What causes Arteriovenous (AV) fistulas to rupture?

What Causes AV Fistulas to Rupture

The primary causes of AV fistula rupture are aneurysm/pseudoaneurysm formation with progressive enlargement that compromises overlying skin integrity, graft degeneration, and infection—all of which can lead to severe hemorrhage, exsanguination, and death. 1

Primary Mechanisms of Rupture

Aneurysm and Pseudoaneurysm Formation

Progressive enlargement of aneurysms or pseudoaneurysms represents the most direct pathway to rupture by compromising circulation to the overlying skin. 1

• In AV grafts: Pseudoaneurysms that exceed twice the diameter of the graft or demonstrate rapid expansion should be surgically corrected due to their increased rupture risk 1
• Mechanism of failure: The expanding aneurysm compromises skin viability above the access, leading to incomplete hemostasis upon needle withdrawal and ultimately to graft rupture 1
• Critical threshold: When pseudoaneurysm expansion threatens the viability of overlying skin, the patient is at immediate risk of rupture and requires surgical intervention 1

Graft Degeneration

Degenerative changes within the graft material and overlying skin create structural weakness that predisposes to rupture. 1

• These degenerative changes occur over time with repeated needle punctures and hemodynamic stress 1
• The combination of graft material breakdown and compromised skin integrity creates a high-risk scenario for catastrophic bleeding 1

Infection

Untreated access infection directly leads to hemorrhage through tissue destruction and can result in bacteremia, sepsis, and death. 1, 2

• Infected grafts require surgical exploration and removal of the infected segment, as the graft material acts as a foreign body that perpetuates infection 1
• Infection compromises tissue integrity around the access site, increasing rupture risk 2

Contributing Factors That Increase Rupture Risk

Venous Stenosis and Hemodynamic Stress

Hemodynamically significant stenosis creates elevated pressures within the access that contribute to aneurysm formation and eventual rupture. 1, 2

• Stenosis from neointimal hyperplasia augments pressure within the access and decreases blood flow 1
• If stenosis ≥50% of lumen diameter is left untreated, it progressively damages the vessel wall 1

Repeated Needle Trauma

Cannulation into areas of pseudoaneurysm or compromised tissue directly precipitates hemorrhage and should be strictly avoided. 1, 2, 3

• Needle insertion into pseudoaneurysm areas may result in immediate hemorrhage 1
• Repeated punctures in the same location accelerate degenerative changes 1

Clinical Warning Signs of Impending Rupture

Monitor for these high-risk features that indicate imminent rupture:

• Rapid expansion of aneurysm or pseudoaneurysm 1
• Skin changes: thinning, discoloration, or compromised integrity over the access 1, 2
• Spontaneous bleeding or poor eschar formation after needle withdrawal 4
• Pseudoaneurysm exceeding twice the graft diameter 1
• Signs of infection: erythema, warmth, tenderness, or drainage 2, 4

Critical Pitfalls to Avoid

Delaying evaluation of access dysfunction leads to thrombosis, progressive aneurysm enlargement, and ultimately rupture with catastrophic bleeding. 2, 3

• Never cannulate through or near areas of aneurysm, pseudoaneurysm, or compromised skin—this directly precipitates rupture 1, 2, 3
• Never underestimate the significance of progressive aneurysm enlargement—even asymptomatic expansion requires intervention before skin compromise occurs 1
• Never delay surgical referral for infected grafts—infection rapidly progresses to tissue destruction and hemorrhage 1, 2