Method to simulate distal flow resistance in coronary arteries in 3D printed patient specific coronary models

Abstract

Background: Three-dimensional printing (3DP) offers a unique opportunity to build flexible vascular patient-specific coronary models for device testing, treatment planning, and physiological simulations. By optimizing the 3DP design to replicate the geometrical and mechanical properties of healthy and diseased arteries, we may improve the relevance of using such models to simulate the hemodynamics of coronary disease. We developed a method to build 3DP patient specific coronary phantoms, which maintain a significant part of the coronary tree, while preserving geometrical accuracy of the atherosclerotic plaques and allows for an adjustable hydraulic resistance. Methods: Coronary computed tomography angiography (CCTA) data was used within Vitrea (Vital Images, Minnetonka, MN) cardiac analysis application for automatic segmentation of the aortic root, Left Anterior Descending (LAD), Left Circumflex (LCX), Right Coronary Artery (RCA), and calcifications. Stereolithographic (STL) files of the vasculature and calcium were imported into Autodesk Meshmixer for 3D model optimization. A base with three chambers was built and interfaced with the phantom to allow fluid collection and independent distal resistance adjustment of the RCA, LAD and LCX and branching arteries. For the 3DP we used Agilus for the arterial wall, VeroClear for the base and a Vero blend for the calcifications, respectively. Each chamber outlet allowed interface with catheters of varying lengths and diameters for simulation of hydraulic resistance of both normal and hyperemic coronary flow conditions. To demonstrate the manufacturing approach appropriateness, models were tested in flow experiments. Results: Models were used successfully in flow experiments to simulate normal and hyperemic flow conditions. The inherent mean resistance of the chamber for the LAD, LCX, and RCA, were 1671, 1820, and 591 (dynes • sec/ cm 5), respectively. This was negligible when compared with estimates in humans, with the chamber resistance equating to 0.65-5.86%, 1.23-6.86%, and 0.05-1.67% of the coronary resistance for the LAD, LCX, and RCA, respectively at varying flow rates and activity states. Therefore, the chamber served as a means to simulate the compliance of the distal coronary trees and to allow facile coupling with a set of known resistance catheters to simulate various physical activity levels.

Clinical Applications of Patient-Specific 3D Printed Models in Cardiovascular Disease: Current Status and Future Directions

“…A 3D printed chamber was designed to enable the 3D printed coronary model connected to a physiological flow Further to the above-mentioned applications, 3D printed coronary artery models can also be used to simulate blood flow to the coronary arteries with regard to the hemodynamic changes associated with the development of atherosclerosis. Sommer and colleagues created 3D printed coronary models aiming to simulate the distal resistance and compliance of the coronary arteries [64]. Figure 10 is a workflow showing the steps from creation of the 3D segmented coronary artery tree to 3D printed model for investigation of the hemodynamic flow.…”

“…Limited research is done in this area and a study by Hossien et al reported interesting findings [67]. 3D printing models of aortic dissection, in particular, reproducing the intimal flap is very challenging due to the very thin structure separating true lumen from false lumen (Figure 13) [64,65]. Limited research is done in this area and a study by Hossien et al reported interesting findings [67].…”

“…LAD-left anterior descending, LCX-left circumflex, RCA-right coronary artery. Reprinted with permission under open access from Sommer et al [ 64 ].…”

“…(j) The model is 3D printed, cleaned, and ready to be attached to a flow loop. Reprinted with permission under open access from Sommer et al[64].…”

Investigation of Wall Shear Stress in Cardiovascular Research and in Clinical Practice—From Bench to Bedside

“…3D printing and tissue engineering are promising approaches to fabricating new 3D tubular devises for the in vitro modeling of hemodynamics. 3D microfluidic chambers [ 62 , 63 ], as well as synthetic tubular branching vessels with complex geometries, namely phantoms [ 64 ], have been fabricated and are intended to be employed in cardiovascular research. Furthermore, artificially stenosed vessels or valves in a microfluidic system have been established, often combined with CFD, focusing on hemodynamic properties depending on vessel diameter and/or the degree of stenosis [ 65 , 66 ], which allows for the investigation of the effect of different degrees of stenosis on WSS or shear stress gradients in atherosclerotic lesions.…”