AV Fistula vs. Graft: Why Fistulas are Preferred over Grafts

You are probably reading this because you have a catheter and are facing the choice of either an arteriovenous fistula or an arteriovenous graft.

As you might already know, there are 3 types of vascular access for haemodialysis patients:

  1. Catheter – available for immediate use and with minimal short-term complications, catheters are generally used as a temporary central venous access.In the long term, catheters carry a high risk of infection and other complications that may damage the blood vessel. They are, therefore, the least preferred access.
  2. Arteriovenous graft – a method of gaining vascular access for patients who lack the veins suitable for fistula creation. AV grafts can be used 2-3 weeks after the surgery and have a life span of approximately 3 years.They carry a relatively high risk of infection and clotting.
  3. Arteriovenous fistula – considered the gold standard for vascular access in hemodialysis patients and the first choice whenever possible.AV fistulas are associated with decreased mortality and morbidity among hemodialysis patients.

Short history review of AVF in hemodialysis

AV fistulas (AVF) were first seen as a reliable form of hemodialysis (HD) vascular access in 1966. At first many end-stage renal disease (ESRD) patients used prosthetic grafts and permanent catheters when autogenous AV fistulas were not feasible. This led to increased patient care costs and was a major cause of morbidity and mortality.

In 1997 the National Kidney Foundation published the Kidney Disease Outcomes Quality Initiative (K/DOQI) Clinical Practice Guidelines for Vascular Access which changed the entire clinical approach.

In 2003 the Fistula First Initiative was formed—a landmark initiative to improve vascular access care. AV fistulas have been promoted as the best form of HD VA on the basis of their superior patency, low complication and procedure rates, and subsequent lower overall cost.

Over the years we have seen several attempts to change AV grafts — the use of different materials, different designs etc. — in an attempt to optimize the graft outcomes.

However, AV fistulas, which use the patients’ own blood vessels — have not change dramatically over the years and still show better results. They therefore remain the preferred vascular access type.

Read more about the pros and cons of AV grafts and AV fistulas.

 

The effectiveness of fistulas vs. grafts

The effectiveness of a vascular access is measured by: (1) the primary patency rate and (2) the complications.

The primary patency rate is defined in the literature as the time of access creation or placement until any first intervention (endovascular or surgical) to maintain or restore blood flow, first occurrence to access thrombosis, or reaching a censored event (death, transfer to another hemodialysis unit, transfer to peritoneal dialysis, transplantation, and end of study period)2.

A wide systematic review of 34 studies showed that both the primary and secondary patency rates for autogenous accesses were significantly greater than for graft accesses. The primary patency rate for autogenous accesses was 72% at 6 months and 51% at 18 months; the corresponding primary patency rate for graft accesses was 58% and 33% respectively.

The most common complications of AV fistulas and AV grafts include thrombosis, infection, access-related hand ischemia (vascular steal syndrome), aneurysmal dilation, venous hypertension, seroma, heart failure, and local bleeding.

  • AV grafts are 3.8 times more likely to require a thrombectomy and 3 times more likely to require access intervention than AV fistulas.
  • Infection is the second most likely cause of mortality in the dialysis population. It has been reported that the vascular access site is responsible for 23% to 73% of bacteremias in hemodialysis patients. AV fistulas have the lowest rates of infection when compared with AV PTFE grafts and catheters.
  • AV fistulas normally produce an alteration in blood flow patterns, a “physiological” steal phenomenon that is seen in forearm AV fistulas and even more so in elbow/upper-arm AV fistulas.Physiological steal occurs in 73% of AV fistulas and 91% of AV grafts.

It is thus clear that arteriovenous fistulas have a definite advantage over arteriovenous grafts.

Today there is a consensus preferring AV fistulas over AV grafts. In 1997 the KDOQI guidelines and the Fistula First Initiative were adopted by professionals. The number of fistulas increased dramatically from approximately 20% before 1997 to 40% in 2004 and continues to grow (see figure below).

AV grafts vs. AV fistuals

 

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Literature:
http://cjasn.asnjournals.org/content/2/5/1043.full.pdf+html