Matsushita T, Takaki M, Fujii W, Matsubara H, Suga H
Department of Physiology II, Okayama University Medical School, Japan.
Jpn J Physiol. 1995;45(6):991-1004. doi: 10.2170/jjphysiol.45.991.
Coronary perfusion pressure (CPP) is well known to affect left ventricular (LV) mechanoenergetics (Gregg's phenomenon). The garden hose effect via the Frank-Starling mechanism caused by coronary distension has long been considered to be the underlying mechanism of this phenomenon. However, recent studies have revealed a close correlation between CPP and the excitation-contraction coupling in myocytes. The aim of this study was to investigate the mechanoenergetic aspects of Gregg's phenomenon by the ventricular contractility (Emax) dependency of the myocardial oxygen consumption (VO2)-total mechanical energy (PVA, systolic pressure-volume area) relationship. Experiments were performed in the excised, cross-circulated guinea pig heart preparation. The protocol consisted of LV volume loading (VOL run), changing coronary perfusion pressure at a fixed LV volume (CPP run) and intracoronary calcium (Ca) infusion also at the same LV volume (Ca run). In all seven hearts, we obtained a linear VO2-PVA relation in VOL run. The VO2-PVA relations in CPP and Ca runs, which equally enhanced Emax, were highly linear and had no significant difference in their slopes, both significantly steeper than in VOL run. These findings suggest no significant difference in the oxygen cost of Emax between CPP and Ca runs. The enhanced LV mechanoenergetics under increasing CPP is characterized by increases in the VO2 component primarily for the excitation-contraction coupling to a greater degree than expected from the mechanical (garden hose) effect.
众所周知，冠状动脉灌注压（CPP）会影响左心室（LV）的机械能量学（格雷格现象）。长期以来，人们一直认为冠状动脉扩张通过弗兰克 - 斯塔林机制产生的花园软管效应是这一现象的潜在机制。然而，最近的研究揭示了CPP与心肌细胞兴奋 - 收缩偶联之间的密切相关性。本研究的目的是通过心肌耗氧量（VO2）与总机械能（PVA，收缩压 - 容积面积）关系对心室收缩力（Emax）的依赖性，研究格雷格现象的机械能量学方面。实验在离体交叉循环豚鼠心脏标本上进行。实验方案包括左心室容量负荷（VOL实验）、在固定左心室容量下改变冠状动脉灌注压（CPP实验）以及在相同左心室容量下进行冠状动脉内钙（Ca）输注（Ca实验）。在所有七颗心脏中，我们在VOL实验中获得了线性的VO2 - PVA关系。在CPP实验和Ca实验中增强Emax的VO2 - PVA关系高度线性，且斜率无显著差异，两者均明显比VOL实验中的斜率更陡。这些发现表明CPP实验和Ca实验中Emax的氧耗成本无显著差异。在CPP增加时左心室机械能量学增强的特征是，VO2成分的增加主要用于兴奋 - 收缩偶联，其程度大于机械（花园软管）效应所预期的程度。
