

Single-centre experience of an early cannulation graft for haemodialysis access

INTRODUCTION

As the demographics of the population changes, increasing challenges are being faced in providing reliable access for dialysis. This article reports on the outcomes from the largest series to date using the early cannulation graft Flixene in a single centre.

METHODS

Between May 2012 and March 2018, 141 Flixene grafts were placed for dialysis access. The outcomes of the arteriovenous grafts were reviewed retrospectively from electronically held records and imaging.

RESULTS

In 75 patients, placement of Flixene graft was performed on an emergency basis and in 66 patients on a planned elective list. The 12-month primary, assisted primary and secondary patency rates were 48.7%, 56.6% and 83.6%, respectively. Eight (5.7%) patients developed infections of the graft during the follow-up period.

CONCLUSION

In our experience, we have found the use of the early cannulation graft Flixene to be safe with a low complication rate and favourable patency rates. We believe these early cannulation grafts provide a useful addition for vascular access surgeons preventing the use of tunnelled lines and providing more flexibility in the timing of placing a graft for dialysis.

Results of aggressive graft surveillance and endovascular treatment on secondary patency rates of Vectra Vascular Access Grafts

OBJECTIVE

The aim of the present study was to determine the effect of an aggressive graft surveillance and endovascular treatment protocol on secondary patency rates of a polyetherurethaneurea vascular access graft, specially designed to provide early access and rapid hemostasis.

METHODS

One hundred and ninety Vectra Vascular Access Grafts (C. R. Bard, Inc, Murray Hill, NJ) were placed in 176 patients (78 females and 98 males, mean age 61.7 years). There were 41 forearm grafts, 145 upper arm grafts and four thigh grafts. Graft surveillance was performed by using clinical and hemodialysis parameters to detect a failing/failed graft and followed by endovascular treatment, rheolytic thrombectomy (AngioJet, Possis Medical Inc, Minneapolis, Minn) and/or angioplasty +/- stenting of the anatomical lesion (arterial anastomosis, graft, venous outflow, draining or central veins).

RESULTS

Hemodialysis started after a median of 15.5 days, as soon as from the day of the operation in some cases. Bleeding complications occurred in six patients (3.2%), venous hypertension in seven (3.7%), steal syndrome in two (1.1%), neurological complications in two (1.1%), while late infection (range 2.7-14.6 months) was seen in six patients (3.2%). Thrombectomy and angioplasty (median number of sessions 1, interquartile range 1-2) was performed in 43 grafts. Isolated angioplasty, not associated with thrombosis (median number of sessions 1, interquartile range 1-2), was performed in 50 grafts. These interventions increased primary assisted patency from 69% and 63% at 12 and 18 months, respectively to a secondary patency rate of 86%. Taking into account grafts removed for late infection, functional secondary patency rate dropped to 83% and 81%, at 12 and 18 months, respectively. Arterial anastomosis angioplasty was performed more frequently in thrombosed grafts (28.6%) than failing grafts (6.7%), P < .001 and had a significant negative predictive value on secondary patency rates at 12 and 18 months, which were 60.5% compared with 89% for grafts that had no interventions performed (P = .007) and 90.9% for grafts that had any intra-graft, venous outflow, or draining or central vein stenosis treated with angioplasty at any stage (P = .002). Multivariate analysis identified the presence of arterial anastomosis stenosis as the single predictor of secondary patency (relative risk 0.247, P = .002).

CONCLUSIONS

Aggressive graft surveillance and endovascular treatment increases significantly secondary patency rates of Vectra Vascular Access Grafts. Longer follow-up will determine the effectiveness of this policy. The role of inflow stenosis on graft longevity and alternative treatment options warrant further investigation.

Incidence and Management of Seroma after Arteriovenous Graft Placement

BACKGROUND

Perigraft seromas are rare complications of insertion of PTFE hemodialysis grafts. They are often difficult to treat and recurrence is common. This study evaluates the incidence, potential etiologic variables, and management strategies for seromas after prosthetic arteriovenous graft (AVG) placement.

STUDY DESIGN

A retrospective analysis of all patients undergoing AVG placement between August 2002 and December 2005 was performed to identify all patients diagnosed with seroma requiring surgical intervention. Multiple variables were analyzed to determine potential risk factors for seroma formation and outcomes of various forms of surgical management.

RESULTS

In this interval, 535 AVG were inserted in 427 patients. Ten patients presented with a seroma and underwent surgical treatment. Overall incidence of seroma formation was 1.7%. There was no significant difference in seroma formation based on gender, age, diabetes, lower extremity versus upper extremity placement, or loop forearm versus straight forearm grafts. A statistically significant difference was found between upper arm (p = 0.007) and lower arm grafts (p = 0.04), with upper arm grafts more prone to seroma formation. Patients undergoing bypass of the seromatous segment of graft have not had a recurrence, compared with those who were simply evacuated and have had a mean patency of 402 days.

CONCLUSIONS

Seroma complications after AVG insertion are higher in patients with upper arm grafts. To minimize this complication, meticulous operative technique is required. If a seroma develops, the graft might still be salvageable with aggressive management, including bypass of the involved segment.