Nishioka O, Maruyama Y, Ashikawa K, Isoyama S, Satoh S, Watanabe J, Shimizu Y, Takishima T
First Department of Internal Medicine, Tohoku University School of Medicine, Sendai, Japan.
Jpn Heart J. 1988 Sep;29(5):709-22. doi: 10.1536/ihj.29.709.
If characteristic muscle properties such as myocardial viscosity and/or shortening deactivation influence left ventricular ejection in the whole heart, the slope of the left ventricular end-systolic pressure-volume relation should be a function of both the contractile state and the loading mode. Thus, the load dependence of the end-systolic pressure-volume relation was examined using isolated, perfused canine hearts ejecting saline into a hydraulic loading system. The instantaneous left ventricular volume was measured with a plethysmograph. Under constant coronary flow and heart rate, two regression lines for end-systolic pressure-volume relations in two sets of loading modes were obtained: (1) Preload (left ventricular end-diastolic pressure; 4-15 mmHg) changes under fixed afterload impedance (preload changes); (2) Afterload impedance (peripheral resistance; 1.9-9.6 x 10(3) dyn sec cm-5) changes under fixed left ventricular end-diastolic volume (afterload changes). The slope of the end-systolic pressure-volume relation with afterload changes was steeper than that with preload changes (6.3 +/- 0.7 vs 4.8 +/- 0.6 mmHg/ml, p less than 0.05). Accordingly, under constant coronary flow, the slope of the end-systolic pressure-volume relation depended on loading conditions within the physiological range of afterload impedance and preload. This finding supports our hypothesis and implies that the slope change is of limited value as a contractile index in the ejecting heart.
如果诸如心肌粘性和/或缩短失活等特征性肌肉特性影响全心的左心室射血，那么左心室收缩末期压力-容积关系的斜率应该是收缩状态和负荷模式两者的函数。因此，使用向液压加载系统中喷射盐水的离体灌注犬心，研究了收缩末期压力-容积关系的负荷依赖性。用体积描记器测量瞬时左心室容积。在冠状动脉流量和心率恒定的情况下，获得了两组负荷模式下收缩末期压力-容积关系的两条回归线：（1）在固定后负荷阻抗下前负荷（左心室舒张末期压力；4 - 15 mmHg）变化（前负荷变化）；（2）在固定左心室舒张末期容积下后负荷阻抗（外周阻力；1.9 - 9.6×10³ dyn sec cm⁻⁵）变化（后负荷变化）。后负荷变化时收缩末期压力-容积关系的斜率比前负荷变化时更陡（6.3±0.7 与 4.8±0.6 mmHg/ml，p＜0.05）。因此，在冠状动脉流量恒定的情况下，收缩末期压力-容积关系的斜率取决于后负荷阻抗和前负荷生理范围内的负荷条件。这一发现支持了我们的假设，并意味着在射血心脏中，斜率变化作为收缩指数的价值有限。
