Key result
In computational models of right ventricular pressure overload, a longitudinally aligned myocardial fiber orientation contributed to an increase in right ventricular ejection fraction.
Computational modeling suggests that longitudinal realignment of myocardial fibers serves as a systolic compensatory mechanism to maintain right ventricular ejection fraction during pressure overload.
Longitudinal fiber alignment may aid RV function in pressure overload; hypothesis-generating from animal models, needs in vivo validation before clinical translation.
Right ventricular failure (RVF) is a lethal condition in diverse pathologies. Pressure overload is the most common etiology of RVF, but our understanding of the tissue structure remodeling and other biomechanical factors involved in RVF is limited. Some remodeling patterns are interpreted as compensatory mechanisms including myocyte hypertrophy, extracellular fibrosis, and changes in fiber orientation. However, the specific implications of these changes, especially in relation to clinically observable measurements, are difficult to investigate experimentally. In this computational study, we hypothesized that, with other variables constant, fiber orientation alteration provides a quantifiable and distinct compensatory mechanism during RV pressure overload (RVPO). Numerical models were constructed using a rabbit model of chronic pressure overload RVF based on intraventricular pressure measurements, CINE magnetic resonance imaging (MRI), and diffusion tensor MRI (DT-MRI). Biventricular simulations were conducted under normotensive and hypertensive boundary conditions using variations in RV wall thickness, tissue stiffness, and fiber orientation to investigate their effect on RV pump function. Our results show that a longitudinally aligned myocardial fiber orientation contributed to an increase in RV ejection fraction (RVEF). This effect was more pronounced in response to pressure overload. Likewise, models with longitudinally aligned fiber orientation required a lesser contractility for maintaining a target RVEF against elevated pressures. In addition to increased wall thickness and material stiffness (diastolic compensation), systolic mechanisms in the forms of myocardial fiber realignment and changes in contractility are likely involved in the overall compensatory responses to pressure overload.
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Gomez et al. (2017) studied Right ventricular failure and pressure overload. Longitudinally aligned myocardial fiber orientation vs. Other fiber orientations under normotensive and hypertensive conditions was evaluated on Right ventricular ejection fraction (RVEF) and required contractility. In computational models of right ventricular pressure overload, a longitudinally aligned myocardial fiber orientation contributed to an increase in right ventricular ejection fraction.
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