Multi-Modal in Vitro Experiments Mimicking the Flow Through a Mitral Heart Valve Phantom.

PURPOSE: Fluid-structure interaction (FSI) models are more commonly applied in medical research as computational power is increasing. However, understanding the accuracy of FSI models is crucial, especially in the context of heart valve disease in patient-specific models. Therefore, this study aimed to create a multi-modal benchmarking data set for cardiac-inspired FSI models, based on clinically important parameters, such as the pressure, velocity, and valve opening, with an in vitro phantom setup. METHOD: An in vitro setup was developed with a 3D-printed phantom mimicking the left heart, including a deforming mitral valve. A range of pulsatile flows were created with a computer-controlled motor-and-pump setup. Catheter pressure measurements, magnetic resonance imaging (MRI), and echocardiography (Echo) imaging were used to measure pressure and velocity in the domain. Furthermore, the valve opening was quantified based on cine MRI and Echo images. RESULT: The experimental setup, with 0.5% cycle-to-cycle variation, was successfully built and six different flow cases were investigated. Higher velocity through the mitral valve was observed for increased cardiac output. The pressure difference across the valve also followed this trend. The flow in the phantom was qualitatively assessed by the velocity profile in the ventricle and by streamlines obtained from 4D phase-contrast MRI. CONCLUSION: A multi-modal set of data for validation of FSI models has been created, based on parameters relevant for diagnosis of heart valve disease. All data is publicly available for future development of computational heart valve models.

Validation of fluid-structure interaction simulations of the opening phase of phantom mitral heart valves under physiologically inspired conditions.

BACKGROUND AND OBJECTIVE: Atrioventricular valve disease is a common cause of heart failure, and successful surgical or interventional outcomes are crucial. Patient-specific fluid-structure interaction (FSI) modeling may provide valuable insights into valve dynamics and guidance of valve repair strategies. However, lack of validation has kept FSI modeling from clinical implementation. Therefore, this study aims to validate FSI simulations against in vitro benchmarking data, based on clinically relevant parameters for evaluating heart valve disease. METHODS: An FSI model that mimics the left heart was developed. The domain included a deformable mitral valve of different stiffnesses run with different inlet velocities. Five different cases were simulated and compared to in vitro data based on the pressure difference across the valve, the valve opening, and the velocity in the flow domain. RESULTS: The simulations underestimate the pressure difference across the valve by 6.8-14 % compared to catheter measurements. Evaluation of the valve opening showed an underprediction of 5.4-7.3 % when compared to cine MRI, 2D Echo, and 3D Echo data. Additionally, the simulated velocity through the valve showed a 7.9-8.4 % underprediction in relation to Doppler Echo measurements. Qualitative assessment of the velocity profile in the ventricle and the streamlines of the flow in the domain showed good agreement of the flow behavior. CONCLUSIONS: Parameters relevant to the diagnosis of heart valve disease estimated by FSI simulations showed good agreement when compared to in vitro benchmarking data, with differences small enough not to affect the grading of heart valve disease. The FSI model is thus deemed good enough for further development toward patient-specific cases.

Mitral valve repair using leaflet expansion and subpartial annuloplasty in children.

Objective: Mitral valve reconstruction in the pediatric population is a challenge due to the frequent combination of annular dilatation and leaflet restriction and the need for growth. We present a novel strategy using leaflet expansion and subpartial annuloplasty with polytetrafluoroethylene reinforcement. Methods: From January 2014 through May 2021, 11 children aged 5 months to 14 years (median, 24 months) underwent elective mitral valve repair due to severe mitral valve regurgitation. The mitral valve abnormalities included congenital malformations (n = 7), postoperative leakage following commissurotomy (n = 1), and functional mitral valve regurgitation due to dilated cardiomyopathy (n = 3). Surgery consisted of leaflet expansions with autologous, untreated pericardium and subpartial annuloplasty with polytetrafluoroethylene reinforcement. Results: All children survived their surgeries with uneventful postoperative courses, except for 1 patient who needed an early reoperation to resolve a functional stenosis due to a spinnaker phenomenon. At discharge, mean gradient was 3.5 ± 3.9 mm Hg, with trivial mitral regurgitation in 9 patients (82%). All patients were alive and asymptomatic during the median follow-up of 3 years (range, 1-7 years). Their echocardiographic data showed a mean transmitral gradient of 4.4 ± 1.7 mm Hg and remained unchanged. Residual mitral valve regurgitation was trivial or mild in 9 patients (82%) and moderate in 2 patients (18%). Conclusions: Leaflet expansion with autologous pericardium and subpartial annuloplasty with polytetrafluoroethylene reinforcement for mitral regurgitation in the pediatric population gives stable and satisfactory results both early and at intermediate follow-up, permitting growth of the mitral valve.