Satoh S, Maruyama Y, Ashikawa K, Isoyama S, Suzuki H, Watanabe J, Nishioka O, Ino-Oka E, Takishima T
Jpn Circ J. 1986 Nov;50(11):1100-12. doi: 10.1253/jcj.50.1100.
We examined the effects of preload alteration on global and regional (i.e., non-ischemic and ischemic areas) function in the presence of regional myocardial ischemia and on the degree of ischemia using 18 isolated, metabolically supported canine left ventricles. For this purpose, cardiac output (CO), systolic segment length change (SL), myocardial CO2 tension (PmCO2) and ST level of epicardial ECG were measured at 3 levels of left ventricular end-diastolic pressure (LVEDP), i.e., approximately 7 (low LVEDP), 11 (middle LVEDP), and 16 mmHg (high LVEDP) without and with left circumflex artery (LCx) stenosis under a constant mean aortic pressure (90 mmHg), mean coronary perfusion pressure (90 mmHg) and heart rate. In the Pre-ischemic stage, CO and SL increased significantly when LVEDP was elevated in a stepwise fashion by changing the height of the reservoir connected to the left atrium. There were no significant changes in PmCO2 or ST level. On the other hand, with LCx stenosis, CO did not show a subsequent increase at higher LVEDPs (i.e., from 796 +/- 103 ml/min at middle LVEDP to 931 +/- 153 ml/min at high LVEDP). Furthermore, there was no significant SL response in the LCx area following alterations of LVEDP, although there was considerable lengthening of end-diastolic length. Both increased PmCO2 and ST level of the LCx area, following LCx stenosis, further increased significantly with elevation of LVEDP. These results suggest the possibility that considerable elevation of LVEDP worsens the degree of ischemia and does not significantly augment ischemic regional myocardial function or global function, while mild elevation of preload improves or tends to improve simultaneously regional ischemic and global functions without aggravating the ischemic injury significantly. Therefore, we conclude that the preload level is quite important in managing ischemia induced myocardial dysfunction.
我们使用18个分离的、代谢支持的犬左心室，研究了在存在局部心肌缺血的情况下，前负荷改变对整体和局部（即非缺血区和缺血区）功能的影响以及对缺血程度的影响。为此，在恒定的平均主动脉压（90 mmHg）、平均冠状动脉灌注压（90 mmHg）和心率下，于左心室舒张末期压力（LVEDP）的3个水平，即大约7（低LVEDP）、11（中LVEDP）和16 mmHg（高LVEDP），在左旋支动脉（LCx）狭窄和无狭窄的情况下，测量心输出量（CO）、收缩期节段长度变化（SL）、心肌二氧化碳张力（PmCO2）和心外膜心电图的ST段水平。在缺血前期，通过改变连接左心房的贮液器高度使LVEDP逐步升高时，CO和SL显著增加。PmCO2或ST段水平无显著变化。另一方面，在LCx狭窄时，较高LVEDP水平下CO未出现后续增加（即从中LVEDP时的796±103 ml/min到高LVEDP时的931±153 ml/min）。此外，尽管舒张末期长度有相当程度的延长，但LVEDP改变后LCx区域无显著的SL反应。LCx狭窄后，LCx区域的PmCO2和ST段水平均升高，随着LVEDP升高进一步显著增加。这些结果提示，LVEDP显著升高可能会加重缺血程度，且不会显著增强缺血区域心肌功能或整体功能，而前负荷轻度升高可改善或倾向于同时改善局部缺血和整体功能，且不会显著加重缺血损伤。因此，我们得出结论，前负荷水平在处理缺血性心肌功能障碍中非常重要。
