Campbell K B, Kirkpatrick R D, Knowlen G G, Ringo J A
Department of Veterinary and Comparative Anatomy, Physiology, and Pharmacology, Washington State University, Pullman 99164-6520.
Circ Res. 1990 Jan;66(1):218-33. doi: 10.1161/01.res.66.1.218.
Elastance-resistance [E(t)-R] representations of the left ventricle (LV) were evaluated for their ability to reproduce instantaneous pressure [P(t)] and outflow [Q(t)]. Experiments were performed in open-chest rats. P(t) and Q(t) were measured during steady-state ejecting beats and during a beat in which the aorta was suddenly clamped. The degree of clamping varied from partial to total occlusion. The total occlusion beat was considered an isovolumic beat that generated an isovolumic pressure [Piso(t)] with a characteristic time to maximal Piso(t) [Tpisomax]. In ejecting beats, 34% of stroke volume was delivered after Tpisomax. P(t) and Q(t) from the steady-state ejecting beats and Piso(t) from the clamped beat were then used to estimate parameters of an E(t)-R model. Components of P(t) and Q(t) not accounted for by E(t)-R were identified and termed extra-pressure [Pext(t)] and extra-outflow [Qext(t)]. Pext(t) and Qext(t) were near-zero valued until Tpisomax; then they became systematically positive and finally negative valued after end ejection. During partial aortic occlusion, P(t) was elevated and Q(t) was reduced. However, the time of ejection was extended, and the fraction of stroke volume delivered after Tpisomax increased as P(t) was made higher. Partial occlusion also prolonged the positive phase of Pext(t) and Qext(t). Elements possessing "active" and "deactive" properties were added to the E(t)-R model in an attempt to account for Pext(t) and Qext(t) during partial occlusion. Optional forms of these elements were considered. These expanded E(t)-R models were fitted to basal ejecting data and then asked to predict data from a partial occlusion beat. All expanded models failed to adequately predict the partial occlusion pressure and/or outflow. It was concluded that 1) late ejection was quantitatively important to LV pumping, 2) behavior during late ejection was inconsistent with E(t)-R, and 3) ad hoc modification of E(t)-R models was not likely to yield LV pumping models that could satisfactorily reproduce instantaneous P(t) and Q(t) behavior over the entire ejection period.
评估了左心室（LV）的弹性 - 阻力[E(t)-R]表征重现瞬时压力[P(t)]和流出量[Q(t)]的能力。实验在开胸大鼠身上进行。在稳态射血期以及主动脉突然夹闭的一个心动周期中测量P(t)和Q(t)。夹闭程度从部分夹闭到完全闭塞不等。完全闭塞的心动周期被视为等容心动周期，其产生具有特征性达到最大等容压力[Piso(t)]时间[Tpisomax]的等容压力[Piso(t)]。在射血期，34%的搏出量在Tpiso max之后输送。然后将稳态射血期的P(t)和Q(t)以及夹闭心动周期的Piso(t)用于估计E(t)-R模型的参数。识别出E(t)-R未解释的P(t)和Q(t)的组成部分，并将其称为额外压力[Pext(t)]和额外流出量[Qext(t)]。在Tpiso max之前，Pext(t)和Qext(t)的值接近零；然后它们系统性地变为正值，在射血末期最终变为负值。在部分主动脉夹闭期间，P(t)升高而Q(t)降低。然而，射血时间延长，随着P(t)升高，在Tpiso max之后输送的搏出量比例增加。部分夹闭还延长了Pext(t)和Qext(t)的正值期。在E(t)-R模型中添加具有“主动”和“去激活”特性的元件，试图解释部分夹闭期间的Pext(t)和Qext(t)。考虑了这些元件的可选形式。将这些扩展的E(t)-R模型拟合到基础射血数据，然后要求它们预测部分夹闭心动周期的数据。所有扩展模型都未能充分预测部分夹闭时的压力和/或流出量。得出的结论是：1）射血后期对左心室泵血在数量上很重要；2）射血后期的行为与E(t)-R不一致；3）对E(t)-R模型进行特别修改不太可能产生能够在整个射血期令人满意地重现瞬时P(t)和Q(t)行为的左心室泵血模型。
