Biomechanical Modeling to Inform Pulmonary Valve Replacement in Tetralogy of Fallot Patients after Complete Repair

Abstract : 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 end-diastolic 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 Qeff –both 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.