Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, The Netherlands.
Biomech Model Mechanobiol. 2024 Dec;23(6):1889-1907. doi: 10.1007/s10237-024-01874-y. Epub 2024 Sep 13.
During the Ross procedure, an aortic heart valve is replaced by a patient's own pulmonary valve. The pulmonary autograft subsequently undergoes substantial growth and remodeling (G&R) due to its exposure to increased hemodynamic loads. In this study, we developed a homogenized constrained mixture model to understand the observed adaptation of the autograft leaflets in response to the changed hemodynamic environment. This model was based on the hypothesis that tissue G&R aims to preserve mechanical homeostasis for each tissue constituent. To model the Ross procedure, we simulated the exposure of a pulmonary valve to aortic pressure conditions and the subsequent G&R of the valve. Specifically, we investigated the effects of assuming either stress- or stretch-based mechanical homeostasis, the use of blood pressure control, and the effect of root dilation. With this model, we could explain different observations from published clinical studies, such as the increase in thickness, change in collagen organization, and change in tissue composition. In addition, we found that G&R based on stress-based homeostasis could better capture the observed changes in tissue composition than G&R based on stretch-based homeostasis, and that root dilation or blood pressure control can result in more leaflet elongation. Finally, our model demonstrated that successful adaptation can only occur when the mechanically induced tissue deposition is sufficiently larger than tissue degradation, such that leaflet thickening overrules leaflet dilation. In conclusion, our findings demonstrated that G&R based on mechanical homeostasis can capture the observed heart valve adaptation after the Ross procedure. Finally, this study presents a novel homogenized mixture model that can be used to investigate other cases of heart valve G&R as well.
在罗斯手术中，主动脉心脏瓣膜被患者自身的肺动脉瓣所替代。由于肺动脉瓣暴露于增加的血流动力学负荷下，随后会发生显著的生长和重塑（G&R）。在本研究中，我们开发了一种均匀化约束混合物模型，以了解观察到的自体瓣叶对变化的血流动力学环境的适应性。该模型基于这样的假设，即组织 G&R 的目的是为每个组织成分保持机械平衡。为了模拟罗斯手术，我们模拟了肺动脉瓣暴露于主动脉压力条件以及随后的瓣膜 G&R。具体来说，我们研究了假设基于应力或应变的机械平衡、血压控制的使用以及根部扩张的效果的影响。通过该模型，我们可以解释发表的临床研究中的不同观察结果，例如厚度增加、胶原组织变化和组织成分变化。此外，我们发现基于应力的机械平衡的 G&R 可以比基于应变的机械平衡的 G&R 更好地捕获组织成分的观察到的变化，并且根部扩张或血压控制可以导致瓣叶伸长更多。最后，我们的模型表明，只有当机械诱导的组织沉积足够大于组织降解时，才能发生成功的适应，从而使瓣叶增厚超过瓣叶扩张。总之，我们的研究结果表明，基于机械平衡的 G&R 可以捕获罗斯手术后观察到的心脏瓣膜适应性。最后，本研究提出了一种新的均匀化混合物模型，可用于研究其他心脏瓣膜 G&R 病例。
