SIR 2024
Renal and GU Interventions
Maxwell B. Lohss, BS (he/him/his)
Medical Student
University of Pittsburgh School of Medicine
Financial relationships: Full list of relationships is listed on the CME information page.
Elliott Hammersley, BS
Lead Biomedical Engineer 3D Printing Program
UPMC
Disclosure information not submitted.
Anish Ghodadra, M.D.
Interventional Radiology Attending Physician
University of Pittsburgh Medical Center
Disclosure information not submitted.
To evaluate the feasibility of a method using three-dimensional ultrasound (3DUS), 3D printing, and computation fluid dynamics (CFD) to optimize endovascular arteriovenous fistula (endoAVF) creation.
Materials and Methods:
3DUS with active probe tracking of the superficial vasculature of a patient’s antecubital fossa was done with a GE Voluson S10 Ultrasound (GE, Boston, MA) for endoAVF evaluation. The patient underwent the creation of an ulnar-ulnar endoAVF with the WavelinQ (Becton, Dickinson and Company; Franklin Lakes, NJ) and coiling of the medial brachial vein with the basilic vein targeted for cannulation. At 2 weeks post-procedure, flows were measured with doppler ultrasound.
The 3DUS image of the antecubital fossa was segmented and converted into a surface mesh using Mimics Medical 25.0 (Materialise, Haasrode, Belgium) and 3D printed with the MJF 580 (HP Inc, Palo Alto, CA) for visualization. The mesh was modified to create 2 endoAVF fistula models: a 2mm ulnar-ulnar fistula and a 2mm radial-radial fistula. CFD was performed on the models in Solidworks (SolidWorks Corporation, MA, USA) using the patient’s 2-week measured flow rates and mean arterial pressure as boundary conditions with non-Newtonian blood at 37.0⁰C, assuming laminar flow and rigid vessel walls {1,2}. Average velocities were recorded at the anastomosis site of each model. Additional feasibility testing was performed substituting boundary conditions with flow rates recorded distal to brachial vein coiling to simulate pre-coiling conditions.
Results:
The fistula models produced anastomosis velocities (97 ± 4 cm/s) comparable to previously published CFD fistula models (Cohen’s d < 0.1) {2}. The pre-coiling conditions resulted in a 63 mL/min and 43 mL/min reduction in basilic vein flow in the ulnar-ulnar and radial-radial model, respectively. Pressure gradients remained within physiological limits ranging from 150 to 40 mmHg.
Conclusion:
Our method for modeling endoAVFs is comparable to previously established models and demonstrated physiologically accurate changes in flow when modifying boundary conditions to simulate interventions. We also show that 3D printing vascular anatomy for endoAVF planning is feasible. We plan to recruit more patients to further verify and validate our method by collecting additional flow data and accounting for pulsatile flow and vessel remodeling.