Redaelli A, Montevecchi F M
Dipartimento di Bioingegneria, Politecnico di Milano, Milan, Italy.
Med Eng Phys. 1998 Jun;20(4):231-41. doi: 10.1016/s1350-4533(98)00036-8.
This paper presents a computational approach to ventricular fluid mechanics to evaluate three inotropic indices of early ejection: the intraventricular pressure drop (deltap). the first derivative of aortic flow rate (df/dt) and the first derivative of aortic pressure dp/dt. dp/dt is one of the most frequently used indices for assessing myocardial inotropy. Deltap and df/dt are characteristic of inertia driven flows and reflect the impulsive nature of the flow inside the ventricle during the ejection phase. The study is based on an axisymmetric fluid dynamics model of the left ventricle, developed according to the finite element approach. The fluid cavity is bounded by a shell containing two sets of counter-rotating contractile fibres. Two simulation sets were performed: the former to investigate the sensitivity of deltap and df/dt peaks (deltap(max) and df/dt(max)) with respect to changes in the inotropic state of the fibre. The latter allows the evaluation of the dependency of deltap(max) and df/dt(max) on afterload by means of two supravalvular stenoses of 50% and 70%. The model simulates the inertial features of ventricle behaviour. The calculated values of the indices investigated are in close agreement with those reported in the literature. The sensitivities of deltap(max) df/dt(max) and dp/dt(max) are calculated for the two simulation sets. Data are normalised with respect to the maximum values reached in the simulation set. The comparison indicates that deltap(max) has a greater sensitivity (3.4 vs. 3.1 ) and a more linear pattern than dp/dt(max) for changes in the inotropic state of the fibre. df/dt(max), shows a sensitivity close to dp/dt(max). Results confirm that the afterload does not affect dp/dt(max), in accordance with experimental observations, while deltap(max) and, to a major degree, df/dt(max) decrease when the afterload is increased.
本文提出了一种用于心室流体力学的计算方法，以评估早期射血的三个变力指数：心室内压降（Δp）、主动脉血流速率的一阶导数（df/dt）和主动脉压力的一阶导数dp/dt。dp/dt是评估心肌收缩力最常用的指数之一。Δp和df/dt是惯性驱动血流的特征，反映了射血期心室内血流的冲动性质。该研究基于根据有限元方法建立的左心室轴对称流体动力学模型。流体腔由包含两组反向旋转收缩纤维的壳界定。进行了两组模拟：前者研究Δp和df/dt峰值（Δp(max)和df/dt(max)）对纤维变力状态变化的敏感性。后者通过两个50%和70%的瓣上狭窄来评估Δp(max)和df/dt(max)对后负荷的依赖性。该模型模拟了心室行为的惯性特征。所研究指数的计算值与文献报道的值密切一致。计算了两组模拟中Δp(max)、df/dt(max)和dp/dt(max)的敏感性。数据相对于模拟集中达到的最大值进行归一化。比较表明，对于纤维变力状态的变化，Δp(max)比dp/dt(max)具有更高的敏感性（3.4对3.1）和更线性的模式。df/dt(max)显示出与dp/dt(max)接近的敏感性。结果证实，与实验观察结果一致，后负荷不影响dp/dt(max)，而当后负荷增加时，Δp(max)以及在很大程度上df/dt(max)会降低。
