Duwel C M, Westerhof N
Laboratory for Physiology, Free University, Amsterdam, The Netherlands.
Pflugers Arch. 1988 Sep;412(4):409-16. doi: 10.1007/BF01907560.
We studied the dependency of myocardial oxygen consumption on the mechanical events during left ventricular relaxation in isolated supported cat hearts. The volume of the left ventricle was controlled by means of a balloon connected to a membrane pump. Oxygen consumption (MVO2 in cm3.min-1.100 g-1) for three protocols (PROT) performed at peak isovolumic pressure, was studied: (1) rapid ejection to zero pressure, (2) partial rapid ejection followed by redevelopment of pressure, (3) volume expansion during relaxation, and compared with oxygen consumption of isovolumic (ISOV) beats. We found (mean +/- SD): (table; see text) In the protocols 1 and 3 the differences were not significant (paired Student's t-test, p greater than 0.05). In protocols 1 and 2 left ventricular volume was decreased up to 2.15 cm3 (i.e. stroke volume, SV) during the pressure release. We studied the specific effect of ejection (i.e., wall muscle shortening) in a fourth protocol in which the ventricle ejected up to 2.7 cm3 under nearly zero pressure load (isobaric contraction). There was a small amount of oxygen consumption associable with this unloaded ejection i.e. MVO2 = 3.38 (+/- 0.47) + 0.30 (+/- 0.16) SV, but it was too small to compensate for a decrease in MVO2 expected from the pressure release according to the tension time index. These findings suggest that oxygen consumption does not depend on the mechanical events during ventricular relaxation.
我们研究了在离体支持的猫心脏中，左心室舒张期心肌耗氧量对机械事件的依赖性。左心室容积通过连接到膜泵的球囊进行控制。研究了在等容压力峰值时进行的三种方案（PROT）的耗氧量（MVO2，单位为cm³·min⁻¹·100g⁻¹）：（1）快速射血至零压力；（2）部分快速射血后再恢复压力；（3）舒张期容积扩张，并与等容（ISOV）搏动的耗氧量进行比较。我们发现（均值±标准差）：（表格；见正文）在方案1和3中，差异不显著（配对学生t检验，p＞0.05）。在方案1和2中，压力释放期间左心室容积减少至2.15cm³（即每搏量，SV）。我们在第四个方案中研究了射血（即壁肌缩短）的特定效应，在该方案中，心室在几乎零压力负荷（等压收缩）下射血至2.7cm³。这种无负荷射血存在少量可归因的耗氧量，即MVO2 = 3.38（±0.47）+ 0.30（±0.16）SV，但它太小，无法根据张力时间指数补偿压力释放预期的MVO2降低。这些发现表明，耗氧量不依赖于心室舒张期的机械事件。
