Akaishi M, Weintraub W S, Schneider R M, Klein L W, Agarwal J B, Helfant R H
Circ Res. 1986 Feb;58(2):209-17. doi: 10.1161/01.res.58.2.209.
To determine the mechanical factors affecting regional segmental motion after acute coronary occlusion, we studied seven conscious dogs, instrumented with sonomicrometers. Loading conditions were changed by the withdrawal of 500 ml of blood and the transfusion of 800 ml of blood. To express segmental motion, percent systolic shortening, percent systolic elongation, and early diastolic shortening were calculated. Blood withdrawal decreased left ventricular preload, increased percent systolic elongation (from 6.9 +/- 3.1% to 9.9 +/- 3.5%) and early diastolic shortening (12.9 +/- 5.3% to 16.6 +/- 5.3%), and decreased percent systolic shortening. Blood transfusion increased left ventricular preload, decreased percent systolic elongation (to 5.2 +/- 1.8%) and early diastolic shortening (8.8 +/- 2.9%), and increased percent systolic shortening. Manipulation of loading did not change regional myocardial blood flow. In acutely ischemic myocardium, the tension-length loop showed an exponential upstroke during isovolumic systole and a nearly superimposed exponential downstroke during the isovolumic relaxation phase after systole, compatible with essentially passive movement as seen with an elastic material. The changes in loading conditions affected the tension-length curve to a very minor extent. The uniformity of the curve and its exponential shape explain the load-dependency of systolic bulging and segmental motion. It is concluded that systolic bulging depends on the change in the preload tension due to the compliant portion of tension-length curve, and that shortening of ischemic myocardium during the isovolumic relaxation phase is a completely passive phenomenon.
为了确定急性冠状动脉闭塞后影响局部节段运动的力学因素，我们对7只清醒犬进行了研究，这些犬均植入了超声微测仪。通过抽取500ml血液和输入800ml血液来改变负荷条件。为了表示节段运动，计算了收缩期缩短百分比、收缩期伸长百分比和舒张早期缩短百分比。抽血降低了左心室前负荷，增加了收缩期伸长百分比（从6.9±3.1%增至9.9±3.5%）和舒张早期缩短百分比（从12.9±5.3%增至16.6±5.3%），并降低了收缩期缩短百分比。输血增加了左心室前负荷，降低了收缩期伸长百分比（降至5.2±1.8%）和舒张早期缩短百分比（降至8.8±2.9%），并增加了收缩期缩短百分比。负荷的改变并未改变局部心肌血流量。在急性缺血心肌中，张力-长度环在等容收缩期显示指数上升，在收缩期后的等容舒张期显示几乎重叠的指数下降，这与弹性材料所见的基本被动运动相符。负荷条件的改变对张力-长度曲线的影响非常小。曲线的均匀性及其指数形状解释了收缩期膨出和节段运动的负荷依赖性。得出的结论是，收缩期膨出取决于张力-长度曲线顺应部分引起的前负荷张力变化，并且等容舒张期缺血心肌的缩短是一种完全被动的现象。
