Little W C, Rassi A, Freeman G L
J Clin Invest. 1987 Sep;80(3):613-20. doi: 10.1172/JCI113113.
Because catecholamines and digitalis have different effects on the time course of myocardial intracellular calcium concentration, their effects on the time course of left ventricular contraction and relaxation may also be different. To study this question, dogs were instrumented to measure left ventricular pressure and determine left ventricular volume from three ultrasonic dimensions. After full recovery from the instrumentation, the effects of dobutamine (2-10 micrograms/kg), ouabain (0.5 mg i.v.) alone, and ouabain given after propranolol (2 mg/kg i.v.), or phentolamine (5 mg i.v.) and incremental doses of ouabain (0.25-0.75 mg i.v.) were assessed on different days. Left ventricular pressure and volume were varied by caval occlusions. Dobutamine significantly increased the slope of the left ventricular end-systolic pressure-volume relation (Emax) and the slope of the dP/dtmax-end-diastolic volume relation (dE/dtmax), while significantly decreasing the time from end-diastole to end-systole (tmax) and the time constant (T) of the isovolumic fall in left ventricular pressure. Ouabain also increased Emax and dE/dtmax but did not alter tmax or T. Dobutamine produced a greater increase in dE/dtmax than in Emax, whereas ouabain produced similar increases in both. These effects of ouabain were not altered by pretreatment with propranolol or phentolamine. We conclude that although dobutamine and ouabain are both positive inotropes that increase Emax, dobutamine speeds the rate of left ventricular contraction (tmax) and relaxation (T), whereas ouabain does not. These effects of ouabain and dobutamine on global parameters of left ventricular chamber performance mirror their influence on intracellular calcium availability. Furthermore, these observations are consistent with the predictions of the time-varying elastance model of the left ventricle and support its usefulness as a conceptual framework to understand and link events occurring during isovolumic contraction, end-systole, and isovolumic relaxation.
由于儿茶酚胺和洋地黄对心肌细胞内钙浓度的时程有不同影响，它们对左心室收缩和舒张时程的影响也可能不同。为研究这个问题，对犬进行仪器植入以测量左心室压力，并通过三个超声维度确定左心室容积。在仪器植入完全恢复后，在不同日期评估多巴酚丁胺（2 - 10微克/千克）、单独使用哇巴因（静脉注射0.5毫克）、普萘洛尔（静脉注射2毫克/千克）后给予哇巴因、或酚妥拉明（静脉注射5毫克）以及递增剂量的哇巴因（静脉注射0.25 - 0.75毫克）的作用。通过腔静脉阻断改变左心室压力和容积。多巴酚丁胺显著增加左心室收缩末期压力 - 容积关系斜率（Emax）和dP/dtmax - 舒张末期容积关系斜率（dE/dtmax），同时显著缩短从舒张末期到收缩末期的时间（tmax）以及左心室压力等容下降的时间常数（T）。哇巴因也增加Emax和dE/dtmax，但未改变tmax或T。多巴酚丁胺使dE/dtmax的增加幅度大于Emax，而哇巴因使两者增加幅度相似。哇巴因的这些作用不受普萘洛尔或酚妥拉明预处理的影响。我们得出结论，尽管多巴酚丁胺和哇巴因都是增加Emax的正性肌力药物，但多巴酚丁胺加快左心室收缩速率（tmax）和舒张速率（T），而哇巴因则不然。哇巴因和多巴酚丁胺对左心室腔功能整体参数的这些作用反映了它们对细胞内钙可用性的影响。此外，这些观察结果与左心室时变弹性模型的预测一致，并支持其作为理解和联系等容收缩、收缩末期和等容舒张期间发生事件的概念框架的有用性。
