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Abstract：
The controversy between passive and active ventricular filling has been debated for decades and the question about the existence of an active diastole remains open. In this work, we advocate the model of active diastole by considering the heart as a suction pump and we add some more clues to support this point of view by the analysis of the pressure-volume (PV) loops of the left heart, comprising of the left ventricle (LV) and atrium (LA). Our working hypothesis is based on the dichotomy motor-brake: the cardiac muscle can act as a motor, when shortening against a load, or as a brake, when lengthening to a load. We discuss our hypothesis by means of a lumped model of the left heart, where both chambers are considered as hollow spherical shells. The notion of active stretch, introduced to describe the contractile behavior of the muscle fibers, plays a major role in our model. Then, the contraction of the muscle is related to the pressure and volume of the chamber through a nonlinear hyperelastic energy density function. Despite its simplicity, the model enlightens some important features of the LV-LA coupling and of the pumping function of the heart. Based on experimental PV data of the left heart of a normal human subject, it is shown that the contraction patterns of the LV and LA are synchronized with each other and have distinguishing features in each phase of the cardiac cycle. These results highlight the interplay between the two chambers and support the idea that the heart may act as a suction pump functioning in turn as a motor or a brake in order to meet specific demands in each phase of the cardiac cycle.
摘要：
被动和主动心室充盈之间的争议已经争论了几十年，关于存在主动舒张的问题仍然存在。在这项工作中,我们通过将心脏视为抽吸泵来倡导主动舒张模型，并通过分析左心的压力-容积（PV）回路来增加更多线索来支持这一观点，由左心室(LV)和心房(LA)组成。我们的工作假设基于运动制动二分法：心肌可以充当运动，当缩短负载时，或者作为刹车，当加长到负载时。我们通过左心的集中模型来讨论我们的假设，其中两个腔室都被认为是空心球形壳。主动拉伸的概念，介绍描述肌肉纤维的收缩行为，在我们的模型中起着重要作用。然后，肌肉的收缩通过非线性超弹性能量密度函数与腔室的压力和体积有关。尽管它简单，该模型启发了LV-LA耦合和心脏泵功能的一些重要特征。根据正常人左心的实验PV数据，结果表明，LV和LA的收缩模式彼此同步，并且在心动周期的每个阶段都具有不同的特征。这些结果突出了两个腔室之间的相互作用，并支持以下观点：心脏可以充当抽吸泵，进而充当电动机或制动器，以满足心动周期每个阶段的特定需求。
