LEFT VENTRICULAR TIME-VARYING ELASTANCE

评价左心室（LV）性能仍然是一个困难， 临床实践和生理学研究中的问题。 数据从 离体犬心脏表明左心室表现为弹性结构 在收缩期以可预测的方式变硬，因此，它可以是 被描述为随时间变化的弹性。 该项目的目标是 测试该假设描述LV之间关系的能力 原位心脏的收缩压和容积;并研究两个 新的方法来评估左心室的性能，我们已经从时间 变弹性假说 第一种方法涉及关系 LV压力升高的峰值速率（dP/dt-max）与LV 舒张末期容积 我们将测试假设，支持我们的 初步数据表明，这种关系是线性的，对变化不敏感 在负荷条件下，和非常敏感的变力状态。 其次我们 将评估一种计算E-max（LV斜率）的新方法 收缩末期压力-容积关系，使用从 时变弹性假说，并得到初步数据的支持。 这 关系描述了E-max作为dP/dt-max的函数，LV收缩末期 舒张末期容积和收缩末期时间。 因此，E-max可以是 根据单组条件下的测量结果确定，避免了 需要改变负荷条件，以产生一系列LV收缩末期 压力-容积点。 这些研究将在长期使用以下器械的犬中进行： 用于测量LV压力的微压计和3对超声晶体 以确定LV容量。 主动脉血流量将使用 电磁流量探头 左心室压力和容积将因腔静脉而异 闭塞。 多巴酚丁胺输注可改变正性肌力状态， 通过输注甲氧胺和葡聚糖改变加载条件 以及降主动脉的短暂闭塞。 等容搏动将 由升主动脉的暂时性完全闭塞产生。 这些研究将为LV的描述提供新的信息 在体心脏收缩功能及评价左室功能的两种新方法 性能可以独立于负载条件。

The evaluation of left ventricular (LV) performance remains a difficult problem in clinical practice and physiologic investigation. Data from isolated canine hearts suggest that the LV behaves as an elastic structure that stiffens in a predictable manner during systole, thus, it can be described as a time-varying elastance. The goals of this project are to test the ability of this hypothesis to describe the relation between LV systolic pressure and volume in the in situ heart; and to investigate two new methods of evaluating LV performance that we have derived from the time varying elastance hypothesis. The first method involves the relation between the peak rate of LV pressure rise (dP/dt-max) and the LV end-diastolic volume. We will test the hypothesis, supported by our preliminary data, that this relation is linear, insensitive to alterations in loading conditions, and very sensitive to inotropic state. Secondly, we will evaluate a new method of calculating E-max, the slope of the LV end-systolic pressure-volume relation, using a relation derived from the time-varying elastance hypothesis and supported by preliminary date. This relation describes E-max as a function of dP/dt-max, the LV end-systolic and end-diastolic volumes, and the time to end-systole. Thus E-max can be determined from measurements under a single set of conditions, avoiding the need to alter loading conditions to produce a range of LV end-systolic pressure-volume points. These studies will be carried out in dogs chronically instrumented with a micromanometer to measure LV pressure, and 3 pairs of ultrasonic crystals to determine LV volume. Aortic flow will be measured with an electromagnetic flow probe. LV pressure and volume will be varied by caval occlusions. Inotropic state will be altered by dobutamine infusion, while loading conditions will be varied by infusion of methoxamine and dextran and by transient occlusions of the descending aorta. Isovolumic beats will be produced by transient complete occlusion of the ascending aorta. These studies will provide new information on the descriptors of LV systolic function in the in situ heart and two new methods of evaluating LV performance that may be independent of loading conditions.