Tobias A H, Slinker B K, Kirkpatrick R D, Campbell K B
Department of Veterinary and Comparative Anatomy, Washington State University, Pullman 99164-6520.
Am J Physiol. 1995 Jan;268(1 Pt 2):H170-7. doi: 10.1152/ajpheart.1995.268.1.H170.
Both pressure and volume have been proposed to determine the speed of left ventricular (LV) relaxation, but their relative importance is not known. Accordingly, we used isolated, buffer-perfused, isovolumically beating ferret hearts to study the effects of maximal developed pressure (Pdmax) and LV volume (V) on the speed of LV relaxation. Experiments were performed at 30 degrees C, and the hearts were paced at a baseline interbeat interval (BI) of 800 ms. Pdmax was varied independently of V by use of seven BI (75 to 133% of baseline BI), which resulted in test beats that developed a range of Pdmax due to varying degrees of restitution. Pdmax was also varied by setting V at five levels (80 to 120% of baseline V) during the test beats. Speed of relaxation was quantified as the time period of pressure decay from 75 to 25% Pdmax (T75-25). Data were analyzed by multiple linear regression. Increases in both Pdmax and V independently prolonged T75-25, and T75-25 was 1.45 times more sensitive to Pdmax than to V. However, when Pdmax and V were combined to estimate maximal wall stress (sigma max), the effects of Pdmax and V, as well as relative circumferential muscle length (estimated by V1/3), were not important determinants, and T75-25 depended on sigma max alone. Thus we conclude that 1) Pdmax and V are both determinants of the speed of LV relaxation and that Pdmax is approximately 1.5 times more important than V, and 2) the effects of Pdmax and V on relaxation act via the common mechanism of sigma max.
压力和容积都被认为可用于确定左心室（LV）舒张速度，但其相对重要性尚不清楚。因此，我们使用离体的、缓冲液灌注的、等容搏动的雪貂心脏来研究最大发育压力（Pdmax）和左心室容积（V）对左心室舒张速度的影响。实验在30℃下进行，心脏以800毫秒的基线搏动间期（BI）起搏。通过使用七个BI（基线BI的75%至133%）使Pdmax独立于V而变化，这导致测试搏动因不同程度的恢复而产生一系列Pdmax。在测试搏动期间，还通过将V设置为五个水平（基线V的80%至120%）来改变Pdmax。舒张速度通过压力从75% Pdmax衰减至25% Pdmax的时间段（T75 - 25）来量化。数据通过多元线性回归进行分析。Pdmax和V的增加均独立地延长了T75 - 25，并且T75 - 25对Pdmax的敏感性比对V高1.45倍。然而，当将Pdmax和V结合以估计最大壁应力（σmax）时，Pdmax和V以及相对圆周肌长度（由V1/3估计）的影响并非重要决定因素，T75 - 25仅取决于σmax。因此我们得出结论：1）Pdmax和V都是左心室舒张速度的决定因素，且Pdmax比V重要约1.5倍；2）Pdmax和V对舒张的影响通过σmax这一共同机制起作用。
