Computational analysis for competition flows in arteriovenous fistulas based on non-contrast magnetic resonance imaging

Introduction: Characteristics of hemodynamics strongly affect the patency of arteriovenous fistula (AVF) in hemodialysis patients. Because of pressure balance changes among arteries after AVF construction, regurgitating flow occurs in some patients. Methods: Based on phase-contrast MRI measurements, flow types around the anastomotic site are classified to the three different types of splitting, merging, and one-way, where merging type incorporates regurgitating flow. We have performed computational simulations to analyze characteristic differences among these types. Results: In the merging type, a characteristic spiral flow is observed in AVF causing strong wall shear stress and large pressure drop, whereas the splitting type shows a smooth flow and gives a smaller pressure drop. The one-way case is intermediate between splitting and merging types. Conclusion: Regurgitation brings about high wall shear stress near the anastomotic site because of instabilities induced by merging phenomena, for which type careful follow-up examinations are regarded as necessary.