Feasibility study of three-dimensional printing combined with mock circulatory system to make compliant mitral valve model for hemodynamic testing in vitro based on ultrasound image data

Abstract

Objective To explore the feasibility of three-dimensional(3D) printing combined with mock circulatory system of flexible mitral valve model for hemodynamic testing in vitro based on ultrasound image data, making the transformation of 3D printing valve model from static to dynamic and from anatomical to functional, as well as assisting surgical plan for mitral valve diseases. Methods A total of 10 subjects underwent three-dimensional transesophageal echocardiography (3D-TEE) and proved to be without mitral diseases were collected as mitral normal group from February 2017 to December 2018 in Renmin Hospital of Wuhan University, 10 mitral stenosis patients were collected as mitral stenosis group, and 10 mitral regurgitation patients were collected as mitral regurgitation group. Hemodynamic parameters of velocity (peak E), pressure gradient were obtained by two-dimensional transthoracic echocardiography in three groups, and the degree of mitral valve stenosis and regurgitation were also evaluated. Then 3D-TEE was performed to obtain the 3D volume image of mitral valve. After image post-processing and 3D modeling, the valve mold was printed with soluble material polyvinyl alcohol (PVA). The mixture of human skin silicone, silicone oil, starch and curing agent were poured into the mitral valve mold in a certain proportion to make flexible silicone mitral valve model. Then, the compliant valve model was placed in mock circulatory system (MCS), regularly opening and closing as it in vivo in the heart cycle. The hemodynamic parameters of mitral valve were measured again in vitro and the degree of stenosis and regurgitation was also evaluated respectively. Paired t test was used for statistical analysis of in vivo and in vitro measurements in two groups, and the consistency test was performed. Results The mitral valve 3D-TEE images of all patients were successfully post-processed, mitral valve molds were printed and flexible models were made. In vitro hemodynamic tests were all completed. The opening and closing state of the valve model in vitro was similar to that in vivo. Mitral valve regurgitation was detected in mitral regurgitation group in vitro, with degree to that in vivo. There were no statistically significant differences in hemodynamic parameters measured in vivo and in vitro models (all P>0.05), with a high consistency (r=0.76). Among the 10 patients with mitral stenosis and 10 patients with mitral regurgitation, 18 patients were evaluated as same degree as in vivo. Conclusions 3D printing of compliant mitral valve model based on ultrasound image is feasible, which reproduced hemodynamic features of mitral valve in vitro, setting foundation for further surgery simulation and clinical decision-making. Key words: Three-dimensional printing; Mitral regurgitation; Mitral regurgitation; Hemodynamics; Mock circulation system