CorFix: Virtual Reality Cardiac Surgical Planning Software for Designing Patient-Specific Vascular Grafts: Development and Pilot Usability Study (Preprint)

Abstract

Patients with single ventricle heart defects receives three stages of surgeries culminating in the Fontan surgery. During the Fontan surgery, a vascular graft is sutured between the inferior vena cava and pulmonary artery to divert deoxygenated blood flow to the lungs via passive flow. Customizing the graft configuration can maximize the long-term benefits of Fontan surgery. However, planning patient-specific surgery has several challenges including the ability for physicians to customize grafts and evaluate its hemodynamic performance.

The aim of this study was to develop a virtual reality (VR) Fontan graft modeling and evaluation software for physicians. User study was performed to achieve three additional goals: 1) evaluate the software when used by medical doctors and engineers, 2) identify if doctors have a baseline intuition about hemodynamic performance of Fontan grafts in a VR setting, and 3) explore the impact of viewing hemodynamic simulation results in numerical and graphical formats.

A total of 5 medical professionals including 4 physicians (1 fourth-year resident, 1 third-year cardiac fellow, 1 pediatric intensivist, and 1 pediatric cardiac surgeon) and 1 biomedical engineer voluntarily participated in the study. The study was pre-scripted to minimize the variability of the interactions between the experimenter and the participants. Unless a participant was familiar with the Fontan surgery, a quick information session was provided at the start. Then, all participants were trained to use the VR gear and our software, CorFix. Each participant designed one bifurcated and one tube-shaped Fontan graft for a single patient. Then a hemodynamic performance evaluation was completed, allowing the participants to further modify their tube-shaped design. The design time and hemodynamic performance for each graft design were recorded. At the end of the study, all participants were provided surveys to evaluate the usability and learnability of the software and rate the intensity of VR sickness.

The average time for creating one bifurcated and one tube-shaped grafts after a single 10-minute training were 13.40 and 5.49 minutes, accordingly. Three out of 5 bifurcated and 1 out of 5 tube-shaped graft designs were in the benchmark range of hepatic flow distribution. Reviewing hemodynamic performance results and modifying the tube-shaped design took an average time of 2.92 minutes. Participants who modified their tube-shaped graft designs were able to improve the non-physiologic wall shear stress percentage by 7.02%. All tube-shaped graft designs improved wall shear stress compared the native surgical case of the patient. None of the designs met the benchmark indexed power loss.

VR graft design software can quickly be taught to physicians without any engineering background and VR experience. Improving the system of CorFix could improve performance of the users in customizing and optimizing grafts for patients. With graphical visualization, physicians were able to improve wall shear stress of a tube-shaped graft, lowering the chance of thrombosis. Bifurcated graft designs showed potential strength in better flow split to the lungs, reducing the risk for pulmonary arteriovenous malformations.