INTERACTION BETWEEN AFTERLOAD AND CONTRACTILITY IN THE NEWBORN HEART - EVIDENCE OF HOMEOMETRIC AUTOREGULATION IN THE INTACT CIRCULATION
INTERACTION BETWEEN AFTERLOAD AND CONTRACTILITY IN THE NEWBORN HEART - EVIDENCE OF HOMEOMETRIC AUTOREGULATION IN THE INTACT CIRCULATION
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DOI：
10.1016/0735-1097(94)00562-5
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发表时间：
1995-05-01
影响因子：
24
通讯作者：
BAAN, J
中科院分区：
文献类型：
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作者：
KLAUTZ, RJM;TEITEL, DF;BAAN, J
目标。我们进行了本研究以确定后负荷和收缩力是否在新生羔羊的心脏中相互作用。我们专门研究了后负荷的逐步增加是否会增加收缩性。背景。对孤立且完整的成年狗心脏进行的几项研究表明，后负荷和收缩力并不是心脏性能的独立决定因素。相反，它们相互作用。后负荷和收缩力在新生儿心脏中不太可能相互作用，因为在新生儿中缺少可能介导成人相互作用的因素。方法。我们在完全麻醉下测量了七只新生羔羊在不同稳态后负荷水平下的收缩力。收缩性通过三个不同的指标来测量：收缩末期压力-容积关系（斜率和容积位置）；左心室压力的前负荷校正一阶导数 (dP/dt(max))；和预载校正冲程功。分别用微压计和电导导管测量左心室压力和容量。分别通过对下腔静脉和胸降主动脉中的球囊导管进行充气或放气来控制前负荷和后负荷。数据表示为平均值 +/- 1 SD。结果。后负荷的逐步增加会增加收缩性，与使用三个指标中的哪一个无关。在最高后负荷水平下，收缩末期压力-容积关系的斜率从平均基线值 4.44 +/- 2.43 增加到 6.69 +/- 2.89 kPa/ml。与此同时，收缩末压-容积关系在 14 kPa 时的容积从基线时的 3.34 +/- 1.52 ml 降至最高后负荷时的 1.12 +/- 0.83 ml。其他两项指标显示出类似的质量变化。根据每个后负荷水平的相同舒张末期容积从卸载干预中选择的节拍显示每搏输出量没有差异。结论。这项针对新生羔羊的研究表明，后负荷的逐步增加可显着增加收缩性，这使得心脏能够将每搏输出量维持在不同的后负荷水平。这形成了完整新生儿心脏中存在等压自动调节的直接证据。
Objectives. We undertook the present study to determine whether afterload and contractility interact in the hearts of newborn lambs. We specifically investigated whether stepwise increases in afterload increase contractility.Background. Several studies in the isolated and intact adult dog heart have shown that afterload and contractility are not independent determinants of cardiac performance; rather, they interact. Afterload and contractility are unlikely to interact in the neu born heart because the factors that may mediate the interaction in the adult are missing in the newborn.Methods. We measured contractility at different steady state levels of afterload in seven newborn lambs under complete anesthesia. Contractility was measured by three different indexes: end-systolic pressure-volume relations (slope and volume position); preload-corrected first derivative of left ventricular pressure (dP/dt(max)); and preload-corrected stroke work. Left ventricular pressure and volume were measured with a micromanometer and conductance catheter, respectively. Preload and afterload were manipulated by inflating or deflating a balloon catheter in the inferior vena cava and descending thoracic aorta, respectively. Data are expressed as mean value +/- 1 SD.Results. Stepwise increases in afterload increased contractility, independent of which of the three indexes was used. The slope of the end systolic pressure-volume relation increased from a mean baseline value of 4.44 +/- 2.43 to 6.69 +/- 2.89 kPa/ml at the highest level of afterload. Concomitantly, volume at 14 kPa of the end-systolic pressure-volume relation decreased from 3.34 +/- 1.52 ml at baseline to 1.12 +/- 0.83 ml at the highest afterload, The other two indexes showed qualitatively similar changes. Beats selected from unloading interventions on the basis of the same end-diastolic volume for each level of afterload showed no difference in stroke volume.Conclusions. This study in newborn lambs demonstrates that stepwise increases in afterload increase contractility considerably and that this enables the heart to maintain stroke volume at different levels of afterload. This forms direct evidence for the existence of homeometric autoregulation in the intact newborn heart.