Yasumura Y, Nozawa T, Futaki S, Tanaka N, Suga H
Department of Cardiovascular Dynamics, National Cardiovascular Center Research Institute, Osaka, Japan.
Circ Res. 1989 Apr;64(4):764-78. doi: 10.1161/01.res.64.4.764.
We studied whether the oxygen cost of mechanical energy is time-invariant in the excised, cross-circulated canine heart. The total mechanical energy generated by ventricular contraction can be quantified by the total pressure-volume area (PVA) according to the time-varying elastance model. In this model, mechanical energy generated until a specified time (t) during systole can be quantified by the partial pressure-volume area, PVA(t). PVA(t) was obtained by quickly releasing ventricular volume at a varied time during isovolumic contraction. The quick release aborted further development of mechanical energy. We found that PVA(t) at a constant end-diastolic volume linearly correlated with myocardial oxygen consumption (VO2). This indicates that the oxygen cost of mechanical energy is time-invariant. However, we also found that the slope of the VO2-PVA(t) relation decreased with increasing quick-release speed. This indicates a decrease in VO2 by the quick release despite the same PVA(t). The time-invariant oxygen cost of mechanical energy is consistent with the time-varying elastance model of the ventricle, but the decreased VO2 with increasing quick-release speed despite the same PVA(t) is not.
我们研究了机械能的氧耗在离体交叉循环犬心脏中是否随时间不变。根据时变弹性模型，心室收缩产生的总机械能可通过总压力-容积面积（PVA）来量化。在该模型中，收缩期特定时间（t）之前产生的机械能可通过部分压力-容积面积PVA（t）来量化。PVA（t）是通过在等容收缩期的不同时间快速释放心室容积获得的。快速释放中止了机械能的进一步发展。我们发现，在恒定舒张末期容积下，PVA（t）与心肌氧耗（VO2）呈线性相关。这表明机械能的氧耗随时间不变。然而，我们还发现，VO2-PVA（t）关系的斜率随快速释放速度的增加而降低。这表明尽管PVA（t）相同，但快速释放会使VO2降低。机械能随时间不变的氧耗与心室的时变弹性模型一致，但尽管PVA（t）相同，VO2随快速释放速度增加而降低的情况却并非如此。
