Slinker B K
Department of Medicine, University of Vermont, Burlington 05405.
Circ Res. 1991 Jul;69(1):2-11. doi: 10.1161/01.res.69.1.2.
Previous studies of the beat-to-beat regulation of left ventricular performance in the intact cardiovascular system have shown that the performance of the left ventricle on any one beat is influenced by the mechanical events of the previous beat, so-called previous beat contraction history. The general hypothesis investigated in this study is that previous beat contraction history occurs because of the perturbation of one or more biochemical processes with time courses that are long relative to one cardiac cycle. If this is true, then previous beat contraction history should depend on the interval between beats and, therefore, should extend beyond the previous beat to two, or even three, previous beats as heart rate is increased. Hemodynamic responses to random preload and afterload changes were measured in 11 anesthetized open-chest dogs on right heart bypass at three paced heart rates. Multiple linear regression was used to analyze these hemodynamic sequences and identify variables from the previous one, two, or three beats that were important in the mechanical history dependence of left ventricular function. The results of this analysis showed that under baseline conditions, all 11 hearts showed one beat of history dependence, with only two of 11 hearts showing a dependence on the previous two or three beats. At the highest heart rate, all 11 hearts still showed one beat of history dependence, but 10 of 11 hearts showed two beats of history dependence, and four of 11 showed three beats of history dependence (p less than 0.05). A general framework for the mechanism underlying these findings, which relates previous beat contraction history to the interval-dependent mechanical restitution phenomenon, is proposed and discussed.
先前对完整心血管系统中左心室功能逐搏调节的研究表明，左心室在任何一次搏动时的功能都受前一次搏动机械事件的影响，即所谓的前次搏动收缩历史。本研究探讨的一般假设是，前次搏动收缩历史的出现是由于一个或多个生化过程受到扰动，其时间进程相对于一个心动周期较长。如果这是真的，那么前次搏动收缩历史应该取决于搏动间期，因此，随着心率增加，应该延伸到前一次搏动之外，至前两次甚至三次搏动。在11只麻醉开胸、进行右心旁路手术的犬中，以三种起搏心率测量对随机预负荷和后负荷变化的血流动力学反应。采用多元线性回归分析这些血流动力学序列，并从前一次、两次或三次搏动中识别出对左心室功能机械历史依赖性重要的变量。分析结果显示，在基线条件下，所有11颗心脏均表现出一次搏动的历史依赖性，只有2颗心脏表现出对前两次或三次搏动的依赖性。在最高心率时，所有11颗心脏仍表现出一次搏动的历史依赖性，但11颗心脏中有10颗表现出两次搏动的历史依赖性，11颗中有4颗表现出三次搏动的历史依赖性（p<0.05）。提出并讨论了一个将前次搏动收缩历史与间期依赖性机械恢复现象联系起来的这些发现背后机制的总体框架。
