Takano H, Glantz S A
Department of Medicine, University of California, San Francisco 94143-0124, USA.
Circulation. 1995 May 1;91(9):2423-34. doi: 10.1161/01.cir.91.9.2423.
Two types of ischemia, pacing-induced and coronary occlusion-induced, have different effects on left ventricular diastolic properties. During pacing-induced ischemia, the diastolic pressure-volume relation is said to shift upward, whereas during coronary occlusion, it is said to shift rightward or downward. However, recent studies have shown that the relation can shift in any direction during both types of ischemia. The purpose of this study was to identify determinants of the shift of the end-diastolic pressure-volume relation (EDPVR) during pacing-induced ischemia.
We retrospectively analyzed 46 pacing-induced ischemia experiments performed in 15 open-pericardium anesthetized dogs. Pacing ischemia was induced by constricting left anterior descending and left circumflex coronary arteries and pacing the left atrium at 150 to 180 beats per minute for 3 minutes. Left ventricular volume was measured with a conductance catheter. Hemodynamics were recorded during baseline, coronary stenosis, rapid pacing, and pacing-induced ischemia (immediately after rapid pacing). For each condition, hemodynamics were recorded in steady state and then during a brief inferior vena caval occlusion (except for during rapid pacing) to obtain left ventricular end-diastolic and end-systolic pressure-volume relations. The shift of the EDPVR from coronary stenosis to pacing-induced ischemia was assessed by an upward shift index (end-diastolic pressure during pacing-induced ischemia minus the pressure during coronary stenosis at the largest end-diastolic volume common to both conditions, SI-S) and a rightward shift index (the largest end-diastolic volume during pacing-induced ischemia minus the largest volume during coronary stenosis, delta EDVI-S). The index of left ventricular contractility, the end-systolic elastance (Ees), or the slope of the dP/dtmax-end-diastolic volume relation (dE/dtmax) during pacing-induced ischemia was the strongest determinant of the magnitude of SI-S and delta EDVI-S and thus of the shift of the EDPVR. As Ees or dE/dtmax decreased, SI-S decreased and delta EDVI-S increased.
Our results suggest that left ventricular contractility is the best determinant of the shift of the EDPVR during pacing-induced ischemia. The more left ventricular contractility decreases, the more the EDPVR shifts downward and rightward.
两种类型的缺血，即起搏诱导型和冠状动脉闭塞诱导型，对左心室舒张特性有不同影响。在起搏诱导的缺血过程中，舒张期压力-容积关系据说向上移位，而在冠状动脉闭塞时，据说向右或向下移位。然而，最近的研究表明，在两种类型的缺血过程中，该关系可向任何方向移位。本研究的目的是确定起搏诱导缺血期间舒张末期压力-容积关系（EDPVR）移位的决定因素。
我们回顾性分析了在15只开胸麻醉犬身上进行的46次起搏诱导缺血实验。通过收缩左前降支和左旋支冠状动脉并以每分钟150至180次的频率起搏左心房3分钟来诱导起搏缺血。用导电导管测量左心室容积。在基线、冠状动脉狭窄、快速起搏和起搏诱导缺血（快速起搏后立即）期间记录血流动力学。对于每种情况，在稳态下记录血流动力学，然后在短暂的下腔静脉闭塞期间（快速起搏期间除外）记录，以获得左心室舒张末期和收缩末期压力-容积关系。通过向上移位指数（起搏诱导缺血期间的舒张末期压力减去两种情况共有的最大舒张末期容积时冠状动脉狭窄期间的压力，SI-S）和向右移位指数（起搏诱导缺血期间的最大舒张末期容积减去冠状动脉狭窄期间的最大容积，δEDVI-S）评估从冠状动脉狭窄到起搏诱导缺血时EDPVR的移位。起搏诱导缺血期间左心室收缩性指数、收缩末期弹性（Ees）或dP/dtmax-舒张末期容积关系（dE/dtmax）的斜率是SI-S和δEDVI-S大小以及因此EDPVR移位的最强决定因素。随着Ees或dE/dtmax降低，SI-S降低而δEDVI-S增加。
我们的结果表明，左心室收缩性是起搏诱导缺血期间EDPVR移位的最佳决定因素。左心室收缩性降低越多，EDPVR向下和向右移位就越多。
