Ilebekk A, Lekven J, Kiil F
Am J Physiol. 1980 Nov;239(5):H594-600. doi: 10.1152/ajpheart.1980.239.5.H594.
Myocardial contractions were examined in the left ventricle of anesthetized, open-chest dogs during infusion of a beta-adrenergic agent, isoproterenol (0.1-0.5 micrograms/min) into a shunt line to the left anterior descending coronary artery. Myocardial chord lengths were continuously monitored by pairs of ultrasonic elements inserted into the isoproterenol-infused and control regions. Heart rate remained constant, but isoproterenol altered contraction patterns in both control and infused regions. Contraction in the infused region started before ejection and stretched the control myocardium in early systole. Because of early relaxation, however, the infusion region was stretched at the end of ejection and in early diastole, while the control myocardium continued to shorten. Thus, isoproterenol infusion to a part of the left ventricle induces asynergic muscle contractions and despite localized inotropic stimulation stroke volume may not be significantly increased.
在麻醉开胸犬的左心室中进行心肌收缩研究。将β-肾上腺素能药物异丙肾上腺素（0.1 - 0.5微克/分钟）注入到左前降支冠状动脉的分流管中。通过插入注入异丙肾上腺素区域和对照区域的成对超声元件连续监测心肌弦长。心率保持恒定，但异丙肾上腺素改变了对照区域和注入区域的收缩模式。注入区域的收缩在射血前开始，并在收缩早期拉伸对照心肌。然而，由于早期舒张，注入区域在射血末期和舒张早期被拉伸，而对照心肌继续缩短。因此，向左心室的一部分注入异丙肾上腺素会诱导不协调的肌肉收缩，尽管有局部正性肌力刺激，但心输出量可能不会显著增加。
