Background: A biomechanical model of the heart can be used to incorporate multiple data sources (ECG, imaging, invasive hemodynamics). The purpose of this study was to use this approach in a cohort of tetralogy of Fallot patients after complete repair (rTOF) to assess comparative influences of residual right ventricular outflow tract obstruction (RVOTO) and pulmonary regurgitation on ventricular health. Methods: 20 rTOF patients who underwent percutaneous pulmonary valve replacement (PVR) and cardiovascular magnetic resonance (CMR) were included in this retrospective study. Biomechanical models specific to individual patient and physiology (pre-and post-PVR) were created and utilized to estimate the RV myocardial contractility. The ability of models to capture post-PVR changes of RV enddiastolic volume (EDV) and effective flow in pulmonary artery (Qeff) was also compared to expected values. Results: RV contractility pre-PVR (65±17 kPa, mean ± SD) was increased in rTOF patients in comparison to normal RV (39-45 kPa) (p<0.05). The contractility decreased significantly in all patients post-PVR (p<0.05). Patients with predominantly RVOTO demonstrated greater reduction in contractility (median decrease 35%) post-PVR than those with predominant pulmonary regurgitation (median decrease 12%). The model simulated post-PVR decreased EDV for majority and suggested an increase of Qeffboth in line with published data. Conclusions: This study uses a biomechanical model to synthesize multiple clinical inputs and give an insight into RV health. Individualized modeling allows us to predict the RV response to PVR. Initial data suggest that residual RVOTO imposes greater ventricular work than isolated pulmonary regurgitation.

The lung vital function of providing oxygen to the body heavily relies on its mechanical behavior, and the interaction with its complex environment. In particular, the large compliance and the porosity of the pulmonary tissue are critical for lung inflation and air inhalation, and the diaphragm, the pleura, the rib cage and intercostal muscles all play a role in delivering and controlling the breathing driving forces. In this paper, we introduce a novel poromechanical model of the lungs. The constitutive law is derived within a general poromechanics theory via the formulation of lung-specific assumptions, leading to a hyperelastic potential reproducing the volume response of the pulmonary mixture to a change of pressure. Moreover, physiological boundary conditions are formulated to account for the interaction of the lungs with their surroundings, including a following pressure and bilateral frictionless contact. A strategy is established to estimate the unloaded configuration from a given loaded state, with a particular focus on ensuring a positive porosity. Finally, we illustrate through several realistic examples the relevance of our model and its potential clinical applications.