Background: Hemodynamics has been postulated to be an important factor contributing to successful versus failed AVF maturation. Pigs, in general, have hemodynamic features that are similar to those in humans, and thus are an attractive animal model for investigating the mechanisms underlying and the interventions for promoting AVF maturation. Since geometry is a critical determinant of hemodynamics, we investigated the geometry of pig AVFs using magnetic resonance imaging (MRI) technology.
Methods: Carotid-jugular AVFs were created in pigs. MRIs were obtained at 1, 2, and 6-10 weeks (wks) post-AVF creation (n=3 per time point) and used to reconstruct AVF lumen geometries. Lumen area, anastomosis angle, venous tortuosity, and nonplanarity angle magnitude were quantified.
Results: The AVF vein lumen area (mean ± standard deviation) significantly (p=0.0370) increased from 25.3 +/- 11.1 mm2 in wk 1, to 32.3 +/- 4.3 mm2 in wk 2, then to 62.7 +/- 21.3 mm2 in wks 6-10 suggesting that our pig AVF is a model for successful AVF maturation. Importantly, we also observed an increasing trend in the lumen areas from wk 1 to wks 6-10 of the proximal artery and the distal artery. The anastomosis angles were similar in wk 1 and 2 (51.6 +/- 23.2° vs 50.2 +/- 21.0°) then decreased to 25.8 +/- 17.3° in wks 6-10. Venous tortuosity slightly increased from wk1 to wk2 then to wks 6-10. Non-planarity angle magnitude initially decreased from wk 1 to wk 2 then increased to in wks 6-10.
Conclusion: This is the first serial and detailed study of pig AVF geometric parameters. The anastomosis angles of our pig AVFs were in line with human radiocephalic AVFs in the literature (~30-60°). Our study sets the stage for examining the role of geometry in alterations in hemodynamic forces and in AVF maturation processes.