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The importance of experimental setups able to reproduce cardiac functions was well established in the field of clinical innovations. The mock circulatory loops acquired rising relevance, and the possibility to have a complete reproduction of different and specific fluid dynamic conditions within the setup is pivotal. A system with enough versatility to reproduce the physiologic range of both flows and pressures is required. This study describes the design of a versatile setup composed by a custom pulsatile left ventricular pump system and a 3D-printed mock circulatory loop for the in vitro analysis of a patient-specific case of an aortic complex. The performances of the pump were validated first with a set of test flow profiles. It was demonstrated that the system was able to cover a wide range of aortic and mitral flows. Second, the pump system was inserted within the full mock circulatory loop. A patient-specific case was reproduced, both in terms of flow and pressure profiles. A successful validation of the flow and pressure waveforms was obtained by using patient-specific in vivo data from magnetic resonance analysis.

This work presents the development of a Hybrid Mock Circulatory Loop (HMCL) to simulate hemodynamics at patient-specific level in terms of both 3D geometry and inlet/outlet boundary conditions.Clinical data have been processed to define the morphological and functional patient-specific settings. A piston pump is used to impose a parametric flow rate profile at the inlet of the hemodynamic circuit. In order to guarantee the physiological pressure and flow conditions, a specific hybrid chamber system including a real-time control has been designed and implemented. The developed system was validated firstly in a single outlet branch model and, secondly, on a 3D printed patient-specific multi-branch phantom. Finally, for the 3D phantom, the outlet flow profiles were compared with the corresponding in-vivo flow data.Results showed that the root mean squared error between the prescribed setpoint and the measured pressures was always below 3 mmHg (about 2.5%) for all cases. The obtained flow profiles for the patient-specific model were in agreement with the related functional in-vivo data.The capability to reproduce physiological hemodynamics condition, with high-fidelity, plays a significant role in the cardiovascular research. The developed platform can be used to assess the performances of cardiovascular devices, to validate numerical simulations, and to test imaging systems.

Background: 3D printing represents an emerging technology in the field of cardiovascular medicine. 3D printing can help to perform a better analysis of complex anatomies to optimize intervention planning. Methods: A systematic review was performed to illustrate the 3D printing technology and to describe the workflow to obtain 3D printed models from patient-specific images. Examples from our laboratory of the benefit of 3D printing in planning interventions were also reported. Results: 3D printing technique is reliable when applied to high-quality 3D image data (CTA, CMR, 3D echography), but it still needs the involvement of expert operators for image segmentation and mesh refinement. 3D printed models could be useful in interventional planning, although prospective studies with comprehensive and clinically meaningful endpoints are required to demonstrate the clinical utility. Conclusion: 3D printing can be used to improve anatomy understanding and surgical planning.

Computational models of cardiovascular structures rely on their accurate mechanical characterization. A validated method able to infer the material properties of patient-specific large vessels is currently lacking. The aim of the present study is to present a technique starting from the flow-area (QA) method to retrieve basic material properties from magnetic resonance (MR) imaging. The proposed method was developed and tested, first, in silico and then in vitro. In silico, fluid-structure interaction (FSI) simulations of flow within a deformable pipe were run with varying elastic modules (E) between 0.5 and 32 MPa. The proposed QA-based formulation was assessed and modified based on the FSI results to retrieve E values. In vitro, a compliant phantom connected to a mock circulatory system was tested within MR scanning. Images of the phantom were acquired and post-processed according to the modified formulation to infer E of the phantom. Results of in vitro imaging assessment were verified against standard tensile test. In silico results from FSI simulations were used to derive the correction factor to the original formulation based on the geometrical and material characteristics. In vitro, the modified QA-based equation estimated an average E = 0.51 MPa, 2% different from the E derived from tensile tests (i.e. E = 0.50 MPa). This study presented promising results of an indirect and non-invasive method to establish elastic properties from solely MR images data, suggesting a potential image-based mechanical characterization of large blood vessels.

Cardiovascular diseases are the leading cause of death in the western countries. Robotic surgery recently emerged as a confirmed strategy in the cardiovascular field, especially thanks to the improvement of soft robotics. These techniques have demonstrated their potential in terms of speed of execution and precision. In this context, a deeper knowledge of the material properties of the blood vessels is required, especially for computational soft robotics applications. A constitutive model including the contribution of the collagen fibers families is needed to take hyperelasticity and anisotropy into account. For this purpose, four different models are presented: two fiber families with dispersion (2FFD), two fiber families without dispersion (2FF), four fiber families with dispersion (4FFD), and four fiber families without dispersion (4FF). A set of experimental biaxial data obtained from ex-vivo specimens was used to assess the model performances. Two fitting procedures were imposed: a procedure with no weighting of scores and a procedure with a weight set to enhance the model performances in the contact range. A finite element simulation of a contact procedure was developed to evaluate the effect on the contact pressures and forces according to the different model implementations. In particular, a minimally invasive aortic valve positioning process through a previously designed soft robot was simulated. The results confirmed the overall fitting procedure. The adoption of the weighting process for the fitting was successful, as it permitted an accurate prediction in the region of interest through models with less parameters.

The insight of biological microstructures is at the basis of understanding the mechanical features and the potential pathologies of tissues, like the blood vessels. Different techniques are available for this purpose, like the Small Angle Light Scattering (SALS) approach. The SALS method has the advantage of being fast and non-destructive, however investigation of its physical principles is still required. Within this work, a numerical study for SALS irradiation of soft biological fibrous tissues was carried out through in-silico simulations based on a Monte Carlo approach to evaluate the effect of the thickness of the specimen. Additionally, the numerical results were validated with an optical setup based on SALS technique for the characterization of fibrous samples with dedicated tests on four 3D-printed specimens with different fibers architectures. The simulations revealed two main regions of interest according to the thickness (thk) of the analyzed media: a Fraunhofer region (thk &lt, 0.6 mm) and a Multiple Scattering region (thk &gt, 1 mm). Semi-quantitative information about the tissue anisotropy was successfully gathered by analyzing the scattered light spot. Moreover, the numerical results revealed a remarkable coherence with the experimental data, both in terms of mean orientation and dispersion of fibers.

Insights into the mechanical and microstructural status of biological soft tissues are fundamental in analyzing diseases. Biaxial traction is the gold standard approach for mechanical characterization. The state of the art methods for microstructural assessment have different advantages and drawbacks. Small angle light scattering (SALS) represents a valuable low energy technique for soft tissue assessment. The objective of the current work was to develop a bench test integrating mechanical and microstructural characterization capabilities for tissue specimens. The setup’s principle is based on the integration of biaxial traction and SALS analysis. A dedicated control application was developed with the objective of managing the test procedure. The different components of the setup are described and discussed, both in terms of hardware and software. The realization of the system and the corresponding performances are then presented.

The Modified Blalock Taussig Shunt (MBTS) is one of the most common palliative operations in case of cyanotic heart diseases. Thus far, the decision on the position, size, and geometry of the implant relies on clinicians’ experience. In this paper, a Medical Digital Twin pipeline based on reduced order modeling is presented for fast and interactive evaluation of the hemodynamic parameters of MBTS. An infant case affected by complete pulmonary atresia was selected for this study. A three-dimensional digital model of the infant’s MBTS morphology was generated. A wide spectrum of MBTS geometries was explored by introducing twelve Radial Basis Function mesh modifiers. The combination of these modifiers allowed for analysis of various MBTS shapes. The final results proved the potential of the proposed approach for the investigation of significant hemodynamic features such as velocity, pressure, and wall shear stress as a function of the shunt’s morphology in real-time. In particular, it was demonstrated that the modifications of the MBTS morphology had a profound effect on the hemodynamic indices. The adoption of reduced models turned out to be a promising path to follow for MBTS numerical evaluation, with the potential to support patient-specific preoperative planning.

Cardiovascular diseases (CVD) are disorders of the heart and blood vessels and represent 31% of all global deaths. In the contest of CVD, the use of animal experiments has been a contentious subject for many years. In recent years, in vitro and in silico models and methods have been proposed according to the 3Rs statement. However, an exhaustive report regarding the state of art in terms of in vitro and in silico experiments has not been reported yet. This work is focused on providing a collection of non-animal models and methods in use for basic and applied CVD research. The standardized descriptions of such studies will ultimately feed into EURL ECVAM database on alternative methods. Two are the research main phases. Firstly, the exclusion/ inclusion criteria and the list of relevant information resources of the research have been defined. The second phase regards the search, selection and detailed description of the literature papers by analysing records on Scopus and Pubmed databases.

The possibility to obtain in-vitro evaluation of hemodynamic flows and pressures is of capital importance in understanding cardiovascular pathologies and validating new devices. The in-vitro approach brings different advantage including the possibility to evaluate fluid dynamic parameters non invasively and to support in-silico simulations.

Mechanical properties and microstructural modifications of vessel tissues are strongly linked, as established in the state of the art of cardiovascular diseases. Techniques to obtain both mechanical and structural information are reported, but the possibility to obtain real-time microstructural and macrostructural data correlated is still lacking. An experimental approach to characterize the aortic tissue is presented. A setup integrating biaxial traction and Small Angle Light Scattering (SALS) analysis is described. The system was adopted to test ex-vivo aorta specimens from healthy and aneusymatic (aTAA) cases. A significant variation of the fiber dispersion with respect to the unloaded state was encountered during the material traction. The corresponding microstructural and mechanical data were successfully used to fit a given anisotropic constitutive model, with satisfactory R 2 values (0.97 ± 0.11 and 0.96 ± 0.17, for aTAA and healthy population, respectively) and fiber dispersion parameters variations between the aTAA and healthy populations (0.39 ± 0.23 and 0.15 ± 0.10). The method integrating the biaxial/SALS technique was validated, allowing for real-time synchronization between mechanical and microstructural analysis of anisotropic biological tissues.

Experimental methods offer the ability to recreate physical state and conditions in a controlled environment in terms of input and output variables. In the context of the cardiovascular system, mock circulatory systems (MCSs) are important experimental tools to provide information such as blood flow and pressures at different locations that, currently, can be difficult to be measured clinically. In literature several types of MCSs were proposed for fluid dynamic investigation of different vascular districts as well as to test new medical devices. However, these MCSs suffer the main drawback of being not fully controllable for flow reproduction waveform in terms of times and amplitudes of the physiological heart cycle.

The development of accurate replicas of the circulatory and cardiac system is fundamental for a deeper understanding of cardiovascular diseases and the testing of new devices. Although numerous works concerning mock circulatory loops are present in the current state of the art, still some limitations are present. In particular, a pumping system able to reproduce the left ventricle motion and completely compatible with the magnetic resonance environment to permit the four-dimensional flow monitoring is still missing. The aim of this work was to evaluate the feasibility of an actuator suitable for cardiovascular mock circuits. Particular attention was given to the ability to mimic the left ventricle dynamics including both compression and twisting with the magnetic resonance compatibility. In our study, a left ventricle model to be actuated through vacuum was designed. The realization of the system was evaluated with finite element analysis of different design solutions. After the in silico evaluation phase, the most suitable design in terms of physiological values reproduction was fabricated through three-dimensional printing for in vitro validation. A pneumatic experimental setup was developed to evaluate the pump performances in terms of actuation, in particular ventricle radial and longitudinal displacement, twist rotation, and ejection fraction. The study demonstrated the feasibility of a custom pneumatic pump for mock circulatory loops able to reproduce the physiological ventricle movement and completely suitable for the magnetic resonance environment.

We present a novel framework for the fluid dynamics analysis of healthy subjects and patients affected by ascending thoracic aorta aneurysm (aTAA). Our aim is to obtain indications about the effect of a bulge on the hemodynamic environment at different enlargements. Three-dimensional (3D) surface models defined from healthy subjects and patients with aTAA, selected for surgical repair, were generated. A representative shape model for both healthy and pathological groups has been identified. A morphing technique based on radial basis functions (RBF) was applied to mold the shape relative to healthy patient into the representative shape of aTAA dataset to enable the parametric simulation of the aTAA formation. Computational fluid dynamics (CFD) simulations were performed by means of a finite volume solver using the mean boundary conditions obtained from three-dimensional (PC-MRI) acquisition. Blood flow helicity and flow descriptors were assessed for all the investigated models. The feasibility of the proposed integrated approach pertaining the coupling between an RBF morphing technique and CFD simulation for aTAA was demonstrated. Significant hemodynamic changes appear at the 60% of the bulge progression. An impingement of the flow toward the bulge was observed by analyzing the normalized flow eccentricity (NFE) index.

Heart diseases are one of the commonest causes of death worldwide. These include valve pathologies such as valve stenosis, regurgitation, failure and similar, for which usually a valve substitution...